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Ann Thorac Surg 1995;60:985
© 1995 The Society of Thoracic Surgeons
DR JOHN E. CONNOLLY (Newport Beach, CA): I congratulate Dr Slater on his presentation. I think this will be a real advanced modality for transplantation. He was kind enough to send me his manuscript, and I thought you might be interested in some of our experiences with veno-arterial shunting.
I gave a paper before the Society of University Surgeons 37 years ago. At that time the problem that we found was with prolonged administration of heparin, causing adverse hematologic effects. It was about 10 years after that, that Dr Wakabayashi in our department devised a nonthrombogenic coating for tubing, which we then applied for left heart bypass very successfully, and found that this eliminated the problems with bleeding. Using this tubing, we resurrected veno-arterial bypass, and applied it clinically in 6 patients. At that time we carried a roller pump and coated veno-arterial tubing in our automobile trunk and told our cardiology friends if they needed acute circulatory support, we were available. At a community hospital that did not have any facilities for heart catheterization, we were asked to assist one particular patient, who was stabilized by veno-arterial bypass successfully for 31 hours, at which time we transported the patient in a van with veno-arterial assist to our facility where the patient underwent heart catheterization. A large ventricular aneurysm and mitral insufficiency were diagnosed, both of which were corrected, and postoperatively circulatory veno-arterial support was continued for 41 hours. The total period of nonthrombogenic veno-arterial bypass was 3 days, and we were very pleased to find that the hematologic problems were minimal.
However, as mentioned by Slater and associates, at that time intraaortic balloon pumping became the popular form of cardiac assistance and we did not pursue clinical veno-arterial bypass further. It is of interest, though, to note that the results of our physiologic studies performed on these 6 patients were very much like those reported today. Both showed that right-sided pressures were reduced and cardiac output increased as pulmonary flow increased; second, that aortic root pressure was increased; third, that left ventricular end-diastolic pressure and left ventricular stroke work were decreased; and finally, that the augmented pulmonary artery blood flow led to a proportional increase in oxygenated blood, which offset the shunt.
I not only congratulate Slater and associates on a technique that I think may help one of the major complications of transplantation, but I also wonder if it might be appropriate for them or other young surgeons to try veno-arterial bypass in combination with intraaortic balloon pumping for other types of heart failure.
DR DAVIS C. DRINKWATER, JR (Los Angeles, CA): I have a question concerning the appropriateness of the approach toward the shunt. In fenestrated Fontans, we take advantage of this concept of shunting at the atrial level. Of course, the carotids then see a lower saturation of 85% also, which is well tolerated among these hypoxic patients. I have a concern about how well the kidneys and other organs of noncyanotic patients will tolerate this desaturation of the lower body. Would you comment on this?
Also, your abstract talks about experience in 2 patients, 1 of whom was on a right ventricular assist device and could not be weaned. Do you have any more information that you could share with us concerning these patients?
DR SLATER: We have done this now in 4 patients. To take one patient as an example, the patient had a heart transplant. He had fixed pulmonary hypertension, which is a little bit different than our model. He did have normal left ventricular function by echocardiography. He was receiving six drips, had low cardiac output, had very high right-sided pressures, and a low mixed venous oxygen saturation. We decided to place a shunt in him and we used clinically a femorofemoral configuration. We used small catheters of 10 and 14 mm, arterial and venous, respectively, to minimize the obstructive flow to the lower extremity. We used a heparin-bonded circuit so that we did not have to heparinize him or anticoagulate him systemically.
We graphed his cardiac output over time. His effective cardiac output increased immediately during shunting. His native cardiac output drifted downward, but never to an amount equal to the shunt itself. When we turned the shunt off 36 hours later, his cardiac output returned to its original level, but all of his drips were off.
We saw an obvious benefit to mixed venous oxygen saturation, indicating that we improved his oxygen delivery, and his arterial saturation remained greater than 90%, which was consistent with our experimental studies. This patient, as I said, was shunted for 36 hours, after which the shunt was successfully weaned; he died 1 week out of other complications. We think that this case answers a number of questions that our experimental model raised about becoming acidotic-he did not become acidotic-becoming hypoxic-he did not become hypoxic-and his lower extremities showed no adverse effects of the shunt.
DR ALI GHEISSARI (Los Angeles, CA): I congratulate Dr Slater and his co-workers on this study and ask: What is the advantage of this technique over the creation of an atrial septal defect, which you can adjust with a snare? If you get the shunting at the atrial level, why wouldn't that work?
DR SLATER:We think the advantage of this is that it can be done after leaving the operating room. Our patient was already in the open heart recovery room when right sided failure developed. We were able to place cannulas via cut-downs at the bedside. When we were ready to remove the shunt we were able to wean it off very precisely and then remove it. In addition, we have done animal studies comparing a central shunt with a peripheral shunt. The deoxygenated blood during the central shunt, or, in your case, an atrial septal defect, is shared with the coronary circulation, the brain, and the visceral organs, whereas the peripheral shunt causes the less oxygenated blood to be directed to the lower extremity, away from the vital organs.
DR CONNOLLY: I would like to answer your question. In the patient who we had on bypass for 3 days and 3 nights, we were only bypassing between 600 and 900 mL/min, and there was more desaturation in the lower extremities than elsewhere, but it was very tolerable.
Related Article
Ann. Thorac. Surg. 1995 60: 978-984.
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