Garrigue Stephane, Bordachar Pierre, Reuter Sylvain, Jaïs Pierre, Haïssaguerre Michel, Clementy Jacques
Hopital Cardiologique du Haut-Leveque, University of Bordeaux, Bordeaux-Pessac, France.
Card Electrophysiol Rev. 2003 Dec;7(4):315-24. doi: 10.1023/B:CEPR.0000023167.11038.8f.
Left ventricular pacing (LVP) and biventricular pacing (BVP) have been proposed as treatments for patients with advanced heart failure complicated by discoordinate contraction due to intraventricular conduction delay. For patients in sinus rhythm, BVP works in part by modulating the electronic atrial-ventricular time delay and thus optimizing contractile synchrony, the contribution of atrial systole, and reducing mitral regurgitation. However, little is known of the mechanisms of BVP in heart failure patients with drug-resistant chronic atrial fibrillation. HYPOTHESIS AND METHODS: LVP differs from BVP because hemodynamic and clinical improvement occurs in association with prolongation rather than shortening of the QRS duration. We sought to determine if LVP or BVP improves mechanical synchronization in the presence of atrial fibrillation. Thirteen patients with chronic atrial fibrillation, severe heart failure and QRS >or=140 ms received (after His bundle ablation) a pacemaker providing both LVP and BVP. The mean age was 62 +/- 6 years and left ventricular ejection fraction was 24 +/- 8%. After a baseline phase of one month with right ventricular pacing, all patients underwent in random order 2 phases of 2 months (LVP and BVP). At the end of each phase, an echocardiogram, a hemodynamic analysis at rest and during a 6-minute walking test and a cardio-pulmonary exercise test were performed.
LVP and BVP provided similar performances at rest (p = ns). The 6-minute walking test revealed similar performances in both pacing modes but patients were significantly more symptomatic at the end of the test with LVP ( p = 0.035). The cardio-pulmonary exercise test showed higher performances with BVP (92 +/- 34 Watts) vs. LVP (77 +/- 23; p = 0.03). LVP was associated with significantly more premature ventricular complexes recorded during the 6 minute walking test (49 +/- 71) than BVP (10 +/- 23; p = 0.04).
In this small series of patients with atrial fibrillation, congestive heart failure and a prolonged QRS duration, LVP and BVP provided similar hemodynamic effects at rest whereas BVP was associated with better hemodynamic effects during exercise and fewer premature ventricular complexes. Although the mechanisms for the observed differences are uncertain, it is possible that there is worsening of right ventricular function due to a rise in left-to-right electromechanical delay during exercise. Increased catecholamines release might contribute to the lower exercise tolerance and greater number of premature ventricular complexes recorded during exercise observed during LVP compared to BVP.
Patients with atrial fibrillation, heart failure and QRS prolongation who are candidates for His-bundle ablation and cardiac resynchronization therapy may respond better to BVP rather than to LVP.
左心室起搏（LVP）和双心室起搏（BVP）已被提议用于治疗因室内传导延迟而并发不协调收缩的晚期心力衰竭患者。对于窦性心律患者，BVP部分通过调节电子房室时间延迟，从而优化收缩同步性、心房收缩的贡献并减少二尖瓣反流来发挥作用。然而，对于药物难治性慢性房颤的心力衰竭患者，BVP的机制知之甚少。
LVP与BVP不同，因为血流动力学和临床改善与QRS时限延长而非缩短相关。我们试图确定在存在房颤的情况下LVP或BVP是否能改善机械同步性。13例慢性房颤、严重心力衰竭且QRS≥140 ms的患者（在希氏束消融术后）接受了一种既能提供LVP又能提供BVP的起搏器。平均年龄为62±6岁，左心室射血分数为24±8%。在进行1个月右心室起搏的基线期后，所有患者按随机顺序接受2个为期2个月的阶段（LVP和BVP）。在每个阶段结束时，进行超声心动图检查、静息和6分钟步行试验期间的血流动力学分析以及心肺运动试验。
LVP和BVP在静息时表现相似（p = 无显著差异）。6分钟步行试验显示两种起搏模式下表现相似，但在试验结束时LVP组患者症状明显更重（p = 0.035）。心肺运动试验显示BVP（92±34瓦）的表现优于LVP（77±23；p = 0.03）。在6分钟步行试验期间记录到的室性早搏复合波，LVP组（49±71）明显多于BVP组（10±23；p = 0.04）。
在这一小系列房颤、充血性心力衰竭且QRS时限延长的患者中，LVP和BVP在静息时提供相似的血流动力学效应，而BVP在运动期间与更好的血流动力学效应相关且室性早搏复合波更少。尽管观察到的差异机制尚不确定，但有可能是由于运动期间左向右机电延迟增加导致右心室功能恶化。与BVP相比，LVP期间运动时儿茶酚胺释放增加可能导致运动耐量降低和运动期间记录到的室性早搏复合波数量更多。
对于房颤、心力衰竭且QRS延长且适合希氏束消融和心脏再同步治疗的患者，BVP可能比LVP反应更好。
