Abstract
ABSTRACT: 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. Action potential characteristics in the ventriculotomy region of the postventriculotomy dogs were similar to a comparable region in the control animals: maximum diastolic potential—86 ± 1 versus 86 ± 2 mv, action potential amplitude—117 ± 3 versus 119 ± 3mv, maximuin velocity of phase zero upstroke—486 ± 47 versus 543 ± 48 V/s, and action potential duration to full repolarization—208 ± 10 versus 208 ± 16 ms, respectively (p = NS). We conclude that 1) ventriculotomy-induced disruption of the subendocardial Purkinje network does not produce macroscopic conduction delay and is not a mechanism of RBBB, and 2) the homogeneous scar of a right ventriculotomy, healed under low right ventricular pressure, produces few abnormalities in action potential characteristics.
Similar content being viewed by others
Article PDF
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Moak, J., Garson, A. Experimental Right Ventriculotomy: Effects on Local Propagation at a Small Size Scale. Pediatr Res 23, 433–438 (1988). https://doi.org/10.1203/00006450-198804000-00019
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1203/00006450-198804000-00019