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 f rom HCM. BACKGROUNDS Regular intensive training may cause mild increases in left ven tricular wall thickness (LVWT). Although the degree of left ventricular hyp ertrophy (LVH) is typically less than chat seen in hypertrophic cardiomyopa thy (HCM), genetic studies have shown that a substantial minority of patien ts with HCN have an LVWT in the same range. The differentiation of physiolo gic and pathologic LVH in this "gray zone" can be problematic using echocar diography 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 (pVO(2)), anaerobic threshold, oxygen pulse and re spiratory exchange ratios were measured in both groups and compared with th ose observed in 12 elite and 12 recreational age- and size-matched athletes without LVH. RESULTS Elite athletes with LVH had significantly greater pVO(2) (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 predic ted 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 pVO(2), >50 ml/k g/min or >20% above the predicted maximum VO2 differentiated athlete's hear t from HCM. CONCLUSIONS Metabolic exercise testing facilitates the differentiation betw een physiologic LVH and HCM in individuals in the "gray zone" (C) 2000 by t he American College of Cardiology.