Distinctive Left Ventricular Activations Associated With ECG Pattern in Heart Failure Patients
Résumé
T he deleterious impact of abnormal left ventricular (LV) activation in heart failure (HF) is well established. 1 Cardiac resynchronization therapy (CRT) represents a highly effective intervention in selected patients with HF and abnormal LV activation. The QRS pattern emerged as a more specific selection criterion in the latest American Heart Association (AHA)/European Heart Rhythm Association guidelines. These recommendations are based on multiple subgroup analyses demonstrating a clear benefit to CRT depending on the preim-plantation QRS pattern. 2-4 Therefore, patients with baseline left bundle branch block (LBBB) have a class I indication for CRT implantation and represent the best responders to CRT. Patients with narrow QRS currently have a class III indication for CRT as a result of large trial, demonstrating that CRT has a neutral or deleterious effect in this group of patients. 5-8 In patients with nonspecific intraventricular conduction delay (NICD), the guidelines are less clear, with a class IIa or IIb indication depending on the QRS duration. These patients represent a more heterogeneous group that is not clearly characterized. Its definition wide QRS without the appearance of left or right bundle block corresponds to a definition by default. Results obtained after CRT include only small numbers of patients, with no dedicated randomized studies. 9-11 The electrophysiological mechanisms of lack of response in narrow QRS and NICD are not well understood. The use of a more detailed electric activation map rather than QRS analysis could significantly enhance our understanding of the electric activation sequence in HF patients, especially in narrow QRS and NICD patients and, therefore, refine selection criteria for CRT. Original Article Background-In contrast to patients with left bundle branch block (LBBB), heart failure patients with narrow QRS and nonspecific intraventricular conduction delay (NICD) display a relatively limited response to cardiac resynchronization therapy. We sought to compare left ventricular (LV) activation patterns in heart failure patients with narrow QRS and NICD to patients with LBBB using high-density electroanatomic activation maps. Methods and Results-Fifty-two heart failure patients (narrow QRS [n=18], LBBB [n=11], NICD [n=23]) underwent 3-dimensional electroanatomic mapping with a high density of mapping points (387±349 LV). Adjunctive scar imaging was available in 37 (71%) patients and was analyzed in relation to activation maps. LBBB patients typically demonstrated (1) a single LV breakthrough at the septum (38±15 ms post-QRS onset); (2) prolonged right-to-left transseptal activation with absence of direct LV Purkinje activity; (3) homogeneous propagation within the LV cavity; and (4) latest activation at the basal lateral LV. In comparison, both NICD and narrow QRS patients demonstrated (1) multiple LV breakthroughs along the posterior or anterior fascicles: narrow QRS versus LBBB, 5±2 versus 1±1; P=0.0004; NICD versus LBBB, 4±2 versus 1±1; P=0.001); (2) evidence of early/pre-QRS LV electrograms with Purkinje potentials; (3) rapid propagation in narrow QRS patients and more heterogeneous propagation in NICD patients; and (4) presence of limited areas of late activation associated with LV scar with high interindividual heterogeneity. Conclusions-In contrast to LBBB patients, narrow QRS and NICD patients are characterized by distinct mechanisms of LV activation, which may predict poor response to cardiac resynchronization therapy.
Origine : Publication financée par une institution
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