Torsades de pointes induced by erythromycin.

We describe two patients who develop torsades de pointes in a temporal relationship to the intravenous administration of erythromycin lactobionate in the absence of other drugs or metabolic abnormalities known to cause the arrhythmia. We also review the current literature regarding this topic, including other case histories and the evidence for erythromycin's effect on cardiac tissue. Due to the increasing use of erythromycin in clinical practice, we believe it is important that all physicians be made aware of this potential complication, which was not recognized at our institutions until these patients were seen by one of us (B.G.).

Dipyridamole-induced myocardial ischemia.

Angina and ischemic electrocardiographic changes occurred after administration of oral dipyridamole in four patients awaiting urgent myocardial revascularization procedures. To our knowledge, this has not previously been reported as a side effect of preoperative dipyridamole therapy, although dipyridamole-induced myocardial ischemia has been demonstrated to occur in animals and humans with coronary artery disease. Epicardial coronary collateral vessels were demonstrated in all four patients; a coronary "steal" phenomenon may be the mechanism of the dipyridamole-induced ischemia observed.

Use of electrocardiographic-thallium exercise testing in clinical practice.

Although there is a great deal of data on the accuracy of combined electrocardiographic-thallium exercise testing, little is known about the use of these tests in clinical practice. A quantitative likelihood system was employed to characterize referral patterns for such testing, and the impact of test results on the likelihood of coronary artery disease was examined. Two hundred thirteen subjects consecutively referred for the purpose of establishing or excluding the presence of coronary artery disease were studied. No subject had a history of a prior myocardial infarction. By historical evaluation, 96 had a low likelihood of coronary disease (less than or equal to 0.20), 88 an intermediate likelihood (0.21 to 0.80) and 29 a high likelihood (greater than 0.80). As anticipated from theoretical analyses, testing produced the greatest shifts in disease likelihood in subjects with an intermediate pretest disease likelihood, and confirmed the historical evaluation in patients at the extremes of pretest disease likelihood. Therefore, although electrocardiographic-thallium stress testing is best suited for subjects with intermediate pretest disease likelihood, the majority of referrals had either a high or low likelihood. Clinicians appear to value confirmatory results in patients at the extremes of pretest disease likelihood. Electrocardiographic exercise testing would serve a similar purpose.