Left Ventricular Outflow Indices in Chronic Systolic Heart Failure: Thresholds and Prognostic Value

The assessment of left ventricular (LV) outflow velocity time integral (LVOT-VTI) has gained favor in the stratification of patients with heart failure (HF). We evaluated the prognostic significance of LVOT-VTI compared with the commonly used indices of LV outflow: cardiac index (CI) and stroke volume index (SVI), their reproducibility and cut-off values.

A total of 424 outpatients diagnosed with HF and LV systolic dysfunction (LV ejection fraction < 50%) underwent a Doppler echocardiographic examination, including the assessment of CI, SVI, and LVOT-VTI. The Bland-Altman analysis showed LVOT-VTI the most reproducible outflow index. The study follow-up duration was 3.5 years (interquartile range 1.6-6.5), at the end of which there were 94 cardiovascular deaths (29%). Cox regression univariate analysis showed that LVOT-VTI was the most predictive of the study end-point. The ratio of tricuspid annular displacement-to-pulmonary artery systolic pressure (TAPSE/PASP) (p < 0.0001), LVOT-VTI (p = 0.0011), and end-systolic volume index (p = 0.0036) independently predicted the study end-point. At receiver-operating characteristic (ROC) analysis, LVOT-VTI < 12.0 cm had the best sensitivity and specificity for predicting cardiovascular mortality. Reduced LV EF (p = 0.0011), raised BNP levels (p = 0.0053), and high LV filling pressure (p = 0.044) were associated with low LVOT-VTI in multivariate logistic regression analysis. Patients with low LVOT-VTI and TAPSE/PASP < 0.32 mm/mmHg exhibited the worst prognosis on Kaplan-Meier survival curves (p < 0.0001).

A LVOT-VTI < 12.0 cm represents the best predictor of the cardiovascular outcome and proved the most reproducible index of LV forward flow in patients with chronic HF and systolic dysfunction. The combination of impaired LVOT-VTI with TAPSE/PASP showed the worst survival.