**1.3 Intraluminal ringed prosthesis**

266 Front Lines of Thoracic Surgery

With this in mind first of all we tried to simplify the procedure by severing the stapling device (fig 3) from the activating handle, which in our device consisted in a flexible, cameratype, firing guide-wire that could be connected to the stapler after its coupling with vascular stumps just before firing (fig. 4,c), at the more convenient of the two opposite sides connectors (fig. 3). Moreover the two stapler parts were designed in such a way that each one could be mounted on the vascular stump by independent surgical teams without taking care for their reciprocal orientation; the connectors of the two parts of the stapler in fact

One of the crucial points mechanically implicit in any vascular stapler model, is related to the requirement of temporary fixation of the vascular stumps to the device ends in preparation for the anastomosis. The vascular stump link to each device end in fact must be, on one side, strong enough to be maintained during device manipulation for ends coupling but, on the other side, should be weak enough to be easily released after stapler firing, to

Being our stapler ideated for use in organ transplantation to reduce the warm ischemic phase, we could solve this problem by temporarily suturing vascular stumps to the stapler end by single thread on predisposed little rings (fig 3, d); this can be done independently by the donor surgical team at back table to one stapler end (fig 4, a) and by the recipient team to the other stapler end, without interfering with time critical surgical phases. When the donor organ is at the recipient operative table (fig 4, b) the two stapler ends can be easily and quickly connected and the stapler fired (fig. 4,c). Only when the circulation is resumed the sutures temporarily connecting the vascular stumps to the stapler ends can be sectioned and

To temporarily connect coronary artery stumps to the stapler ends, vacuum is applied to the predisposed device whose surface then sucks and holds the vascular wall (red arrows).

An elegant technical solution to this problem was provided by V. Kolesov (Kolesov VI et al 1970, 1991), credited for the first LIMA-coronary artery by pass (Konstantinov IE, 2004) and the first (and at this point in time the only one) surgeon to have clinically used coronary stapling device. He devised to realize this vascular stump-stapler end temporary link by applying vacuum to each device end whose surface was appropriately predisposed (Fig. 5, red arrows) thus sucking and holding the vascular stump in position. This seems a simple and effective method that can ideally fit with the surgical need and possibly solve this part

the device removed (fig 4, d) without impacting on the organ warm ischemia time.

allowed to limit the maximal possible vascular axis torsion to 30°.

allow the device ends to be divided and removed.

Fig. 5. Kolesov VI vacuum assisted vascular stapler.

of the vascular stapler problems.

In the 1970–1980s, a simplified Payr concept was revived with the introduction of intraluminal ringed prostheses, whose use in aortic substitution was quite extensively reported (Lemole et al, 1982; Berger et al, 1983; Crawford ES & JL, 1984).

Fig. 6. Intraluminal ringed prosthesis. Aortic anastomotic device commercially available (FDA) in 70-90ies.

The reasons for their clinical failure have been numerous. Facts mechanically implicit in the method (fig 7) are related both to the elastic retraction of the vessel when is clamped, already outlined in the Payr report (Payr, 1900), and to the floppy consistency of the vascular wall that requires a further significant gap to be left between the clamped internal aortic wall and the external ring diameter to allow the ring to be easily slipped into the vascular stump without friction. Accordingly a ringed prosthesis with a diameter significantly smaller than appropriate must be used to keep the cross-clamping time shorter than that attainable with manual suturing (Nazari, 1996a). Thus when the aorta is reperfused, the resulting discrepancy between perfused vascular stump and intraluminal ring diameter generates conditions greatly favouring coupling instability (fig. 7, C); moreover possible generation of systolic movements of the aortic wall at ligature hinge may potentially cause mechanical friction/erosion and thus eventually rupture. (fig 7, D).

Many other inappropriate constructive features of those devices were probably responsible for their eventual failure. Thus the rigid ring was too short to be easily identified from outside the aorta, making very difficult the appropriate positioning of the external ligature; moreover the groove shape and dimension were inappropriate to maintain coupling stability.

This latter point offers the occasion for some important consideration. Vascular anastomosis must guarantee two essential mechanical facts: haemostatic sealing and stability of the coupling. This may seem a self-evident, unnecessary distinction since both are obviously provided at once by the standard hand suture; not so however with the "Payr" coupling principle, which is at basis of 70-80ies intraluminal prosthesis as well as of our expandable device.

New Approaches for Treatment and Prevention of Aortic Aneurysms 269

While in fact to achieve haemostatic seal is sufficient to apply on the vascular stump external surface a pressure equal or just exceeding the blood pressure, that pressure or even a much higher pressure may not be enough to prevent the vascular stump from slipping off from the inner sleeve (fig. 8, large square). Then means to increase friction (i.e. groove or hooks, etc) between the opposing surfaces or to permanently link them together (i.e. full thickness stitches) must be put in place to prevent vascular stump from sliding off. Although this was soon appreciated (and solved!) by gardeners since many years (fig. 8, upper right square), the failure of the 70-80ies intraluminal prosthesis may have been caused

In the last decade of the past century, preceded by pioneering work of C. Gianturco (Charnsangavej et al, 1985; Wright et al, 1985; Yoshioka et al, 1988) and popularized by J.C Parodi clinical reports (Parodi 1991, 1994), endovascular techniques burst into clinical vascular surgery, allowing prosthesis positioning into the aneurysm and excluding it from blood stream without open surgery. This provided a less invasive and lower complications rate therapeutic tool that allowed cure for patients previously not amenable to open surgery for age, general conditions or associated risk factors. First successfully popularized in infrarenal aortic aneurysm, techniques and materials continuing improvements allowed endovascular prosthetic substitution of virtually all segments of aorta, including arch, even though sometime with hybrid procedures (Canaud et al, 2010;Antoniou et al, 2010; Tsagakis

