Silent myocardial ischaemia: to treat or not to treat?

Silent myocardial ischaemia is now recognized with increasing frequency in patients with coronary artery disease. It is estimated to occur in 30-70% of patients with stable or unstable angina pectoris or with previous myocardial infarction, while, in totally asymptomatic healthy subjects, a prevalence of 2-4% is reported. However, these data must be evaluated with caution, because the predictive value of the tests employed in detecting silent ischaemia, depends on each test's sensitivity and specificity as well as on the prevalence of the disease in the evaluated population (Bayes's theorem). Available data suggest there is an important relationship between silent myocardial ischaemia, total ischaemic burden and adverse clinical outcome (non fatal myocardial infarction and cardiac death), especially in patients with documented coronary lesions. However, an elusive link between silent myocardial ischaemia and sudden cardiac death has currently been observed. Many reports have demonstrated that therapy with nitrates, beta-blockers and calcium channel blockers or revascularization procedures are effective in reducing silent myocardial ischaemia and its duration, but it remains unclear whether these treatments influence prognosis. A resolution of these uncertainties by controlled clinical trials will be necessary in order to choose therapeutic strategies, especially in totally asymptomatic subjects.