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Ann Thorac Surg 1998;66:307-308
© 1998 The Society of Thoracic Surgeons
a Department of Cardiac Surgery, Southampton General Hospital, Southampton, England SO16 6YD, United Kingdom
To the Editor
We read with great interest the article by Sundt and associates [1] and congratulate them on their excellent results. We fail to understand, however, why their experience is different from ours and the majority of the literature. We question their conclusions.
In common with other series we found that replacement of the aortic valve after previous coronary artery bypass grafting (CABG) is associated with a higher mortality than aortic valve replacement (AVR) as a primary procedure. Between 1982 and 1996, 6,722 patients underwent isolated CABG and 1,712 isolated AVR in our unit. A further 744 patients underwent combined AVR and CABG, and 16 patients underwent AVR after previous CABG. Early (30-day) mortality was 2.06% for isolated CABG, 2.85% for isolated AVR, 4.02% for AVR and CABG, and 18.75% for AVR after CABG. Two of the 3 patients who died after AVR that followed CABG had an ejection fraction of less than 0.20 at the second operation.
Unlike the series of Sundt and associates, all our patients had their gradient measured preoperatively. The mean pull-back gradient (± standard deviation) across the aortic valve at the time of CABG was 21.31 ± 7.55 mm Hg (range, 10 to 35 mm Hg). The mean pull-back gradient across the aortic valve at replacement (± standard deviation) was 73.1 ± 19.2 mm Hg (range, 35 to 100 mm Hg). The mean length of time between CABG and the need for AVR was 69 months (range, 4 to 190 months).
We believe that the decision to replace the aortic valve must be balanced between the increased early mortality (2.06% for CABG versus 4.02% for AVR and CABG), the risk of valve-related complications (2% to 5% per patient per year) versus the risk of replacing the valve as a secondary procedure (18%). It is difficult to predict those patients with mild aortic stenosis in whom a significant gradient will develop [2]. We now therefore recommend the following strategies in patients undergoing a coronary artery operation with mild aortic stenosis.
In elderly patients in whom long-term survival is not expected, we leave the valve because the likelihood of enough time lapsing for the valve gradient to become significant is low. In patients whom we expect to survive a number of years, if the valve looks stiff on cardiac catheterization, results in a withdrawal gradient of greater than 25 mm Hg, or is morphologically abnormal (bicuspid), we replace it.
When these conditions do not apply and the valve is morphologically normal, ventricular function becomes critical. When ventricular function is impaired we replace the valve because a low gradient may either be or could become significant. In addition, impaired function increases the risk at second operation. When left ventricular function is well preserved we leave the valve in situ. We think that a conservative valve operation at the time of CABG is not so easy to recommend [3].
References
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