Pacemaker-induced apnoea in a patient with cervical medullary trauma: a case report.

Background: Phrenic nerve capture is a well-known complication of pacemaker (PM) implantation. In contrast, vagus nerve stimulation resulting in apnoea has not been previously described. We report a unique case of pacing-induced apnoea, likely due to stimulation of vagal afferents during atrial lead capture. Case summary: A 65-year-old man was admitted following a C3-C4 spinal cord injury resulting in tetraplegia. The patient developed complete third-degree heart block followed by asystolic cardiac arrest, complicated by ventricular tachycardia during cardiopulmonary resuscitation.After return of spontaneous circulation, a temporary single-chamber PM with a screw-in lead was inserted without complication. Transthoracic echocardiography showed a left ventricular dysfunction. The aetiology of the initial syncope remained unexplained (a primary arrhythmia could not be ruled out) and a permanent dual-chamber defibrillator was implanted. The right ventricular lead was placed at the apex and the right atrial lead at the right atrial appendage. During intraprocedural atrial lead testing, the patient presented a sudden drop in respiratory rate followed by apnoea. This event was reproducibly triggered by atrial capture. Relocation of the atrial lead to the right atrial lateral wall resolved the apnoea, which did not recur. Discussion: This case describes dual-chamber defibrillator implantation in a patient with cervical spinal cord trauma, who developed sudden apnoea associated with atrial capture. This may have inadvertently stimulated the vagus nerve, sending an inhibitory signal to the brain stem, resulting in a sudden respiratory rate drop. Although rare, this phenomenon should be considered when implanting pacing systems in patients with high cervical injuries.