Biological similarities between Cpc-PH and PAH identified
medwireNews: Research published in the Journal of the American College of Cardiology suggests that there could be a pathophysiological overlap between combined post-capillary and pre-capillary pulmonary hypertension (Cpc-PH) and pulmonary arterial hypertension (PAH).
The study provides “the first biological evidence to position Cpc-PH closer to PAH than isolated postcapillary PH-[left heart disease] on the PH disease spectrum,” says Jane Leopold (Brigham and Women’s Hospital, Boston, Massachusetts, USA) in an accompanying editorial.
Tufik Assad and fellow researchers, from Vanderbilt University in Nashville, Tennessee, USA, used the university’s electronic medical record system linked to a DNA biorepository to investigate the clinical, hemodynamic, and genetic profiles of the three PH subtypes.
They found that 364 patients with Cpc-PH had “nearly identical” clinical characteristics to 1456 patients with isolated post-capillary (Ipc)-PH, with a higher burden of metabolic and vascular disease than 564 patients with PAH.
Echocardiographic measures of left ventricular (LV) remodeling and stress were also more severe in patients with either Cpc-PH or Ipc-PH compared with PAH; LV hypertrophy occurred in a corresponding 33%, 35%, and 23% of patients, and LV ejection fraction was measured as 42%, 40%, and 51%.
However, patients with Cpc-PH had hemodynamic profiles that were distinct from those of patients with Ipc-PH but closely resembled PAH profiles, the researchers report.
All indices of pulmonary vascular disease were more severe in patients with Cpc-PH compared with Ipc-PH, including right atrial pressure (14 vs 12 mmHg), systolic and diastolic pulmonary arterial pressure (69 vs 53 and 34 vs 23 mmHg, respectively), and pulmonary vascular resistance (5.8 vs 2.6 Wood units).
The occurrence of these hemodynamic differences “despite similar, or less severe, left heart dysfunction” in Cpc-PH “raise[s] doubts that Cpc-PH is simply a consequence of prolonged exposure to elevated left-sided pressures,” note the authors.
In an analysis of single-nucleotide polymorphism data from 254 patients, Assad and colleagues identified 75 genetic variants that were differentially expressed in patients with Cpc-PH or PAH compared with Ipc-PH. A number of these variants were associated with biological processes relevant to PAH and vascular remodeling.
These genetic findings suggest that vascular remodeling is “the key phenotypic feature in the overlap between Cpc-PH and PAH,” comments Leopold in her editorial.
The study authors note that “these findings are exploratory,” but “may represent an important step forwards in understanding the pathobiology of Cpc-PH.”
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