It is not the aim of this chapter to describe, even summarily, the historical evolution of these techniques, but rather to try to outline the proved facts of these new therapeutic tools at this

While obviously technological evolution will further extend indications and improvements in clinical results, superiority of endovascular method vs open surgery at this point in time was conclusively proved in infrarenal aortic aneurysms and in uncomplicated, non genetic, isolated descending aorta aneurysms (Gopaldas et al, 2010). An interesting result of several recent studies (The UK EVAR Trial Investigators, 2010; De Bruin, 2010; Schermerhorn, 2008) showed that, despite a two-thirds decrease in 30-day operative mortality rate after endovascular abdominal aortic aneurism repair (EVAR) compared with open repair, the allcause mortality curves converge during the first 2-3 years thereafter, with no significant difference in all-cause mortality beyond this time. A recent study (Brown et al, 2011) seems to indicate that more cardiovascular deaths in the EVAR patients group contribute to the

Quite wide clinical experience however already showed that endovascular procedures cannot protect from spinal chord ischemia and consequent paraplegia in extended descending aorta prosthetic substitution. It has been hypothesized that this could be due, at least in some case, to the fact that while endoprosthesis immediately prevents intercostal branches to be physiologically perfused, cannot prevent, at least for a certain time in the initial phase, backwards blood flow into the space between endoprosthesis and aortic wall, thus generating conditions for a blood flow "steal" from perfusion of the spinal chord

Last but not least overall recent USA Nationwide Inpatient Sample data 2006-2007 review (Gopaldas et al, 2010) showed that only 23% (2,563/11,669) of ideal candidate to endovascular treatment (uncomplicated, elective descending aortic aneurysms) underwent endovascular procedure (TEVAR), while the remaining 77% (9,106/11,669) still underwent

also by underestimation (fig. 8, lower right square) of this not irrelevant detail.

**1.4 Endovascular surgery** 

et al, 2010, Di Eusanio, 2011).

(Kawaharada et al, 2010).

open surgical repair.

convergence in all-cause mortality during the first 2 years.

point in time.

Fig. 7. Facts related to intraluminal ringed prosthesis (Payr type coupling). When the vessel is clamped there is a significant reduction of the stump diameter due to its elastic retraction (a); moreover because of the floppy consistency of the vascular wall a significant gap (b) must be left between outer ring and inner stump diameter for a rapid positioning. When blood flow is resumed the resulting significant diameter mismatch (c) generates conditions for coupling instability and device dislocation. It may also be hypothesized that systolic movements on ligature hinge (d) may generate mechanical erosion and possibly rupture.

Fig. 8. Haemostasis and stability in Payr coupling type.

While hemostasis can be achieved by applying an external pressure ≥ blood pressure, even much higher pressure may not prevent the stump from slipping over the inner sleeve and split apart (larger square). Grooves on the inner sleeve outer surface can prevent dislocation only if appropriately dimensioned and shaped (right upper square**)**. Intraluminal prosthesis groove appears inappropriate in deepness, length and shape to keep coupling stability (right lower square).

While in fact to achieve haemostatic seal is sufficient to apply on the vascular stump external surface a pressure equal or just exceeding the blood pressure, that pressure or even a much higher pressure may not be enough to prevent the vascular stump from slipping off from the inner sleeve (fig. 8, large square). Then means to increase friction (i.e. groove or hooks, etc) between the opposing surfaces or to permanently link them together (i.e. full thickness stitches) must be put in place to prevent vascular stump from sliding off. Although this was soon appreciated (and solved!) by gardeners since many years (fig. 8, upper right square), the failure of the 70-80ies intraluminal prosthesis may have been caused also by underestimation (fig. 8, lower right square) of this not irrelevant detail.

#### **1.4 Endovascular surgery**

268 Front Lines of Thoracic Surgery

Fig. 7. Facts related to intraluminal ringed prosthesis (Payr type coupling).

erosion and possibly rupture.

lower square).

Fig. 8. Haemostasis and stability in Payr coupling type.

When the vessel is clamped there is a significant reduction of the stump diameter due to its elastic retraction (a); moreover because of the floppy consistency of the vascular wall a significant gap (b) must be left between outer ring and inner stump diameter for a rapid positioning. When blood flow is resumed the resulting significant diameter mismatch (c) generates conditions for coupling instability and device dislocation. It may also be hypothesized that systolic movements on ligature hinge (d) may generate mechanical

While hemostasis can be achieved by applying an external pressure ≥ blood pressure, even much higher pressure may not prevent the stump from slipping over the inner sleeve and split apart (larger square). Grooves on the inner sleeve outer surface can prevent dislocation only if appropriately dimensioned and shaped (right upper square**)**. Intraluminal prosthesis groove appears inappropriate in deepness, length and shape to keep coupling stability (right In the last decade of the past century, preceded by pioneering work of C. Gianturco (Charnsangavej et al, 1985; Wright et al, 1985; Yoshioka et al, 1988) and popularized by J.C Parodi clinical reports (Parodi 1991, 1994), endovascular techniques burst into clinical vascular surgery, allowing prosthesis positioning into the aneurysm and excluding it from blood stream without open surgery. This provided a less invasive and lower complications rate therapeutic tool that allowed cure for patients previously not amenable to open surgery for age, general conditions or associated risk factors. First successfully popularized in infrarenal aortic aneurysm, techniques and materials continuing improvements allowed endovascular prosthetic substitution of virtually all segments of aorta, including arch, even though sometime with hybrid procedures (Canaud et al, 2010;Antoniou et al, 2010; Tsagakis et al, 2010, Di Eusanio, 2011).

