Echocardiographic Evaluation of Left Ventricular Output in Patients with Heart Failure: A Per-Beat or Per-Minute Approach?

Background: Left ventricular (LV) output is a predictor of adverse outcome in patients with heart failure. It can be evaluated using a per-beat approach, measuring stroke volume index (SVI), or a per-minute approach, calculating cardiac index (CI). However, the prognostic value of these two approaches has never been compared.

Methods: A single-center retrospective observational study was conducted in 396 hospitalized patients who underwent echocardiography for suspected heart failure. In a group of 138 consecutive patients, SVI and CI cutoff values of 30 mL/m and 2.3 L/min/m, respectively, were derived to separate normal from low LV forward flow conditions. Subsequently, the association of these values with all-cause mortality was compared in a group of 258 consecutive patients. Median follow-up duration was 2.6 years (interquartile range: 2-3.2 years).

Results: After adjustment for other outcome predictors, SVI <30 mL/m was independently associated with all-cause mortality with a hazard ratio of 2.67 (95% confidence interval, 1.74-4.1; P < .001), whereas CI was not. Additionally, three different subgroups of SVI (<30, 30-35, and >35 mL/m) and CI (<1.8, 1.8-2.2, and ≥2.3 L/min/m) were compared, and no incremental benefit of this risk stratification model was observed.

Conclusions: Low LV output on the basis of a per-beat definition (SVI <30 mL/m) is strongly associated with all-cause mortality in patients hospitalized with heart failure. A per-minute approach seems to add no further information to risk stratification. These findings may have implications for selecting the LV output index when evaluating prognosis in patients with heart failure.