Effects of hyperbaric exposures on cardiac pacemakers.

Data on tolerance of cardiac pacemakers during diving are very scarce. The aim of this study was to test electronic and mechanical tolerances of pacemakers exposed to experimental reproductions of pressures encountered during diving. Two samples each of 20 different models of cardiac pacemakers were exposed to compression during continuous telemetric monitoring. The first sample of each model was exposed to a pressure of 60 metres of sea water (msw). Each second sample was first exposed to a pressure of 30 msw then to 60 msw hyperbaric testing, with a period of 1 month between the two tests. Electronic function and structural integrity of the cans were evaluated. No electronic dysfunction was noted. We merely observed in some devices a transient increase of the pacing rate during pressurisation. No significant deformation of the can (< or =0.2 mm) was observed after the 30 msw hyperbaric test. However, after the 60 msw test, more than half of the devices tested were significantly and definitively deformed. These results show that tested pacemakers preserved a normal electronic function up to 60 msw but most of the tested devices demonstrated significant deformations of the pacemaker can for the hyperbaric exposure observed deeper than 30 msw. Without prejudging diving aptitude for implanted pacemaker patients, it therefore seems prudent to advise them against diving beyond 30 msw because of the potential for electronic dysfunction beyond that depth.