Peak Power Output to Left Ventricular Mass: An Index to Predict Ventricular Pumping Performance and Morbidity in Advanced Heart Failure

Background: Similar to power-to-weight ratio and weight-to-power ratio, which are measurements of the actual performance of any engine, the ratios of peak power output to left ventricular (LV) mass (peak power/mass) and of peak LV mass to power output (peak mass/power) are indices of LV performance potentially useful in heart failure (HF). This Doppler echocardiographic study was designed to evaluate peak power/mass and peak mass/power in patients with advanced HF compared with healthy subjects and to assess their prognostic value. Methods: Power output was measured at rest and at peak exercise in 75 subjects, 60 patients with advanced HF (LV ejection fraction <= 35%) and 15 controls. Peak LV power output (W) was calculated as the maximal product of (133 x 10(-6)) x stroke volume (mL) x mean arterial pressure (mm Hg) x heart rate (beats/min). LV mass was assessed using a standard M-mode echocardiographic method. Results: Peak power/mass was 1.84 +/- 0.46 W/100g and 0.76 +/- 0.31 W/100g, and peak mass/power was 32610 g/m(2)/W and 84638 g/m(2)/W in controls and in patients with HF, respectively (both P values < .0001). Peak power/mass was a powerful predictor of outcome on multivariate logistic regression analysis (hazard ratio, 0.907; P = .009). On receiver operating characteristic curve analysis, the areas under the curve for HF-related events were greater for peak power/mass (P = .002) and peak mass/power (P = .011) with respect to resting ejection fraction. Comparisons of Cox models showed that peak power/mass added prognostic value to a model that included age, New York Heart Association class, etiology, ejection fraction, and diastolic dysfunction (P < .0001). Conclusion: Peak power/mass is useful to discriminate and risk stratify patients with advanced HF with additional power with respect to ejection fraction. (J Am Soc Echocardiogr 2010;23:1259-65.)