Introduction and objectives: Using gadolinium-enhanced cardiovascular magnetic resonance, it is possible to evaluate the presence of myocardial fibrosis in hypertrophic cardiomyopathy. Classical disease markers are weak predictors of functional disability in affected patients. Our objective was to study the relationship between the degree of myocardial fibrosis observed by cardiac magnetic resonance and exercise capacity.
Methods: We performed cardiac magnetic resonance, echocardiography, exercise testing and Holter monitoring, along with the usual clinical assessments, in 98 patients (age, 46.3+/-15.4 years, 71.4% male) referred from two specialist hypertrophic cardiomyopathy clinics. Cardiac magnetic resonance assessment included quantifying the degree of fibrosis (i.e., the percentage of the myocardium showing enhancement) 10 min after gadolinium infusion. Symptom-limited exercise testing was used to determine exercise capacity (in metabolic equivalent [MET] units). In 71 patients, the basal N-terminal probrain natriuretic peptide (NT-proBNP) level was also measured.
Results: Late enhancement was observed on cardiac magnetic resonance in 67 (68.4%) patients. These patients had a lower exercise capacity (8.04+/-3.56 MET vs. 10.41+/-3.57 MET; P=.003). There was an inverse correlation between the percentage of fibrosis and exercise capacity (r=-0.21; P=.044). The best predictor of exercise capacity was the logarithm of the NT-proBNP level (r=-0.5; P< .0001). Multivariate analysis confirmed that age, a history of atrial fibrillation, the basal NT-proBNP level and the presence of fibrosis were independent predictors of exercise capacity (r2 for the model=0.47).
Conclusions: The observation of areas of late gadolinium enhancement on cardiac magnetic resonance was independently associated with poor exercise capacity in patients with hypertrophic cardiomyopathy.