Refining risk in pulmonary arterial hypertension: should we look to the right heart?

Background

Risk stratification is essential in pulmonary arterial hypertension (PAH), guiding both prognosis and therapeutic decisions. Current models are mainly based on clinical and functional variables such as WHO functional class, six-minute walk distance, and natriuretic peptides. However, these tools do not include right ventricular (RV) function, an important determinant of outcome in PAH. Echocardiographic parameters reflecting RV contractility and ventriculo-arterial coupling may refine risk assessment.

Purpose

To evaluate the prognostic performance of echocardiographic indices of RV systolic function in group 1 PAH.

Methods

Seventy-eight patients with PAH were followed for 12 months in a referral center. The composite endpoint included death, lung transplantation or initiation of intravenous prostanoids. Baseline echocardiography evaluated included tricuspid annular plane systolic excursion (TAPSE), systolic pulmonary artery pressure (sPAP), TAPSE/sPAP and TAPSE/tricuspid regurgitant velocity (TRV) ratios, tricuspid annular systolic velocity (tricuspid S′), right atrial (RA) area, and tricuspid regurgitation (TR) severity. Prognostic performance was assessed with Cox regression and ROC analyses; optimal thresholds were derived using the Youden index. Survival distributions were compared using Kaplan–Meier.

Results

The mean age was 52 ± 17 years, 69% were female. WHO functional class III–IV was present in 79.5% of the cohort. Eleven patients (14%) reached the endpoint.

In univariate Cox analysis, lower TAPSE (HR 0.85, p = 0.018), S′ (HR 0.77, p = 0.039), TAPSE/TRV (HR 0.56, p = 0.037) and TAPSE/sPAP (HR 0.09, p = 0.064) were associated with events.

ROC analysis demonstrated good discriminative ability: TAPSE < 18 mm (AUC 0.738, sensibility 73%, specificity 70%); tricuspid S′ < 9 cm/s (AUC 0.747, sensibility 75%, specificity 71%); TAPSE/TRV < 3.7 mm·s/m (AUC 0.719, sensibility 70%, specificity 68%), TAPSE/sPAP < 0.25 mm/mmHg (AUC 0.710, sensibility 67%, specificity 70%).

The AUC-derived TAPSE/PSAP ratio cut-off separated the cohort into two prognostic groups, with the high-risk category showing significantly poorer survival (Log-Rank p=0.042) (Figure 1).

Conclusions

TAPSE, tricuspid S′, TAPSE/TRV, and TAPSE/sPAP were associated with adverse outcomes and exhibited moderate predictive accuracy. These simple, non-invasive measures may complement current clinical risk scores, refining prognostic stratification in PAH.For image description, please refer to the figure legend and surrounding text.