Mechanisms of exercise intolerance in patients with hypertrophic cardiomyopathy

Division of Cardiovascular Medicine, Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA.
American heart journal (Impact Factor: 4.46). 10/2009; 158(3):e27-34. DOI: 10.1016/j.ahj.2009.06.006
Source: PubMed


To determine the relation between echocardiogram findings and exercise capacity in hypertrophic cardiomyopathy (HCM).
Sixty-three patients (48 +/- 15 years) were referred for cardiopulmonary testing and exercise echocardiography. They were classified by morphology: proximal (n = 11), reverse curvature (n = 32), apical (n = 7), and concentric HCM (n = 13). There were more women in proximal and reverse curvature groups. Proximal HCM patients were older. Maximal left ventricular thickness was highest in reverse curvature group. At peak exercise, concentric HCM achieved the lowest percent predicted maximal Vo2. Excluding apical group, no significant differences in gradient were noted between groups. Overall, no statistically significant correlation was found between peak Vo2, wall thickness, and gradient. Significant correlations were noted between peak Vo2 and indexed left atrial (LA) volume (r = -0.52), lateral E' (r = 0.50), and lateral E/E' ratio (r = -0.46). A multivariate model including age, lateral E', indexed LA volume, and mitral A wave explained 46% of the variance in peak Vo2 (P = .01).
Lateral E' and indexed LA volume are negatively correlated with functional capacity. Although patients with concentric morphology achieved the lowest peak Vo2, wall thickness and gradient did not predict exercise capacity.

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    ABSTRACT: The risk of sudden cardiac death (SCD) associated with vigorous athletic competition in individuals with hypertrophic cardiomyopathy (HCM) is well documented, and is the basis for recommended exclusion from competitive sports independent of other risk factors. Although SCD risk with recreational exercise is less well defined, published guidelines for participation in recreational sports, based on a consensus of expert opinion, offer a valuable framework for counseling patients. Exercise stress testing is an important diagnostic and prognostic tool in the evaluation of HCM patients, providing an objective measure of functional capacity, physiologic hemodynamic responses to stress, presence of ischemia, and provocable left ventricular outflow tract obstruction. The value of cardiopulmonary exercise testing in HCM is less well studied than in the heart failure population, but can be used to set a safe target for exercise intensity as part of an individualized exercise prescription. The long-term effects of exercise on HCM pathophysiology are largely theoretical at this stage. Potential harmful effects of fatiguing exercise include prolonged contractile dysfunction resulting from microvascular ischemia and energetic compromise. Conversely, several animal studies have shown that voluntary exercise prevents or reverses many pathologic features of HCM, including those related to apoptosis and energetics. Substantial evidence for health-promoting benefits of exercise in the general population, in addition to promising safety and efficacy data in patients with chronic heart failure, emphasizes the need to attain a reasonable balance between potential risks and benefits of aerobic fitness in individuals with HCM.
    No preview · Article · Dec 2009 · Journal of Cardiovascular Translational Research
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    ABSTRACT: Aims: Most patients with hypertrophic cardiomyopathy (HCM) show a limited exercise capacity. A correlation between exercise tolerance and diastolic dysfunction has already been demonstrated. On the contrary, the role of rest-induced or exercise-induced obstruction as a determinant of exercise capacity is still open to debate. The aim of the present study was to analyse the exertional behaviour of patients with HCM presenting different left ventricle (LV) obstructive profiles. Methods: Thirty-five consecutive patients with HCM (mean age 45 ± 14 years, 23 men) underwent echocardiography during cardiopulmonary exercise (CPX) testing. Non-invasive measurement of cardiac output was obtained with an inert gas rebreathing system at the beginning and at peak of exercise. Results: Fifteen patients (43%) had neither resting nor provocable obstruction (group A: non-obstructive profile), 12 patients (34%) showed provocable obstruction during exercise (group B: latent-obstructive profile) and eight patients (23%) presented obstruction at rest (group C: rest-obstructive profile). Group A and B patients showed higher peak oxygen consumption in comparison with group C patients (24 ± 6 and 23 ± 6 vs. 17 ± 3 ml/kg per min; P = 0.016) and a greater increment of cardiac index during exercise (6.6 ± 1.3 and 6.0 ± 1.4 vs. 4.6 ± 0.8 l/min per m; P = 0.004). Conclusion: In comparison with the rest-obstructive profile, latent and non-obstructive HCM patients seem to share a similar exertional behaviour characterized by a greater increment of cardiac index during exercise and a minor impairment of exercise tolerance. Accordingly, in HCM patients not obstructive at rest, latent obstruction cannot be suspected based on exertional behaviour and functional capacity. Echocardiography performed during CPX test providing an important adjunct, may be valuable in guiding treatment in patients with substantial exercise limitation.
    No preview · Article · Jun 2012 · Journal of Cardiovascular Medicine
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    ABSTRACT: Hypertrophic cardiomyopathy is a prevalent genetic disease characterized by left ventricular hypertrophy, presenting dynamic obstruction of outflow tract with subaortic gradient happening at rest in 30% of the cases. It is attributed to the intricate interaction between the anterior mitral leaflet, the interventricular septum and altered flow vectors generated in left ventricle along with changes in outflow tract geometry. Mitral regurgitation in varying degrees is found with or without association with structural deformities of the valve apparatus. The exercise echocardiogram evidences latent obstruction easily induced by exercise in 60 to 75% of non-obstructive forms. The determination of the gradient under this condition must be considered in routine investigation of patients with mild or no obstruction at rest. The evaluation of hypertrophic cardiomyopathy incorporates methods based on the ultrasound image, which, along with MRI, allow recognizing ventricular obstruction generating mechanisms, thus facilitating the diagnosis and management of obstructive and latent obstructive forms.
    Full-text · Article · Jul 2012 · Arquivos brasileiros de cardiologia
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