Influencia del ejercicio prolongado, sobre la función cardíaca. (Inglés)

SHAVE, R., E. DAWSON, G. WHYTE, K. GEORGE, M. NIMMO, J. LAYDEN, P. COLLINSON.

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:
colon; Eight highly trained male athletes (mean +/- SD; age: 28.2 +/- 8.8 yr; height: 1.78 +/- 0.07 m; body mass: 74.9 +/- 7.6 kg; [latin capital V with dot above]O2max: 65.6 +/- 7.0 mL[middle dot]kg-1[middle dot]min-1) performed two 100-mile cycle trials, the first in an ambient temperature of 0[degrees]C, the second in an ambient temperature of 19[degrees]C. 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 [19[degrees]C] vs 1.8 +/- 0.3 [0[degrees]C]) (P < 0.05). CK-MBmass was significantly elevated immediately after exercise in both trials (P < 0.05). Positive cTnT concentrations were observed in two subjects immediately after the 19[degrees]C trial (0.012 [mu]g[middle dot]L-1 and 0.034 [mu]g[middle dot]L-1).

Conclusions:
Cycling 100 miles in an ambient temperature of 19[degrees]C is associated with an acute change in diastolic filling that is not observed after prolonged exercise at 0[degrees]C. 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.