Noninvasive PAH diagnosis on the horizon

By Eleanor McDermid, Senior medwireNews Reporter

Measuring the duration of vortical blood flow in the main pulmonary artery allows accurate estimation of pulmonary blood pressure and diagnosis of pulmonary arterial hypertension (PAH), say researchers.

Michael Fuchsjäger (Medical University of Graz, Austria) and colleagues measured vortical blood flow using phase-contrast magnetic resonance imaging, offering a noninvasive alternative to diagnosis with right heart catheterisation.

The predictive accuracy of the method was “substantially higher” than that achievable using echocardiographic measurement of tricuspid regurgitation, suggesting this to be “an accurate noninvasive method” for the diagnosis of PAH, the researchers write in Radiology.

They found a linear relationship between the duration of vortical blood flow per cardiac cycle and mean pulmonary arterial pressure (mPAP), measured on right heart catheterisation. Vortical blood flow (measured by two readers) first appeared at an mPAP of 16 mmHg, and its duration increased by 1.59% per 1 mmHg increase in mPAP.

A total of 145 patients underwent cardiac imaging, of whom 69 had elevated mPAP (≥25 mmHg) on right heart catheterisation, 19 had borderline elevated mPAP (21–24 mmHg) and 57 had normal mPAP (≤20 mmHg).

The team found that a vortical blood flow duration of 14.3% was the best cutoff for diagnosing elevated mPAP, giving a sensitivity of 97% and a specificity of 96%.

A cutoff of 7.9% was best for predicting borderline elevated mPAP. However, identifying and measuring these very short durations of vortical blood flow was highly reader-dependent, with the sensitivity being 47% for one reader and 68% for the other.

When detected, however, short-lived vortices were highly specific for borderline elevated mPAP, with specificities of 98% and 100% for the two readers, “and may therefore potentially allow for identification of patients who have an increased risk of developing [pulmonary arterial hypertension]”, say the researchers.

The team notes that “a reproducibility study is clearly needed”, but says that the accuracy demonstrated in the current study suggests that “detection of vortical blood flow in the main pulmonary artery may become the noninvasive, nonionizing method of choice for early recognition and longitudinal follow-up of patients who have or who are at risk for developing [pulmonary arterial hypertension].”

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