CHANGES OF CARDIAC-FUNCTION IN UNDERWATER DIVING

Underwater diving is a widely practised leisure activity. As cardiac p atients may wish to participate, cardiologists should be aware of pote ntial changes of cardiac function during diving. Multiple factors may affect haemodynamics. Firstly, changes in pressure, secondary to venti lation of a high density gas mixture which increases afterload. Hypero xia is the principal factor which slows the heart rate, a commonly obs erved phenomenon. Excitability and conduction speed may be modified by the increase in hydrostatic pressure. During decompression, gaseous p ulmonary embolism may increase right heart pressures and cause a parad oxical embolism may increase right heart pressures and cause a paradox ical embolism in patients with a right-to-left shunt. Immersion increa ses the preload. Exposure to cold also plays a role increasing afterlo ad and slowing the heart rate. These factors may disturb cardiac funct ion and expose cardiac patients to accidents during underwater diving.