**1.1 Background**

#### **1.1.1 The beginning**

Vascular surgery was quite obviously conditioned by the development and evolution of the techniques for vascular anastomosis, started around the beginning of the past century. Apart in fact from few episodic and lucky clinical cases of lateral laceration repair as well as many experimental endeavours of vascular suture, accurately described and illustrated in a detailed historical italian review (Zannini G 1967), before that point in time vascular surgery clinical practice was substantially confined to vascular ligature.

Fig. 1. Payr and Carrel pioneering techniques.

Payr first reported device for vascular anastomosis substantially derived from elaboration of the common method for rubber tubing connection (left square) while Carrel triangulation was apparently derived from refinements of gastrointestinal suture (right square).

In 1900 Erwin Payr reported to the German Surgical Society results on animal experiments of the apparently first device for vascular anastomosis, which is essentially based on external legature of vascular stumps over a rigid and absorbable magnesium ring (Payr E, 1900), thus trying to adapting to surgery a method already universally used for coupling floppy/elastic tubing. In spite of its elegance (intima-to-intima facing, absorbable magnesium ring) one of its implicit mechanical limits was already outlined in the original report: elastic retraction of the vascular wall when clamped significantly reduces its diameter, thus making quite difficult to put in place a rigid ring of appropriate diameter.

In those very years Alexis Carrel, as well as many others in fact (Zannini G 1967), was focusing his attention on suture techniques, already currently adopted in the gastrointestinal tract, and was able to realize blood-tight, low thrombogenic vascular anastomoses by careful refinements of the needles, threads and techniques for their use

New Approaches for Treatment and Prevention of Aortic Aneurysms 265

Fig. 3. Vascular stapler for reducing warm ischemia in organ transplantation.

et al 1990). Video at http://www.fondazionecarrel.org/tsb2/tsb2.html

With our model each stapler end can be mounted on donor and recipient by independent surgical teams without care for reciprocal orientation, being the maximal possible vascular axis torsion ≤30°. Activating guide-wire is connected just immediately before firing (Nazari

Fig. 4. Vascular stapler for reducing warm ischemia in experimental lung transplantation. In a canine model of left single lung transplantation one stapler end was applied on donor pulmonary artery at back table (a) and the other by the recipient surgical team; then the two ends are quickly connected together (b), the firing wire connected and activated (c). After having sectioned the two sutures linking the vascular stumps to the device ends, the two stapler parts were divided and removed (d) and anastomosis checked (e) still preventing

graft perfusion until atrial connection was established (Nazari et al 1990).

Video at http://www.fondazionecarrel.org/tsb2/tsb2.html

(Carrel A, 1902, 1907), thus establishing the standard technique of vascular surgery. Although technically demanding, its versatility allowed to deal with virtually all clinical occurrences, from large aortic to microsurgical anastomosis, so that the many and significant improvements in needles (i.e. curved, atraumatic), threads (i.e. polypropylene) and surgical technique (i.e. parachute, etc) developed throughout more than a century could not break the ideal line linking the Nobel prize acknowledged (1912) Carrel original work with today clinical practice.

Interestingly enough for more than a century vascular anastomosis technique research moved forward, very slowly to say the truth, with occasional brief clinical applications essentially along these two basic principles only, with the possible exception of gluing based methods.

### **1.2 Vascular staplers**

It was in fact substantially a technological evolution of the Carrel coupling principle (full thickness wall stump stitching) that gave origin, around the middle of the past century, to stapling devices with the aim of automating the anastomoses.

Fig. 2. Models of URSS vascular staplers (1960-70).

Similar bulky and cumbersome devices were also realized at that time in Canada, USA and Japan.

However, while stapling devices have long since allowed standardization and simplification of digestive tract circular anastomosis, despite extensive research (see exhaustive reviews: Tesauro 1967; Tesauro & Persico 1979), including our own (Nazari S et al, 1990), the stapling principle has so far failed to be of significant use for vascular anastomosis, which remains substantially the only basic surgical task still to be automated.

