To evaluate the electrophysiologic changes in the cardiac conduction system that occur during percutaneous mitral or aortic balloon valvotomy, we prospectively studied the conduction system in 19 patients (10 mitral, 8 aortic, and 1 both) undergoing this procedure. A His bundle electrogram was recorded in all patients, and when sinus rhythm was present, the atrioventricular (AV) node effective refractory period was measured. Holter monitoring was performed during and for 24 hours after the procedure. Follow-up electrocardiograms (ECG) were available in 11 patients 2.3 ± 1.5 months after the procedure. The AV node effective refractory period before (276 ± 86 msec) and after valvotomy (298 ± 85 msec) were not significantly different. The maximum His-Purkinje conduction time (HV interval) observed during valvotomy (66 ± 20 msec) was significantly longer (p < 0.01) than that measured before (57 ± 10 msec) or after (60 ± 18 msec) valvotomy. The mean HV intervals before and after valvotomy were not significantly different. The mean QRS complex duration increased from 95 ± 28 to 112 ± 28 msec during valvotomy and remained significantly prolonged (109 ± 26 msec) 24 hours after the procedure (p < 0.01). A new intraventricular conduction defect (QRS complex duration > 100 msec) or bundle branch block occurred in five of 13 patients who had normal QRS duration before the procedure. The change in HV interval did not correlate with the change in QRS complex duration. In four patients, the newly acquired intraventricular conduction defect was still present on follow-up ECG tracing. Complete heart block was not observed in any patient. Age, New York Heart Association functional classification, coronary artery disease, the valve dilated, annular area, effective balloon dilating area, change in valve area, and use of digoxin did not correlate with the change in HV interval or QRS complex duration by multiple regression analysis. Analysis of ECG data in a much larger group of 207 patients undergoing percutaneous mitral and aortic balloon valvotomy showed an 18% incidence of new-onset intraventricular conduction defect after valvotomy.
Carlson, M. D., Palacios, I., Thomas, J. D., Rottman, J. N., Freeman, C. S., Block, P. C., … Garan, H. (1989). Cardiac conduction abnormalities during percutaneous balloon mitral or aortic valvotomy. Circulation, 79(6), 1197–1203. https://doi.org/10.1161/01.CIR.79.6.1197