Predictive Value of QRS Complex Morphology in Treatment Response to Cardiac Resynchronization

Abstract

Background: Cardiac resynchronization therapy (CRT) is the standard treatment for end-stage heart failure (HF) patients who do not respond to medication. Widening, fragmentation, and notching of the QRS complex can be markers of ventricular dyssynchrony and response to CRT. Some patients with left bundle branch block (LBBB) exhibit marked notching in the electrocardiogram, while others do not. Objectives: The present study investigated the prediction of CRT treatment response using QRS complex morphology. Methods: Ninety-nine HF patients who volunteered for CRT were studied in 2015. The patients’ New York Heart Association (NYHA) functional class, left ventricular ejection fraction (LVEF), and end-systolic volume (LVESV) were measured by echocardiography before CRT placement. Based on the electrocardiogram, patients with two or more R waves or a notch on R or S waves in at least two consecutive leads were considered to have a notched QRS complex (nQRS), while those without a notch were considered to have a smooth QRS complex (sQRS). Six months after CRT placement, patients were reassessed. An echocardiographic response was defined as a 5% increase in LVEF or a 15% decrease in LVESV, and a clinical response was regarded as a one-class improvement in NYHA class. Results: The LVESV was significantly greater in the sQRS group before CRT insertion (P = 0.02). After CRT implantation, however, there was no longer a statistically significant difference in LVEF, LVESV, and clinical response (NYHA) between the nQRS and sQRS groups (P = 0.87, 0.27, and 0.89, respectively). Conclusions: The results of the present study indicated that there was no significant relationship between the presence of a notch in the QRS complex of HF patients and the rate of response to CRT based on clinical and echocardiographic responses. Their electrocardiographic characteristics should not be used as criteria for selecting patients for CRT, but CRT could be recommended to all LBBB HF patients.