Cardiac Dysfunction, Congestion and Loop Diuretics: their Relationship to Prognosis in Heart Failure
The relationship of QRS morphology with cardiac structure and function in patients with heart failure is uncertain. Patients with a clinical diagnosis of heart failure and objective evidence of cardiac dysfunction [either a left ventricular ejection fraction (LVEF) <50 % or an amino-terminal pro-brain natriuretic peptide (NT-proBNP) ≥400 pg/ml] who had been investigated by cardiac magnetic resonance imaging (CMRI) were identified. QRS duration ≥120 ms was grouped morphologically as left (LBBB), right bundle branch block (RBBB) or indeterminate. Of 877 patients, 320 (36 %) had QRS ≥ 120 ms. Compared to patients with LBBB, those with RBBB had a lower median [inter-quartile range (IQR)] right ventricular (RV) ejection fraction [RBBB: 46 (37–57); LBBB: 52 (42–61) %; p = 0.014], greater median (IQR) RV mass [RBBB: 53 (42–73); LBBB: 45 (36–56) g; p < 0.001], higher median (IQR) plasma NT-proBNP [RBBB: 2013 (659–3573); LBBB: 1159 (589–2207) pg/ml, p = 0.026], more signs of peripheral congestion and higher prevalence of atrial fibrillation but had similar LVEF. During a median follow-up of 1302 days (IQR: 742–2237), 311 patients died. Compared with patients who had QRS < 120 ms, those with RBBB [HR 1.98, 95 % CI (1.37–2.86); p < 0.001] had a higher mortality. Age and NT-proBNP were the strongest independent predictors of mortality; neither QRS nor CMRI variables improved prediction. In patients with heart failure and QRS ≥ 120 ms, RBBB is associated with more severe RV dysfunction and congestion and a worse prognosis. However, neither QRS morphology nor CMRI data provide independent prognostic information in a multivariable analysis including NT-proBNP.