Vectorcardiographic QRS Area Identifies Delayed Left Ventricular Lateral Wall Activation Determined by Electroanatomic Mapping in Candidates for Cardiac Resynchronization Therapy

Background: Delayed left ventricular (LV) lateral wall (LVLW) activation is considered the electrical substrate underlying LV dysfunction amenable to cardiac resynchronization therapy (CRT).

Objective: The purpose of this study was to assess LVLW activation in CRT candidates using coronary venous electroanatomic mapping (EAM) and to investigate whether the QRS area (QRSAREA) on the vectorcardiogram (VCG) can identify delayed LVLW activation.

Methods: Fifty-one consecutive CRT candidates (29 left bundle branch block [LBBB], 15 intraventricular conduction delay [IVCD], 7 right bundle branch block [RBBB]) underwent intraprocedural coronary venous EAM using EnSite NavX. VCGs were constructed from preprocedural digital 12-lead ECGs using the Kors method. QRSAREA was assessed and compared to QRS duration and 5 different LBBB definitions.

Results: Delayed LVLW activation (activation time >75% of QRS duration) occurred in 38 of 51 patients (29/29 LBBB, 8/15 IVCD, 1/7 RBBB). QRSAREA was larger in patients with than in patients without delayed LVLW activation (108 ± 42 µVs vs 51 ± 27 µVs, P < .001), and identified delayed LVLW activation better than QRS duration (area under the curve 0.89 [95% confidence interval 0.79-0.99] vs 0.49 [95% confidence interval 0.33-0.65]). QRSAREA >69 µVs diagnosed delayed LVLW activation with a higher sum of sensitivity (87%) and specificity (92%) than any of the LBBB definitions. Of the different LBBB definitions, the European Society of Cardiology textbook definition performed best with sensitivity of 76% and specificity of 100%.

Conclusion: Coronary venous EAM can be used during CRT implantation to determine the presence of delayed LVLW activation. QRSAREA is a noninvasive alternative for intracardiac measurements of electrical activation, which identifies delayed LVLW activation better than QRS duration and LBBB morphology.