Institute of Cardiology, University of Bologna, Bologna, Italy.
Circ Arrhythm Electrophysiol. 2012 Aug 1;5(4):815-20. doi: 10.1161/CIRCEP.112.971317. Epub 2012 Jul 11.
Phrenic nerve stimulation (PNS) is a common complication of cardiac resynchronization therapy when left ventricular (LV) pacing occurs via a coronary vein. The purpose of this study was to evaluate the effects of bipolar electrode spacing on PNS and LV pacing thresholds.
Electrophysiology catheters with standard (2 mm-5 mm-2 mm) or modified (1 mm-5 mm-1 mm) interelectrode spacing was, respectively, inserted in a posterior/lateral cardiac vein in a randomized order in 6 anesthetized dogs via jugular access. The phrenic nerve was dissected via a left minithoracotomy and repositioned over the vein as close as possible to one of the electrodes. The presence of PNS was verified (ie, PNS threshold <2 V at 0.5 ms in unipolar configuration). Bipolar pacing was delivered using the electrode closest to the phrenic nerve as the cathode, and multiple bipolar electrode spacing configurations were tested. During bipolar pacing, PNS threshold increased as bipolar electrode spacing was reduced (P<0.05), whereas LV pacing thresholds did not change significantly (P>0.05). Compared with a standard bipolar electrode spacing of 20 mm for LV leads, 1 and 2 mm bipolar electrode spacing resulted in a PNS threshold increase of 5.5±2.2 V (P=0.003) and 2.8±1.7 V (P<0.001), respectively. Similarly, PNS threshold increased by 6.5±3.7 V with 1 mm and by 3.8±1.9 V with 2 mm bipolar pacing (both P<0.001), compared with unipolar pacing.
This study suggests that reducing LV bipolar electrode spacing from the standard 20 mm to 1 or 2 mm may significantly increase the PNS threshold without compromising LV pacing thresholds.
左心室（LV）经冠状静脉起搏发生时，膈神经刺激（PNS）是心脏再同步治疗的常见并发症。本研究旨在评估双极电极间距对 PNS 和 LV 起搏阈值的影响。
通过颈静脉入路在 6 只麻醉犬的后/外侧心静脉中以随机顺序分别插入具有标准（2mm-5mm-2mm）或改良（1mm-5mm-1mm）电极间距的电生理导管。通过左小开胸术解剖膈神经，并将其重新定位在尽可能靠近其中一个电极的静脉上。验证有无 PNS（即，在单极配置下 PNS 阈值<2V 时为 0.5ms）。使用最接近膈神经的电极作为阴极进行双极起搏，并测试多种双极电极间距配置。在双极起搏期间，随着双极电极间距的减小，PNS 阈值增加（P<0.05），而 LV 起搏阈值没有显著变化（P>0.05）。与 LV 导联的标准双极电极间距 20mm 相比，1mm 和 2mm 的双极电极间距分别导致 PNS 阈值增加 5.5±2.2V（P=0.003）和 2.8±1.7V（P<0.001）。同样，与单极起搏相比，1mm 时 PNS 阈值增加 6.5±3.7V，2mm 时增加 3.8±1.9V（均 P<0.001）。
本研究表明，将 LV 双极电极间距从标准的 20mm 减小至 1mm 或 2mm 可能会显著增加 PNS 阈值，而不会影响 LV 起搏阈值。
