The changes that occur with an athletic heart, which are also referred to as cardiac remodeling, are not felt to be pathologic and so a true athletic heart usually should not be associated with an increased mortality risk.
Structural changes that can occur with an athletic heart include increased thickness and dilation of the left ventricle, the chamber that pumps freshly oxygenated blood throughout most of the body.
It is also possible to see dilation of the left atrium, the chamber that supplies blood to the left ventricle, usually in proportion to the amount of left ventricular enlargement. The type of exercise performed helps determine the pattern of structural changes that are observed in the athletic heart.
Endurance training results in dilation of the heart and can cause an increase in the thickness of the heart muscle. This type of training (also called dynamic, isotonic or aerobic training) includes cycling, swimming and long distance running. The pattern of combined dilation and thickening of the heart seen with endurance training is called eccentric hypertrophy.
Strength training (also called static, isometric, anaerobic or power exercise), which includes wrestling and weight lifting, exposes the heart to large increases in blood pressure. This predominantly results in increased wall thickness, known as concentric hypertrophy. Engagement in both endurance and strength training can result in a mixed pattern.
Most athletes only have a modest increase in left ventricular wall thickness, and many have normal heart thickness. Only a small percentage of elite athletes have a wall thickness as high as 13 mm to 15 mm. The normal thickness of the left ventricular wall is usually less than 12 mm.
A number of abnormalities can be seen on the electrocardiogram of athletic hearts. This includes slow heart rate, increased voltage, incomplete right bundle branch block and other types of heart block. While T wave inversions have been described in athletic hearts, their presence should probably prompt investigation of other causes that may be pathologic.
Trained athletes may also experience complex arrhythmias, including ventricular tachycardia, which tend to have a favorable outcome and may resolve or substantially decrease with deconditioning (cessation of the intense exercise regimen).
While it can sometimes be difficult to differentiate an athletic heart from pathologic cardiac conditions, the results of cardiac testing can provide clues. For example, diastolic dysfunction, which is a stiffening of the left ventricle, should not be present on echocardiography in an athletic heart. If there is hypertrophy localized only to the interventricular septum, which is the heart muscle that separates the left ventricle from the right ventricle, one should suspect the presence of hypertrophic cardiomyopathy, a primary disease of heart muscle.
APPLICANT 1 is a 45 year old former marathon runner who stopped exercising one year ago due to a leg injury. His echocardiogram shows a hypertrophied intraventricular septum of 1.8 cm and the electrocardiogram has inverted T waves. This is suspicious for hypertrophic cardiomyopathy and would be highly rated at best.
APPLICANT 2 is a 50 year old applicant who cycles for two hours daily and has mild left ventricular dilation and minimal increased thickness of the left ventricle. This is consistent with an athletic heart and can be Preferred Plus.
APPLICANT 3 is a 28 year old elite athlete who was noted on echocardiography to have a left ventricular wall thickness of 15 mm one year ago just before retiring from competition. A recently performed echocardiogram was normal. This is consistent with an athletic heart and can be Preferred Plus.