SAN DIEGO – A massive effort to better understand and treat patients with pulmonary hypertension and right heart dysfunction is underway.
The endeavor, funded by the National Heart, Lung, and Blood Institute and the Pulmonary Hypertension Association and known as Redefining Pulmonary Hypertension Through Pulmonary Vascular Disease Phenomics (PVDOMICS), began recruiting participants in 2017, with a goal of 1,500 by 2019. The aim is to perform comprehensive phenotyping and endophenotyping across the World Health Organization–classified pulmonary hypertension (PH) clinical groups 1 through 5 in order to deconstruct the traditional classification and define new meaningful subclassifications of patients with pulmonary vascular disease.
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At an international conference of the American Thoracic Society, one of the study’s investigators, Robert P. Frantz, MD, discussed the role of echocardiography and MRI in the overall PVDOMICS program, which he characterized as a work in progress. “Imaging is critically important as we try to integrate severity of pulmonary vascular disease along with how well the ventricle functions as way to try and understand why some patients have a failing RV at a given pulmonary resistance and others don’t,” said Dr. Frantz, who directs the Mayo Pulmonary Hypertension Clinic in Rochester, Minn. The goals are to be able to integrate cardiac morphology and function with contemporaneous hemodynamics, he said. This will allow for validation of noninvasive hemodynamics versus right heart catheterization across all the phenotypes.
“In addition, we’ll have imaging parameters as predictors of hemodynamics at rest and with exercise, particularly in conditions like heart failure with preserved ejection fraction or concerns about left atrial stiffness,” he said. “In these cases, our ability on the basis of echocardiography or MRI to guess what the wedge pressure is at rest or exercise, or to think about other more recently described phenotypes like left atrial stiffness in patients who have left atrial ablation procedures, will be enabled by looking at parameters such as left atrial strain.”
Ultimately, he continued, a key goal of PVDOMICS is to be able to correlate the “-omics” with markers of RV compensation in an effort to understand what the determinants of RV compensation are across the varying types of pulmonary vascular disease.
“If we could do that, we might be able to develop new targets for therapy,” said Dr. Frantz. To illustrate how this might work, he cited findings from researchers who set out to identify and characterize homogeneous phenotypes by a cluster analysis in scleroderma patients with pulmonary hypertension, who were identified from two prospective cohorts in the United States and France (PLoS One 2018 May 15;13[5]:e0197112).
The researchers identified four different clusters of scleroderma patients: those with mild to moderate PAH with no or minimal interstitial lung disease and low-diffusing capacity for carbon monoxide; those with precapillary PH with severe ILD and worse survival; those with severe PAH, who trended toward worse survival, and those similar to the first cluster but with higher DLCO.
Dr. Frantz then shared preliminary findings of echocardiographic parameters by primary WHO group in PVDOMICS, on behalf of his PVDOMICS collaborators. They found, for example, that the mean right ventricular systolic pressure in group 3 was 45 mm Hg, as opposed to group 1, which was 64 mm Hg. “In general we had some patients in group 3 with less severe elevation of PA pressures,” he said.
Other parameters that can be compared across WHO groups include ventricular fractional area change, tricuspid annular plane systolic excursion, and RV free wall strain. “That strain of the right ventricle is one of the most important ways of looking at how the right ventricle works,” Dr. Frantz explained. “With this, we can integrate the concept of severity of RV dysfunction with severity of pulmonary vascular disease. This is where the rubber hits the road. It’s going to be very complicated and time consuming, but I think critically important. Ultimately, we can make proteomic heat maps that track these correlates, and ultimately identify pathways that may be driving RV compensation in pulmonary vascular disease.”
Dr. Frantz reported having no relevant financial disclosures.