Heart-lung imaging ratio may predict long-term PAH survival

A measure derived from heart and lung imaging data can predict the long-term risk of death for people with newly diagnosed pulmonary arterial hypertension (PAH), a study found.

The measure, called FAC/PASP, was better at predicting long-term death rates than a more established measure, TAPSE/PASP, the study showed. Both measures are ratios derived from imaging data that aim to capture dysfunction in the right side of the heart and the lungs’ blood vessels, but the two use different assessments of heart health.

“These findings suggest that integrating FAC/PASP into contemporary risk-stratification frameworks may enhance predictive accuracy,” the researchers wrote.

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. 

PAH is marked by abnormally high pressure in the vessels that carry blood from the heart through the lungs. This puts strain on the heart, particularly the right ventricle, the part responsible for pumping blood to the lungs.

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Under normal circumstances, the right ventricle moves in sync with the lungs’ vessels to ensure a steady flow of blood. In PAH, they fall out of sync, and this tends to get worse as the disease progresses. Noninvasive measures that can track the disconnect between these two parts of the circulatory system are useful for prognostic predictions in people with PAH.

TAPSE/PASP is a well-established measure for tracking this disconnect.

Tricuspid annular plane systolic excursion, or TAPSE, is a measure of right ventricle health calculated by tracking the movement of the junction between the right heart’s atrium and ventricle. Meanwhile, pulmonary artery systolic pressure (PASP) reflects blood pressure in the lung vessels. TAPSE/PASP is the ratio between these two measurements, and it’s been well established that a lower TAPSE-PASP is associated with heightened death risk in people with PAH.

But TAPSE-PASP has some notable limitations. TAPSE, the measure used to track right ventricle function, may not be sensitive to subtle changes that occur early in the course of PAH. TAPSE is also prone to inaccuracy when the disease is advanced and can be influenced by blood flowing backward into the heart’s upper right chamber in the setting of tricuspid regurgitation.

Fractional area change (FAC) is a measure of right ventricle health that looks at how this part of the heart changes size when it squeezes to pump blood. FAC may be less likely than TAPSE to generate inaccurate results in advanced disease, the scientists said.

The team, led by researchers in Italy, wanted to see if FAC/PASP — the ratio between FAC and PASP, the marker of lung vessel pressure — might yield better prognostic insight than the established TAPSE/PASP ratio. The scientists compared the long-term predictive power of these two measures using data from 347 people with newly diagnosed PAH who were followed as part of an observational registry.

Statistical analyses showed that both FAC/PASP and TAPSE/PASP were significantly associated with short-term risk of death: Patients with low scores on either measure were significantly more likely to die after one year of follow-up. A low FAC/PASP, but not TAPSE/PASP, was also significantly associated with death risk after five years of follow-up.

“A low FAC/PASP ratio at PAH diagnosis significantly predicts both 1-year and 5-year all-cause mortality, whereas a low TAPSE/PASP ratio is significantly associated with all-cause mortality at one year but not at five years,” the researchers concluded.

The scientists stressed that the analysis was limited to a relatively small group of patients. And since the patients were in a long-running observational registry, they received different types of PAH treatments.

The researchers said the results “should be interpreted as hypothesis-generating rather than definitive,” and that further work is needed to verify them. Still, they said, the findings suggest that FAC/PASP may be a useful tool for predicting outcomes in PAH.

“FAC/PASP provides an independent and comprehensive [imaging-based measure of disconnect between the right ventricle and the lungs’ vessels] that carries robust longitudinal prognostic relevance,” the researchers wrote. “Future work should validate these findings and assess whether FAC/PASP improves clinical decision-making when integrated into risk scores.”