Speaker's Highlight

• Don Sin University of British Columbia, St. Paul Hospital (Canada)
  Kenneth R. Chapman Toronto General Hospital Research Institute (Canada)
• Parameswaran Nair McMaster University (Canada)
  Carolyn Calfee UCSF (U.S.A.)
• Gregory P. Downey University of Colorado School of Medicine (U.S.A.)
  David A. Schwartz University of Colorado School of Medicine (U.S.A.)
• Neil Schluger Tuberculosis Control Branch, California Department of Public Health (U.S.A.)
  Nick Kim Critical Care & Sleep Medicine, University of California San Diego (U.S.A.)
• Nicola Hananiah Baylor College of Medicine (U.S.A.)
  Jae-Joon Yim Seoul National University College of Medicine (Republic of Korea)
• Koichiro Asano Tokai University School of Medicine (Japan)
  Diahn-Warng Perng Taipei Veterans General Hospital (Taiwan)
• Konstantinos Kostikas University of Ioannina (Greece)
  Karin Klooster University Medical Center Groningen (Kingdom of the Netherlands)

• Obstructive sleep apnea and cardiovascular outcomes in clinical practice

  Obstructive sleep apnea (OSA) is a common chronic respiratory condition in Australian outpatient clinics whose cardiovascular consequences remain underappreciated. Repeated upper airway collapse triggers intermittent hypoxia, sympathetic surges, and systemic inflammation that place sustained stress on the heart and vasculature. With one in four middle-aged adults estimated to carry at least mild disease, OSA has become a quiet driver of preventable cardiac events.

  The condition sits at the crossroads of pulmonology, cardiology, and primary care, and the evidence linking it to hypertension, atrial fibrillation, heart failure, and stroke has matured substantially. This article summarises the mechanisms, major endpoints, and practical considerations for clinicians managing affected patients across Australia, and remains a relevant topic for forums such as APSR 2022 in Sydney.

  The sleep-heart axis and cardiovascular strain

  Each obstructive event produces a steep fall in arterial oxygen saturation, followed by a sympathetic surge as arousal restores airway patency. Heart rate and blood pressure fluctuate in parallel, and over time these oscillations contribute to arterial remodelling, endothelial dysfunction, oxidative stress, and accelerated atherogenesis.

  The intensity of these changes correlates with the apnea-hypopnea index but also with the depth and duration of nocturnal desaturation. Patients with predominantly REM-related events and a low overall AHI but prolonged desaturations can still develop cardiovascular complications, so sleep study reports should be interpreted holistically rather than through a single threshold.

  Hypertension as a recognised secondary cause

  OSA is now recognised as a leading secondary cause of hypertension, particularly in resistant cases where blood pressure remains elevated despite multiple medications. Repeated nocturnal sympathetic activation blunts baroreflex sensitivity, and daytime fatigue compounds the problem by limiting physical activity.

  For Australian GPs, any patient with apparent resistant hypertension deserves a screening sleep history. Snoring, witnessed apnoeas, and morning headaches are useful pointers, especially in middle-aged men and postmenopausal women. Where suspicion is high, referral for home sleep testing is straightforward, with Medicare rebates available through accredited GP or specialist referral.

  Atrial fibrillation and other rhythm disturbances

  The link between OSA and atrial fibrillation is among the strongest cardiovascular associations. Intermittent hypoxia and negative intrathoracic pressure stretch the atrial wall and promote electrical remodelling, while autonomic surges act as triggers. Cohort studies suggest untreated severe OSA roughly doubles the risk of incident AF, and recurrence rates after cardioversion or ablation are higher when OSA goes unmanaged.

  In Australian cardiology practice, screening before elective AF ablation is increasingly standard. Many arrhythmia units in Melbourne and Brisbane now request a recent sleep study before scheduling procedures, and consistent CPAP adherence has been linked to improved maintenance of sinus rhythm on follow-up.

  Coronary artery disease and heart failure

  OSA accelerates coronary atherosclerosis and worsens outcomes once ischaemic heart disease is established. Patients presenting with acute myocardial infarction frequently have undiagnosed OSA, and untreated disease is associated with larger infarct size and reduced recovery of left ventricular function.

