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Synopsis: About 15% of highly trained athletes have left ventricular (LV) cavity dimensions associated with cardiomyopathy, but with normal ventricular performance and a benign course, suggesting that this dilation represents a physiologic adaptation to intensive aerobic training.
Source: Pelliccia A, et al. Ann Int Med 99;130:23-31.
Much has been written about increases in left ventricular (LV) mass and wall thickness in well-trained athletes, but there is little information about increases in cavity dimensions. Thus, Pelliccia and colleagues evaluated echocardiograms done in 1309 Italian Olympic athletes who were judged to be free of structural heart disease. The athletes participated in 38 sports, ranged in age from 13 to 59 years, and were 73% men. All had trained for at least two years, 26% were competitive at the world level, and the remaining were competitive at the national level. The LV diastolic dimension was less than 54 mm in 55% and was greater than 60 mm in 14%. The range was 38-66 mm (95th percentile 56 mm) in women and 43-70 mm (95th percentile 63 mm) in men. Intraventricular septal thickness ranged from 5 to 15 mm in diastole, and was greater than 12 mm in 1%. In general, wall thickness paralleled cavity dimension (r = 0.64), but only three of 185 athletes with a cavity dimension of 60 mm had a wall thickness greater than 13 mm. Multivariate analysis showed that body surface area and type of sport were the most significant variables associated with cavity dimension, followed by heart rate, sex, and age. Sports associated with large LV cavity size were cycling, ice hockey, basketball, rugby, canoeing, and rowing. All the athletes with large cavities had normal LV systolic and diastolic function, and they had no segmented wall motion abnormalities and no significant valvular regurgitation. Follow-up of the athletes with cavity size greater than 60 mm for a mean of five years (2-12 years) was uneventful. Pelliccia et al conclude that about 15% of highly trained athletes have LV cavity dimensions usually associated with cardiomyopathy, but with normal ventricular performance and a benign course, suggesting that this dilation represents a physiologic adaptation to intensive aerobic training.
Comment by Michael H. Crawford, MD
Because of the association between the rare sudden death in an athlete and hypertrophic cardiomyopathy, there has been considerable work on wall thickness in athletes. Cardiomyopathy has played a role in the deaths of some recent well-known athletes, yet less is known about LV cavity enlargement in highly trained athletes. In this report from Italy, most athletes had normal LV cavity sizes, but 15% had strikingly enlarged ventricular size (> 60 mm), almost always with normal wall thickness. By contrast, only 1% had markedly thickened walls (>12 mm). Since cavity dilation can herald the onset of reduced LV systolic function, this raises the concern of cardiomyopathy vs. athlete’s heart. The athletes with marked cavity dilation had normal systolic function and remained well for an average follow-up of five years (2-12 years). Thus, there is no reason to suspect cardiomyopathy in these athletes.
Enlarged hearts in athletes have been well recognized for more than 100 years, but modern imaging studies have shown mainly right ventricular dilation and LV hypertrophy. Why do some athletes develop large LV cavities? This study showed that it was largely related to the type of sport and the size of the individual. However, genetic factors cannot be excluded since some athletes may be born, not made. In this regard, the results of this study in a relatively homogeneous Italian athlete population cannot necessarily be extrapolated to other populations, such as Africans or Asians. Also, certain sports popular in the United States, such as football and baseball, were not represented. Finally, the long-term consequences of these extremely large ventricles are unclear. Whether they will regress after cessation of training or remain large is unknown. In fact, the echo assessments were not made at any specific point in the training season in this study. Data from my laboratory on college athletes suggests that LV cavity size is greatest at the peak of training just before competition starts as compared to the off-season. Thus, the extreme cavity enlargement observed in these athletes may represent the peak of training subgroup.
For the clinician faced with deciding whether this is structural heart disease or athlete’s heart, several considerations are important: 1) LV systolic and diastolic function are normal in the athlete. Remember, ejection fraction in a large heart at a slow heart rate often will be in the low normal range, 50-55%, which was observed in this study. 2) The athletes will often be male and large. 3) They will be well trained and competitive in sports that combine aerobic endurance and strength (i.e., cycling or rowing). 4) They will have slow heart rates. 5) They will be young.