It is not the aim of this chapter to describe, even summarily, the historical evolution of these techniques, but rather to try to outline the proved facts of these new therapeutic tools at this point in time.

While obviously technological evolution will further extend indications and improvements in clinical results, superiority of endovascular method vs open surgery at this point in time was conclusively proved in infrarenal aortic aneurysms and in uncomplicated, non genetic, isolated descending aorta aneurysms (Gopaldas et al, 2010). An interesting result of several recent studies (The UK EVAR Trial Investigators, 2010; De Bruin, 2010; Schermerhorn, 2008) showed that, despite a two-thirds decrease in 30-day operative mortality rate after endovascular abdominal aortic aneurism repair (EVAR) compared with open repair, the allcause mortality curves converge during the first 2-3 years thereafter, with no significant difference in all-cause mortality beyond this time. A recent study (Brown et al, 2011) seems to indicate that more cardiovascular deaths in the EVAR patients group contribute to the convergence in all-cause mortality during the first 2 years.

Quite wide clinical experience however already showed that endovascular procedures cannot protect from spinal chord ischemia and consequent paraplegia in extended descending aorta prosthetic substitution. It has been hypothesized that this could be due, at least in some case, to the fact that while endoprosthesis immediately prevents intercostal branches to be physiologically perfused, cannot prevent, at least for a certain time in the initial phase, backwards blood flow into the space between endoprosthesis and aortic wall, thus generating conditions for a blood flow "steal" from perfusion of the spinal chord (Kawaharada et al, 2010).

Last but not least overall recent USA Nationwide Inpatient Sample data 2006-2007 review (Gopaldas et al, 2010) showed that only 23% (2,563/11,669) of ideal candidate to endovascular treatment (uncomplicated, elective descending aortic aneurysms) underwent endovascular procedure (TEVAR), while the remaining 77% (9,106/11,669) still underwent open surgical repair.

New Approaches for Treatment and Prevention of Aortic Aneurysms 271

re-dissection and/or false lumen persistent perfusion at suture lines, particularly in acute

The device consists of loops of nitinol wires, wrapped within a Dacron fabric and connected to a prosthesis end (Type I). The nitinol wire loops can be expanded and tightened by activating a removable guide in such a way that device end varies its diameter, while maintaining a regular cylindrical shape. This allows the easy and quick insertion of the retracted device into the vascular stump and then its expansion to perfectly fit with the vessel diameter; haemostasis and permanent device fixation is provided by external

The expandable configuration of the ring allows to solve all the insertion, positioning and

Its quite evident that the expandable configuration of the ring allows to solve all the insertion, positioning and stability problems of the 70ies intraluminal prosthesis (fig. 10). That makes performing an anastomosis a very simple task, which can be carried out in seconds vs the 10-15 min per anastomosis at best required with standard hand suture. The aortic wall being not perforated by the suture, the coupling is immediately blood-thigh ("air-tight" in fact!) and independent by the integrity of the physiological coagulation

The device underwent many modifications and refinements, finally resulting in three main models (Type I, II and III) applying the same working mechanism, but with different shape

Extensive "ex vivo" and "in vivo" animal experiments (Nazari et al 1994, 1996a, 1996d, 1997, 2006, 2009; Rossella et al 2008) were carried out and few clinical cases were also successfully

Device type I and II differ because of the orientation of the activating guide in respect to the main axis of the device wireframe expandable sleeve (fig 11, upper right and lower left squares); that allows the devices to be ideally used for the first and second anastomosis respectively. Thus the type I device, activated by guide-wire coaxial to the lumen, is sutured at one end of the tube graft of appropriate size before clamping, can be quickly and easily positioned either in the proximal or distal end of the aortic tract to be replaced (fig. 11, top

treated with this device (Nazari et al.1999; Aluffi et al, 2002, Buniva et al 2002).

Fig. 10. Expandable device vs intraluminal ringed prosthesis.

diameter mismatch problems of the 70ies intraluminal prosthesis.

to fit with all aorta segments as well as special conditions of use.

**2.1 Device description and operational details** 

dissection repairs.

ligature/suture.

mechanisms.

**2.1.1 Device type I and II** 

These facts prompted us to consider new strategies against aortic aneurysm based on new tools we developed for its treatment and prevention.

### **2. New expandable devices for easier, safer and more efficient open surgery for large thoracic or thoracoabdominal aneurysms**

Even though endovascular techniques will continuously gain wider indications for prosthetic substitution of the aorta, more complex cases will always remain in which open surgery is the only or the best option. Moreover while acute aortic syndrome is obviously spread throughout the territory only highly specialized centers can offer endovascular techniques as an emergency measure; current data show that vast majority (77%) of uncomplicated, non genetic elective descending aorta aneurisms still underwent standard open surgery in US (Gopaldas et al, 2010). On the other hand open thoracic aorta prosthetic substitution still carries significant risk of serious complications that cannot be prevented even in very highly specialized centers, in particular to CNS and spinal cord.

Although the pathogenesis of these complications is multifactorial, there is general agreement that the length of clamping/circulatory arrest time is an extremely important factor. Since nearly all the clamping/arrest time is spent for vascular anastomosis construction, a device able to quicken and simplify the vascular anastomosis can be expected to have a significant impact on the incidence of these complications.

Suture line haemostasis is another important source of intra- and postoperative complications with standard open technique. In fact due to the altered aortic wall mechanical features, impaired by the underlying aortic pathology (arteriosclerosis, medial cystic degeneration, Marfan disease etc.), the suture line haemostasis may be difficult to achieve in spite of appropriate surgical technique or may require additional surgical maneuvers (buttressing, gluing etc.) that imply prolongation of the ischemia time.

Moreover in cases of dissection, it may be difficult to achieve firm layers approximation and to prevent re-dissection and false lumen persistent perfusion, in particular at suture lines.

