[abstract] THE EFFECT OF IMMERSION AND EXERCISE ON RIGHT-TO-LEFT SHUNT THROUGH A PATENT FORAMEN OVALE.

Abstract

BACKGROUND: Recent studies have suggested that patent foramen ovale (PFO) is a risk factor for decompression illness. This study was performed to determine the effect of immersion and exercise upon right-to-left shunt (RLS) through a PFO. METHODS: After obtaining approval from the Institutional Review Board ten normal volunteers (mean age 33 y; M = 6, F = 4)with previously demonstrated PFO were studied. Individuals were studied both dry and immersed to the neck in thermoneutral water while seated on an exercise bicycle. Observations were performed at rest or while exercising at 360 or 720 kp*m*min^(-l). Each subject was then studied while lying supine on a stretcher. During the 6th-8th minute of each exercise 10 ml of pre-agitated isotonic saline solution was injected IV while imaging the heart (Hewlett-Packard Sonos 1000 transthoracic probe). Images were recorded on high fidelity video tape. Poor quality studies were not included. Right-to-left shunt was examined using an apical four-chamber view. Left ventricular diameter (LVEDD) was measured using a standard parasternal long axis view. Shunt was scored as 0 (none), 1(<50% opacification of LV), 2 (50% opacification of LV). RESULTS: [table] Condition, Exercise (kp*m/min), VO2 (L/m), HR, LVEDD (cm), Shunt (# subjects): 0, 1, 2; Dry: Rest, .30 +- .04, 77.2, 3.83 +- .36, 6, 2, 2; Dry: 360, 1.26 +- .09, 119.6, 3.82 +- .18, 5, 3, 2; Dry: 720, 2.15 +- .23, 160.8, 4.03 +- .41, 2, 3, 2; Immersed: Rest, .27 +- .05, 78.8, 4.19 +- .24, 4, 2, 4; Immersed: 360, 1.77 +- .16, 149.7, 4.15 +- .47, 4, 4, 2; Immersed: 720, 2.54 +- .27, 176.0, 4.03 +- .53, 3, 3, 2; Dry: Supine, -, -, 4.19 +- .46, 3, 1, 4; [end table] LVEDD (+-95 CI) increased with immersion (P<.04, ANOVA) but was unaffected by exercise. CONCLUSION: While immersion caused cardiac dilatation, neither immersion nor exercise affect RLS through a PFO.