Cardiac structural and electrical adaptation in male active athletes. QT interval could it be the clue to sudden cardiac death?

ABSTRACT

In humans, cardiac morphological adaptations to athletes training have been exhaustively described. Top-level training is often associated with morphological changes in the heart, including increases in left ventricular chamber size, wall thickness, and mass. The increase in left ventricular mass because of training is called [athlete's heart]. Left ventricular structural changes in competitive athletes represent adaptation to hemodynamic overload induced by training and are consisted with different kinds of sport activity. Work capacity during exercise is positively influenced by preload increase in top-level endurance athletes, while increased after load due do isometric training in strength-trained athletes determines higher systemic resistance due do physical effect. This work aimed to study the effects of prolonged physical training on the structure of the heart. A cross-sectional comparative study had been conducted in Cardiology Department, Suez Canal University Hospital and included active and control subjects in Ismailia Governorate Clubs. The study included 27 competitive endurance active male athletes, 27 power active male athletes, and 27 male healthy control subjects leading an ordinary sedentary life. The study population were subjected to general clinical examination, electrocardiographic and echocardiograghic examinations. Standard resting 12-lead ECGs were obtained a few minutes before the echocardiography investigation and >/= 24 hours after the last athletic activity for active athletes. Results of electrocardioraphic data showed that PR intervals, QT interval QTc dispersion were significantly higher in active athletes than that in control subjects. These prolonged QTc dispersion may predispose to further ventricular arrhythmic events and sudden death. In this study, comparative assessment of electrocardrgraphic pattern was done between active athletes and control subjects. 74.1% of active athletes showed completely normal ECG while the remaining 25.9% showed minor alterations that have been consistently reported in trained athletes and that are regarded as part of athlete's heart syndrome. Comparing LVM and mass index in power versus endurance active athletes it was shown that LVM and LVMI were significantly higher in power active athletes. From the present study, we can conclude that there were certain structural adaptive changes occurring in athletic heart; these adaptive changes vary according to the type of training whether being mainly isometric or isotonic. In the former one, the heart adapts mainly by concentric hypertrophy, whereas training with isotonic [dynamic] exercise leads to eccentric hypertrophy. However, the geometric pattern of athlete's heart is more complicated than expected as there is overlap between isometric and isotonic activities. Our findings are most consistent with the benign and physiological nature of LV hypertrophy in athletes. But we can suggest that careful assessment of the QT interval may be a clue to sudden cardiac death in athletes. The 12-lead ECG has been suggested as a relatively simple and inexpensive test to strengthen the limited diagnostic efficacy of the medical history and physical examination