Subthreshold stimulation of Purkinje fibers interrupts ventricular tachycardia in intact hearts. Experimental study with voltage-sensitive dyes and imaging techniques.

摘要: The effects of subthreshold stimulation (STS) delivered during right atrial pacing and ventricular tachycardia (VT) were investigated in Langendorff-perfused guinea pig hearts. hearts stained with a voltage-sensitive dye (RH 421) to map the propagation optical action potentials. Sustained VT was reliably induced by 5-second trains (cycle length [CL], 25 50 milliseconds; duration, 0.5 10 voltage, 2x threshold voltage) impulses (n = 12 hearts) or single premature beat 6). location extrastimuli not critical induction VT, but diameter heart had be > 14.5 mm. During rate increased from 200 600 beats per minute; potential durations decreased 112 175 milliseconds 60 105 milliseconds, no diastolic interval. Activation on epicardium spread anisotropically, "apparent" maximum conduction velocity (theta max) 68% altered orientation major axis beat. patterns theta max measured similar recorded direct ventricle indicated that Purkinje fibers longer propelled excitation. STS (CL, 0.5x 0.8x threshold; 2.0 2.5 seconds) interrupted when applied lining endocardium 6) failed interrupt 8). In pacing, 2.44 +/- 0.32 (mean SEM) 3.63 0.21 m/s local region surrounding first activation sites 4). Alternatively, could terminated reducing (approximately 55%) procainamide (10 mumol/L) terminates synchronizing excitation most likely increasing and/or improving coupling between cells.