Effect of changing left ventricular afterload and isolated perfused rabbit heart on ventricular refractory period measured by subthreshold conditioning train stimulation

AIM: To study the effect of changing left ventricular afterload and isolated perfused rabbit heart on ventricular refractory period measured by subthreshold conditioning train stimulation (S_t). METHODS: Ventricular refractory period strength-interval relation was measured by S_t method under the condition of changing left ventricular afterload and eliminating action of nervous and body fluid. RESULTS: Reducing left ventricular afterload pro- longed ventricular refractory period measured by S_t method (P＜0.05, P＜0.01). and S_t (200 Hz,100 ms) and S_t (50 ms,100 Hz) caused maximal prolongation of ventricular refractory period (P＜0.05, P＜0.01). CONCLUSION: Changing left ventricular afterload and eliminating action of nervous and body fluid could cause alteration of characteristic of ventricular refractory period strength-interval relation measured by S_t method.