1323 Beyond Atrial Fibrillation and Heart Failure: Central Sleep Apnea as a Marker of Occult Atrioventricular Conduction Disease

Abstract Introduction Central sleep apnea (CSA) results from ventilatory instability driven by heightened chemoreflex sensitivity and prolonged circulation time. Well-recognized contributors include atrial fibrillation (AF) and heart failure (HF), where rhythm disturbance, impaired contractility, and fluctuations in cardiac output increase loop gain and promote central events. In contrast, cardiac conduction disease is an underrecognized contributor to the development of central apnea. We describe a case in which new central apneas emerging during long-standing continuous positive airway pressure therapy (CPAP) led to the diagnosis of high-grade atrioventricular (AV) block, with subsequent improvement in CSA after dual-chamber pacemaker implantation (PPM). Report of case(s) A 79-year-old man with obstructive sleep apnea well controlled for years on CPAP and a prior myocardial infarction with stents presented for routine follow-up. CPAP downloads showed a new residual AHI of 15.2/hr with a predominantly central pattern despite stable pressures, minimal leak, and excellent adherence. Ambulatory ECG monitoring performed after ruling out other common etiologies of CSA demonstrated high-grade AV conduction disease, including 3:1 block, progressive PR prolongation, nocturnal pauses up to 5.2 seconds, and intermittent Mobitz I and II events. A PPM was implanted after an electrophysiology evaluation. Repeat CPAP download within 30 days post-PPM insertion showed marked improvement, with the residual AHI falling to 7.1/hr without changes to medications, sleep habits, or pressure settings. Rhythm control in AF improves CSA by stabilizing cardiac output and circulatory timing. Optimization of HF therapy similarly reduces loop gain by improving stroke volume and relieving pulmonary congestion. Chronotropic impairment and AV conduction disturbances, however, are less appreciated contributors. Intermittent high-grade block reduces cardiac output and prolongs circulation time, destabilizing ventilatory control and promoting respiratory overshoot and undershoot. These pauses weaken circulatory feedback and amplify chemoreflex oscillations that trigger central events. Restoration of AV synchrony through PPM appears to correct this instability. Conclusion PPM for high-grade AV block resulted in a significant improvement in CSA burden. Newly developed central apneas in a previously stable CPAP user should prompt evaluation for occult conduction disease alongside other causes such as AF, HF, cerebrovascular disease, opioid use, high-altitude exposure, and medication effects. Support (if any)