167 EXERCISE-INDUCED VENTRICULAR ECTOPY IN COMPLETE HEART BLOCK

Abstract

Twenty-four patients(pts)with complete heart block(CHB), ages 3 to 29 years(mean 17), underwent graded maximal treadmill exercise tests. Leads II, AVF and V5 were recorded continuously for 3 minutes prior to, during and 15 minutes following exercise. Fifty normal children and young adults served as controls. Of 24 pts with CHB, 16(67%)developed Lown grade 2(frequent premature ventricular contractions(PVC)or higher ventricular ectopic activity(VEA)on effort; 2(8%)of these also had VEA at rest. None of the controls had resting VEA and in only one(2%)was it elicited by exercise (p < 0.001). Among 13 pts with CHB without associated heart disease(NHD), none had VEA at rest; 9(69%)had VEA on effort. VEA was elicited in 4/7(57%)pts with CHB and associated cardiac defects(HD)and in 1/4(25%) with surgically(S)induced CHB. Of 8 pts with QRS width > 0.10 seconds(3 NHD, 2 HD, 2 S), 7 (88%)developed severe VEA, Lown grade 3(multifocal PVC) or higher; 2/8 of these(25%)had severe VEA at rest. Of the 16 pts with QRS ≤ 0.10, none had severe VEA at rest and it was induced in 4 (25%) (p=0.005). Unsuspected significant VEA was elicited by exercise testing in a majority of pts with CHB, most pronounced in those with QRS widening. We think that VEA may represent a threat to the lives of some CHB pts, and recommend exercise testing in pts with CHB, including those without associated defects.