Effect of Bipolar Electrode Spacing on Phrenic Nerve Stimulation and Left Ventricular Pacing Thresholds

Abstract

Background-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. Methods and Results-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. Conclusions-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. (Circ Arrhythm Electrophysiol. 2012;5:815-820.)

Preventing Phrenic Nerve Stimulation by a Patch Insulation in an Intact Swine Heart Model

“…The longest MID was observed during the LV-tip to RV-coil unipolar pacing configuration, indicating that this pacing configuration resulted in a wider electrical field. Most PN threshold were above 10 V if the distance between the LV lead and PN was over 20 mm, which was consistent with the study by Biffi et al [14]. Biffi et al also showed that the PN threshold rapidly increased when the cathode moved away from the PN, reaching a PN threshold of 10 V at a 0.5 ms PW with a distance of 20 mm.…”

Acute Response to Unilateral Unipolar Electrical Carotid Sinus Stimulation in Patients With Resistant Arterial Hypertension

“…10 On the other hand, current spread to adjacent structures may precipitate side effects.28 Smaller electrode spacing may increase the threshold for unwanted side effects without compromising the desired response. 29 Development of multichannel electrodes may further improve stimulation selectivity. 30 Finally, engagement of carotid chemoreceptors, which are known to regulate sympathetic activity and BP, 31 could differ between electrode designs.…”

Performance of a novel left ventricular lead with short bipolar spacing for cardiac resynchronization therapy: Primary results of the Attain Performa Quadripolar Left Ventricular Lead Study

“…The narrowspaced electrodes, "short bipolar," were designed to reduce the chance of stimulation of the phrenic nerve without compromising pacing capture thresholds (PCTs). 21 The VectorExpress feature of the accompanying pulse generator allows for automatic and rapid testing of the PCT and impedance for all possible vectors. This is usually accomplished in less than 3 minutes.…”