| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||
Ann Thorac Surg 1996;62:29-30
© 1996 The Society of Thoracic Surgeons
DR SIDNEY LEVITSKY (Boston, MA): Doctor Allen, this is a very interesting presentation of your clinical experience using a combination of antegrade and retrograde cardioplegia. We have been using a modification of the same technique for the past 4 years except we do not use warm induction or a "hot shot." For coronary revascularization procedures, we use cold cardioplegia while performing the distal anastomoses and warm continuous retrograde cardioplegia while performing the proximal anastomoses in association with a single-clamp technique. My question is related to the methodology of your study. There are no controls, either simultaneous controls or matched retrospective controls. Thus, the apparent good results may just be a reflection of your excellent technical surgery and totally unrelated to the method of myocardial protection.
DR ALLEN: I agree that because there is no control group it is impossible to definitely demonstrate that this is a better method of myocardial protection. However, I am not sure any other method of myocardial protection would allow a patient with aortic regurgitation and mitral insufficiency to have his or her aorta cross-clamped for 4
hours and be discharged on the fifth postoperative day. Numerous experimental and clinical studies have examined each method alone, or in combination. For instance, retrograde delivery has been shown to complement antegrade. Adding warm induction or a warm reperfusate ("hot shot") to cold cardioplegic techniques has also been shown to be beneficial. All we have done is to combine ("integrate") all of these various accepted and previously investigated techniques into a comprehensive strategy to limit each method's weaknesses. More importantly, because there are numerous different cardioplegic strategies in clinical use, the question would be which method of myocardial protection should represent the control group. No matter which one we choose, people would complain we did not compare the integrated strategy to what they consider to be the optimal method. Therefore, what we tried to do was examine integrated cardioplegia in a high-risk group of patients with prolonged cross-clamp times and compare this with historic controls. We hoped that if a high-risk group of patients did well with cross-clamp times averaging 2 to 3 hours, it would be sufficient to conclude this myocardial protection strategy was superior.
DR CONSTANTINE L. ATHANASULEAS (Birmingham, AL): I congratulate you, Dr Allen, on your excellent results in these complex cases. I too cannot offer a prospective, randomized study, but can comment on a study that we carried out retrospectively shortly after adopting the integrated method of myocardial protection in all adult cardiac surgical procedures in 1994.
We compared the conventional versus integrated techniques with regard to operative efficiency, outcome, and cost in coronary and combined coronary procedures. Each group included 100 patients. The conventional method included moderate systemic hypothermia to 28°C, antegrade and retrograde infusions of cold blood cardioplegia every 15 minutes, and tangential clamping for proximal anastomoses with warm blood infusion through unconnected conduits. The Buckberg integrated method of protection was exactly as you describe here.
Procedures included coronary operations alone or in combination with other procedures. Several patient characteristics that identified this population as high risk were compared and did not reflect significant differences between the conventional and integrated groups: congestive failure (26 versus 25), unstable angina (57 versus 48), infarction within a week (22 versus 28), ejection fraction less than 0.30 (10 versus 7), reoperation (19 versus 13), New York Heart Association class IV (76 versus 63), and associated procedures (15 versus 14).
Comparison of the techniques revealed no significant change in hospital mortality (9 versus 7), but several major clinical outcomes were significantly reduced in the integrated group. These included intraoperative balloon use (15 versus 5), prolonged ventilation beyond 1 day (45 versus 22), multiple organ failure (9 versus 1), pump time (96 versus 81), and postoperative length of stay (14 versus 9). Financial data on 67 of the conventionally treated patients and 88 of the integrated group demonstrated a reduction in hospital cost from $40,100 to $28,400.
It is very interesting to me that such clinical changes were achieved by changing the method of cardioplegia delivery, which included continuous blood infusion at times, because the cardioplegia solution was the same in both groups.
DR ALLEN: Thank you for your comments. These are impressive results in a sick group of patients. In general, I would agree with your findings as this was exactly what we saw when we retrospectively studied the first 250 consecutive patients (167 coronary artery bypass grafting, 83 valve) undergoing open heart operations after we started using an integrated cardioplegia strategy and compared them with the 150 consecutive patients (92 coronary artery bypass grafting, 58 valve) undergoing operation immediately before our use of integrated cardioplegia. These 150 patients received only cold intermittent antegrade/retrograde blood cardioplegia every 20 minutes. The two groups were similar with respect to age, sex, type of procedure, preoperative New York Heart Association functional class (3.1), and severity score (Parsonnet), which averaged 13 predicting a mortality of approximately 6% to 10%. Although there was no difference in mortality, those patients receiving an integrated myocardial protective strategy had lower inotropic requirements (22% versus 48%), less need for electrical defibrillation or lidocaine infusion, and shorter postoperative hospitalization (10 versus 14 days). I am sure that if we had pulled the financial records as you did, the use of an integrated cardioplegic strategy also would have resulted in a significant cost reduction.
