Exposure to extreme cold lowers the ischemic threshold in coronary artery disease patients.

BACKGROUND

Cold temperature is known to commonly precipitate angina pectoris in patients with symptomatic coronary artery disease (CAD). It was previously shown that the ischemic threshold was lower during exercise testing at -8 degrees C than at +20 degrees C in patients with a history of cold-induced angina, whereas it was unchanged in patients without cold-induced angina. Few data exist on the impact of more severe cold exposure on myocardial ischemia.

OBJECTIVE

To determine the effect of extreme cold exposure (-20 degrees C) on the ischemic threshold among CAD patients.

METHODS

Thirteen men with CAD and documented exercise-induced ischemia performed two treadmill exercise tests, one at +20 degrees C and one at -20 degrees C, in random order. Electrocardiograms were recorded every 30 s and analyzed separately in random order by two experienced readers blinded to temperature.

RESULTS

The mean (+/- SD) time to ischemic electrical threshold was 53+/-60 s lower at -20 degrees C than at +20 degrees C (P=0.008), corresponding to a relative change of -8.0+/-10.5%. All other exercise parameters, including total exercise time and rate-pressure product, were unchanged during exposure to extreme cold.

CONCLUSION

Exposure to extreme cold (-20 degrees C) lowers the ischemic threshold during exercise testing in patients with CAD, even if asymptomatic or without a history of cold-induced angina. Patients with CAD and evidence of exertional angina or myocardial ischemia wishing to perform exercise at extremely low temperatures should discuss this matter with their physicians.