Electrocardiographic findings in athletes: The prevalence of left ventricular hypertrophy and conduction defects

BACKGROUND: Cardiac adaptation to sport activities differs between athletes and sedentary subjects, and among different sports disciplines. OBJECTIVES: To determine whether there are electrocardiographic differences or distinctive abnormalities between athletes and sedentary subjects, and to verify the relationship between vagal activity measured by heart rate va riability (SD of all normal-to-normal intervals [SDNN]) and possible electr ocardiographic abnormalities. SUBJECTS AND METHODS: Resting electrocardiograms and heart rare variability measurements were performed sepa rarely during a single visit on 100 athle tes and 50 nonathlete control subjects aged 18 to 55 years. The athletes we re from the following various sports disciplines: long-distance running, mo untain biking, cross-country skiing, biathlon, speed skating, swimming and triathlon. RESULTS AND CONCLUSIONS: There were significantly longer RR intervals, PR i ntervals and QT intervals in athletes than in control subjects tall P <0.05 ). The QRS complex and QTc did not show significant differences (both P >0. 05). The prevalence of left ventricular hypertrophy (LVH) and incomplete ri ght bundle branch block (IRBBB) was 10% and 7%, respectively, in athletes, but these conditions were absent in control subjects; among athletes, 2% pr esented with both condition. LVH and IRBBB were more common among long-dist ance runners (six of 14 and four of 14, respectively) and could be attribut ed to normal, long term adaptation to intense, repeated exercise. LVH was r elated to age (P=0.04), whereas IRBBB was influenced by the number of years of training in the respective spurts discipline (P=0.03). The mean SDNN va lue was significantly more elevated in athletes (P=0.0001), reflecting a hi gher parasympathetic tune than in sedentary control subjects. However, ther e was no relationship between vagal activity and LVH or IRBBB (both P >0.05 ).