**5. References**

140 Special Topics in Cardiac Surgery

The propensity for clot to propagate as well as to organize renders treatment of thromboembolic disease difficult. Anticoagulation addresses further propagation of thrombus; however, once a patient presents with a significant mass of clot, vascular recanalization becomes a formidable task. Complete occlusions in major or great venous vessels tend to be unresponsive to thrombolytic therapy, as circulating thrombolytic agents are unable to access the inner mass of a substantial body of clot that typifies massive pulmonary embolism or total vena cava occlusion. Thrombolytic dissolution occurs at the periphery of the occlusion, proceeding progressively inwards with time. Hemodynamic instability may curtail the opportunity window for therapeutic intervention, and immediate bulk extraction of occlusive material is warranted. Percutaneous interventional devices utilizing mechanical or rheolytic fragmentation of clot increase the rate of thrombolysis. Dissolution is a function of the amount of interaction achieved by the device with the clot. Higher surface contact area between the active components of the device and resident clot yields greater thrombolytic activity. Presently available percutaneous devices are limited by their size relative to clot in the great vessels. The luminal cross-sectional area of a 7F catheter is equal to 3 mm2, which encompasses 0.5% of the surface area of a 30 mm diameter inferior vena cava or pulmonary artery with a luminal cross-sectional area of 615 mm2. This means that a 7F catheter approaching an occluding thrombus in the vena cava contacts only 0.5% of the cross-sectional area of a clot on a single pass. An impractical number of catheter passes

The large bore of the funnel cannula facilitates material removal from the great vessels. The large conduit size also minimizes the potential for hemolysis during vacuum extraction. Suction therapy is conducted by a centrifugal pump which generates typical flow rates up to 5 liters per minute via the 22 F cannula. At this flow rate and cannula size, laminar flow is maintained in the extracorporeal circuit, providing atraumatic passage for circulating

Removal of undesirable intravascular material using extracorporeal recirculation with a funnel venous drainage cannula seeks to mimic surgical removal of massive emboli, by maximizing physical contact with the leading edge of the occlusion, and conducting en bloc removal of substantial embolic masses. The significant flow rates (on the order of 4 or 5 liters per minute) established in the drainage cannula while extracting major emboli, are matched by simultaneous reinfusion to maintain hemodynamic stability during the embolectomy process. A funnel cannula tip that matches the size of the occluded vessel and a high circulating flow rate are necessary elements to facilitate embolectomy. Bench top tests indicate that backflow must be present to support the level of pump flow rate that generates vacuum sufficient to remove large masses. In some of the procedures that yielded little or no material extraction, it is possible that a lack of backflow was exhibited due to absent or severely limited retrograde collateralization. Guidewire or angiographic catheter passage through the thrombotic substrate may yield partial recanalization that provides the requisite degree of retrograde flow for successful embolic removal. Another cause of unsuccessful extraction may be an advanced degree of fibrotic attachment associated with aged thrombus that is not amenable to vacuum dislodgment. Further clinical experience will delineate additional associated techniques and define best patient selection criteria for optimal

would be required to clear a total occlusion in the great vessels.

**3.4.7 Discussion** 

erythrocytes.

**4. Conclusion** 


http://emedicine.medscape.com/article/191103-print


**6** 

*USA* 

**Conduit Selection for Improved** 

*Medical Center Asheville, NC* 

**Outcomes in Coronary Artery Bypass Surgery** 

Coronary artery bypass grafting (CABG) is one of the most studied operations in medical history, but many of the data forming the basis for clinical decisions in patients with coronary artery disease (CAD) were derived in the 1970s and 1980s, when the procedure and medical therapy were in their relative infancy. Advances in medical therapy (beta adrenergic blockers, thienopyridines, statins, and others), percutaneous coronary interventions (PCI), and surgical techniques have changed the decision making for patients with CAD. In addition, patient populations referred for surgery have changed since the

Since percutaneous transluminal coronary angioplasty (PTCA) was introduced, significant advances have been made in the percutaneous treatment of CAD. When drug-eluting stents (DES) were introduced in the early 2000s, many predicted the demise of CABG surgery. Enthusiasm for percutaneous treatment of CAD has most recently led to promoting PCI for unprotected left main coronary artery (LMCA) disease, an anatomical state typically reserved for CABG [1-3]. Percutaneous options have indelibly changed the face of CABG surgery and raise questions concerning the "gold standard" of care in coronary revascularization. For instance, recent reports document that patients referred for redo coronary artery surgery have declined, presumably due to the increased enthusiasm, possibly among surgeons themselves, for PCI in this setting [4]. Despite this, few studies have actually compared PCI with CABG. Two notable studies are recently available, both demonstrating advantages for CABG over PCI for left main CAD and/or three-vessel CAD

Concurrently, details pertaining to short-term outcomes of CABG have been questioned. For example, historical saphenous vein graft (SVG) patencies were reported as approximately 50% at 10 years [7]. However, several studies published in the mid-2000s indicate that earlyterm patencies of aorto-coronary SVG conduits are not as good as the historical figures that are still often quoted [8-10]. While the long-term patency and performance of the left internal mammary artery (LIMA) has not been questioned, the recent poor performance of

original studies documenting advantages of CABG over other forms of therapy.

**1. Introduction** 

[5, 6].

 \*

Corresponding Author

Zane B. Atkins1,2,\*, Kristine V. Owen3 andWalter G. Wolfe1,2 *1Department of Surgery, Veterans Affairs Medical Center Durham, NC 2Department of Surgery, Duke University Hospital Durham, NC 3Department of Medicine, Charles George Veterans Affairs* 


http://emedicine.medscape.com/article/1911303-overview

