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Mechanisms of exercise limitation in hypertrophic cardiomyopathy
T Chikamori1, P J Counihan, Y L Doi
1Department of Cardiological Sciences, St. George's Hospital Medical School, London, England.
Insights
Exercise capacity in hypertrophic cardiomyopathy is linked to systolic and diastolic function. Impaired left ventricular and atrial function predict reduced exercise capacity, aiding in patient stratification.
Area of Science:
- Cardiology
- Exercise Physiology
Background:
- Hypertrophic cardiomyopathy (HCM) is a complex heart condition affecting systolic and diastolic function.
- Exercise capacity is a crucial indicator of functional status and prognosis in cardiovascular diseases.
Purpose of the Study:
- To investigate the relationship between exercise capacity and measures of systolic and diastolic function in patients with hypertrophic cardiomyopathy.
- To identify predictors of reduced exercise capacity in this patient population.
Main Methods:
- Eighty-one patients with hypertrophic cardiomyopathy underwent two-dimensional echocardiography, radionuclide angiography, and maximal treadmill exercise testing to measure maximal oxygen consumption (VO2 max).
- Patients were assessed for New York Heart Association functional class and left ventricular outflow tract pressure gradients.
- Ratios reflecting left ventricular systolic performance and atrial systolic function were calculated and correlated with VO2 max.
Main Results:
- Forty-four percent of patients had a VO2 max less than or equal to 70% of age-predicted values, often correlating with higher functional class.
- In patients with a left ventricular outflow tract gradient, specific ratios of systolic and atrial function were significantly related to VO2 max.
- These functional ratios were strong predictors of reduced exercise capacity (sensitivity 90%, specificity 100%).
Conclusions:
- Exercise capacity in hypertrophic cardiomyopathy is significantly influenced by impaired left ventricular systolic performance and atrial systolic failure.
- These functional parameters can predict reduced exercise capacity, aiding in the clinical assessment and management of HCM patients.
Abstract:
To assess the relation of exercise capacity to indexes of systolic and diastolic function in hypertrophic cardiomyopathy, 81 patients underwent two-dimensional echocardiography, technetium-99m equilibrium radionuclide angiography acquired in list mode and maximal, symptom-limited, treadmill exercise testing with measurement of maximal oxygen consumption (VO2 max). VO2 max for the group was 13.9 to 49.3 (mean 25.4) ml/min per kg. Thirty-six patients (44%) achieved less than or equal to 70% of age-predicted VO2 max. Patients with such a degree of limitation were more likely to be in New York Heart Association functional class II or III (23 of 36 vs. 14 of 45; p = 0.005); there was no such relation between VO2 and the incidence and magnitude of rest left ventricular outflow tract pressure gradient greater than 30 mm Hg (11 of 36 vs. 11 of 45; p = NS and 58 +/- 24 vs. 65 +/- 19 mm Hg; p = NS). In the 22 patients with a left ventricular outflow tract gradient, the ratios of peak ejection to peak filling rate and of atrial contribution to left atrial dimension were related to percent of the age-predicted VO2 max (r = 0.49, p = 0.02 and r = 0.54, p less than 0.02). These ratios reflect impaired left ventricular systolic performance and atrial systolic failure, respectively. Stepwise discriminant analysis revealed these two ratios to be the two strongest predictors (p = 0.0001) of patients with a left ventricular outflow tract gradient whose VO2 max was less than or equal to 70% of the age-predicted value (sensitivity 90%, specificity 100%).(ABSTRACT TRUNCATED AT 250 WORDS)