Electrophysiological effects of quinidine alone and of the combination quinidine‐verapamil on av conduction in humans

Abstract

Summary:The influence of 320 mg quinidine administered intravenously (i.v.), as well as subsequent administration of 5 mg verapamil i.v. on atrioventricular conduction was studied in 8 patients during sinus rhythm and atrial stimulation with the aid of His bundle electrography. Among the electrophysiologic parameters of the atrium the sinus rate increased significantly after quinidine and again increased slightly after subsequent administration of verapamil. During sinus rhythm the PA interval was not influenced by either substance. Conversely, during atrial stimulation the STA interval increased significantly under the effect of quinidine, while verapamil had no further influence. As an indicator of conduction time in the AV node, the AH interval was decreased significantly by quinidine during sinus rhythm and atrial stimulation. This effect was significantly counteracted by the additional administration of verapamil. The HV interval as a measure of the His-Purkinje conduction was not significantly affected. The QRS duration was increased significantly by quinidine and was not further influenced by verapamil. The QT, and QT intervals increased significantly after administration .of quinidine and were again slightly, but significantly shortened by verapamil. Our investigations show that the combination of quinidine and verapamil, which has clinically been found to have a higher conversion rate than quinidine alone, is well justified from an electrophysiologic point of view and that undesirable quinidine-related effects, such as rapid AV conduction in cases of atrial fibrillation and flutter, can be avoided by the subsequent administration of verapamil.

Effect of Verapamil Enantiomers and Metabolites on Cardiac K⁺ Channels Expressed in <i>Xenopus</i> Oocytes

“…Whereas in some studies prolongation of the Q-T C interval has been observed, other studies failed to confirm these findings [34][35][36]. The results of our experiments could explain these controversial findings.…”

Drug-drug interactions and QT prolongation as a commonly assessed cardiac effect - comprehensive overview of clinical trials

“…On the contrary, subsequent administration of verapamil may have a protective effect against quinidine-related TdP arrhythmia. In the study described by Theisen and Scheininger [ 35 ] verapamil i.v. was shown to slightly (10 ms) but significantly shorten prolonged QTc interval supervene as a result of quinidine i.v.…”

In Silico Assessment of Class I Antiarrhythmic Drug Effects on Pitx2-Induced Atrial Fibrillation: Insights from Populations of Electrophysiological Models of Human Atrial Cells and Tissues

“…By slowing the rate of atrial flutter/fibrillation, quinidine can decrease the degree of atrioventricular blocking and cause an increase, sometimes marked, in the rate at which supraventricular impulses are successfully conducted by the atrioventricular node, with a resultant paradoxical increase in ventricular rate [104]. The previous study showed that quinidine causes greater QT prolongation in women than in men at equivalent serum concentrations.…”