Elucidation of the Influence of Sleep Apnea on Risk of Atrial Fibrillation

Sleep-disordered breathing (SDB) is common in patients with cardiovascular disease and its attendant hypoxemia and autonomic dysfunction create a milieu that is likely to enhance AF propensity. Thus, SDB may represent a novel target for AF prevention and treatment strategies. Although our prior cross-sectional work has shown a 2-4 fold higher odds of AF related to SDB, these and other reports have not included cardiac structural data or autonomic/biochemical measures, and have addressed only arrhythmic events occurring during an overnight sleep study. In this proposal, we will examine paroxysmal AF (PAF), an early stage risk factor for persistent AF, and relevant to this proposal because it occurs prior to extensive cardiac electrical remodeling/fibrosis.

OUTLINE OF STUDY VISITS Baseline Visit (SA 1 and 2). After informed consent, eligible participants will be scheduled to arrive for an overnight visit in the CRU. During the evening, participants will undergo questionnaire administration, blood pressure measurements, and anthropometry. They will be provided dinner and undergo polysomnography (PSG). In the morning, participants will undergo fasting venipuncture, overnight urine collection, ECHO, 6 minute walk test, vascular measures and blood pressure measurements. For those with PAF (cases), hook-up for continuous ECG monitoring will be performed along with education regarding how to handle the device and bathing instructions, etc. All measurements in the DCRU/CRU will be performed blinded to PAF status. The only unblinded staff will be a dedicated research assistant who will perform the ECG monitoring hook-up. Blinded staff will collect and process data and perform data entry. After the baseline visit, participants with PAF (n=150) will undergo hook-up of the ECG monitor and an activity monitor at the baseline visit to wear for a 7-21 day period.

Follow-Up Visit (SA3). Those with SDB (AHI>=15) without evidence of central apnea (central apnea index>5) or Cheyne Stokes Respirations via baseline visit PSG and who have PAF will undergo the following. A 5-7 day home-based auto-titration (APAP, Respironics Autopap System One with humidifier) to identify the optimal positive airway pressure (PAP) setting will be performed (with settings 4-20cm H2O). At the end of the 5-7 day titration, the goal will be to identify the pressure that results in an AHI<5 events/hour (optimally). The research assistant will re-set the device to deliver this optimal fixed pressure identified by the PI through the secure wireless web-site. An overnight DCRUCRU visit will be scheduled after 3 months of wearing CPAP during which the same measures performed at the baseline visit will be collected.

STUDY PROCEDURES 2-DIMENSIONAL DOPPLER ECHOCARDIOGRAPHY. Parasternal, apical and subcostal 2-D views and apical 3D views will be obtained with transducer orientation and gain settings adjusted to optimally define endocardial surface of each cardiac chamber.

POLYSOMNOGRAPHY (PSG). Procedure for PSG: Research PSG will be performed using the Compumedics E-series system (Abbottsford, AU) which will include 3 cortical encephalograms, bilateral electro-oculograms, a bipolar submental electromyogram, thoracic and abdominal respiratory inductance plethysmography, airflow (by nasal-oral thermocouple and nasal cannula pressure recording), oximetry (using highly sensitive finger pulse oximeter, sampling frequency 25Hz), electrocardiogram (ECG) at 250Hz (used to derive HRV measures of autonomic function); body position (mercury switch sensor), bilateral leg movements. EEGs are recorded at 125Hz. 3) 7-21 Day CONTINUOUS ECG MONITORING.