Hypertrophic cardiomyopathy (HCM) is the encompassing term used to describe the pathologic state of malignant myocardial hypertrophy which is out of proportion to expected hemodynamic load. Macroscopically, there is significant increased wall thickness which appears out of proportion to left ventricular cavity size. Idiopathic concentric left ventricular hypertrophy is a less common cause of exercise-induced sudden death. Whereas morphologically it appears similar to HCM, with concentric hypertrophy out of proportion to eccentric left ventricular cavity enlargement, there is no evident histologic abnormality and no genetic link has been identified. Whether this is purely an excessive hypertrophic response to physiologic hemodynamic loads, a variation of HCM, or a pathologic state induced by anabolic steroid use is not known.
Describe the clinical features of HCM.
Although most patients with HCM are asymptomatic, the initial presentation in some may be sudden death, and others may have complaints of new exertional dyspnea, chest pains, palpitations, dizziness, or syncope. The pathophysiologic processes underlying these symptoms include an interrelation between systolic and diastolic dysfunction, with or without dynamic left ventricular outflow obstruction, with or without ischemia, and with or without brady- or tachyarrhythmias. It is easy to see how extreme exercise can exacerbate symptoms in HCM, including triggering sudden death.
Numerous electrocardiographic “abnormalities” have been noted among athletes, attributable to physiologic hypertrophy and increased vagal tone. Name several.
What echocardiographic features differentiate physiologic left ventricular (LV) hypertrophy in the athlete from HCM?
Characteristics of the Physiologic Athletic Heart
Upper limit of LV thickness rarely 13 mm, except in world-class athletes Uniform hypertrophy, with adjacent wall segments never differing by 2 mm Septal-to-free wall thickness ratio 1.3 (except in highly trained weight-lifters) Proportionality of LV thickness to LV internal dimension (LVID)
Endurance athlete—Septum:LVID 0.22 Power athlete—Septum:LVID 0.28 Proportionate papillary muscle hypertrophy Normal LV outflow tract dimensions Normal left atrial size (45 mm)
Normal systolic function
Absence of clinically relevant mitral regurgitation Normal Doppler transmitral LV filling pattern
Systolic anterior motion of the mitral valve suggests HCM. Transmitral Doppler evidence of impaired LV filling, including diminished early filling phase, augmented late filling of atrial contraction, and prolongation of deceleration between early and late filling phases, also suggest HCM if there is significant left ventricular hypertrophy without hypertension. Left atrial enlargement and mitral valve thickening are abnormal findings in a normotensive athlete and suggest HCM.
Are there gender and racial differences in the expression of physiologic left ventricular hypertrophy seen in athletes?
There are limited data on women, but of the elite female endurance athletes studied, LV septal thickness did not exceed 12 mm and the ratio of LV septum to LV free wall remained 1.3. In a study of male athletes, 11% of 265 black collegiate athletes had septal thickness 13 mm, compared with only 1.7% of elite white athletes with septal thickness 13 mm. This more pronounced hypertrophy seen among black athletes may represent a racial difference. However, black and white athletes were not matched for type of activity.
Outline a cost-effective approach to athletic preparticipation screening.