An evaluation of the effectiveness of continuous positive airway pressure therapy in participants with obstructive sleep apnoea and angina

INTERVENTION: Participants with angina and no obstructive coronary artery disease from NOCAD1 study will be screened and recruited. Recruited participants will undergo type 2 ambulatory sleep study at participants' residence for the diagnosis of obstructive sleep apnoea. Participants who have obstructive sleep apnoea and fulfilled the study inclusion/exclusion criteria as outlined for CPAP therapy will be randomly assigned to either "initial CPAP therapy" or "delayed CPAP therapy (no CPAP)" for 6 months, followed by crossover between group's therapy for further 6 months to assess the difference in effects on angina burden and quality of life. Participants on CPAP therapy will received autoPAP (Philips Respironics, Murrayville, PA) for 1 week, followed by fixed CPAP pressure, set at 90th percentile of autoPAP pressure, as determined by Sleep Physician. Delivery of CPAP device and its accessories by Philips SleepEasy Device Consultant, including education and supports in conjunction with a Sleep Physician. This will take place at the Lyell McEwin Hospital Cardiology Clinical Trial Unit. Data will be available electronically via remote downloading using Encoreanywhere program. Participant's adherence is monitored by accessing device analytics which will be downloaded remotely. Satisfactory adherence towards CPAP therapy will be assessed by Sleep Physician at 1 months, 3 months and 6 months. Minimum amount of usage time should be > 4 hours per night. Participants will be contacted to troubleshoot any difficulties and if any problems arose. There will be 6 months of no CPAP therapy prior to follow‐up outcome assessment after cessation of CPAP therapy. CONDITION: Angina Obstructive Sleep Apnoea PRIMARY OUTCOME: Prevalence of obstructive sleep apnoea in participants with angina and no obstructive coronary artery disease. ; The information will be obtained from type 2 ambulatory sleep study. Recurrent angina which is defined as one or more episodes of pain per week determined from the Seattle Angina Questionnaire. SECONDARY OUTCOME: Aortic pulse wave velocity (PWV). ; PWV is measured with TensioMed arteriography. Augmentation Index (Ax). ; Ax is measured with TensioMed arteriography. Cardiovascular death. ; The information will be obtained from linkage to medical records. Central retinal vessel calibre (CRVC). ; CRVC is obtained with Smartscope® Pro by Optomed will be used. (Non‐mydriatic fundus camera) ; Contractile reserve (CR). ; CR is measured with strain imaging on low dose dobutamine stress echocardiography (DSE). Health Status. ; This information obtained from EQ‐5D questionnaires which is a standardized instrument for measuring generic health status. Hospital admission with recurrent angina. ; The information will be obtained from linkage to medical records. Myocardial infarction. ; The information will be obtained from linkage to medical records. Stroke. ; The information will be obtained from linkage to medical records. INCLUSION CRITERIA: 1. Met NOCAD1 study INCLUSION CRITERIA: ‐ Clinical diagnosis of angina ‐ Persistent angina ‐ Coronary angiography demonstrating normal or no obstructive coronary disease (<50% diameter stenosis) 2. Participants for CPAP therapy with obstructive sleep apnoea diagnosis ‐ AHI>20 ‐ AHI<20; REM‐AHI>45 3. Patients are able and willing to give appropriate informed consent.