Supraventricular tachyarrhythmias. Characteristics and care.

Physicians often see patients with supraventricular tachycardia of some kind. How does the primary care physician distinguish between a benign, bothersome condition and a life-threatening emergency? What is the proper treatment for various manifestations? Drs Lawhorn and Emmot describe these arrhythmias and their mechanisms and discuss both acute and long-term treatment options.

Therapies to limit infarct size. Timing, dosage, and effectiveness.

Rapid diagnosis of an evolving acute myocardial infarction and institution of thrombolytic therapy in appropriate patients can markedly decrease infarct size and thus reduce cardiovascular morbidity and mortality. Streptokinase (Kabikinase, Streptase) and recombinant tissue plasminogen activator (Activase) are both widely used, effective clot-dissolving agents. Patients who are not candidates for thrombolytic therapy can be treated with other methods, such as anticoagulant therapy, which can greatly reduce infarct size. Intravenous heparin, beta blockers, nitroglycerin, and aspirin have all been shown to limit infarct size, decrease mortality, or do both in patients with acute myocardial infarction.

Hemodynamic effects of dopexamine hydrochloride infusions of 48 to 72 hours' duration for severe congestive heart failure.

Dopexamine hydrochloride, a new dopaminergic derivative with potent beta 2-agonist activity, was administered to 10 patients with severe congestive heart failure. Initially, the drug was infused at increasing dosage to achieve a maximal tolerated dose and then titrated to maintain acceptable clinical parameters over the next 48 to 72 hours. Cardiac index increased significantly during the initial titration and at peak effect. Tolerance over the duration of the study was noted in most patients, although further increases in cardiac index could usually be achieved by modest increases in the infusion rate. The peak hemodynamic effect was noted at an average infusion rate of 4.8 micrograms/kg/min. Both stroke volume and stroke work indexes increased during dopexamine hydrochloride infusion in association with decreases in mean arterial, right atrial, mean pulmonary artery and pulmonary capillary wedge pressures, systemic vascular resistance and pulmonary arteriolar resistance. Cardiac output increased by 60% during the infusion and this was out of proportion to the 12% increase in heart rate at peak effect. Most of the increase in cardiac index appeared to be due to the strong vasodilatory profile of the medication producing afterload reduction, with direct inotropic and chronotropic effects contributing to a lesser degree. Drug-related side effects occurred in 4 patients and were easily controlled by down-titration. Dopexamine hydrochloride is an effective and well-tolerated sympathomimetic agent that increases cardiac index while promoting vasodilatation.

Metastatic malignant melanoma presenting clinically as obstruction of the right ventricular inflow and outflow tracts. Characterization by magnetic resonance imaging.

Metastatic disease involving the heart may present in a variety of fashions. A patient with melanoma metastatic to the right ventricle which was diagnosed clinically by evidence of recent onset of right ventricular inflow and outflow tract obstruction is described. Important information regarding the extent of the metastatic process and potential resectability of the tumor was gained by magnetic resonance imaging.