Determinants of QRS duration in a diverse cardiomyopathy population of the Western Cape : implications for eligibility for cardiac resynchronization therapy

Abstract

Background Cardiac resynchronization therapy (CRT) improves quality of life in heart failure patients who have a QRS duration ≥120 ms. Relatively few patients presenting with heart failure to the Division of Cardiology at Tygerberg Hospital are candidates for CRT, mainly because of a QRS duration <120 ms. Objectives The objectives of this study were to determine the QRS duration in a diverse cardiomyopathy population served by Tygerberg Hospital and to identify possible determinants of QRS duration in this cardiomyopathy population. Method Approval for this study was obtained from Stellenbosch University Health Research Ethical Committee and Tygerberg Hospital and all patients signed informed consent. Patients with a left ventricular systolic function (LVEF) <35% were recruited prospectively from the cardiac clinic. LVEF was determined by echocardiography using Simpson’s biplane method. QRS duration was measured on a standard 12 lead ECG. Results Two hundred patients were included. The mean age was 52 years (range 18-84). Self identified ethnicity revealed 63% coloured, 22% black and 15% white patients. The mean QRS width was 105 ms. On univariate analysis, parameters associated with a QRS width ≥120 ms included: ethnicity (White >Coloured >Black) (p = 0.01), ischaemic heart disease (<0.01), age (<0.01), left ventricular size (p = 0.03) and male gender (p = 0.05). After correcting for covariates in a multivariate analysis, ethnicity and sex were no longer predictive of a broad QRS. Conclusion Although it appeared on first evaluation that there was a gender and ethnic disparity in candidates for CRT, multivariate analysis revealed that this is more likely due to differences in age, ischaemic aetiology and LV size.