The impact of prolonged exercise in a cold environment upon cardiac function

Purpose: The purpose of the present study was to examine the impact of cold exposure coupled with prolonged exercise upon postexercise left ventricular (LV) function and markers of myocardial damage. Methods: Eight highly trained male athletes (mean +/- SD; age: 28.2 +/- 8.8 yr; height: 1.78 +/- 0.07 in; body mass: 74.9 +/- 7.6 kg; VO2max: 65.6 +/- 7.0 mL(.)kg(-1.)min(-1)) performed two 100-mile cycle trials, the first in an ambient temperature of 0degreesC, the second in an ambient temperature of 19degreesC. Echocardiographic assessment was completed and blood samples drawn before, immediately postexercise, and 24-h postexercise. Left ventricular systolic (stroke volume [SV], ejection fraction [EF], and systolic blood pressure/end systolic volume ratio [SBP/ESV]) and diastolic (early [E] to late [A] filling ratio [E:A]) parameters were calculated. Serum was analyzed for creatine kinase isoenzyme MB (CK-MBmass) and cardiac troponin T (cTnT). cTnT was analyzed descriptively whereas other variables were assessed using two-way repeated-measures ANOVA. Results: No significant change was observed in systolic function across time or between trials. A significant difference between trials was observed in E:A immediately after exercise (1.4 +/- 0.4 [19degreesC] vs 1.8 +/- 0.3 [0degreesC]) (P < 0.05). (CKMBmass)-M-. was significantly elevated immediately after exercise in both trials (P < 0.05). Positive cTnT concentrations were observed in two subjects immediately after the 19degreesC trial (0.012 mug(.)L(-1) and 0.034 mug(.)L(-1)). Conclusions: Cycling 100 miles in an ambient temperature of 19degreesC is associated with an acute change in diastolic filling that is not observed after prolonged exercise at 0degreesC. Prolonged exercise is associated with minimal cardiac damage in some individuals; it appears that this is a separate phenomenon to the change in diastolic filling.