We read with great interest the recently published article by Spiess and colleagues. 1 In an observational study of 2202 patients undergoing coronary artery bypass grafting (CABG) in 24 different centers, they found on multivariate analysis that the most significant predictor of Q-wave myocardial infarction was a hematocrit greater than 33% on entry to the intensive care unit. They also noted that patients with a hematocrit less than 25% had the lowest rates of both Q-wave myocardial infarction and severe left ventricular dysfunction and concluded that morbidity after CABG might be decreased by allowing the hematocrit to be low immediately postoperatively. These findings have the potential to make an enormous clinical and financial impact given the frequency of this operation world-wide. However, before these results can be accepted as valid, it is essential to know whether any of the patients included in this study had perioperative administration of aprotinin, either as part of a clinical protocol or as part of a concurrent trial. This information is not detailed in the article.Aprotinin administration has been shown to reduce bleeding and increase postoperative hemoglobin levels after CABG when compared with placebo. 2,3 Its use has been associated in some studies with increased perioperative myocardial infarction 4,5 and decreased vein graft patency rates, 2,5,6 although these findings are not universal. 3,7 Patients who have been given aprotinin would be expected to have a higher postoperative hematocrit level but may also have been at increased risk of myocardial infarction as a result of an independent effect of aprotinin causing a hypercoagulable state. 8 Therefore, if any patients in the study reported by Spiess and associates had received aprotinin, the multivariate analysis should be repeated to confirm that a higher hematocrit value was indeed an independent risk factor for Q-wave myocardial infarction and severe left ventricular dysfunction.
