The prognostic value of right ventricular outflow tract velocity time integral in patients with pulmonary hypertension

Aims Right ventricular (RV) failure is one of the leading causes of death in patients with pulmonary hypertension (PH). Conventional echocardiographic parameters are not included in risk stratification and follow-up for prognostic assessment due to PH's diverse nature and the RV's complex geometry. RV outflow tract velocity time integral (RVOT VTI) is a simple, non-invasive estimate of pulmonary flow and an echocardiographic surrogate of RV stroke volume. In this study, we aimed to define the prognostic value of RVOT VTI in PH patients. Methods Sixty-three subjects with idiopathic PAH (IPAH) (n = 23), connective tissue disease-associated PAH (CTD-associated PAH) (n = 19) and chronic thromboembolic pulmonary hypertension (CTEPH) (n = 21) were retrospectively included. A comprehensive two-dimensional echocardiographic evaluation, including RVOT-VTI measurement, was performed during the follow-up and the New York Heart Association functional class (NYHA FC), 6 min walk distance (6MWD) and brain natriuretic peptide (BNP) levels were recorded. Results The median age of the whole cohort was 63 years (52-68), and 47 (74.6%) of the patients were women. The median follow-up period was 20 months (11-33), and 20 (31.7%) patients died in this period. BNP values were higher [317 (210-641) vs 161 (47-466), P = 0.02], and 6MWD values were lower [197.5 +/- 89.5 vs 339 +/- 146.3, P < 0.0001] in the non-survivor group, and the non-survivor group had a worse NYHA-FC (P = 0.02). Among echocardiographic data, tricuspid annular plane systolic excursion (TAPSE) (15.4 +/- 4.8 vs 18.6 +/- 4.2, P = 0.01) and RVOT VTI (11.9 +/- 4.1 vs 17.2 +/- 4.3, P < 0.0001) values were lower whereas right atrial area (RAA) (26.9 +/- 10.1 vs 22.2 +/- 7.1, P = 0.04) values were higher in the non-survivor group. The area under curve of the RVOT VTI for predicting mortality was 0.82 [95% confidence interval (CI) 0.715-0.940, P < 0.0001], and the best cut-off value was 14.7 cm with a sensitivity of 80% and specificity of 77%. Survival was significantly lower in subjects with RVOT VTI <= 14.7 cm (log-rank P < 0.0001). Survival rates for patients with RVOT VTI <= 14.7 cm were 70% at 1 year, 50% at 2 years, %29 at 3 years and 21% at 5 years. The univariate determinants of all-cause mortality were BNP [hazard ratio (HR) 1.001 (1.001-1.002), P = 0.001], 6MWD [HR 0.994 (0.990-0.999), P = 0.012] and NYHA-FC III-IV [HR 3.335 (1.103-10.083), P = 0.03], TAPSE [HR 0.838 (0.775-0.929), P = 0.001], RAA [HR 1.072 (1.013-1.135), P = 0.016] and RVOT VTI [HR 0.819 (0.740-0.906), P < 0.0001]. RVOT VTI was found to be the only independent determinant of mortality [HR 0.857 (0.766-0.960), P = 0.008]. Conclusions The decreased RVOT VTI predicts mortality in patients with PH and each 1 mm decrease in RVOT VTI increases the risk of mortality by 14.3%. This parameter might serve as an additional parameter in the follow-up of these patients especially when 6MWD and NYHA-FC could not be determined.