Detection and Hemodynamic Significance of Cardiac Pacemaker–Induced Phrenic Nerve Stimulation

Abstract

The authors investigated acoustic cardiography, the digital analysis of electrocardiogram (ECG) and heart sounds, to detect phrenic nerve stimulation (PNS) and assess its hemodynamic significance. They studied 42 patients and induced 46 instances of PNS induced through cardiac pacing at various locations in the heart. These 46 instances of PNS were either independently documented using fluoroscopy or were symptomatic. The authors collected acoustic cardiography data including the electromechanical activation time (interval from Q onset to the first heart sound [S1]) as a percentage of the RR interval (%EMAT) to assess systolic function. Acoustic cardiography provided evidence of PNS when it occurred. They also found significant %EMAT prolongation when right ventricular pacing was associated with PNS (Delta%EMAT=2.7, P=.012), but none beyond the normal range with right ventricular pacing in the absence of PNS. Documented PNS occurred in 33 episodes (60%) in patients with noticeable symptoms. Stimulation amplitudes could be found that generated asymptomatic PNS for all of the five participants explicitly tested for it. PNS can be asymptomatic. PNS due to right ventricular pacing is associated with impaired left ventricular systolic function. Acoustic cardiography is an effective method of detecting and assessing the hemodynamic significance of pacemaker-related PNS.

Improvement of cardiac function with device‐based diaphragmatic stimulation in chronic heart failure patients: the randomized, open‐label, crossover Epiphrenic II Pilot Trial

“…First, the diaphragmatic contractions occasionally observed as a side effect during CRT are known to be symptomatic, causing hiccups and/or pain for the patient. Complementary to our previous reports, this study confirms that it is possible to find a pacing energy setting that stimulates the diaphragm without causing noticeable symptoms . Secondly, previous in vitro studies have suggested that a permanent high‐frequency stimulation of the diaphragm might induce diaphragmatic fatigue and, occasionally, irreversible damage to the lower motor neuron .…”

“…Accordingly, it appears to be important to optimize the timing between the onset of ventricular contraction and PIDS so that the timing and impact of the caudal and the cranial components of PIDS on cardiac function are maximized. This hypothesis is supported by our own previous studies having shown that asymptomatic PIDS, if synchronized to the onset of ventricular contraction, can improve LV systolic function in the acute setting reproducibly up to 1 h without causing patient symptoms . Secondly, there might be additional mechanisms by which PIDS improves functional outcomes.…”

“…PIDS is usually thought of as an effective but probably painful way of controlling respiration in breathing disorders or a symptomatic side effect during CRT . Zuber et al showed that there is a range of stimulation voltages in which patients are asymptomatic despite the presence of diaphragmatic pacing . If the asymptomatic activation of the diaphragm is time‐synchronized to the onset of the LV contraction, it was shown that PIDS can improve LV systolic function reproducibly up to 1 h in a post‐open heart surgery population with preserved EF .…”

“…13 -18 As previously demonstrated by our group, pacing-induced diaphragmatic stimulation (PIDS) could have the potential to provide benefits similar to CRT. 19,20 PIDS is usually thought of as an effective but probably painful way of controlling respiration in breathing disorders or a symptomatic side effect during CRT. 21,22 Zuber et al showed that there is a range of stimulation voltages in which patients are asymptomatic despite the presence of diaphragmatic pacing.…”

“…21,22 Zuber et al showed that there is a range of stimulation voltages in which patients are asymptomatic despite the presence of diaphragmatic pacing. 19 If the asymptomatic activation of the diaphragm is time-synchronized to the onset of the LV contraction, it was shown that PIDS can improve LV systolic function reproducibly up to 1 h in a post-open heart surgery population with preserved EF. 20 The study reported herein intended to investigate the haemodynamic and clinical benefit of asymptomatic PIDS in a moderate and severe heart failure cohort over multiple weeks.…”