Silent
myocardial ischemia, whether it occurs at rest or during exercise, is associated with an unfavorable prognosis and may lead to
sudden cardiac death. Agents used to treat silent
myocardial ischemia have included
nitrates, beta-blockers, and
calcium antagonists (CAs). Despite treatment with traditional anti-ischemic agents, studies have shown that up to 40% of patients who receive what is considered to be clinically optimal antianginal
therapy continue to have daily episodes of silent
myocardial ischemia. The use of
nitrates and beta-blockers is sometimes confounded by issues of tolerance and tolerability. Although the CAs have been found to be effective in decreasing the duration and frequency of episodes of silent
ischemia, in general beta-blockers produce a greater reduction in these variables. Thus a need for effective and tolerable anti-ischemic agents persists. A new class of CAs, the
tetralol derivatives, may show promise in this regard. The first of this new class,
mibefradil, is characterized by selective blockade of T-type
calcium-ion channels and has been shown in a few studies to reduce the frequency and duration of asymptomatic ischemic episodes in patients with stable exertional
angina pectoris. Large-scale clinical trials are necessary before the efficacy and tolerability of this new CA can be compared fully with those of the beta-blockers and currently available CAs.