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Effect of Posterolateral Scar Tissue on Clinical and Echocardiographic Improvement After Cardiac Resynchronization Therapy
Background— Currently, one third of patients treated with cardiac resynchronization therapy (CRT) do not respond. Nonresponse to CRT may be explained by the presence of scar tissue in the posterolateral left ventricular (LV) segments, which may result in ineffective LV pacing and inadequate LV resynchronization. In the present study, the relationship between transmural posterolateral scar tissue and response to CRT was evaluated.
Methods and Results— Forty consecutive patients with end-stage heart failure (NYHA class III/IV), LV ejection fraction 35%, QRS duration >120 ms, left bundle-branch block, and chronic coronary artery disease were included. The localization and transmurality of scar tissue were evaluated with contrast-enhanced MRI. Next, LV dyssynchrony was assessed at baseline and immediately after implantation with tissue Doppler imaging. Clinical parameters, LV volumes, and LV ejection fraction were assessed at baseline and at a 6-month follow-up. Fourteen patients (35%) had a transmural (>50% of LV wall thickness) posterolateral scar. In contrast to patients without posterolateral scar tissue, these patients showed a low response rate (14% versus 81%; P<0.05) and did not show improvement in clinical or echocardiographic parameters. In addition, LV dyssynchrony remained unchanged after CRT implantation (84±46 versus 78±41 ms; P=NS). Patients without posterolateral scar tissue and severe baseline dyssynchrony ( 65 ms) showed an excellent response rate of 95% compared with patients with a posterolateral scar and/or absent LV dyssynchrony (11%).
Conclusions— CRT does not reduce LV dyssynchrony in patients with transmural scar tissue in the posterolateral LV segments, resulting in clinical and echocardiographic nonresponse to CRT.

后侧壁瘢痕组织对心脏再同步化治疗后临床和超声心动图改善的影响

背景 目前，有三分之一接受心脏再同步化治疗（CRT）的患者病情没有得到改善。其原因可能是左室（LV）后侧壁存在瘢痕组织，导致LV无效起搏和再同步化不充分。本研究旨在评价后侧壁透壁性瘢痕组织与CRT疗效的关系。

方法和结果 40例合并有终末期心力衰竭（NYHA分级Ⅲ－Ⅳ）、LV射血分数≤35％、QRS时限>120ms、左束支传导阻滞和慢性冠状动脉疾病的患者纳入本研究。首先采用对比增强MRI明确瘢痕组织的定位和透壁性，然后以组织多普勒成像技术于基线水平和植入起搏器后即刻评价LV失同步。对患者基线水平和随访6个月后的临床指标、LV容量、LV射血分数进行评估。共有14例患者（35％）伴透壁性（>左室壁厚度的50％）后侧壁瘢痕组织。与没有透壁性瘢痕组织的患者相比，这些患者CRT的有效率较低（14% 对 81%; P<0.05)，临床和超声心动图指标均无改善，CRT后LV失同步亦无改变（86±46对78±41ms；P值无统计学意义）。与伴后侧壁瘢痕组织有/或无左室失同步（11％）的患者相比，不伴后侧壁瘢痕组织和严重失同步（≥65ms）的患者显示出95％的较高有效率。

结论 CRT不能减轻伴有左室后侧壁瘢痕组织者的LV失同步，这部分患者行CRT后临床和超声心动图均无改善。