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Ann Thorac Surg 1999;68:1971-1973
© 1999 The Society of Thoracic Surgeons
a Department of Surgery, University of Virginia School of Medicine, Charlottesville, Virginia, USA
Address reprint requests to Dr Kron, Department of Surgery, University of Virginia Medical Center, Box 310, Charlottesville, VA 22908
e-mail: ikron{at}virginia.edu
Presented at the International Symposium on Myocardial Protection From Surgical Ischemic-Reperfusion Injury, Asheville, NC, Sep 21–24, 1997.
Abstract
Myocardial protection for surgical procedures on the failing heart can be broken down into three areas. The first area involves selection of the appropriate patient with enough myocardial viability and contractile reserve to permit a substantial cross-clamp time. Secondly, there should be adequate targets to revascularize or adequate tissue for reparative surgery. Thirdly, and most importantly, antegrade and retrograde blood cardioplegia given in sufficient amounts to satisfy myocardial oxygen needs is of prime importance.
Myocardial protection in the failing heart is a controversial subject. Clearly, if any form of myocardial protection is going to make a difference, it is going to be in the marginal ventricle. Unfortunately, there is little data to support any one method of myocardial protection in the highest risk patients with chronic ventricular dysfunction. It is important to define the failing ventricle. For the purposes of this discussion, this will not include individuals who have ventricular dysfunction due to acute ischemia. In those situations, one might expect the ventricle to rapidly improve after appropriate revascularization. Also, it should not be considered in situations where the patient has tight aortic stenosis or some other obstructive lesion in that, in these situations, the ventricular function is also likely to rapidly improve. It would therefore be difficult in terms of outcome to define whether or not the differences in survival were related to better myocardial protection versus just relieving the surgical lesion.
For the purpose of this discussion, the failing heart will be defined arbitrarily as a ventricle with chronic injury that is not likely to improve acutely after surgery. Most would define this clinical situation as an ejection fraction of 
25%. There is logic, however, to consider revascularization in patients with very poor ventricular function. In these situations, the individuals often have excellent long-term results that are equivalent to that of heart transplantation [1].
Surgical approaches to the failing ventricle
There are three schools of thought about the best approach to the chronically failing ventricle. The first is to focus on proper selection of patients and then perform standard cardiac surgery with standard myocardial protection. The second approach is to prevent injury to the heart during anesthesia and prior to cardiopulmonary bypass. This is usually performed with mechanical adjuncts such as preoperative use of the intraaortic balloon pump. The final approach relates to different myocardial protection schemes to enhance metabolic support in the failing ventricle.
Our group has been among those that would suggest that good selection probably is the major way to ensure good results in coronary bypass for ischemic cardiomyopathy. Our initial report included 39 patients operated on between 1983 and 1989. All patients had ejection fractions of 20% and underwent coronary artery bypass. The myocardial protection scheme was antegrade crystalloid cardioplegia which certainly should not offer any metabolic support other than reducing myocardial oxygen consumption. There was only one operative death in this group of patients (2.6%). The 3-year survival was 83% [2]. Subsequent to these results, our group slowly became much more aggressive about revascularization for ischemic cardiomyopathy. Following a more aggressive approach, we noted the hospital mortality rate increased to 8% in 96 consecutive patients. All patients had ejection fractions of 25%. The myocardial protection scheme was changed to antegrade blood cardioplegia. Upon further analysis of these data, the most notable finding was that poor vessel quality had 100% predictive value for perioperative death (7 deaths). When the vessel quality was good or fair, there was no mortality [3]. We concluded by this analysis that the patient with good distal coronaries with some evidence of ischemia likely would do well when undergoing coronary bypass for ischemic cardiomyopathy. There seemed to be no relationship to the type of myocardial protection in comparing this group to the patients who have been operated on under crystalloid cardioplegia. We also concluded from these data that proper patient selection was the most important predictor of patient survival.
Elefteriades and his group from Yale have popularized the approach of prophylactic intraaortic balloon pump prior to high-risk coronary bypass in patients with ischemic cardiomyopathy [4, 5]. They analyzed 83 patients with ejection fractions of 30% who underwent coronary bypass grafting. The intraaortic balloon pump was placed therapeutically in 19% and prophylactically in 43% for a total usage in 62% of patients with poor ventricular function. They noticed a hospital mortality of 8.4%. However, when the analysis was more complete, they noticed that the mortality rate was only 3.3% in those patients who did not require admission to the intensive care unit prior to surgery. There were also complications in the use of the balloon pump. In the 52 patients who had an intraaortic balloon pump placed, there were a total of three vascular complications and 1 of these patients lost a limb due to ischemia. The Yale group, therefore, demonstrated that they can perform these operations safely, and concluded that mechanical support of the heart was important prior to anesthesia and placement of the patient on cardiopulmonary bypass.
