CLINICAL CORRELATES OF THE MYOCARDIAL FORCE-FREQUENCY-RELATIONSHIP INPATIENTS WITH END-STAGE HEART-FAILURE

Background: This study tested the hypothesis that in patients with sus pected heart failure, peak oxygen consumption was the best predictor o f heart muscle failure. Failing human myocardium is characterized by a n abnormal force-frequency relationship, which has been previously sho wn to be altered in parallel with the severity of heart failure. Metho ds: We examined whether seven different functional parameters of isola ted electrically driven ventricular trabeculae carneae obtained from 3 4 explanted hearts of patients undergoing heart transplantation for en d-stage heart failure correlated with any of 47 separate pretransplant ation clinical parameters. The functional muscle parameters were activ e force at 0.33 Hz, time to 80% relaxation (RT80%) of twitch force at 0.33 Hz, optimal frequency (OF), active force at 1.0 Hz (AF(1)), diast olic force at 1.0 Hz (DF1), active force at 2.0 Hz (AF(2)), and diasto lic force at 2.0 Hz (DF2). Results: Before transplantation the mean le ft ventricular ejection fraction was 21% +/- 10%, and all patients wer e in New York Heart Association class III or IV. Mean peak whole body Vo(2) was 10.9 +/- 3.3 ml/min/kg and percent body mass/age/sex-adjuste d maximum Vo(2) oxygen consumption was 34.7% +/- 10.4%. Univariate ana lysis of Vo(2) yielded the following significant correlations: active force at 33 Hz, RT80%, OF, AF(1), DF1, AF(2), DF2; whereas univariate analysis of percent body mass/age/sex-adjusted Vo(2) yielded the follo wing significant correlations: RT80%, OF, DF1, AF(2), DF2. Multivariat e analysis showed that OF and DF, were independent predictors of peak Vo(2). Conclusion: In this study we show that peak oxygen uptake measu red during cardiopulmonary exercise testing obtained before transplant ation is correlated with the force-frequency behavior of isolated musc les at the time of transplantation. Peak Vo(2) seems to be a strong in dicator of the severity of cardiac contractile dysfunction inpatients with heart failure. J Heart Lung Transplant 1997.