Aortic Root Size in Athletes
Abstract & Commentary
By Michael H. Crawford, MD, Professor of Medicine, and Chief of Clinical Cardiology, at the University of California, San Francisco. Dr. Crawford is on the speaker's bureau for Pfizer.
Source: Babaee Bigi, M, et al. Aortic Root Size and Prevalence of Aortic Regurgitation in Elite Strength Trained Athletes. Am J Cardiol 2007;100:528-530.
Little is known about aortic root size in strength trained athletes, yet the transient increase in central aortic pressure during weight lifting could increase aortic size over time and lead to aortic regurgitation. Thus, these investigators from Iran evaluated 100 strength trained male athletes who were competitive at the national level and 128 healthy age and height-matched men by echocardiography. Resting blood pressure was higher in the athletes (138 vs 113 mmHg, p < 0.05). Aortic diameters at the annulus, sinuses of Valsalva, sinotubular junction and the proximal ascending aorta were all greater in the athletes. Multivariate analysis showed that the duration of high intensity strength training, height and systolic blood pressure had the strongest association with aortic root diameters. Aortic regurgitation of any severity was absent in the controls (mean age 22 years) but found in 9 athletes (5 mild and 4 moderate). The authors concluded that elite strength trained athletes had larger aortic roots than age and height matched controls.
Debate has raged back and forth for over a century as to whether the athlete's heart is a pathological condition or an adaptation to exercise training, and the pendulum has swung back and forth on this issue. Currently we are in an era where most believe that cardiac enlargement is a harmless physiologic adaptation as evidenced by the fact that despite left ventricular hypertrophy, diastolic function is normal. This is one of the few cautionary tales published recently. It makes biologic sense that repeated bouts of high blood pressure during training, which can be as high as 480/350 mmHg during weight lifting, could eventually dilate the aorta. This could be viewed as physiologic, but the persistently higher blood pressures and the 9% vs 0% aortic regurgitation can't be good. So perhaps isotonic exercise is adaptive and good for you, but isometric is not.
Before we jump to this conclusion, here are a few caveats. We are not given the weight of the subjects. Although matched for height, I doubt they were matched for weight or the authors would have said so. It is reasonable to presume that weight per se would not affect aortic size, since gaining fat weight is not associated with longer aortas. However, the larger muscle mass of a weight lifter may require a larger cardiac output and hence a larger aorta. Also, the extent to which obesity is present may lead to persistent hypertension which could enlarge the aorta. In addition, individuals with large aortas may be able to withstand the pressure increases of weight lifting more and self-select for this type of sporting activity. Finally, we don't know if anabolic steroids or growth hormone were used by these athletes and what effect they would have on the aorta. So there may be other explanations or confounders that were not considered in this study.
This is a provocative study that will certainly stimulate more work in this area. It may be an early push that will start the pendulum back toward a less benign view of extreme athleticism.