Fig. 9. Expandable device working principle.

Loops of nitinol wire wrapped by Dacron fabric form a rigid sleeve whose diameter can be modified by varying the diameter of the nitinol loops, while the regular cylindrical shape is maintained.

For these reasons several years ago we started research (Nazari et al, 1994) to develop a new expandable device aimed: **1**-to simplify the surgical technique; **2**-to significantly reduce the ischemic time and thus the ischemic complications rate; **3**-to enhance suture line anastomosis; **4**-to achieve firm and reliable dissected layers approximation, thus preventing

These facts prompted us to consider new strategies against aortic aneurysm based on new

**2. New expandable devices for easier, safer and more efficient open surgery** 

Even though endovascular techniques will continuously gain wider indications for prosthetic substitution of the aorta, more complex cases will always remain in which open surgery is the only or the best option. Moreover while acute aortic syndrome is obviously spread throughout the territory only highly specialized centers can offer endovascular techniques as an emergency measure; current data show that vast majority (77%) of uncomplicated, non genetic elective descending aorta aneurisms still underwent standard open surgery in US (Gopaldas et al, 2010). On the other hand open thoracic aorta prosthetic substitution still carries significant risk of serious complications that cannot be prevented

Although the pathogenesis of these complications is multifactorial, there is general agreement that the length of clamping/circulatory arrest time is an extremely important factor. Since nearly all the clamping/arrest time is spent for vascular anastomosis construction, a device able to quicken and simplify the vascular anastomosis can be

Suture line haemostasis is another important source of intra- and postoperative complications with standard open technique. In fact due to the altered aortic wall mechanical features, impaired by the underlying aortic pathology (arteriosclerosis, medial cystic degeneration, Marfan disease etc.), the suture line haemostasis may be difficult to achieve in spite of appropriate surgical technique or may require additional surgical

Moreover in cases of dissection, it may be difficult to achieve firm layers approximation and to prevent re-dissection and false lumen persistent perfusion, in particular at suture lines.

Loops of nitinol wire wrapped by Dacron fabric form a rigid sleeve whose diameter can be modified by varying the diameter of the nitinol loops, while the regular cylindrical shape is

For these reasons several years ago we started research (Nazari et al, 1994) to develop a new expandable device aimed: **1**-to simplify the surgical technique; **2**-to significantly reduce the ischemic time and thus the ischemic complications rate; **3**-to enhance suture line anastomosis; **4**-to achieve firm and reliable dissected layers approximation, thus preventing

even in very highly specialized centers, in particular to CNS and spinal cord.

expected to have a significant impact on the incidence of these complications.

maneuvers (buttressing, gluing etc.) that imply prolongation of the ischemia time.

tools we developed for its treatment and prevention.

Fig. 9. Expandable device working principle.

maintained.

**for large thoracic or thoracoabdominal aneurysms** 

re-dissection and/or false lumen persistent perfusion at suture lines, particularly in acute dissection repairs.

The device consists of loops of nitinol wires, wrapped within a Dacron fabric and connected to a prosthesis end (Type I). The nitinol wire loops can be expanded and tightened by activating a removable guide in such a way that device end varies its diameter, while maintaining a regular cylindrical shape. This allows the easy and quick insertion of the retracted device into the vascular stump and then its expansion to perfectly fit with the vessel diameter; haemostasis and permanent device fixation is provided by external ligature/suture.

Fig. 10. Expandable device vs intraluminal ringed prosthesis.

The expandable configuration of the ring allows to solve all the insertion, positioning and diameter mismatch problems of the 70ies intraluminal prosthesis.

Its quite evident that the expandable configuration of the ring allows to solve all the insertion, positioning and stability problems of the 70ies intraluminal prosthesis (fig. 10). That makes performing an anastomosis a very simple task, which can be carried out in seconds vs the 10-15 min per anastomosis at best required with standard hand suture.

The aortic wall being not perforated by the suture, the coupling is immediately blood-thigh ("air-tight" in fact!) and independent by the integrity of the physiological coagulation mechanisms.

The device underwent many modifications and refinements, finally resulting in three main models (Type I, II and III) applying the same working mechanism, but with different shape to fit with all aorta segments as well as special conditions of use.

Extensive "ex vivo" and "in vivo" animal experiments (Nazari et al 1994, 1996a, 1996d, 1997, 2006, 2009; Rossella et al 2008) were carried out and few clinical cases were also successfully treated with this device (Nazari et al.1999; Aluffi et al, 2002, Buniva et al 2002).

#### **2.1 Device description and operational details 2.1.1 Device type I and II**

Device type I and II differ because of the orientation of the activating guide in respect to the main axis of the device wireframe expandable sleeve (fig 11, upper right and lower left squares); that allows the devices to be ideally used for the first and second anastomosis respectively. Thus the type I device, activated by guide-wire coaxial to the lumen, is sutured at one end of the tube graft of appropriate size before clamping, can be quickly and easily positioned either in the proximal or distal end of the aortic tract to be replaced (fig. 11, top

New Approaches for Treatment and Prevention of Aortic Aneurysms 273

With type I and II devices, the vascular stump encirclement can be avoided and substituted by endovascular (full or partial) purse-string polipropilene suture prepared at the site of expandable device positioning. The required full thickness security stitches can be passed

The solution of positioning and stability problems of the 70ies intraluminal prosthesis (fig. 10) allows for the first time the clinical appreciation of the most important feature of the "Payr principle" of anastomosis (vascular stumps compression against/between rigid structures i.e. an inner rigid ring and external ligature/outer rigid ring) *which is to achieve an immediate hermetic seal* ("air-tight" in fact) ensuring reliable haemostasis at the anastomosis line, not dependent from coagulation. Interestingly enough were just the positioning problems of Payr model as well as of its more recent modification (Intraluminal ringed prosthesis), that prevented in fact the clinical implementation of this coupling method, which is the most intuitive (and in fact was the first to be attempted in vascular surgery) and whose application failed only in the surgical field, while was in use (and still is) in all other technological fields where connectors between elastic/floppy

