Impact of Left Bundle Branch Block on Left Ventricular Mechanics in Patients with Idiopathic Dilated Cardiomyopathy

Objectives: Left bundle branch block (LBBB) is commonly associated with heart failure. We evaluated the prevalence and impact of LBBB on left ventricular mechanics using 2D strain imaging in patients with idiopathic dilated cardiomyopathy (IDCM). Methods: We included 101 patients with IDCM with mean age 38 ± 18 years: 74% were males and 13.9% of them were in NYHA Class III-IV. LBBB was present in 26 (37%) of included patients. Myocardial mechanics including longitudinal, circumferential strain and rotation and LV synchronization were assessed using two-dimensional strain imaging. Results: LBBB group had higher LV volumes, and PAP compared with non LBBB. Peak LV longitudinal systolic strain (εsys) of the septum and global LV SRsys were significantly lower in LBBB compared to non LBBB group (P 0.01, 0.03). TTP-d was greater in LBBB in comparison to non LBBB group (274.5 ± 116 versus 209.4 ± 139, P 0.02). The electromechanical delay between septal segments was 35 ± 18 ms and between lateral wall segments: 48 ± 24 ms, between anterior wall segments: 21 ± 11 and between inferior wall segments: 41 ± 12. Consequently, LV mechanical dyssynchrony was more evident in IDCM patients with LBBB. QRS width was correlated inversely with LV longitudinal strain and strain rate and electromechanical delay (P 0.0001) in non LBBB group. In LBBB QRS width was not related to cardiac mechanics. Using univariate analysis and after a multiple covariate adjustment, the baseline LBBB was associated with a significantly increased LV dysfunction. Conclusion:After correcting for potential confounders, LBBB was found to be associated with more deterioration of LV mechanics and exaggerated LV dyssynchrony in patients with IDCM.

Right Ventricular Mechanical Changes after Septal Myectomy for Obstructive Hypertrophic Cardiomyopathy: Vector Velocity Imaging Study

Objectives: The impairment of right ventricular (RV) myocardial mechanics is evident in hypertrophic cardiomyopathy (HCM). It is independently influenced by LV mechanics and correlated to the severity of LV phenotype. We investigated the changes in RV global and regional deformation following surgical septal myectomy using vector velocity imaging (VVI). Methods: 25 HCM patients, 68% males with mean age (34.5 ± 12 years) were examined before and within two months after surgical myectomy using VVI. In addition to conventional echocardiographic parameters, peak systolic strain (εsys), strain rate (SR) and time to peak εsys (TTP) of regional RV free wall (RVFW) & septal walls were analyzed in longitudinal (long) directions from apical four-chamber view and their (Δ) changes were calculated. Similar parameters were quantified in LV from apical 2 & 4 CH views. Intra-V-delay was defined as SD of TTP and inter-V dyssynchrony was estimated from TTP difference between the most delayed LV segment & RVFW. Results: All study patients showed improvement of their functional class from NYHA class III to class I and reduction of LVOT gradient to below 20 mmHg except one patient who had 30 mmHg gradients at rest. There was significant reduction of septal thickness, left atrial diameter & volume, LVOT gradient, LVMI, severity of mitral regurgitation, tricuspid annular velocities (P < 0.0001), RV diameter (P < 0.02) and increase in LV internal dimensions(P < 0.001) post myectomy. However, there was significant reduction of RV and LV systolic mechanics;RV global εsys % (from -16.1% ± 4.4% to -12.9% ± 2.9%, P < 0.0001) and LV global εsys %: from -11.6% ± 2.8% to -9.4% ± 2.2%, P < 0.0001) respectively. The magnitude of reduction of RV strain (ΔRV εsys %, ΔSRsys) was directly correlated LV maximal wall thickness (r = 0.46, P < 0.01) and ΔRV dyssynchrony (TTP-SD) (r = 0.4, P < 0.05) and negatively correlated to age (r = -0.46, P sys (r = -0.52, P < 0.01) and pre-op LV EF % (r = -0.43, P , the reduction in RV diastolic mechanics: ΔRV SRe & SRa were directly correlated to PAP and LVOT gradient before surgery (r = 0.62, P Conclusion: Despite the improvement of patient functional status and reduction LVOT gradient, RV mechanics shows further deterioration after surgical myectomy. The magnitude of reduction is modestly related to cardiac phenotype and pre-op mechanical function.