Author(s): TSIOROS, S., MAIER, L.E., MACDONALD, T.J.A., MANFERDELLI, G., STAPLETON, R.K., GASHO, C.J., MACLEOD, D.B., GABRIELYAN, G., KILLICK, J.A., MINERS, N.I., MCCRONE, J.C., OSEI-BOATENG, C., WIDEMAN, C.D., GIBBONS, T.D., BAIN, A.R., SMITH, K.J., TYMKO, M.M., Institution: UNIVERSITY OF GUELPH, Country: CANADA, Abstract-ID: 2681

INTRODUCTION:
Patent foramen ovale (PFO) is an opening between the right and left atria of the heart, present in ~25-40% of the population [1,2]. As blood passes through the lungs, it acts as a “radiator” to help dissipate heat from the body and aid in cooling. In individuals with a PFO (PFO+), blood bypasses the respiratory “radiator” and does not get cooled through the pulmonary circulation. In support of this theory, previous work has found that PFO+ individuals have elevated core body temperature by ~0.4 degrees Celsius (DegC) at rest, which persists during cycling exercise at sea-level [3,4]; however, this has not been tested at high-altitude, which alters resting alveolar ventilation and thermoregulation. We hypothesized that at sea-level and high-altitude: 1) rectal core temperature (TREC) at rest, and during cycling exercise, would remain elevated in PFO+ compared to PFO-, 2) the partial pressure of arterial oxygen (PaO2) and oxygen saturation (SaO2) would be reduced, but the partial pressure of arterial carbon dioxide (PaCO2) would be elevated, in PFO+ compared to PFO-.
METHODS:
PFO screening was completed via agitated saline contrast echocardiography in 25 individuals (n=6 PFO+, n=19 PFO-). The presence of a PFO was determined if bubbles appeared in the left atria ≤3 cardiac cycles [5]. Participants performed a five-kilometer cycling time-trial at sea-level (334m) and after 4-8 days at high-altitude (~3,800m). We recorded TREC and collected arterial blood samples at rest, and at each kilometer of cycling exercise.
RESULTS:
At rest, PFO+ participants had an elevated sea-level TREC compared to PFO- individuals (0.47+0.36 DegC], p=0.02), but this difference became non-significant after acclimatizing to high-altitude (0.35+0.35DegC, p=0.09). The TREC response to cycling exercise was not different between PFO+ and PFO- at both sea-level and high-altitude (both p≥0.66). Additionally, at rest SaO2 was difference between PFO+ verses PFO-, but no interaction effect (p=0.016). In contrast, during exercise there was no SaO2 difference between groups at sea-level (p=0.21), but there was a trend toward reduction in PFO+ at high-altitude (p=0.052). With regards to arterial blood gases, there was no difference at rest or exercise between groups at sea-level or high-altitude in PaO2 and PaCO2 (both p>0.74).
CONCLUSION:
We found that the resting TREC difference between PFO+ and PFO- individuals observed at sea-level may be attenuated at high-altitude, with no group differences in the TREC response to exercise. Additionally, there were no differences in arterial blood data between groups. These data indicate that presence of PFO has minimal response to core temp and arterial blood gases during exercise at sea-level and high-altitude. [1] Lechat 1988/ [2] Hagen 1984/ [3] Lovering 2011/ [4] Davis 2015/ [5] Silvestry 2015