Effects of propafenone on electrophysiologic changes caused by alteration of left ventricular afterload in anesthetized rabbits

AIM: To study effects of propafenone (Pro) on ventricular electrophysiologic
changes caused by alteration of left ventricular afterload of rabbit heart.
METHODS: Before and after i.v. Pro 3 mg.kg-1, changing afterload of left
ventricle (LV), occurrence of ventricular arrhythmia, left ventricular diastolic
thresholds (VDT), relative refractory period (RRP), effective refractory period
(ERP), dispersion of refractory period, and ventricular fibrillation threshold
(VFT) were recorded.
RESULTS: Increasing afterload of LV increased temporal dispersion of RRP and ERP
[from 11 +/- 4 and 6 +/- 3 ms to 18 +/- 8 and 13 +/- 8 ms (+delta P = 8.4 +/- 2.9
kPa) individually (P < 0.05)] and decreased VFT [from 5.5 +/- 1.0 V to 3.9 +/-
0.9 V (P < 0.01)]; Ventricular arrhythmia was seen in all rabbits. But reducing
left ventricular afterload did not alter the electrophysiologic parameters in LV
and did not induce ventricular arrhythmia. Pro i.v. prolonged RRP and ERP,
increased VDT and VFT (P < 0.01); Increasing or decreasing left ventricular
afterload did not cause much alteration of ventricular electrophysiologic
parameters (P > 0.05).
CONCLUSION: Pro inhibited increase of dispersion of refractory period and
decrease of VFT caused by increase of left ventricular afterload and has an
effect of anti-ventricular arrhythmia.