Experimental right ventriculotomy: effects on local propagation at a small size scale.

Repair of tetralogy of Fallot and ventricular septal defect frequently requires righ ventriculotomy. Although the mechanisms for right bundle branch block (RBBB) have been frequently discussed, the pathogenesis of this electrocardiographic abnormality is still unknown. To determine if disruption of the distal subendocardial Purkinje fiber network in the right ventricular free wall produced RBBB and if cellular electrophysiologic abnormalities in or near the ventriculotomy scar could provide a substrate for conductance disturbances, we investigated the electrocardiographic and electrophysiologic effects of experimental right ventriculotomy in 12 beagles. On the surface electrocardiogram no significant differences in QRS duration (lead II) or morphology were apparent between the control group (n = 6) and the postventriculotomy animals (n = 6) (QRS duration = 34 +/- 4 versus 34 +/- 7 ms, respectively). Using microelectrode techniques, the right ventricular endocardial surface was carefully mapped. To facilitate analysis, data were grouped into five regions: outflow septum, outflow free wall, inflow free wall, and ventriculotomy region. No significant delays of regional activation were noted in the postventriculotomy group compared to the control group: outflow septum--30 +/- 16 versus 36 +/- 16 ms; outflow free wall--33 +/- 10 versus 38 +/- 19 ms, inflow septum--32 +/- 7 versus 33 +/- 13 ms, inflow free wall--35 +/- 11 versus 35 +/- 22 ms, and ventriculotomy region--32 +/- 10 versus 31 +/- 16 ms, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)