[Effect of intermittent variable intensity exercise on QT variation and risk of sudden cardiac death among Cameroonian school adolescents].

INTRODUCTION: Several cases of sudden deaths are observed among students practicing sport and physical activity (SPA). Just few studies have been carried out on the variation of the QT (interval) and risk of sudden death during sporting exercises.

AIM: To determine the effect of variable intermittent stress intensity on the variation of QT and the risk of sudden cardiac death.

PATIENTS AND METHODS: Form 4, lower sixth and upper sixth students were recruited from a high school in Douala (Cameroon). Each subject was tested; starting with a 2-km walk followed by a sprint race or an endurance race, protocol I (P1) or the reverse; protocol II (P2). Two electrocardiograms were recorded; prior to the beginning of the SPA and 5minutes after the last race. QT was corrected using four formulas.

RESULTS: Forty-one subjects (21 women and 20 men), mean age 18±2 years were recruited. At the end of the exercise, corrected QT increased with Bazzet's formula and decreased with Frahmingam's formula. The difference was not significant with Fridericia and Hodges formulas. The frequency of long QT was higher at the end of the exercise with Bazzet's formula (12.2% vs. 24.4%, P=0.009) while the difference was not significant for the other formulas.

CONCLUSION: The risk of sudden cardiac death increases significantly after SPA. More studies on large samples are needed.