The rest of this discussion will relate to the use of unique myocardial protection schemes to enhance metabolic support of the failing ventricle. There has been little in the way of randomized trials in patients with ventricular dysfunction of different myocardial protection schemes. Rashid and colleagues compared 2 groups of patients operated on by the same surgeon with different myocardial protection schemes [6]. The patients were described to have ventricular dysfunction although the ejection fraction was not stated in their article. Rather, they defined ventricular dysfunction as elevated left ventricular end-diastolic pressure and increased Coronary Artery Surgery Study ventricular scores. One group of patients who underwent surgery had moderate hypothermia and antegrade cold-blood cardioplegia followed by intermittent retrograde blood cardioplegia. The second group of patients had normothermic cardiopulmonary bypass with continuous infusion of retrograde warm-blood cardioplegia. They noted no significant differences in outcome between the two groups. Specifically, the cold group had no operative mortality, whereas the warm continuous cardioplegia group had two deaths for a mortality of 3.4% which was not significantly different. The perioperative myocardial infarctions were no different between the groups. The only major difference was that 88% of the warm cardioplegia groups had spontaneous restoration of sinus rhythm as compared to 49% of the cold group (p 0.001). Therefore, warm blood cardioplegia did not seem to markedly improve results in patients in this randomized study of ventricular dysfunction.
There have been several other studies that were not randomized. Borman and colleagues reported 94 patients operated on with ejection fractions of 30%. They noted a 5.3% mortality rate within 6 weeks of surgery. They used lukewarm blood cardioplegia in their groups of patients and suggested that this was superior to patients who either had cold protection or warm blood cardioplegia [7].
Kaul and colleagues reported a large series of patients (210) who had ejection fractions of 20% or less, and were operated on over a 7-year period. Their overall hospital mortality was 10%. However, they noted that a major risk factor was the use of antegrade cardioplegia as compared with combined antegrade and retrograde cardioplegia. This was a notable finding except for the fact that all of the combined antegrade retrograde patients were done after 1988 and the others were done prior to 1988. It is possible that the improvement in survival was related to the myocardial protection scheme but more likely is related to more recent year of operation [8].
Cimochowski and associates had one of the more interesting approaches to patients with ventricular dysfunction. They reported on 111 patients with ejection fractions of 35% between 1992 and 1996. They compared their results with the Society for Thoracic Surgery (STS) database for patients with similar ejection fraction. Their own mortality rate was significantly better than the 7.6% reported by the STS database, in that their mortality was 1.8% [9]. This was achieved by the use of multiple modalities. These techniques included mechanical support with an intraaortic balloon pump in 32% of the patients, ultrafiltration during bypass in 57%, and delayed sternal closure in 2.7%. More importantly, they described a significant metabolic myocardial protective scheme in these patients. This included the use of Triodothyronine (T3) which was used in 50% of the patients, glucose insulin and potassium solution in 50%, aspartate/glutamate in 100%, and various combinations of cold and warm antegrade and retrograde cardioplegia in 100%.
The results from this group certainly are excellent but it is hard to decipher which interventions were necessary and which were not. The authors certainly have a logic to this approach but it is still unclear if all of this is truly necessary to achieve excellent results. It was also suggested, in the discussion of this article, that this cohort of patients had a lower incidence of reoperation as compared with the STS database for similar ejection fractions. Regardless of the critiques, the results were good using this metabolic scheme.
It can be concluded that one certainly can operate on patients with low ejection fractions with excellent short- and long-term results. It is unclear, however, how best to achieve these results with any one given intervention. Preoperative mechanical support can be helpful but it is unclear also how often this needs to be done. If there ever is a role for alternative myocardial protection strategies, it should be in this subset of patients with chronic ventricular dysfunction. However, there is not good enough data to suggest what one scheme, or group of schemes, in myocardial protection are necessary to get improved results. Clearly, there is a need for better data, and it seems surprising that there are not more prospective studies of alternative cardioprotective schemes in patients with ventricular dysfunction.
References
This article has been cited by other articles:
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  F. Nicolini, C. Beghi, C. Muscari, A. Agostinelli, A. M. Budillon, I. Spaggiari, and T. Gherli Myocardial protection in adult cardiac surgery: current options and future challenges Eur. J. Cardiothorac. Surg., December 1, 2003; 24(6): 986 - 993. [Abstract] [Full Text] [PDF]
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 G. B. Luciani, G. Montalbano, G. Casali, and A. Mazzucco Predicting long-term functional results after myocardial revascularization in ischemic cardiomyopathy J. Thorac. Cardiovasc. Surg., September 1, 2000; 120(3): 478 - 489. [Abstract] [Full Text] [PDF]
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