Muscle fiber-type distribution predicts weight gain and unfavorable left ventricular geometry: a 19 year follow-up study

BACKGROUND: Skeletal muscle consists of type-I (slow-twitch) and type-II (fast-twitch) fibers, with proportions highly variable between individuals and mostly determined by genetic factors. Cross-sectional studies have associated low percentage of type-I fibers (type-I%) with many cardiovascular risk factors. METHODS: We investigated whether baseline type-I% predicts left ventricular (LV) structure and function at 19-year follow-up, and if so, which are the strongest mediating factors. At baseline in 1984 muscle fiber-type distribution (by actomyosin ATPase staining) was studied in 63 healthy men (aged 32–58 years). The follow-up in 2003 included echocardiography, measurement of obesity related variables, physical activity and blood pressure. RESULTS: In the 40 men not using cardiovascular drugs at follow-up, low type-I% predicted higher heart rate, blood pressure, and LV fractional shortening suggesting increased sympathetic tone. Low type-I% predicted smaller LV chamber diameters (P ≤ 0.009) and greater relative wall thickness (P = 0.034) without increase in LV mass (concentric remodeling). This was explained by the association of type-I% with obesity related variables. Type-I% was an independent predictor of follow-up body fat percentage, waist/hip ratio, weight gain in adulthood, and physical activity (in all P ≤ 0.001). After including these risk factors in the regression models, weight gain was the strongest predictor of LV geometry explaining 64% of the variation in LV end-diastolic diameter, 72% in end-systolic diameter, and 53% in relative wall thickness. CONCLUSION: Low type-I% predicts obesity and weight gain especially in the mid-abdomen, and consequently unfavourable LV geometry indicating increased cardiovascular risk

Sudden cardiac death in young athletes: time for a Nordic approach in screening?

In 2005, the European Society of Cardiology published recommendations for cardiovascular screening in athletes. Discussion on whether screening is beneficial is ongoing. Recently, the first prospective results on effectiveness of screening in preventing sudden deaths were published from Italy. The results were supportive of screening, but did not provide conclusive evidence. Our suggestion for a Nordic approach on this issue is a directed cardiovascular examination initially involving elite athletes, because this is feasible with respect to the Nordic health care systems and the organization and logistics of elite competitive sports, but also because of the negative aspects of screening large populations. This directed cardiovascular examination would include personal and family history, clinical examination, and electrocardiography (ECG). Further examinations should thereafter be carried out in athletes with suggestive findings in the initial evaluation. The directed cardiovascular examination should be voluntary. It should be conducted at least once, with information on alarming symptoms (syncope, chest pain or dizziness during exercise) and heredity (sudden cardiac death or hereditary heart disease in near relatives) stressed to the athlete as indications for necessary check-ups in the future. The examination would also provide the athlete with an ECG recording, which is valuable as a reference at a later time