Various noninvasive testing procedures can be used to provide information on the underlying cause of a hypertrophied heart. Although an electrocardiogram (ECG) has limitations and cannot fully distinguish an athlete’s heart from HCM, some preliminary information can be derived to determine the need for additional testing. The ECG pattern demonstrated in an athlete’s heart often depicts prolonged conduction intervals and also may include the presence of an incomplete right bundle branch block or high T-waves (5). In situations where the ECG demonstrates deep Q-waves and negative T-waves, the presence of HCM should be considered because these physiological changes are not typical after prolonged training programs (5).
However, echocardiography can provide significant clinical information to differentiate an athlete’s heart from HCM. An athlete’s heart is typically characterized by proportional increases in ventricular diameters and wall thickness, leading to left and right heart walls that are symmetrically affected (5). In HCM, asymmetric left ventricular hypertrophy is present, primarily affecting the interventricular septum. In fact, septal thickness exceeding 15 mm has been clearly linked to HCM (5). Lastly, serial echocardiography could be used to further differentiate between HCM and athlete’s heart by demonstrating evidence of detraining. During this period, marked reduction in the morphological changes associated with training will be noted in the athlete’s heart, where no changes in structural abnormalities will be noted in those with HCM (5).
Although recent recommendations from the American College of Cardiology Foundation (ACC)/American Heart Association list the presence of HCM as a relative contraindication to exercise testing (3), researchers have identified a relatively low incidence of significant cardiovascular complications during testing in this patient population (1,16). Additionally, according to the ACC/European Society of Cardiology, a risk factor for sudden death that often is associated with HCM includes an abnormal systolic blood pressure response to exercise (9). Thus, it seems that exercise testing has a role in distinguishing between HCM and an athlete’s heart, particularly when adjunctive echocardiography or oxygen consumption measures are used. Maron et al. (10) recommend that exercise echocardiography be used to evaluate for outflow track obstruction (a narrowing caused by the thickened ventricle walls that can block or reduce the blood flow from the left ventricle to the aorta) in patients with suspected HCM. Exercise testing also can identify hypotensive or attenuated blood pressure responses that are indicative of HCM but not typically seen with an athlete’s heart (2,6,9,15). Lastly, when concomitant oxygen consumption measures are used during the exercise test, those with an athlete’s heart will demonstrate significantly higher peak oxygen consumption as compared with those with hypertrophy caused by HCM (16). In fact, given available data, it is postulated that oxygen consumption measures below 50 ml/kg per minute in an athlete with diagnosed cardiac hypertrophy can be used to identify probable HCM versus an athletic heart (16).
Identification of potentially dangerous clinical conditions is imperative for the exercise physiologist who works in an exercise testing laboratory or in a clinical rehabilitation center. Abnormal ECG findings may elicit the need for further clinical testing that may be beneficial in clarifying questionable clinical status. When working as part of a team of health professionals and by recognizing the signs and symptoms of HCM, the risks of sudden cardiac death during exercise in this clinical population can be reduced. In addition, recognizing that persistent aerobic and strength training exercise can alter cardiac morphology, which may require alternative clinical testing or adjunctive imaging modalities during exercise testing, improvements in testing processes can be identified and discussed in an effort to better diagnose or rule out the presence of cardiac ischemia and HCM.
1. Drinko JK, Nash PJ, Lever HM, Asher CR. Safety of stress testing in patients with hypertrophic cardiomyopathy. Am J Cardiol
2. Frenneaux MP, Counihan PJ, Caforio AL, et al. Abnormal blood pressure response during exercise in hypertrophic cardiomyopathy. Circulation.
3. Gibbons J, Balady GJ, Bricker JT, et al. ACC/AHA 2002 Guidelines update for exercise testing: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Exercise Testing) [Internet]. [cited 2011 Mar 1]. Available from: www.acc.org/clinical/guidelines/exercise/dirIndex.htm
4. Gilbert CA, Nutter DO, Felner JM, et al. Echocardiographic study of cardiac dimensions and function in the endurance-trained athlete. Am J Cardiol.
5. Lauschke J, Maisch B. Athlete’s heart or hypertrophic cardiomyopathy? Clin Res Cardiol
6. Maki S, Ikeda H, Muro A, et al. Predictors of sudden cardiac death in hypertrophic cardiomyopathy. Am J Cardiol.
7. Maron BJ. Structural features of the athlete heart as defined by echocardiography. J Am Coll Cardiol
8. Maron BJ, Gardin JM, Flack JM, et al. Prevalence of hypertrophic cardiomyopathy in an outpatient population referred for echocardiographic study. Circulation.
9. Maron BJ, McKenna WJ, Danielson GK, et al. American College of Cardiology/European Society of Cardiology Clinical Expert Consensus document on Hypertrophic Cardiomyopathy. A report of the American College of Cardiology Foundation Task Force on Clinical Expert Consensus Documents and the European Society of Cardiology Committee for Practice Guidelines. Eur Heart J.
10. Maron MS, Olivotto I, Betocchi S, et al. Effect of left ventricular outflow tract obstruction on clinical outcome in hypertrophic cardiomyopathy. N Engl J Med
11. Maron MS, Olivotto I, Zenovich AG, et al. Hypertrophic cardiomyopathy is predominantly a disease of left ventricular outflow tract obstruction. Circulation.
12. Morganroth J, Maron B, Henry W, Epstein S. Comparative left ventricular dimensions in trained athletes. Ann Intern Med
13. Morise AP. Exercise testing in nonatherosclerotic heart disease: Hypertrophic cardiomyopathy, valvular heart disease, and arrhythmias. Circulation.
14. Pluim BM, Zwinderman AH, Vand der Laarse A, et al. The athlete’s heart: a meta-analysis of cardiac structure and function. Circulation.
15. Sadoul N, Prasad K, Elliott PM, et al. Prospective prognostic assessment of blood pressure response during exercise in patients with hypertrophic cardiomyopathy. Circulation.
16. Sharma S, Elliott PM, Whyte G, et al. Utility of metabolic exercise testing in distinguishing hypertrophic cardiomyopathy from physiologic left ventricular hypertrophy in athletes. J Am Coll Cardiol
17. Underwood RH, Schwade JL. Noninvasive analysis of cardiac function of elite distance runners- echocardiography, vecterocardiography, and cardiac intervals. Ann N Y Acad Sci