Utility of metabolic exercise testing in distinguishing hypertrophic cardiomyopathy from physiologic left ventricular hypertrophy in athletes

OBJECTIVES This study evaluated the role of metabolic (cardiopulmonary gas exchange) exercise testing in differentiating physiologic LVH in athletes from HCM. BACKGROUND Regular intensive training may cause mild increases in left ventricular wall thickness (LVWT). Although the degree of left ventricular hypertrophy (LVH) is typically less than that seen in hypertrophic cardiomyopathy (HCM), genetic studies have shown that a substantial minority of patients with HCM have an LVWT in the same range. The differentiation of physiologic and pathologic LVH in this “gray zone” can be problematic using echocardiography and electrocardiography alone. METHODS Eight athletic men with genetically proven HCM and mild LVH (13.9 ± 1.1 mm) and eight elite male athletes matched for age, size and LVWT (13.4 ± 0.9 mm) underwent symptom limited metabolic exercise stress testing. Peak oxygen consumption (pVO2), anaerobic threshold, oxygen pulse and respiratory exchange ratios were measured in both groups and compared with those observed in 12 elite and 12 recreational age- and size-matched athletes without LVH. RESULTS Elite athletes with LVH had significantly greater pVO2 (66.2 ± 4.1 ml/kg/min vs. 34.3 ± 4.1 ml/kg/min; p < 0.0001), anaerobic threshold (61.6 ± 1.8% of the predicted maximum VO2 vs. 41.4 ± 4.9% of the predicted maximum VO2; p < 0.001) and oxygen pulse (27.1 ± 3.2 ml/beat vs. 14.3 ± 1.8 ml/beat; p < 0.0001) than individuals with HCM. A pVO2>50 ml/kg/min or >20% above the predicted maximum VO2 differentiated athlete’s heart from HCM. CONCLUSIONS Metabolic exercise testing facilitates the differentiation between physiologic LVH and HCM in individuals in the “gray zone.”