Antiarrhythmic and anti-ischemic properties of calcium-channel antagonists.

The calcium-channel blockers are an ever-enlarging, heterogeneous group of drugs with widely variable effects on myocardium, sinoatrial and atrioventricular nodal function and conduction, peripheral blood vessels, and coronary circulation. Since the development and characterization of calcium-channel antagonists in the 1960s, these agents have become increasingly important in the treatment of many cardiovascular diseases. Nine calcium-channel blockers-nifedipine, nicardipine, amlodipine, felodipine, isradipine, nimodipine, diltiazem, verapamil, and bepridil-are all approved for use in the United States. Each major category has its own unique physiologic features. These drugs are extremely useful in the management of cardiac arrhythmias (particularly supraventricular arrhythmias) and/or ischemia. As future generations of calcium-channel blockers are developed with greater vasoselectivity, less negative inotropic effects, and reduced tendency to activate the renin-angiotensin system, their indications for use will continue to grow.

Outpatient echocardiography as a predictor of perioperative cardiac morbidity after peripheral vascular surgical procedures.

PURPOSE: A variety of preoperative provocative tests have been used to define the risk of cardiac morbidity and mortality after peripheral vascular procedures, including dipyridamole myocardial scintigraphy and dobutamine stress echocardiography. Although highly sensitive, these tests are time-consuming and associated with significant expense. We investigated outpatient echocardiography as a less resource-intensive means of assessing cardiac risk with operation. METHODS: Over a 2-year period 250 consecutive patients underwent outpatient transthoracic echocardiography before elective peripheral vascular operation was performed. The accuracy of the Goldman, Detsky, and the American Society of Anesthesiologists' Physical Status Classification clinical indexes of cardiac risk were assessed with regard to the development of cardiac complications such as unstable angina, myocardial infarction, life-threatening ventricular arrhythmias, severe congestive heart failure, and cardiogenic shock. The accuracy of echocardiographically determined left ventricular ejection fraction was determined at threshold values between 20% and 60%. RESULTS: Perioperative cardiac events developed in 23 (9.2%) of the patients, and nine (3.6%) of the patients died as a result of these complications. Clinical indexes lacked sensitivity in the preoperative prediction of cardiac complications. Receiver operating curve analysis defined a left ventricular ejection fraction of less than 50% as an appropriate threshold for defining patients at high risk, with a sensitivity of 78% and a specificity of 81% in the identification of patients who had cardiac morbidity. The positive predictive value was 27%, and the negative predictive value was 97%. The economic impact of outpatient echocardiography was well below that of dipyridamole myocardial scintigraphy or dobutamine stress echocardiography. CONCLUSIONS: Outpatient echocardiography appears to offer a cost-efficient compromise between clinical criteria alone and provocative cardiac testing such as dipyridamole myocardial scintigraphy and dobutamine stress echocardiography in the preoperative screening of patients undergoing peripheral vascular surgical procedures.

Maternal ventricular tachycardia associated with hypomagnesemia.

We present a rare case of recurrent sustained maternal ventricular tachycardia associated with hypomagnesemia. The frequency of this arrhythmia was markedly reduced with magnesium sulfate therapy. Both maternal and fetal outcomes were good. To the best of our knowledge this is the first description of maternal ventricular tachycardia that was associated with hypomagnesemia and did not require treatment with conventional antiarrhythmic medications. We discuss the possible underlying pathophysiologic causes of this condition.