Fragmented narrow QRS complex: Predictor of left ventricular dyssynchrony in non-ischemic dilated cardiomyopathy

BACKGROUND: Cardiac resynchronization therapy is an important therapeutic modality in drug refractory symptomatic patients of heart failure with wide QRS (≥120 ms) on electrocardiogram. However, wide QRS (considered as a marker of electrical dyssynchrony) occurs in only 30% of heart failure patients, making majority of drug refractory heart failure patients ineligible for resynchronization therapy. Significant numbers of patients with narrow QRS have echocardiographic evidence of left ventricular dyssynchrony. However, there is sparse data about additional features on the surface ECG which can predict intraventricular dyssynchrony. This study was undertaken to assess the utility of fragmented narrow QRS complex to predict significant intraventricular dyssynchrony in symptomatic patients of non-ischemic dilated cardiomyopathy. METHOD: 100 symptomatic patients of non-ischemic dilated cardiomyopathy with narrow QRS complexes (50 each with fragmented and normal QRS) were recruited. Tissue Doppler imaging was used to assess intraventricular dyssynchrony as per 'Yu index'. RESULTS: 78% patients (n = 39) in fQRS complex group and 14% (n = 7) in normal QRS complex group had significant intraventricular dyssynchrony (χ(2) = 20.61; p < 0.000005). fQRS complexes had 84.78% sensitivity, 79.62% specificity, a positive predictive value of 78% and negative predictive value of 86% to detect intraventricular dyssynchrony. fQRS also had sensitivity and specificity of 93% and 90% respectively to localize the dyssynchronous segment. CONCLUSION: fQRS is a marker of electrical dyssynchrony, which results in significant intraventricular dyssynchrony in patients of non-ischemic dilated cardiomyopathy and a narrow QRS interval. fQRS localizes the dyssynchronous segment and might be useful in identifying patients who can benefit from cardiac resynchronization therapy.