60 * Greater mechanical dyssynchrony is demonstrated by cardiac magnetic resonance cine imaging amongst heart failure patients awaiting cardiac resynchronisation therapy with strict left bundle branch block

Abstract

Introduction: The era of cardiac resynchronisation therapy (CRT) has led to improved understanding of left ventricular activation and stricter criteria have been proposed for left bundle branch block (LBBB). These criteria have shown a greater prediction for LV mechanical dyssynchrony with 2D strain echocardiography and cardiac MRI tagging. We have further tested this hypothesis using cardiac cine MRI endocardial tracking technology and also investigated the impact of this measure of mechanical dyssynchrony on CRT response rate. Methods: We investigated a total of 47 patients awaiting CRT with traditional LBBB with a cardiac MRI pre implant. Offline analysis of the cine imaging was undertaken in order to determine the endocardial volume change systolic dyssynchrony index (SDI) of 16 segments. Pre-implant ECGs were analyzed for strict LBBB (QRS ≥ 140ms for men, ≥130ms for women and mid QRS notching/slurring in ≥2 contiguous leads). Reverse remodeling was assessed at 6 months with echocardiography. Response was defined as ≥15% improvement in LV end systolic volume. Results: These patients were aged 66.1±11.7 years, 83% were male, and 45% had an ischaemic etiology. On ECG analysis 83% had strict LBBB. In the strict LBBB group the SDI was 12.3±5.2% where as in the traditional LBBB group it was 6.7±2.5% (p=0.005). Presence of an ischaemic aetiology had no impact on SDI (p=0.216). Linear regression of SDI vs. amount of remodeling (change in LVESV) generates a regression coefficient of 2.02 (p=0.01) and a correlation coefficient of R=0.49 (p=0.01). ROC analysis determines the optimum SDI cut-off for response as 10% with an area under the curve of 0.797, a sensitivity of 81% and a specificity of 79%. Conclusion: In patients with LBBB selected for CRT under current guidance the presence of strict LBBB predicts increased mechanical dyssynchrony demonstrated as SDI with cine MRI. Presence of mechanical dyssynchrony defined as an SDI ≥10% is a good predictor of volumetric response to CRT in this cohort. ![Graphic][1] [1]: /embed/inline-graphic-1.gif