Cardiovascular considerations for scuba divers

Abstract

As the popularity of scuba diving increases internationally, physicians interacting with divers in the clinical setting must be familiar with the cardiovascular stresses and risks inherent to this activity. Scuba presents a formidable cardiovascular challenge by combining unique environmental conditions with the physiologic demands of underwater exercise. Haemodynamic stresses encountered at depth include increased hydrostatic pressure leading to central shifts in plasma volume coupled with cold water stimuli leading to simultaneous parasympathetic and sympathetic autonomic responses. Among older divers and those with underlying cardiovascular risk factors, these physiologic changes increase acute cardiac risks while diving. Additional scuba risks, as a consequence of physical gas laws, include arterial gas emboli and decompression sickness. These pathologies are particularly dangerous with altered sensorium in hostile dive conditions. When present, the appropriate management of patent foramen ovale (PFO) is uncertain, but closure of PFO may reduce the risk of paradoxical gas embolism in divers with a prior history of decompression sickness. Finally, similar to other Masters-level athletes, divers with underlying traditional cardiovascular risk should undergo complete cardiac risk stratification to determine 'fitness-to-dive'. The presence of undertreated coronary artery disease, occult cardiomyopathy, channelopathy and arrhythmias must all be investigated and appropriately treated in order to ensure diver safety. A patient-centred approach facilitating shared decision-making between divers and experienced practitioners should be utilised in the management of prospective scuba divers.

Keywords: arrhythmias; cardiac; coronary artery disease; risk factors.

Figure 1.. Physiologic effects of scuba diving (Panels A and B) and potential pathophysiologic sequelae with rapid ascension (Panel C).

Panel A. Increased hydrostatic pressure leads to increased venous return from the extremities. Panel B. Hemodynamic shifts and mixed autonomic response to depth and temperature lead to increased preload and afterload and decreased, then increased heart rate, all yielding a net increase in cardiac output. Panel C. With rapid ascent, the formation of inert gas bubbles increases the risk of paradoxical arterial gas embolism, including in those with high-grade patent foramen ovale (PFO)

Figure 2.. Evaluation and risk stratification of cardiovascular disease in scuba divers.

Recommendations based off American College of Cardiology / American Heart Association Eligibility and Disqualification Recommendations for Competitive Athletes CAD: coronary artery disease; CT: computed tomography; EF: ejection fraction; MRI: magnetic resonance imaging; VT: ventricular tachycardia