Cardiovascular changes during SCUBA diving: an underwater Doppler echocardiographic study

Abstract

Aim: Body immersion induces blood redistribution (from peripheral to intrathoracic vessels) and is a powerful autonomic stimulus (activating both parasympathetic and sympathetic systems). For these reasons, concerns have been raised about the safety of diving for subjects with previous heart disease. The aim of this study was to evaluate cardiovascular changes occurring during recreational SCUBA diving, as assessed by underwater Doppler echocardiography.

Methods: Eighteen healthy experienced divers underwent a 2D Doppler echocardiography basally, during two 15' steps of still SCUBA diving at different depths (10 m followed by 5 m) and shortly after the end of immersion.

Results: During dive, left ventricular (LV) diastolic volume and early left ventricular filling significantly increased (5 m vs. basal: P < 0.05 and P < 0.01, respectively), while both deceleration time of the early filling rate and late diastolic filling velocity significantly decreased (5 m and 10 m dive vs. basal: P < 0.01). LV volume increase and diastolic filling changes persisted at postdive evaluation, where a significant decrease in heart rate was also observed (P < 0.01 as compared to basal, 5-m and 10-m dive).

Conclusion: This study documents that shallow-depth SCUBA diving induces LV enlargement and diastolic dysfunction. Direct underwater evaluation by Doppler echocardiography could be an appropriate tool for unmasking subjects at risk for underwater-related accidents.

Keywords: diving; echocardiography; immersion; ventricular function.