Singleton Matthew J, Spragg David D
Johns Hopkins Hospital and Johns Hopkins Bayview Medical Center, Baltimore, MD.
J Atr Fibrillation. 2015 Aug 31;8(2):1280. doi: 10.4022/jafib.1280. eCollection 2015 Aug-Sep.
Cardiac resynchronization therapy (CRT) improves cardiac function in many patients with ventricular dyssynchrony. The optimal use of imaging for pre-implantation assessment remains a subject of debate. Here, we review the literature to date on the utility of echocardiography and cardiac MR, as well as conventional ECG, in choosing the best site for LV lead implantation. Prior to the use of imaging for pre-implantation evaluation, LV leads were placed empirically, based on average responses from population-level studies. Subsequently, patient-specific approaches have been used to maximize response. Both echocardiography and cardiac MR allow determination of areas of latest mechanical activation. Some studies have found improved response when pacing is applied at or near the site of latest mechanical activation. Similarly, both echocardiography and cardiac MR provide information about the location of any myocardial scar, which should be avoided when placing the LV lead due to variable conduction and high capture thresholds. Alternative approaches include targeting the region of latest electrical activation via measurement of the QLV interval and methods based on intraoperative hemodynamic measurements. Each of these modalities offers complementary insights into LV lead placement, so future directions include multimodality pre-implantation evaluation, studies of which are ongoing. Emerging technologies such as leadless implantable pacemakers may free implanting electrophysiologists from the constraints of the coronary sinus, making this information more useful and making non-response to CRT increasingly rare.
心脏再同步治疗（CRT）可改善许多存在心室不同步的患者的心脏功能。对于植入前评估而言，影像学检查的最佳应用仍存在争议。在此，我们回顾了迄今为止关于超声心动图、心脏磁共振成像以及传统心电图在选择左心室电极植入最佳部位方面的文献。在使用影像学进行植入前评估之前，左心室电极是根据人群水平研究的平均反应经验性放置的。随后，采用了针对个体患者的方法来使反应最大化。超声心动图和心脏磁共振成像都能确定最晚机械激活区域。一些研究发现，在最晚机械激活部位或其附近进行起搏时反应有所改善。同样，超声心动图和心脏磁共振成像都能提供有关任何心肌瘢痕位置的信息，由于传导可变和捕捉阈值较高，在放置左心室电极时应避开这些部位。其他方法包括通过测量QLV间期来靶向最晚电激活区域以及基于术中血流动力学测量的方法。这些方法中的每一种都为左心室电极放置提供了互补的见解，因此未来的方向包括多模态植入前评估，相关研究正在进行中。诸如无导线植入式起搏器等新兴技术可能使植入电生理学家摆脱冠状窦的限制，使这些信息更有用，并使CRT无反应的情况越来越罕见。