  In heart failure, the relationship is bidirectional: rostral fluid shifts in supine patients with reduced ejection fraction worsen upper airway collapse, while OSA itself raises afterload and myocardial oxygen demand. Identifying OSA within heart failure clinics across Australian public and private hospitals is now part of routine workup.

  Cerebrovascular risk and stroke

  The same prothrombotic, proatherogenic milieu drives a meaningfully higher stroke risk in OSA. Silent cerebral infarcts are more common in patients with moderate to severe disease, even after adjusting for traditional vascular risk factors, and untreated OSA after stroke is associated with poorer functional recovery and higher recurrence rates.

  Stroke units in larger Australian centres are increasingly screening inpatients using simplified portable devices, although access remains uneven outside metropolitan catchments. Telehealth-supported follow-up is being rolled out in some regional services to extend specialist input beyond capital cities.

  Diagnosis across Australian practice

  Diagnostic pathways in Australia rely heavily on level 3 and 4 home sleep studies, which are well-validated for uncomplicated moderate to severe OSA and reimbursable under Medicare when ordered by an accredited practitioner. Laboratory polysomnography is reserved for complex presentations, suspected central sleep apnea, or occupational assessments such as heavy vehicle licensing.

  A thorough upper airway assessment remains important, particularly where atypical features or comorbid respiratory disease are present. Where structural airway lesions are suspected, clinicians can refer to advanced bronchoscopy techniques for guidance on overlapping central airway pathology. The Australasian Sleep Association and the Thoracic Society of Australia and New Zealand publish guidance on triage between community and tertiary sleep services, including telehealth outreach to rural and remote communities.

  Treatment effects on cardiovascular endpoints

  CPAP remains the cornerstone of therapy for moderate to severe disease, and adherent use delivers measurable cardiovascular benefit. Randomised data show modest reductions in blood pressure, particularly in resistant hypertension, while observational studies suggest reduced AF recurrence after ablation and lower cardiovascular event rates with consistent long-term use.

  Mandibular advancement devices, positional therapy, weight loss, and upper airway surgery each have a role in selected patients, although cardiovascular outcome data are still emerging. Multidisciplinary review involving cardiology, sleep medicine, and primary care tends to produce the most consistent risk reduction, and integration of these services within regional cardiac networks is growing.

  Intervention	Effect on BP	Effect on AF recurrence	Effect on major CV events
  CPAP (adherent use)	Modest reduction (2–5 mmHg)	Reduced after ablation	Reduced in observational cohorts
  Mandibular advancement device	Small reduction	Limited data	Inconclusive
  Positional therapy	Minimal	Variable	Not established
  Weight loss (5–10%)	Meaningful reduction	Reduced with sustained loss	Improved long-term risk
  Upper airway surgery	Variable	Variable	No consistent reduction

  Practical considerations for clinicians

  • Screen routinely for OSA in patients with resistant hypertension, AF, heart failure, or unexplained stroke.
  • Use Medicare-rebated home sleep studies as the first-line investigation for uncomplicated moderate to severe disease.
  • Refer to cardiology before elective AF ablation in patients with suspected OSA, and document CPAP status in ablation reports.
  • Encourage sustained weight loss and exercise, which improve both OSA severity and underlying cardiovascular risk factors.
  • Address CPAP adherence early; cardiovascular benefit tracks consistent nightly use rather than intermittent application.
  • Maintain awareness of coexisting airway pathology when respiratory symptoms extend beyond typical OSA presentations, particularly in smokers and those with occupational exposures.

  For Australian clinicians, the practical message is straightforward: assess the airway when managing the heart. Integrating sleep medicine into routine cardiovascular care, supported by TSANZ and ASA guidance, offers a tangible route to reducing preventable cardiac morbidity in a population already carrying a high burden of chronic disease.

  Richard Russell Nuffield Department of Clinical Medicine, University of Oxford (United Kingdom)
• Mona Bafadhel King’s College London (United Kingdom)
  David Jackson Guy’s and St Thomas’ Hospital, King’s College London (United Kingdom)
• James Chalmers University of Dundee (United Kingdom)
  David Price University of Aberdeen (United Kingdom)