QRS Fragmentation Outcome in Patients Receiving Cardiac Resynchronization Therapy

Background: Myocardial scar causes heterogeneous ventricular activation, which results in the fragmentation of QRS (f-QRS) com- plexes. Objectives: The current study aimed to investigate the clinical and echocardiographic benefits of cardiac resynchronization therapy (CRT) implantation in patients with f-QRS versus the patients without it. Patients and Methods: Eighty patients (40 with and 40 without f-QRS) who underwent CRT were enrolled and followed up for six months. The two groups were compared for the functional class, quality of life, echocardiography indices, arrhythmia burden, recur- rent hospitalization and mortality before and after CRT implantation. Results: The mean baseline left ventricular ejection fraction (LVEF), left ventricular end diastolic dimension (LVEDD) and left ventricular end systolic dimension (LVESD) in both groups were not dierent (P > 0.05). Improvements were observed in LVESD, LVEDD and LVEF in patients without f-QRS after CRT (P = 0.003). The functional class and mitral regurgitation (MR) severity improved in both groups. Before implantation, 36 (45%) and 27 (33.8%) patients had mild and moderate MR, respectively. Six months post implantation, 41 (51%) (17 cases with f-QRS) and 20 (25%) (11 cases with f-QRS) patients had mild and moderate MR, respectively (P = 0.003). Improvements in the MR severity and functional class were observed in both groups. Conclusions: Regarding LVEF, LVESD, and LVEDD, a significant dierence was observed in patients without f-QRS after CRT implantation 1. Background Electrical dyssynchrony is present when a wide QRS is evident on electrocardiography (ECG). In a subset of pa- tients with heart failure (HF) and reduced left ventricular ejection fraction (LVEF), this dyssynchrony contributes to the pathophysiology of HF and is associated with negative remodeling and increased risk of clinical events, including mortality. In the majority of HF patients with evidence of dyssynchrony, cardiac resynchronization therapy (CRT) re- stores the appropriate timing of the cardiac contraction and thereby not only reduces cellular, hemodynamic and structural maladaptations of dyssynchrony, but also ulti- mately improves functional status, decreases hospitaliza- tion, and increases survival. Slurring and changes in the morphology of the QRS complex are investigated since the 1960s. Das et al. (1) demonstrated that the presence of fragmented QRS (f- QRS) complexes was more common among patients with prior myocardial infarction and among patients with ei- ther right or left ventricular (LV) enlargement. The f-QRS, in particular late potentials, is investigated as a possi- ble new tool to identify the high-risk cardiac population. Upon the analysis of the data obtained from an epicar- dial and endocardial mapping of the patients undergoing LV aneurysm incision, Pietrasik (2) demonstrated that a fragmented electrical activity was present in all patients with LV aneurysms. However, the patients with ventricu- lar tachycardia had the fragmented electrical activity from a larger proportion of the endocardial border zone and had more prolonged electrogram in this zone than pa- tients without ventricular tachycardia. It was proposed that the endocardial electrical activity mapping and detec- tion of the fragmented activity was a useful tool for surgi- cally guided therapy in ventricular aneurysm and ventric- ular tachycardia (3).