Magnetic resonance imaging assessment of intraventricular dyssynchrony and delayed enhancement as predictors of response to cardiac resynchronization therapy in patients with heart failure of ischaemic and non-ischaemic etiologies

Purpose: To assess the value of dyssynchrony and myocardial viability assessment by cardiac magnetic resonance (CMR) in prediction of response to cardiac resynchronization therapy (CRT) in patients with heart failure (HF) of both ischaemic and non-ischaemic etiologies.

Materials and methods: Patients scheduled for CRT in NYHA class II-IV, left ventricular ejection fraction <35%, QRS ≥ 120 ms were included. Tagged cine and late gadolinium enhancement (LGE) images were performed. Dyssynchrony was assessed with inTag toolbox and LGE was quantified using cutoff value at half of maximal signal in the scar. Cardiopulmonary exercise test, echocardiography and blood testing for NT-proBNP levels were done at baseline and 6 months after CRT.

Results: 52 patients (age 60.3 ± 13 years) were included. 26 patients (50%) met response criteria. The ischaemic etiology of HF was more frequent (69% vs. 31%, p=0.002), the percent of LGE was higher (7.7% [0-13.5%] vs. 19.0% (0-31.9%], p=0.013), regional vector of circumferential strain variance (RVV) was lower (0.27 ± 0.08 vs. 0.34 ± 0.09, p=0.009) and uniformity of radial strain was higher (0.72 ± 0.25 vs. 0.56 ± 0.29, p=0.046) in non-responders vs. responders. Multivariate logistic regression showed that RVV predicted response to CRT (HR 2.3, 95% CI 1.02-5.02, p=0.0430) independently of LGE and the etiology of heart failure. In the subgroup of patients with ischaemic HF the extend of transmural scar within myocardium was higher in non-responders vs. responders (26.3% vs. 15.0% respectively, p=0.01) and was a predictor of response to CRT in univariable analysis (HR 0.87, 95% CI 0.77-0.98, p=0.025) providing the sensitivity of 76% and specificity of 75% at the cutoff point of 18% in the prediction of poor response to CRT. In patients with non-ischaemic HF QRS was wider (162 ms vs. 140 ms, p=0.04), regional vector of strain variance (RVV) was higher (0.39 vs. 0.25, p=0.002) and uniformity of radial strain was lower (0.52 vs. 0.80, p=0.049) in non-responders vs. responders. Univariable logistic regression showed that RVV was a predictor of response to CRT (HR 1.50, 95% CI 1.06-2.13, p=0.022), providing the sensitivity of 94% and specificity of 85% at the cutoff point of 0.31.

Conclusions: CMR derived parameters of dyssynchrony such as RVV may provide an additive value in prediction of response to CRT, especially in patients with non-ischaemic etiology of heart failure. In patients with ischaemic HF the transmurality of LGE is an important predictor of lack of response to CRT.