Of course clinical experience over more than a century has shown that the standard suturing technique does not need to provide an "air-tight" anastomosis to ensure perfect hemostasis in virtually all clinical circumstances. In particular cases however (acute dissection, cystic medial necrosis, etc.), structural impairments of the aortic wall may necessitate additional maneuvers including graft strips buttressing, gluing and a variety of accessory techniques, whose efficacy at achieving hemostasis are not always fully predictable and that obviously further significantly prolong the period of ischemia in this most critical area. A coupling method that provides haemostasis by compression of the stumps' vascular wall between two rigid structures (i.e. inner and outer expandable rigid sleeves) without perforation may be then particularly useful in these cases, not only because of its ease and quickness, but also because it offers the best mechanical chance of immediate blood-tightness. The expected advantages with regards to approximation of dissecting layers and false lumen permanent

An other important difference with 70-80ies intraluminal ringed devices is that the expandable sleeve is much more thin and porous, being formed substantially by a double layer of standard vascular dacron fabric, and can, therefore, be wholly and quickly

after the circulation has been re-estableshed (from Nazari, 2010).

Fig. 12. Purse-string device fixation.

tubing are required.

sealing rely on the same concept.

colonized by fibroblasts and integrated with the aortic wall.

strip). Any further manipulation of the tube graft is then easily possible, including accessory side anastomosis with aortic branches, without any hindrance. The tube graft can then be sectioned at its exact required length and fixed with a single stitch at the rear anastomosis side (fig 11, middle strip); type II device, activated by guide-wire orthogonal to the vascular axis allowing stump connection at both sides, is then inserted, expanded and fixed by external ligature (fig 11, lower strip) ending the ischemia phase.

When the perfusion is resumed, permanent fixation is carried out by tying ligature and applying few full thickness polypropilen 4-0 equidistant stitches, to further stabilize the device thus virtually preventing any possible late dislocation. Activating guide can then be removed by predisposed tools.

#### Fig. 11. Device Type I and II.

Device type I, previously sutured to the appropriate diameter tube graft end, is used for the first anastomosis; then after having carried out any other collateral branch anastomosis possibly required, the tube graft is cut at its final measure, fixed with a single stitch at rear anastomosis side (arrow) and device Type II is applied for the anastomosis. Circulation can be immediately resumed after tourniquets tightening. Thus final ligature, full thickness stabilizing stitches (3 at each anastomosis) and activating guide removal can be carried out without prolonging the ischemic phase.

Use of the external ligature (umbilical tape or polipropilene) allows to minimize ischemic time, since the blood flow can be resumed after the simple tourniquet tension, the final stabilization being carried out afterward. With a very little prolongation of ischemia time however a polypropilene suture can be passed in a purse-string fashion also in the vascular intimal surface, totally or partially, with the same functional results (fig. 12). Even in this case it is important to pass the suture full thickness through the device at least in 3 roughly equidistant points in order to prevent any possible late dislocation.

Fig. 12. Purse-string device fixation.

272 Front Lines of Thoracic Surgery

strip). Any further manipulation of the tube graft is then easily possible, including accessory side anastomosis with aortic branches, without any hindrance. The tube graft can then be sectioned at its exact required length and fixed with a single stitch at the rear anastomosis side (fig 11, middle strip); type II device, activated by guide-wire orthogonal to the vascular axis allowing stump connection at both sides, is then inserted, expanded and fixed by

When the perfusion is resumed, permanent fixation is carried out by tying ligature and applying few full thickness polypropilen 4-0 equidistant stitches, to further stabilize the device thus virtually preventing any possible late dislocation. Activating guide can then be

Device type I, previously sutured to the appropriate diameter tube graft end, is used for the first anastomosis; then after having carried out any other collateral branch anastomosis possibly required, the tube graft is cut at its final measure, fixed with a single stitch at rear anastomosis side (arrow) and device Type II is applied for the anastomosis. Circulation can be immediately resumed after tourniquets tightening. Thus final ligature, full thickness stabilizing stitches (3 at each anastomosis) and activating guide removal can be carried out

Use of the external ligature (umbilical tape or polipropilene) allows to minimize ischemic time, since the blood flow can be resumed after the simple tourniquet tension, the final stabilization being carried out afterward. With a very little prolongation of ischemia time however a polypropilene suture can be passed in a purse-string fashion also in the vascular intimal surface, totally or partially, with the same functional results (fig. 12). Even in this case it is important to pass the suture full thickness through the device at least in 3 roughly

equidistant points in order to prevent any possible late dislocation.

external ligature (fig 11, lower strip) ending the ischemia phase.

removed by predisposed tools.

Fig. 11. Device Type I and II.

without prolonging the ischemic phase.

With type I and II devices, the vascular stump encirclement can be avoided and substituted by endovascular (full or partial) purse-string polipropilene suture prepared at the site of expandable device positioning. The required full thickness security stitches can be passed after the circulation has been re-estableshed (from Nazari, 2010).

The solution of positioning and stability problems of the 70ies intraluminal prosthesis (fig. 10) allows for the first time the clinical appreciation of the most important feature of the "Payr principle" of anastomosis (vascular stumps compression against/between rigid structures i.e. an inner rigid ring and external ligature/outer rigid ring) *which is to achieve an immediate hermetic seal* ("air-tight" in fact) ensuring reliable haemostasis at the anastomosis line, not dependent from coagulation. Interestingly enough were just the positioning problems of Payr model as well as of its more recent modification (Intraluminal ringed prosthesis), that prevented in fact the clinical implementation of this coupling method, which is the most intuitive (and in fact was the first to be attempted in vascular surgery) and whose application failed only in the surgical field, while was in use (and still is) in all other technological fields where connectors between elastic/floppy tubing are required.

