Patients with a mPAP of at least 19 mm Hg and pulmonary artery wedge pressure of 15 mm Hg or less had an adjusted hazard ratio for mortality of 1.71.
In pulmonary hypertension subgroups, elevated pulmonary vascular resistance (PVR) of 3.0 Wood units or more is generally linked to a poor prognosis. However, the spectrum of pulmonary vascular resistance risk in pulmonary hypertension is not currently known.
A team, led by Bradley A. Maron, MD, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, analyzed the relationship between pulmonary vascular resistance and adverse clinical outcomes for patients with pulmonary hypertension.
In the retrospective cohort study, the investigators examined patients undergoing right heart catheterization (RHC) in the US Veterans Fairs health care system. Eligible patients were included if they had a complete RHC with at least one-year of follow-up. Both inpatient and outpatients were included.
However, individuals with missing mean pulmonary artery pressure (mPAP), pulmonary artery wedge pressure, or cardiac output were excluded.
The investigators sought primary outcomes of the time to all-cause mortality assessed by the Veteran Affairs vital status file.
The team used Cox proportional hazards models to assess the association between PVR and outcomes, as well as to validate the mortality hazard ration in a RHC cohort from the Vanderbilt University Medical Center between September 1998 and June 2016.
The primary cohort included 40,082 patients, 38,751 of which were male. This group had a median age of 66.5 years old with a median follow-up of 1153 days.
In addition, 23,201 (57.9%) of these patients had a history of heart failure and 13,348 (33.3%) had a history of chronic obstructive pulmonary disease (COPD). The focus was ultimately on patients with a risk of pulmonary hypertension based on a mPAP of at least 19 mm Hg (n = 32,725).
The investigators found PVR increased at around 2.2 Wood units when modelled as a continuous variable compared to a PVR of 1.0 Wood unit.
For the patients with a mPAP of at least 19 mm Hg and pulmonary artery wedge pressure of 15 mm Hg or less, the adjusted hazard ration (AHR) for mortality was 1.71 (95% CI, 1.59-1.84;P <0.0001). For the patient population, the AHR for heart failure hospitalization was 1.27 (95% CI, 1.13-1.43; P = 0.0001), when comparing PVR of 2.2 Wood units or more to less than 2.2 Wood units.
In the validation cohort, the investigators examined 3699 patients, about half of which were male. The mean age of this group was 60.4 years old, with a median follow-up of 1752. This cohort included 2870 patients (77.6%) with mPAP of at least 19 mm Hg.
The AHR for patients in the mPAP of 19 mm Hg or more group, with PVR of 2.2 units or more, and pulmonary artery wedge pressure of 15 mm or less Hg (n = 1221; 42.5%) was 1.81 (95% CI, 1.33-2.47; P = 0.0002).
“These data widen the continuum of clinical risk for mortality and heart failure in patients referred for RHC with elevated pulmonary artery pressure to include PVR of around 2.2 Wood units and higher,” the authors wrote. “Testing the generalizability of these findings in at-risk populations with fewer cardiopulmonary comorbidities is warranted.”
The study, “Pulmonary vascular resistance and clinical outcomes in patients with pulmonary hypertension: a retrospective cohort study,” was published online in The Lancet Respiratory Medicine.