Transcranial doppler to detect high-risk PFO and predict decompression illness in divers

Abstract Background It has not yet been clearly demonstrated whether it is feasible to diagnose patent foramen ovale (PFO) using transcranial doppler (TCD) and to use it in strategies to prevent decompression illness (DCI) in self-contained breathing apparatus (SCUBA) divers. Purpose DIVER-PFO study confirmed that high-risk PFO is associated with an increased risk of DCI in SCUBA divers. In this prespecified post-hoc analysis, we aimed to prospectively evaluate the accuracy of TCD to diagnose high-risk PFO and to predict the occurrence of DCI. Methods Eighty-two consecutive divers (mean age; 41 years, male 80.5%) underwent transesophageal echocardiogram (TEE) and TCD with a saline bubble test to determine the presence of PFO and were subsequently divided into high-risk and low-risk groups by TEE findings. Divers in the high-risk PFO group included those with the following conditions: PFO with atrial septal aneurysm, hypermobility, PFO size ≥2 mm, or right to left shunt at resting state. The enrolled divers were then followed-up using a self-reported questionnaire through e-mail or telephone interview for 3 years, while they were blinded to their PFO status. The primary endpoint of the study was PFO-related DCI, comprising cases of cutaneous or neurologic DCI, DCI symptoms requiring hyperbaric chamber therapy, DCI symptoms within 30 minutes after surfacing, or unexplained death occurring within 2 weeks after diving. Results PFO was detected in 47 (57.3%) and 59 (72.0%) divers by TCD and TEE, respectively. Diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of TCD were 68.3%, 67.8%, 69.6% 85.1%, and 45.7% for the diagnosis of PFO, and 65.9%, 82.8%, 56.6%, 51.1% and 85.7% for the diagnosis of high-risk PFO, respectively. PFO-related DCI occurred in 9 divers in the PFO group (PFO vs non-PFO: 6.4 vs 0.7 incidences per 10,000 person dives; p=0.03) during a mean follow-up of 25.6 months. Integrated time-dependent Area Under the Curves for TCD and TEE to predict DCI occurrence using Cox’s proportional hazards regression model were 0.714 and 0.675, respectively. Conclusions TCD was moderately accurate to diagnose high-risk PFO in divers. However, it predicted DCI as much as TEE.Study flowIncidence of DCI in the PFO vs No PFO