[abstract] PATENT FORAMEN OVALE (PFO) AND DECOMPRESSION ILLNESS.

Abstract

Right-to-left shunting through a PFO provides a mechanism by which venous gas emboli can enter the arterial circulation. Evidence suggests that PFO is a risk factor for decompression illness (DCI). 90 divers with previous DCI were studied using bubble contrast echocardiography (BCE) and color flow doppler (CFD) imaging in order to detect right-to-left shunt through a PFO. Of these divers 59/90 had experienced serious symptoms (defined as weakness, cerebral symptoms or difficulty with balance); 31/90 divers had experienced pain or sensory symptoms only. A control group of similar age and sex distribution were also studied. After CFD imaging, BCE was performed on each subject during resting breathing (R) while 10 ml of agitated saline was injected IV. If shunt was not evident, repeat injection was administered during the release phase of each of 2-3 Valsalva maneuvers (V). Images were interpreted by a cardiologist unaware of whether the subject was a diver or control. The percentage of subjects with right-to-left shunt detected by BCE and odds ratios (OR [95% confidence interval]) are shown below: Shunt , Controls, Serious DCI, P, OR, Non Serious DCI, P, OR; R or V, 19.8%, 49.2%, 0.0002, 3.9 [1.8-8.4], 35.5%,0.119, 2.23 [0.82-5.821]; R only, 10.9%, 37.3%, 0.0002, 4.9 [2.0-12.2], 19.4%, 0.355, 1.96 [0.54-6.471]; V only, 8.9%, 11.9%, 0.743, 1.4 [0.4-4.4], 16.1%, 0.419, 1.97 [0.47-7.19]. There was a statistically significant relationship between PFO and serious DCI. The presence of a resting shunt increases the risk of serious DCI almost five-fold. The data also suggest increased risk of DCI with shunt after Valsalva but the result is not statistically significant. CFD was poor at detecting inter-atrial shunt: of a total of 60 shunts detected by BCE only one (in a control subject) was detected by CFD. (Supported by NOAA/UNCW Grant # NA88AA-D-VR004)