Author + information
- Received June 10, 1991
- Revision received August 21, 1991
- Accepted August 28, 1991
- Published online March 1, 1992.
- Taishiro Chikamori, MD1,
- Peter J. Counihan, MD1,
- Yoshinori L. Doi, MD1,
- Jun Takata, MD1,
- James T. Stewart, MD1,
- Michael P. Frenneaux, MD1 and
- William J. McKenna, MD, FACC*,1
- ↵*Address for reprints: William J. McKenna, MD, Department of Cardiological Sciences, St. George's Hospital Medical School, Cranmer Terrace, London SW17 ORE, England.
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 (VO2max). VO2max for the group was 13.9 to 49.3 (mean 25.4) ml/min per kg. Thirty-six patients (44%) achieved ≤70% of age-predicted VO2max. 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 VO2and the incidence and magnitude of rest left ventricular outflow tract pressure gradient >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 VO2max (r = 0.49, p = 0.02 and r = 0.54, p < 0.02). These ratios reflect impaired left ventricular systolic performance and atrial systolic failure, respectively. Stepwise dis- criminant analysis revealed these two ratios to be the two strongest predictors (p = 0.0001) of patients with a left ventricular outflow tract gradient whose VO2max was <70% of the age-predicted value (sensitivity 90%, specificity 100%).
In 59 patients without a rest left ventricular outflow tract gradient, peak filling rate and time to end-systole were weakly related to the age-predicted V02 max (r = 0.27, p < 0.05 and r = −0.28, p < 0.05). Stepwise discriminant analysis revealed that in those patients without a left ventricular outflow tract gradient reduced peak filling rate and prolonged time to end-systole best identified (p = 0.004) patients whose VO2max was <70% of the age-predicted value (sensitivity 76%, specificity 62%).
These findings indicate different mechanisms of exercise limitation in hypertrophic cardiomyopathy. In patients with a left ventricular outflow gradient at rest, the main determinants of exercise limitation were impaired left ventricular and left atrial systolic performance. In those without a gradient, however, diastolic function was a more important factor in the limitation of exercise performance.
- Received June 10, 1991.
- Revision received August 21, 1991.
- Accepted August 28, 1991.
- American College of Cardiology Foundation