PE-454609-1 MYOCARDIAL WORK IN VENTRICULAR PREEXCITATION

Abstract

Ventricular preexcitation alters the electromechanical activation sequence and may induce left ventricular (LV) contractile discoordination and pathologic remodelling in selected cases. To evaluate LV myocardial work before and after accessory pathway (AP) ablation in patients with WPW preexcitation and to compare them to normal controls. Mechanical activation mapping and myocardial work calculation was performed in 11 pediatric patients with the WPW syndrome/pattern and left sided or paraseptal APs undergoing catheter ablation (successful in 10/11) and 8 healthy age-matched controls using speckle tracking echocardiography and the GE ECHOPAC version 204.57.0.745 software with the integrated AFI module. An 18-segmental echocardiographic LV model was used. Global LV myocardial work efficiency (GWE) was calculated as the ratio of global constructive work to the sum of global constructive and global wasted work (GWW). The time from delta wave onset to R wave peak in lead V6 (delta to R) was used to quantify the degree of preexcitation. Before ablation GWW was higher (164 vs 102 mmHg%, P=0.015) and GWE lower (median 91 vs 94%, P=0.010) in patients vs controls. After successful ablation GWW decreased from 164 to 93 mmHg% (P=0.006) and GWE increased from 91.1 to 94.0 % (P=0.006). GWE tended to correlate negatively with the delta to R interval (R=0.59, P=0.056). Before ablation, segmental WE increased with distance from ventricular AP insertion from median 69.5 % at AP location to 98.0 % in distant segments (P<0.001). After ablation, WE was equally distributed among LV segments (Figure). Mechanical activation mapping localized APs with a median (IQR) segmental distance of 0 (0-1) segments from the EP mapped location. Ventricular preexcitation induces significant LV myocardial work inefficiency in segments adjacent to AP which correlates with the degree of preexcitation and is normalized after ablation. The amount of wasted work in asymptomatic preexcitation may be considered when assessing the potential for pathologic LV remodelling or discussing the indication for prophylactic ablation. Mechanical activation mapping may be used to localize manifest APs.