Diaphragmatic stimulation caused by cardiac resynchronization treatment.

A 69-year-old man with a history of severe nonischemic cardiomyopathy managed with a cardiac resynchronization-defibrillator presented to the outpatient clinic with uncomfortable pulsation over the left upper-abdominal area when lying on his left side. He was hemodynamically stable. When he was recumbent in a left-lateral position, there were visible and palpable contractions of the left upper-abdominal wall musculature (Figure 1; Appendix 1, available at www.cmaj.ca/ lookup/suppl/doi:10.1503/cmaj.150986/-/DC1). We suspected diaphragmatic contraction caused by inadvertent phrenic nerve stimulation by the left ventricular lead. We confirmed the diagnosis noninvasively by reducing the left ventricular pacing amplitude of the lead.1 Phrenic nerve stimulation has been described in up to one-third of patients with traditional cardiac resynchronization-defibrillator devices because of the proximity of the phrenic nerve to the pericardial veins, which makes the nerve susceptible to stimulation by the high-amplitude left ventricular lead.2 This problem has become much less common with the recent development of quadripolar lead technology.3 Phrenic nerve stimulation can be continuous or paroxysmal and can cause dyspnea, uncomfortable muscle twitching, hiccups and general malaise.2 It can be challenging to diagnose for those not familiar with cardiac resynchronization-defibrillator technology.4 Phrenic nerve stimulation is highly posturedependent. It occurs more often when the patient is in a left-lateral position rather than in a supine position.2 Although phrenic nerve stimulation is not life-threatening, it can cause substantial discomfort to the patient.2 The problem can almost always be mitigated noninvasively with electrical reprogramming of the cardiac resynchronization-defibrillator.5 References 1. Daubert JC, Saxon L, Adamson PB, et al. EHRA/HRS expert consensus statement on cardiac resynchronization therapy in heart failure: implant and follow-up recommendations and management. Heart Rhythm 2012;9:1524-76. 2. Moubarak G, Bouzeman A, Ollitrault J, et al. Phrenic nerve stimulation in cardiac resynchronization therapy. J Interv Card Electrophysiol 2014;41:15-21. 3. Stiles S. Fewer CRT-lead-related complications with quadripolar vs bipolar leads: MORE-CRT Trial. Medscape 2014 Sept. 12. Available: www.medscape.com/viewarticle/831630 (accessed 2015 Dec. 18). 4. Akrawi H, Hulbert D. Unusual cause of a pulsatile abdominal mass. Emerg Med J 2007;24:602. 5. Biffi M, Exner DV, Crossley GH, et al. Occurrence of phrenic nerve stimulation in cardiac resynchronization therapy patients: the role of left ventricular lead type and placement site. Europace 2013;15:77-82. Clinical images