Current status of silent myocardial ischemia

A significant proportion of myocardial ischemia is 'silent' in nature. Furthermore, this asymptomatic ischemia portends an adverse prognosis for patients with known coronary artery disease. Silent myocardial ischemia can be objectively assessed and quantified by a number of noninvasive means; however, ambulatory electrocardiographic monitoring has emerged as a preferred method for both detection and analysis in hospital and during daily life conditions. Silent myocardial ischemia exhibits a circadian pattern. It represents an imbalance between myocardial oxygen supply and myocardial oxygen demand, and can be triggered by both physical and mental stress. The important role of endothelial dysfunction and autonomic nervous system influences has been recently elucidated. Up to 75% of ischemic episodes in patients are silent. Patients with asymptomatic coronary artery disease, chronic stable angina and unstable angina, and those postmyocardial infarction or postrevascularization who exhibit ST segment shift all show adverse short and long term prognosis compared with controls. Treatment modalities have included nitrates, beta-blockers, calcium antagonists, phosphodiesterase inhibitors, anxiolytics, anti-platelet agents and revascularization procedures. While the majority of these studies have demonstrated significant reduction in the frequency of silent myocardial ischemia, limited data on influencing prognosis are available; thus recommendations regarding treatment of these patients await the results of ongoing clinical trials.