Remme Espen W, Niederer Steven, Gjesdal Ola, Russell Kristoffer, Hyde Eoin R, Smith Nicolas, Smiseth Otto A
Institute for Surgical Research, Oslo University Hospital, 0372 Oslo, Norway
Centre for Cardiological Innovation, Oslo University Hospital, Oslo, Norway.
Europace. 2016 Dec;18(12):1905-1913. doi: 10.1093/europace/euv381. Epub 2015 Nov 26.
An abnormal large leftward septal motion prior to ejection is frequently observed in left bundle branch block (LBBB) patients. This motion has been proposed as a predictor of response to cardiac resynchronization therapy (CRT). Our goal was to investigate factors that influence its magnitude.
Left (LVP) and right ventricular (RVP) pressures and left ventricular (LV) volume were measured in eight canines. After induction of LBBB, LVP and, hence, the transmural septal pressure (P = LVP-RVP) increased more slowly (P < 0.01) during the phase when septum moved leftwards. A biventricular finite-element LBBB simulation model confirmed that the magnitude of septal leftward motion depended on reduced rise of P. The model showed that leftward septal motion was decreased with shorter activation delay, reduced global or right ventricular (RV) contractility, septal infarction, or when the septum was already displaced into the LV at end diastole by RV volume overload. Both experiments and simulations showed that pre-ejection septal hypercontraction occurs, in part, because the septum performs more of the work pushing blood towards the mitral valve leaflets to close them as the normal lateral wall contribution to this push is lost.
Left bundle branch block lowers afterload against pre-ejection septal contraction, expressed as slowed rise of P, which is a main cause and determinant of the magnitude of leftward septal motion. The motion may be small or absent due to septal infarct, impaired global or RV contractility or RV volume overload, which should be kept in mind if this motion is to be used in evaluation of CRT response.
在左束支传导阻滞（LBBB）患者中，常观察到射血前室间隔异常大幅度向左运动。这种运动已被提出作为心脏再同步治疗（CRT）反应的预测指标。我们的目标是研究影响其幅度的因素。
在8只犬中测量左心室（LVP）和右心室（RVP）压力以及左心室（LV）容积。诱发LBBB后，在室间隔向左移动的阶段，LVP以及跨壁室间隔压力（P = LVP - RVP）上升得更缓慢（P < 0.01）。双心室有限元LBBB模拟模型证实，室间隔向左运动的幅度取决于P上升的降低。该模型显示，当激活延迟缩短、整体或右心室（RV）收缩力降低、室间隔梗死，或在舒张末期由于RV容量过载使室间隔已移入LV时，室间隔向左运动减少。实验和模拟均表明，射血前室间隔过度收缩部分是因为室间隔承担了更多将血液推向二尖瓣叶以使其关闭的工作，而正常情况下侧壁对此推力有贡献但此时丧失了。
左束支传导阻滞降低了射血前室间隔收缩的后负荷，表现为P上升减慢，这是室间隔向左运动幅度的主要原因和决定因素。由于室间隔梗死、整体或RV收缩力受损或RV容量过载，这种运动可能很小或不存在，在将此运动用于评估CRT反应时应牢记这一点。