The 60-70ies stapling devices (fig 2) have all quite cumbersome and heavy configuration in particular in relation to the delicate structure of the quite small diameter vessel to which they were intended to be used in those years.

(Carrel A, 1902, 1907), thus establishing the standard technique of vascular surgery. Although technically demanding, its versatility allowed to deal with virtually all clinical occurrences, from large aortic to microsurgical anastomosis, so that the many and significant improvements in needles (i.e. curved, atraumatic), threads (i.e. polypropylene) and surgical technique (i.e. parachute, etc) developed throughout more than a century could not break the ideal line linking the Nobel prize acknowledged (1912) Carrel original

Interestingly enough for more than a century vascular anastomosis technique research moved forward, very slowly to say the truth, with occasional brief clinical applications essentially along these two basic principles only, with the possible exception of gluing based

It was in fact substantially a technological evolution of the Carrel coupling principle (full thickness wall stump stitching) that gave origin, around the middle of the past century, to

Similar bulky and cumbersome devices were also realized at that time in Canada, USA and

However, while stapling devices have long since allowed standardization and simplification of digestive tract circular anastomosis, despite extensive research (see exhaustive reviews: Tesauro 1967; Tesauro & Persico 1979), including our own (Nazari S et al, 1990), the stapling principle has so far failed to be of significant use for vascular anastomosis, which remains

The 60-70ies stapling devices (fig 2) have all quite cumbersome and heavy configuration in particular in relation to the delicate structure of the quite small diameter vessel to which

stapling devices with the aim of automating the anastomoses.

Fig. 2. Models of URSS vascular staplers (1960-70).

they were intended to be used in those years.

substantially the only basic surgical task still to be automated.

work with today clinical practice.

methods.

Japan.

**1.2 Vascular staplers** 

Fig. 3. Vascular stapler for reducing warm ischemia in organ transplantation. With our model each stapler end can be mounted on donor and recipient by independent surgical teams without care for reciprocal orientation, being the maximal possible vascular axis torsion ≤30°. Activating guide-wire is connected just immediately before firing (Nazari et al 1990). Video at http://www.fondazionecarrel.org/tsb2/tsb2.html

Fig. 4. Vascular stapler for reducing warm ischemia in experimental lung transplantation. In a canine model of left single lung transplantation one stapler end was applied on donor pulmonary artery at back table (a) and the other by the recipient surgical team; then the two ends are quickly connected together (b), the firing wire connected and activated (c). After having sectioned the two sutures linking the vascular stumps to the device ends, the two stapler parts were divided and removed (d) and anastomosis checked (e) still preventing graft perfusion until atrial connection was established (Nazari et al 1990). Video at http://www.fondazionecarrel.org/tsb2/tsb2.html

New Approaches for Treatment and Prevention of Aortic Aneurysms 267

In synthesis however, even though research restlessly continue to produce new prototypes, the apparently unavoidable critical point is that the intrinsic manual surgical skill required to put in position and operate any stapler on the delicate vascular structure didn't yet (can't?) result in a easier, simpler, quicker and more efficient task than standard hand

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

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

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

suture, even when its use is for very large diameter vessel only (Takata et al 2011).

reported (Lemole et al, 1982; Berger et al, 1983; Crawford ES & JL, 1984).

Aortic anastomotic device commercially available (FDA) in 70-90ies.

**1.3 Intraluminal ringed prosthesis** 

Fig. 6. Intraluminal ringed prosthesis.

stability.

device.

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

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 allow the device ends to be divided and removed.

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

Fig. 5. Kolesov VI vacuum assisted vascular stapler.

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 of the vascular stapler problems.

In synthesis however, even though research restlessly continue to produce new prototypes, the apparently unavoidable critical point is that the intrinsic manual surgical skill required to put in position and operate any stapler on the delicate vascular structure didn't yet (can't?) result in a easier, simpler, quicker and more efficient task than standard hand suture, even when its use is for very large diameter vessel only (Takata et al 2011).
