Athlete’s Heart

Numerous changes in rhythm and ECG morphology can occur; they correlate poorly with level of training and cardiovascular performance. The most common ECG finding is

Rarely, heart rate is < 40 beats/minute. Sinus arrhythmia often accompanies the slow heart rate. Resting bradycardia may also predispose to

Other ECG findings that may occur include

However, third-degree AV block Third-degree AV block Atrioventricular (AV) block is partial or complete interruption of impulse transmission from the atria to the ventricles. The most common cause is idiopathic fibrosis and sclerosis of the conduction... read more is abnormal and should be investigated thoroughly.

These ECG and rhythm changes have not been associated with adverse clinical events, suggesting that various arrhythmias are not abnormal in athletes. The arrhythmias are usually abolished or substantially reduced after a relatively brief period of deconditioning.

Echocardiography can usually distinguish athlete’s heart from cardiomyopathies (see table Features Distinguishing Athlete's Heart From Cardiomyopathy Features Distinguishing Athlete's Heart From Cardiomyopathy ), but the distinction is not always clear because there is a continuum from physiologic to pathologic cardiac enlargement. The zone of overlap between athlete’s heart and cardiomyopathy is left ventricular septal thickness:

In this overlap area, the presence of mitral valve systolic anterior motion strongly suggests hypertrophic cardiomyopathy Hypertrophic Cardiomyopathy Hypertrophic cardiomyopathy is a congenital or acquired disorder characterized by marked ventricular hypertrophy with diastolic dysfunction (eg, due to valvular aortic stenosis, coarctation... read more . Also, diastolic indexes may be abnormal in cardiomyopathy but are usually normal in athlete's heart. In general, echocardiographic changes correlate poorly with level of training and cardiovascular performance. Trace mitral regurgitation and tricuspid regurgitation are commonly detected. Of note, reduction of physical training will result in regression of cardiac enlargement in patients with athlete's heart but not in those with cardiomyopathy. Exercise echocardiography may help to differentiate athlete's heart from dilated cardiomyopathy Dilated Cardiomyopathy Dilated cardiomyopathy is myocardial dysfunction causing heart failure in which ventricular dilation and systolic dysfunction predominate. Symptoms include dyspnea, fatigue, and peripheral edema... read more . In one study, a change during exercise in left ventricular ejection fraction (LVEF) ≤ 11% and a peak LVEF ≤ 63% during exercise predicted dilated cardiomyopathy with a sensitivity of 85.7% and specificity of 92% (2 Diagnosis references Athlete’s heart is a constellation of structural and functional changes that occur in the heart of people who train for prolonged durations (eg,> 1 hour most days) and/or frequently at high... read more ).

Although confirmation in large studies is pending, data so far suggest that CMR may also help differentiate athlete's heart from cardiomyopathy. In hypertrophic cardiomyopathy (3 Diagnosis references Athlete’s heart is a constellation of structural and functional changes that occur in the heart of people who train for prolonged durations (eg,> 1 hour most days) and/or frequently at high... read more ), CMR may identify focal hypertrophy not identified on the echocardiogram, particularly in the apex, anterior free wall, and posterior septum. Delayed imaging after injection of contrast may show a typical pattern of mid-wall fibrosis in some patients with hypertrophic cardiomyopathy, particularly in left ventricular wall segments that exhibit maximal hypertrophy. However, this finding is absent in up to 60% of patients with hypertrophic cardiomyopathy.

Delayed enhancement on CMR is also evident in nonischemic dilated cardiomyopathy and may help differentiate dilated cardiomyopathy from athlete's heart. However, the finding is absent in 68% of patients with genetically proven dilated cardiomyopathy. T1 and T2 mapping, extracellular volume quantification, late gadolinium enhancement, deformation imaging and diffusion tensor imaging are all promising techniques to differentiate between athlete's heart and hypertrophic cardiomyopathy. Further studies are required to better determine the ability of these techniques to detect hypertrophic cardiomyopathy in athletes (4, 5 Diagnosis references Athlete’s heart is a constellation of structural and functional changes that occur in the heart of people who train for prolonged durations (eg,> 1 hour most days) and/or frequently at high... read more ). Although exercise capacity as measured by stress testing does not differentiate between athlete's heart and dilated cardiomyopathy, reduced cardiac contractile reserve with exercise observed on CMR imaging may be useful in establishing a diagnosis of dilated cardiomyopathy in an athlete.

During exercise stress testing Stress Testing In stress testing, the heart is monitored by electrocardiography (ECG) and often imaging studies during an induced episode of increased cardiac demand so that ischemic areas potentially at risk... read more , heart rate remains lower than normal at submaximal stress and increases appropriately and comparably to heart rate in nonathletes at maximal stress; it rapidly recovers after exercise. Blood pressure response is normal if:

Many resting ECG changes decrease or disappear during exercise; this finding is unique to athlete's heart, distinguishing it from pathologic conditions. However, pseudonormalization of T-wave inversions could reflect myocardial ischemia and thus warrants further investigation in older athletes. Also, a normal exercise stress test result does not rule out a cardiomyopathy.