[Electrophysiologic and hemodynamic effects of the new bradycardia-inducing substance AQ-A 39].

AQ-A 39 is a new agent with specific bradycardic action on the sinus node. In this study the electrophysiologic and hemodynamic effects of this compound were investigated in 24 patients with various cardiac diseases. The results show: AQ-A 39 causes a significant decrease in enhanced sinus rate. The bradycardic action is more profound at higher sinus rates. In sinus rhythm of normal frequency or, in sinus bradycardia, sinus rate remains unchanged or increases even in the case of sick sinus node syndrome. Conductivity of the AV-node is significantly improved. QT- and QTc-interval increase dose dependently. Other cardiac conduction times and refractory intervals are not significantly changed. In exercise-induced myocardial ischemia increased left ventricular filling pressures are diminished. The extent of this decrease parallels the reduction in heart rate. AQ-A 39 appears to be suitable to reduce inadaequate increases in sinus rate, and seems to be of particular interest in surgical cases or intensive care emergencies as well as in acute ischemic heart disease.