How to study the prevalence and mechanisms of racial differences in coronary vasomotor response.

The rapid progress of therapeutic modalities of cardiovascular diseases have led to the development of clinical practice guidelines on the basis of large scale clinical trials. However, an individual response of each patient may not match the mean effect of an intervention in these trials. Therefore, recommendations based on clinical trials performed in a given patient population may not be applicable to the other races. Here, we assessed epidemiological and pathophysiological differences in cardiovascular diseases across racial groups. The incidence of coronary artery disease is the lowest in Japan of all the industrialized nations. Our previous study that compared post-hospital course of acute myocardial infarction in Japanese and Caucasians in North America demonstrated that cardiac events were significantly less in Japanese even when the initial infarct size was similar. Ischemic heart disease constitutes the most common cause of heart failure in the United States but nonischemic cardiomyopathy occurs more frequently in Japan. On the other hand, vasospastic angina is by far more common in the Japanese population. The first comparative study we carried out in Japanese and Italian patients with acute myocardial infarction also showed that percentage of vasospasm in the infarct-related arteries is 3 times higher in Japanese. Thus, coronary spasm appears to be more important as well as the pathogenesis of myocardial infarction in Japan. This fact was reflected by the more frequent use of calcium antagonists in Japan during the acute phase of myocardial infarction. On the other hand, the use of inotropic agents has now been contraindicated for the treatment of patients with chronic heart failure, however it may not be the case in the Japanese population in whom mortality is relatively low. Cardiotonic therapy could be justified in Japanese as it allows optimal care in the context of relief of symptoms and an improved quality of life. Therefore, each racial group should obtain specific evidence aimed at developing its own guidelines for therapy rather than translating major guidelines developed for other populations.