Highly trained adolescent athletes have hearts that are larger than average, but the sizes don’t reach those seen with dilated cardiomyopathy, a serious heart disorder, new research shows.

With dilated cardiomyopathy, the inside of the heart’s main pumping chamber, the left ventricle, can measure greater than 60 millimeters across.

The findings suggest that athletes with a left ventricle greater than 60 millimeters should not be written off as simply having normal enlargement, lead author Dr. Jayesh Makan and colleagues, from the University Hospital Lewisham in London, and note.

These patients may need to be tested for dilated cardiomyopathy, they add.

The investigators used heart ultrasound, or echocardiography, to compare the left ventricles of 900 elite adolescent athletes and 250 regular teenagers. The findings are reported in the medical journal Heart.

The average left ventricle size among the athletes was 50.8 millimeters, 6 percent larger than the 47.9 millimeter size seen among regular teenagers, the authors note. Moreover, 18 percent of the athletes had left ventricles that were greater than 54 millimeters, while none of the regular teens had ventricles that reached this size.

Still, none of the athletes had left ventricles that exceeded 60 mm, which is common among patients with dilated cardiomyopathy. In addition, the heart’s pumping ability was not impaired in the athletes, a finding seldom seen with dilated cardiomyopathy.

“This study provides valuable information regarding the upper limit of (left ventricle) size in the highly trained junior athlete and will prove clinically useful in the differentiation of physiological adaptation from cardiomyopathy in this important group of people,” the authors conclude.

SOURCE: Heart, April 2005.