Of course clinical experience over more than a century has shown that the standard suturing technique does not need to provide an "air-tight" anastomosis to ensure perfect hemostasis in virtually all clinical circumstances. In particular cases however (acute dissection, cystic medial necrosis, etc.), structural impairments of the aortic wall may necessitate additional maneuvers including graft strips buttressing, gluing and a variety of accessory techniques, whose efficacy at achieving hemostasis are not always fully predictable and that obviously further significantly prolong the period of ischemia in this most critical area. A coupling method that provides haemostasis by compression of the stumps' vascular wall between two rigid structures (i.e. inner and outer expandable rigid sleeves) without perforation may be then particularly useful in these cases, not only because of its ease and quickness, but also because it offers the best mechanical chance of immediate blood-tightness. The expected advantages with regards to approximation of dissecting layers and false lumen permanent sealing rely on the same concept.

An other important difference with 70-80ies intraluminal ringed devices is that the expandable sleeve is much more thin and porous, being formed substantially by a double layer of standard vascular dacron fabric, and can, therefore, be wholly and quickly colonized by fibroblasts and integrated with the aortic wall.

New Approaches for Treatment and Prevention of Aortic Aneurysms 275

anastomosis in extended descending thoracic aorta substitution be easily and safely carried out though a single space thoracotomy; moreover aortic prosthetic substitution via mini-access

In this version of the device the external ligature is substituted by an expandable sleeve, which is based essentially on the same working principle as the inner sleeve, but activated contrariwise. Thus, the vascular stump is compressed between two sleeves (Fig. 14, upper left little squares), with variable and controllable diameters, allowing full control of the

Operative technique for device type III is illustrated in fig 14 in ascending aorta "ex vivo" model and it is really very simple. First of all both sleeves diameter is set at the predicted value of the aortic tract where the device will be applied. Then the inner sleeve diameter only is reduced as much as possible by acting on its guide-wire; this causes also the backwards eversion and partial rotation of the outer sleeve thus greatly enhancing inner sleeve visibility and then its easy positioning into the vascular stump. The inner sleeve is then re-expanded against the vascular stump inner surface; at this point the outer sleeve is

The primary aim of this new version of the device is to make possible and convenient to apply this coupling principle also to acute ascending aorta and arch dissection, in order to simplify the technique, to reduce the ischemic time, to improve hemostasis of the anastomosis line and to achieve reliable, stable sealing of the dissection layers in this very complex surgical setting. The device in fact allows to actually automate substantially the same aortic wall sandwiching between two graft strips procedure usually carried out in the dissection cases and realizing at once the prosthesis anastomosis, being the tube graft (not shown in the figure) obviously previously sutured to the inner sleeve proximal end. Interestingly enough the particular configuration of the device allows full and easy compliance with aortic anatomy, perfectly adapting also to the elliptic, asymmetric "oblique"stump resulting from inclusion of the arch concavity in the anastomosis line (Fig. 15, B). Full and persistent air-tight sealing of the device-aortic wall coupling was verified at endovascular pressures of up to 150 mmHg in "ex vivo" swine aortic models, including those involving an elliptic, 'oblique' anastomosis (Fig. 15, b) (Nazari, 2010). As expected, standard vascular sutures were not air-tight even at pressures below 10 mmHg (Fig. 15, c). Type III device use is then ideally indicated in dissection cases for distal anastomosis sited at distal ascending aorta, including as much as required of the concavity of the arch during a very brief circulatory arrest phase; proximal anastomosis will be then carried out either by hand suture or with the expandable device version most appropriated for the particular anatomical condition, in normal CEC in no rush and after having performed any additional

Anastomosis at the distal arch/proximal descending aorta in case of full arch substitution is also an ideal indication for type III device use in case of dissection or whenever, for particular aortic wall fragility, graft strips sandwiching buttressing may be advisable. Supra-aortic trunks in these cases can be ideally re-vascularized by devices type I previously appropriately connected to the main tube graft so that they can be plugged in and there fixed by purse-string partially or entirely passed from inside the vascular lumen

thoracotomy or laparotomy video-assisted setting may be also predictably considered.

pressure (amount and surface of its application) applied to the vascular stump.

gently retracted acting on its own activating guide to compress the vascular stump.

procedure possibly required, for example on the valve.

(fig. 11).

**2.1.2 Device type III** 

Fig. 13. Expandable device operational details.

*Left square.* When a clamp is applied the linearization of the stump requires to keep its length significantly longer than usual in order to leave the space necessary for full expansion of the expandable end. It is also important to avoid full longitudinal vascular opening as carried out with current technique and thus keeping intact the entire circumference of the vascular stump for a tract long enough to host the whole device expandable end.

*Right square.* The expandable end also can be positioned against aneurysmal wall, provided that its distal end would reach the healthy vascular wall. Thrombosis of the tract between the ligature and the prosthesis end will soon move the effective anastomosis line (upper right square\*) where it would be with standard suture (mod from Nazari et al, 1997).

The nitinol wire-frame in fact forms a very thin and wide mesh net that accounts for a very small proportion of the device's volume and that offers no significant barrier to fibroblastic invasion of the dacron fabric and thus to stable biological integration of the device. Few technical details must be considered with the expandable devices.

First of all care must be taken when entering the aneurysm not to extend the incision up to both the distal and proximal ends as usually carried out with standard suture; it is in fact very important to keep intact the entire circumference of the vascular stump for a tract long enough to host the device expandable end.

