Ischemia-modified albumin and myocardial ischemia.

Sbarouni et al. (1) reported on “Ischemia-Modified Albumin [IMA] in Relation to Exercise Stress Testing [EST]” in a previous issue of the Journal. Although the investigators found significant differences in the IMA values at baseline, peak exercise, and after EST, there was no relation between the IMA changes and the result of the EST. The researchers stated that changes in IMA levels do not reflect myocardial ischemia and that IMA does not seem to improve the accuracy of EST. Although these are highly interesting results, some important points must be considered in this study. Previous studies have shown that IMA is a marker of myocardial ischemia, and it was accepted that IMA is an early marker to help in ruling out patients with acute coronary syndrome (2,3). Interestingly, Sbarouni et al. (1) concluded that IMA levels do not indicate myocardial ischemia different from these other studies. False negative and false positive results of exercise testing are important clinical problems in diagnosis of coronary artery disease (CAD). The sensitivity and specificity of EST range between 60% and 70% (4,5). Approximately 30% to 40% more false negative results may be obtained in clinical practice. Therefore, each positive EST is not accepted as a sign of myocardial ischemia. However, in the study by Sbarouni et al. (1), a positive stress test is accepted as indicative of myocardial ischemia. It is not mentioned how many patients with positive EST have myocardial ischemia. In our opinion, lack of this important information may change the study results. Other conflicts and controversial subjects are related to results from postexercise IMA levels. Because plasma IMA levels increase within minutes after myocardial ischemia, peak exercise IMA levels may not indicate myocardial ischemia. However, postexercise IMA levels may be helpful to determine myocardial ischemia during exercise. Previously, it was demonstrated that IMA levels decrease after physical exercise, and it was hypothesized that this immediate decrease may have been attributable to interference in the IMA measurement by lactate produced during skeletal muscle ischemia (6,7) However, release of lactate after EST in patients with peripheral vascular disease has been reported (8) Although Sbarouni et al. (1) concluded that a decrease in IMA levels is associated with hemoconcentration, it was unknown whether peripheral vascular disease was present in the study population. Therefore, possible peripheral vascular disease in patients may affect IMA levels via increased lactate concentration.