Turin, Italy – A measure derived from heart and lung imaging may help predict long-term mortality in people newly diagnosed with pulmonary arterial hypertension (PAH), according to a recent study.
The measure, called FAC/PASP, was more strongly associated with long-term survival than the established TAPSE/PASP ratio, the researchers reported. Both measures combine assessments of right-heart function with pulmonary artery pressure to capture the interaction between the right ventricle and the blood vessels in the lungs.
The study, “Prognostic relevance of the right ventricular fractional area change to pulmonary artery systolic pressure ratio in pulmonary arterial hypertension: Insights from the FOCUS-PAH registry,” was published in the International Journal of Cardiology.
Assessing the heart-lung connection
PAH is characterized by abnormally high blood pressure in the pulmonary arteries, which carry blood from the heart to the lungs. The increased pressure places strain on the right ventricle, the chamber responsible for pumping blood through the lungs.
Normally, the right ventricle and pulmonary blood vessels work together to maintain efficient blood flow. In PAH, this relationship can become impaired as the disease progresses. Imaging-based measures that assess this heart-lung interaction may therefore provide useful information about a patient’s prognosis.
TAPSE/PASP is one of the most established measures for assessing this interaction. TAPSE, or tricuspid annular plane systolic excursion, measures right-ventricular function by tracking movement of the junction between the heart’s right atrium and right ventricle. PASP, or pulmonary artery systolic pressure, reflects pressure in the pulmonary arteries.
The ratio between TAPSE and PASP has been linked to outcomes in PAH, with lower values generally associated with a greater risk of death.
However, TAPSE has limitations. It may not detect subtle changes in right-ventricular function early in the disease and can become less reliable in advanced PAH. Its measurement can also be affected by tricuspid regurgitation, a condition in which blood flows backward through the tricuspid valve.
FAC/PASP shows stronger long-term predictive value
Fractional area change (FAC) provides another way to assess right-ventricular function. Rather than measuring movement at a specific point in the heart, FAC evaluates how much the right ventricle changes in size as it contracts. According to the researchers, FAC may be less susceptible than TAPSE to inaccuracies in advanced disease.
Researchers in Italy investigated whether combining FAC with PASP could provide better prognostic information than TAPSE/PASP. They analyzed data from 347 people who had recently been diagnosed with PAH and were followed through an observational registry.
Both ratios were significantly associated with mortality during the first year after diagnosis. Patients with lower FAC/PASP or TAPSE/PASP values were more likely to die during that period.
Over a longer follow-up period, however, FAC/PASP appeared to provide a stronger signal. A low FAC/PASP ratio was significantly associated with mortality after five years, while TAPSE/PASP was not.
The researchers concluded that a low FAC/PASP ratio at the time of PAH diagnosis was associated with both one- and five-year all-cause mortality, whereas a low TAPSE/PASP ratio was associated with mortality at one year but not five years.
More research is needed
The researchers cautioned that the study has important limitations. The analysis included a relatively small number of patients, and participants were treated with different PAH therapies because they were enrolled in a long-running observational registry.
As a result, the findings should be considered hypothesis-generating rather than definitive. Larger studies will be needed to confirm whether FAC/PASP consistently outperforms TAPSE/PASP and whether incorporating it into existing PAH risk-stratification systems improves clinical decision-making.
Still, the researchers said FAC/PASP may offer a useful imaging-based measure of the relationship between right-ventricular function and pulmonary vascular pressure.
They suggested that future studies should validate the findings and determine whether adding FAC/PASP to established risk scores can improve the prediction of outcomes and guide treatment decisions in people with PAH.
Contact
Pier Paolo Bocchino
Città della Salute e della Scienza di Torino