An analysis of 41 trials of angina of all varieties confirms that
calcium antagonists are an important advance and are now established
therapy for these syndromes. In effort angina,
verapamil in a dose of 360-480 mg daily is better than
propranolol in standard doses. Although
nifedipine is highly effective against vasospastic angina, its use in threatened
myocardial infarction or severe
unstable angina is not supported by recent studies, unless combined with a beta-blocker.
Diltiazem has recently been tested with apparent benefit in non-Q-wave
myocardial infarction. Otherwise, these
calcium antagonist agents all seem to have approximate equipotency in clinical ischemic syndromes including effort and vasospastic angina. Subjective side effects seem most troublesome in the case of
nifedipine. All three
calcium antagonists, especially
nifedipine, have been successfully combined with beta-blocker
therapy, yet occasional additive negative inotropic or chronotropic or dromotropic interactions may occur when
verapamil or
diltiazem is added to beta-blockade, and occasionally the direct negative inotropic potential of
nifedipine may become evident. The choice between the
calcium antagonists is determined not only by the clinical picture but also by the anticipated side effects in a given patient and by the overall cardiovascular status. In patients with
supraventricular tachycardias or
sinus tachycardia,
verapamil or
diltiazem is preferred, whereas in patients with a resting
bradycardia or borderline
heart failure nifedipine is likely to be chosen.