Due to the linearization of the vessel diameter induced by the clamp, the length of the vascular stump distal to it must be significantly longer than imagined before clamping; in practice it is advisable to isolate the vessel for a length exceeding its diameter (Fig. 13, left square ).

It may be argued that the use of the device may require a distinct healthy vascular neck, as with endovascular techniques. This is not necessary; the device infact can be expanded even within the aneurysmal wall and fixed there by the external ligature, provided that its end reaches the healthy vascular wall limit, where ideally the standard suture would be placed (Fig 13, right square). The thrombosis developing in the tract between the ligature and the prosthesis end will soon exclude the brief tract of aneurysmal wall from the bloodstream, thus moving the effective anastomosis line (fig 13,\* at upper right square) where it would be with standard suture.

Thus devices type I and II can be ideally used anywhere in descending and abdominal aorta and allow to carry out any required additional surgical maneuver on the tube graft, i.e. collateral branch anastomosis, as well as its appropriate tailoring at the required length measured directly on the operative field as in standard technique without obstacle or hampering condition. Its great simplicity of use allows the devices to be used also in condition of suboptimal operative field exposure. Thus for example both proximal and distal anastomosis in extended descending thoracic aorta substitution be easily and safely carried out though a single space thoracotomy; moreover aortic prosthetic substitution via mini-access thoracotomy or laparotomy video-assisted setting may be also predictably considered.

#### **2.1.2 Device type III**

274 Front Lines of Thoracic Surgery

*Left square.* When a clamp is applied the linearization of the stump requires to keep its length significantly longer than usual in order to leave the space necessary for full expansion of the expandable end. It is also important to avoid full longitudinal vascular opening as carried out with current technique and thus keeping intact the entire circumference of the vascular

*Right square.* The expandable end also can be positioned against aneurysmal wall, provided that its distal end would reach the healthy vascular wall. Thrombosis of the tract between the ligature and the prosthesis end will soon move the effective anastomosis line (upper right square\*) where it would be with standard suture (mod from Nazari et al, 1997).

The nitinol wire-frame in fact forms a very thin and wide mesh net that accounts for a very small proportion of the device's volume and that offers no significant barrier to fibroblastic

First of all care must be taken when entering the aneurysm not to extend the incision up to both the distal and proximal ends as usually carried out with standard suture; it is in fact very important to keep intact the entire circumference of the vascular stump for a tract long

Due to the linearization of the vessel diameter induced by the clamp, the length of the vascular stump distal to it must be significantly longer than imagined before clamping; in practice it is advisable to isolate the vessel for a length exceeding its diameter (Fig. 13, left

It may be argued that the use of the device may require a distinct healthy vascular neck, as with endovascular techniques. This is not necessary; the device infact can be expanded even within the aneurysmal wall and fixed there by the external ligature, provided that its end reaches the healthy vascular wall limit, where ideally the standard suture would be placed (Fig 13, right square). The thrombosis developing in the tract between the ligature and the prosthesis end will soon exclude the brief tract of aneurysmal wall from the bloodstream, thus moving the effective anastomosis line (fig 13,\* at upper right square) where it would be

Thus devices type I and II can be ideally used anywhere in descending and abdominal aorta and allow to carry out any required additional surgical maneuver on the tube graft, i.e. collateral branch anastomosis, as well as its appropriate tailoring at the required length measured directly on the operative field as in standard technique without obstacle or hampering condition. Its great simplicity of use allows the devices to be used also in condition of suboptimal operative field exposure. Thus for example both proximal and distal

invasion of the dacron fabric and thus to stable biological integration of the device.

stump for a tract long enough to host the whole device expandable end.

Few technical details must be considered with the expandable devices.

Fig. 13. Expandable device operational details.

enough to host the device expandable end.

square ).

with standard suture.

In this version of the device the external ligature is substituted by an expandable sleeve, which is based essentially on the same working principle as the inner sleeve, but activated contrariwise. Thus, the vascular stump is compressed between two sleeves (Fig. 14, upper left little squares), with variable and controllable diameters, allowing full control of the pressure (amount and surface of its application) applied to the vascular stump.

Operative technique for device type III is illustrated in fig 14 in ascending aorta "ex vivo" model and it is really very simple. First of all both sleeves diameter is set at the predicted value of the aortic tract where the device will be applied. Then the inner sleeve diameter only is reduced as much as possible by acting on its guide-wire; this causes also the backwards eversion and partial rotation of the outer sleeve thus greatly enhancing inner sleeve visibility and then its easy positioning into the vascular stump. The inner sleeve is then re-expanded against the vascular stump inner surface; at this point the outer sleeve is gently retracted acting on its own activating guide to compress the vascular stump.

The primary aim of this new version of the device is to make possible and convenient to apply this coupling principle also to acute ascending aorta and arch dissection, in order to simplify the technique, to reduce the ischemic time, to improve hemostasis of the anastomosis line and to achieve reliable, stable sealing of the dissection layers in this very complex surgical setting. The device in fact allows to actually automate substantially the same aortic wall sandwiching between two graft strips procedure usually carried out in the dissection cases and realizing at once the prosthesis anastomosis, being the tube graft (not shown in the figure) obviously previously sutured to the inner sleeve proximal end. Interestingly enough the particular configuration of the device allows full and easy compliance with aortic anatomy, perfectly adapting also to the elliptic, asymmetric "oblique"stump resulting from inclusion of the arch concavity in the anastomosis line (Fig. 15, B). Full and persistent air-tight sealing of the device-aortic wall coupling was verified at endovascular pressures of up to 150 mmHg in "ex vivo" swine aortic models, including those involving an elliptic, 'oblique' anastomosis (Fig. 15, b) (Nazari, 2010). As expected, standard vascular sutures were not air-tight even at pressures below 10 mmHg (Fig. 15, c).

