Spectral and correlation analyses of the verapamil-induced conversion of ventricular fibrillation to tachycardia in isolated rat hearts

Prognostic benefits of prior amiodarone or β-blocker use before the onset of ventricular arrhythmia with hemodynamic collapse

Although antiarrhythmic drugs have long been used for the suppression of various types of arrhythmias, their prior use before the onset of ventricular arrhythmia with hemodynamic collapse and the effect on prognosis is not well known. Data from 1004 consecutive patients with cardiovascular shock in the Japanese Circulation Society's Shock Registry were analyzed. Eighty-four cases of ventricular arrhythmia-induced shock and ROSC (return of spontaneous circulation) were divided into the prior amiodarone or β-blockers use group (Aβ group, n = 27) and the non-amiodarone and non-β-blockers use group (non-Aβ group; n = 57) based on treatment before the onset of those arrhythmias. Clinical outcomes related to hemodynamic collapse such as OHCA (out-of-hospital cardiovascular arrest) was less in the Aβ group [Aβ group, 11/26 (42%) vs. non-Aβ group, 41/56 (73%); p = 0.007]. Similarly, syncope was less common in the Aβ group than in the non-Aβ group [Aβ group 4/27 (15%) vs. non-Aβ group 27/57 (47%); p = 0.004]. Furthermore, prior amiodarone or β-blockers use before the onset of ventricular arrhythmias was strongly associated with both survival at discharge (odds ratio 3.19; 95% confidence interval 1.06-9.67; p = 0.040) and neurological outcomes at discharge (odds ratio 3.96; 95% confidence interval 1.32-11.85; p = 0.014) based on multivariate logistic regression analysis. Prior amiodarone or β-blockers use before the onset of malignant ventricular arrhythmia and maintaining appropriate blood concentrations in advance is associated with a good survival rate and better neurological outcomes after recovery from ventricular arrhythmia with hemodynamic collapse.

On the mechanisms for the conversion of ventricular fibrillation to tachycardia by perfusion with ruthenium red

We have recently demonstrated that during pacing-induced sustained ventricular fibrillation (VF), perfusion of the heart with either ruthenium red (RR) or Ru 360, blockers of the mitochondrial Ca2+ uniporter, resulted in the reversible conversion of VF to ventricular tachycardia (VT). Here, we aimed at elucidating the electrophysiological mechanisms for the RR-induced conversion of VF to VT. The experiments were performed using Langendorff-perfused isolated rat hearts in which left ventricular pressure and left ventricular intracellular action potential were recorded. Perfusion with either RR or Ru 360 resulted in decreases in the action potential duration (APD), refractory period, and slope of APD restitution curves. These changes were antagonized by cotreatment with S(-)-Bay K8644. In addition, perfusion with verapamil produced the decreases in APD at 90% repolarization, refractory period and slope of APD restitution curves similar to the RR or Ru 360 perfusion. Such electrophysiological changes may be responsible for the reversible conversion of sustained VF to VT caused by perfusion with RR or Ru 360.