Departments of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
J Cardiovasc Magn Reson. 2010 Jan 5;12(1):2. doi: 10.1186/1532-429X-12-2.
Cardiac resynchronization therapy (CRT) has been shown to decrease mortality in 60-70% of advanced heart failure patients with left bundle branch block (LBBB) and QRS duration > 120 ms. There have been intense efforts to find reproducible non-invasive parameters to predict CRT response. We hypothesized that different left ventricular contraction patterns may exist in LBBB patients with depressed systolic function and applied tagged cardiovascular magnetic resonance (CMR) to assess circumferential strain in this population.
We determined myocardial circumferential strain at the basal, mid, and apical ventricular level in 35 subjects (10 with ischemic cardiomyopathy, 15 with non-ischemic cardiomyopathy, and 10 healthy controls). Patterns of circumferential strain were analyzed. Time to peak systolic circumferential strain in each of the 6 segments in all three ventricular slices and the standard deviation of time to peak strain in the basal and mid ventricular slices were determined.
Dyskinesis of the anterior septum and the inferior septum in at least two ventricular levels was seen in 50% (5 out of 10) of LBBB patients while 30% had isolated dyskinesis of the anteroseptum, and 20% had no dyskinesis in any segments, similar to all of the non-LBBB patients and healthy controls. Peak circumferential strain shortening was significantly reduced in all cardiomyopathy patients at the mid-ventricular level (LBBB 9 +/- 6%, non-LBBB 10 +/- 4% vs. healthy 19 +/- 4%; both p < 0.0001 compared to healthy), but was similar among the LBBB and non-LBBB groups (p = 0.20). The LBBB group had significantly greater dyssynchrony compared to the non-LBBB group and healthy controls assessed by opposing wall delays and 12-segment standard deviation (LBBB 164 +/- 30 ms vs. non-LBBB 70 +/- 17 ms (p < 0.0001), non-LBBB vs. healthy 65 +/- 17 ms (p = 0.47)).
Septal dyskinesis exists in some patients with LBBB. Myocardial circumferential strain analysis enables detailed characterization of contraction patterns, strengths, and timing in cardiomyopathy patients with and without LBBB.
心脏再同步治疗（CRT）已被证明可降低 60-70%伴左束支传导阻滞（LBBB）和 QRS 时限>120ms 的晚期心力衰竭患者的死亡率。人们一直在努力寻找可重复的无创参数来预测 CRT 反应。我们假设在左心室收缩功能降低的 LBBB 患者中可能存在不同的左心室收缩模式，并应用心脏磁共振（CMR）技术来评估该人群的圆周应变。
我们在 35 名患者（10 名缺血性心肌病患者、15 名非缺血性心肌病患者和 10 名健康对照者）中确定了基底、中部和心尖心室水平的心肌圆周应变。分析圆周应变模式。确定每个 6 个节段在 3 个心室切片中的收缩期圆周应变峰值时间以及基底和中部心室切片中应变峰值时间的标准差。
50%（10 例中的 5 例）的 LBBB 患者至少有两个心室水平的前间隔和下间隔的运动障碍，30%的患者前间隔孤立性运动障碍，20%的患者在任何节段均无运动障碍，与所有非 LBBB 患者和健康对照者相似。所有心肌病患者的中部心室水平的圆周应变缩短峰值明显降低（LBBB 为 9±6%，非 LBBB 为 10±4%，健康对照组为 19±4%；均 p<0.0001），但 LBBB 组和非 LBBB 组之间无差异（p=0.20）。LBBB 组与非 LBBB 组和健康对照组相比，壁间延迟和 12 节段标准差评估的同步性差异更大（LBBB 为 164±30ms，非 LBBB 为 70±17ms（p<0.0001），非 LBBB 与健康对照组为 65±17ms（p=0.47））。
一些 LBBB 患者存在室间隔运动障碍。圆周应变分析可详细描述伴或不伴 LBBB 的心肌病患者的收缩模式、收缩力和收缩时间。