Type III device use is then ideally indicated in dissection cases for distal anastomosis sited at distal ascending aorta, including as much as required of the concavity of the arch during a very brief circulatory arrest phase; proximal anastomosis will be then carried out either by hand suture or with the expandable device version most appropriated for the particular anatomical condition, in normal CEC in no rush and after having performed any additional procedure possibly required, for example on the valve.

Anastomosis at the distal arch/proximal descending aorta in case of full arch substitution is also an ideal indication for type III device use in case of dissection or whenever, for particular aortic wall fragility, graft strips sandwiching buttressing may be advisable. Supra-aortic trunks in these cases can be ideally re-vascularized by devices type I previously appropriately connected to the main tube graft so that they can be plugged in and there fixed by purse-string partially or entirely passed from inside the vascular lumen (fig. 11).

New Approaches for Treatment and Prevention of Aortic Aneurysms 277

Thus in all cases where sandwiching buttressing is planned the use of the device type III requires exactly the same aortic stump external wall preparation required for hand suture double graft strips application. When anatomical conditions do not require sandwiching buttressing, device type I or type II may be also used even without external vascular stump encircling, being possible to fix the expanded device end by purse-string passed entirely or

The great simplification and the very significant quickening of this complex surgical part together with the higher accuracy and "mechanical" reliability of this coupling method in comparison with manual suture could potentially have impact that may exceed that strictly related to the anastomosis. For example being possible to carry out even the entire arch revascularization in few minutes of circulatory arrest, the level of hypothermia may be very significantly reduced and even the type of cerebral protection may be tailored to these very

We also realized a variety of modified versions of the device to better fit with the anatomical

In small vessel diameters obviously device dimensions can interfere more significantly with physiological lumen amplitude in their range of use. More in particular the unpredictable way of folding of the inner fabric layer when the device is incompletely opened may significantly reduce the lumen available for the blood flow. Accordingly for diameters ≤ 12 and ≥6 mm we decided to use devices wrapped by fabric only at external layer (fig. 16). Two sizes were prepared respectively for diameter from 6 to 9 (SS) and from 10 to 12 mm (S). This may fit for renal artery, celiac axis and supraortic trunks. The device is previously prepared at the end of collateral branch of the main tube graft tailored at the expected appropriated length or directly on the main tube graft. The particular fabric disposition implies a mandatory blood flow direction, which however allows the use as main tube graft

For small diameters vessels (≥6mm ≤12mm) device type I was prepared with single outer fabric graft in order to prevent the possible significant interference with vascular lumen of unpredictable way of folding of the inner layer when the device cannot be fully expanded.

This type II device modified version is intended for use in ascending aorta substitution in absence of dissection. The two ends of the device can vary their reciprocal axis up to 90° to

partially from inside the aortic lumen (fig. 11).

**2.1.3 Other expandable device models** 

lateral branches for the major aortic branches.

These devices allow one way flow direction only.

Video at http://www.fondazionecarrel.org/tsb2/tsb2.html **2.1.3.2 Type II – BIO (Bending and Independent Opening)** 

Fig. 16. Device type I – SOLD.

restricted time lapses, just to say the firsts coming in mind.

configurations occurring in particular clinical circumstances. **2.1.3.1 Type I – SOLD (Single Outer Layer for small Diameters)** 

#### Fig. 14. Device type III.

The type III device incorporates an external sleeve that substitutes the external ligature, thus allowing standardization of the pressure applied to the vascular stump wall. The wire-frame of the device is quite soft and compliant, and can be easily compressed and widely deformed while maintaining perfect reciprocal alignment of the internal and external sleeves (top left squares). Lower squares: First of all both sleeves are set at predicted final aperture. Acting only on the activating guide of the inner sleeve results in outer sleeve backwards rotation and eversion, bringing the retracted inner sleeve in full visibility, so that can be easily inserted into the vascular stump. Then inner ring is expanded as much as the vascular wall can be distended by acting contrariwise on the same guide. At this point, the outer sleeve is only slightly retracted towards the aortic wall using its own guide. (Nazari, 2010) Video at http://www.fondazionecarrel.org/tsb2/tsb2.html

#### Fig. 15. Device type III seal test.

The outer surface of the inner sleeve was wrapped by a latex cuff (top squares) in order to overcome the problem of the porosity of the dacron graft and the requirement for the connection of the tube graft to the proximal end of the inner sleeve as in its final clinical use. A) The air-tightness of the connection was verified at endovascular pressures of up to 150 mmHg in a regular cylindrical anastomosis of ascending aorta (white bars). (B) The same was verified when the anastomosis is irregularly oriented, such as when involves the arch concavity. (C) As easily predictable, a standard suture (4–0 prolene) of an approximately 3 cm incision of the aortic wall cannot be proved airtight even at minor endovascular pressure. (Nazari, 2010). Video at http://www.fondazionecarrel.org/tsb2/tsb2.html

Thus in all cases where sandwiching buttressing is planned the use of the device type III requires exactly the same aortic stump external wall preparation required for hand suture double graft strips application. When anatomical conditions do not require sandwiching buttressing, device type I or type II may be also used even without external vascular stump encircling, being possible to fix the expanded device end by purse-string passed entirely or partially from inside the aortic lumen (fig. 11).

The great simplification and the very significant quickening of this complex surgical part together with the higher accuracy and "mechanical" reliability of this coupling method in comparison with manual suture could potentially have impact that may exceed that strictly related to the anastomosis. For example being possible to carry out even the entire arch revascularization in few minutes of circulatory arrest, the level of hypothermia may be very significantly reduced and even the type of cerebral protection may be tailored to these very restricted time lapses, just to say the firsts coming in mind.
