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J Thorac Cardiovasc Surg 1999;118:207-208
© 1999 Mosby, Inc.
LETTERS TO THE EDITOR |
Department of Cardiothoracic Surgery
The Milton S. Hershey Medical Center
The Pennsylvania State University
PO Box 850, 500 University Dr
C4608
Hershey, PA 17033-0850
To the Editor:
Doty and associates,
1 who pioneered the development of minimally invasive direct coronary artery bypass grafting (MIDCAB), described a series of 162 consecutive patients undergoing this procedure. It is important to put this series in perspective and clearly define the appropriate conclusions from this retrospective case report.
First, the authors are to be commended for honestly reporting their postoperative morbidity and mortality in great detail. Because of this, these results will serve as an important benchmark for future experiences. The authors have demonstrated that selected patients can safely undergo a MIDCAB procedure and that short-term follow-up indicates an acceptable relief of patients' symptoms. However, it is equally important to point out what cannot be concluded from this study. A 5% early mortality rate in these patients with limited coronary artery disease is high. On the basis of the demographic data provided, most surgeons would not consider this to be a particularly high-risk group. There is also a high incidence of myocardial infarction (4.2%) and wound infection (15%). Without either concomitant or historically matched controls, it is impossible to conclude whether the MIDCAB procedure actually reduces the mortality or even the morbidity of coronary artery bypass grafting (CABG). Perhaps the greatest weakness of this study is the lack of angiographic follow-up. Unfortunately, very few of the patients underwent recatheterization (16.4%). Thus the critical question of graft patency after beating heart revascularization is not answered by this study.
The precise role of the MIDCAB procedure is still waiting to be defined. MIDCAB is a field in evolution, in which techniques are being continually refined and clinical results are improving. At present, the most critical issue is that of graft patency after beating heart surgery. It is imperative that this procedure have a patency rate comparable with that of traditional arrested heart cases. However, the "gold standard" for internal thoracic artery patency has not been established. In a previous report from The Cleveland Clinic, there was a reported graft patency rate of 91.2%. 2 Among 29 patients studied after more than 10 years, the patency rate of the left internal thoracic artery (LITA) graft was 89.7%. In a recent international multicenter randomized trial of 645 patients in which the LITA was anastomosed to the left anterior descending coronary artery (LAD), the LITA was widely patent in 91% of patients. 2,3 It has been established that at early and 6-month follow-up after MIDCAB, similar patency rates of 90% or greater can be achieved by using mechanical stabilization. 4-7 Although longer-term follow-up is needed, initial results are promising. With present technology, many surgeons now feel just as comfortable with their beating heart anastomoses as with those that they perform on the arrested heart.
Despite the encouraging early patency results, it still has not been established whether the MIDCAB procedure significantly reduces postoperative morbidity, the speed of postoperative recovery, or time to return to work. To determine the answer to these questions, there is a critical need for randomized trials. The good news is that there are several randomized trials presently in progress. In this country, the POEM (Patency, Outcome and Economics of MIDCAB) Trial is presently underway. The end point is to evaluate 6-month angiographic patency and outcomes related to safety, efficacy, and event-free survival in patients who undergo LITA-LAD grafting through either a traditional median sternotomy or a MIDCAB procedure. Currently 9 sites are participating in this trial.
In Europe, The Netherlands National Health Insurance Council has funded a multicenter study that began in March of 1998. 9 This study involves 2 randomized trials. One trial will compare multivessel CABG without cardiopulmonary bypass using a mechanical tissue stabilizer versus conventional CABG with cardiopulmonary bypass. The second trial will compare multivessel CABG without bypass using a stabilizer versus stenting. Both trials will include angiographic follow-up at 1 year.
With these data, it will soon be possible to determine both the benefits and the shortcomings of beating heart procedures. Until then, the widespread patient acceptance of these procedures will continue to encourage the rapid progress in minimally invasive cardiac surgery. The increasing number of beating heart cases being performed in this country would suggest that surgeons are becoming more comfortable and confident with these new procedures. As has been the case throughout surgical history, careful evaluation of clinical results will shape and direct this evolving new field.
12/8/99725
References
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