DR JAMES H. OURY (Missoula, MT): I congratulate you, Dr Allen, on your results. We certainly can support the integrated approach to myocardial protection based on more than 50 Ross procedures that we have done with similar results. My question is a very simple one, but I think it has to do with the essence of the myocardial protection, which I think is an important component of this operation: Could you describe your cannulation technique?
DR ALLEN: Cardioplegia or systemic cannulation technique?
DR OURY: No, your cannulation technique for bypass.
DR ALLEN: All patients had a single aorta cannula placed in the ascending aorta and bicaval cannulation for venous return.
DR. OURY: I think the bicaval cannulation is important, and early on in the Ross procedure perhaps was not given enough emphasis. It really allows you to do optimum myocardial protection either antegrade or retrograde and, in cases where the coronary sinus cannula may not be easily placed transatrially, open the atrium and place the cannula under direct vision. I think that is an important component of myocardial protection that gives you a certain degree of comfort as you have these long cross-clamp times. So I think the bicaval cannulation is very important.
DR ALLEN: I would tend to agree. Bicaval cannulation keeps the heart colder by limiting the return of warm systemic blood to the heart. This helps maintain both atrial and ventricular hypothermia when the heart is ischemic. It also avoids development of an air lock or ventricular distention, both of which can occur with single cannulation during Ross procedures. We, therefore, routinely use bicaval cannulation in all complex valve cases.
DR GEORGE E. CIMOCHOWSKI (Wilkes-Barre, PA): I would like to echo Dr Levitsky's comments. I think that without a control group your overall scientific data are weak. I think that the mean age is only 45 years and there were minimal associated coronary artery lesions, and I can tell you that I watched Professor Carpentier for a month last year day-in and day-out do similar cases with one dose of crystalloid cardioplegia in which he basically emphasized cooling the heart. So I am not sure that this group of patients that you chose is the best.
Now, having said that, we in fact use your technique, and we switched from warm heart surgery to this integrated technique several years ago. In our series of consecutive isolated coronary artery bypass grafting patients (1,082 patients) from January 1994 to January 1996, our mortality rate was 1.6%. In comparison, The Society of Thoracic Surgeons database mortality rate for isolated coronary artery bypass grafting in 1994 was 3.3%. Of course, we cannot attribute everything just to the cardioplegia, but I think we would be foolish not to imply anything but that integrated cardioplegia was instrumental in our low mortality.
We also quantitatively looked at the time we ran the cardioplegia in both valves and coronary arteries. We successfully were able to continuously run the cardioplegia 70.1% of the time with coronary arteries and 84.3% of the time with valves. So I think your point is well taken that for the most part these patients are well protected with continuous cardioplegia, and when their cardioplegia is not running, the heart is still protected by hypothermia. Do you have a series of patients in whom in fact you did valve/coronary artery operations or, even better, hypertrophied/valve/coronary artery operations in your last several years of experience with integrated cardioplegia? And what were the results?
DR ALLEN: Let me address several points. First, I do not believe these were low-risk patients. The average Parsonnet score was 16, which predicts the mortality to be approximately 10%. In the complex mitral valve repair group, more than half of the patients had an ejection fraction less than 0.40, 32% a dilated left ventricle with an end-diastolic diameter greater than 57 mm, and 40% a pulmonary artery pressure greater than 60 mm Hg. In the Ross patients, 33% had ejection fractions less than 0.40 and 67% had a dilated left ventricle. All these factors increase the operative risk. The reason for the young age in this series is due more to the fact that Ross procedure patients tend to be younger. We do not routinely do Ross operations in patients who are 60 to 70 years old. In contrast, patients undergoing complex mitral valve repair were in general older, ranging in age up to 79 years.
We chose to study complex valve repair specifically because of the fact these are higher risk patients requiring long cross-clamp times. If we had examined all of our mitral valve repairs, the cross-clamp times would have been much shorter; as some patients only required a ring annuloplasty or a small quadrangular resection and an annuloplasty. In addition, as mentioned in response to Dr Athanasuleas, we did compare 250 consecutive patients undergoing coronary bypass grafting, a valve procedure, or both with 150 patients undergoing operation before we began using an integrated cardioplegic strategy. These results, which are almost identical to those of Dr Athanasuleas, demonstrate a decrease in morbidity and shortened hospital stay. Therefore, based on our retrospective analysis, as well as this investigation, we believe that integrated cardioplegia provides the optimal method of myocardial protection.
Related Article
Ann. Thorac. Surg. 1996 62: 23-29.
| ||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |
