Peak power output to left ventricular mass: an index to predict ventricular pumping performance and morbidity in...

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.

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 × 10⁻⁶) × stroke volume (mL) × mean arterial pressure (mm Hg) × heart rate (beats/min). LV mass was assessed using a standard M-mode echocardiographic method.

Peak power/mass was 1.84 ± 0.46 W/100 g and 0.76 ± 0.31 W/100 g, and peak mass/power was 32 ± 10 g/m²/W and 84 ± 38 g/m²/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).

Peak power/mass is useful to discriminate and risk stratify patients with advanced HF with additional power with respect to ejection fraction.