Study results suggest that a pulmonary vascular resistance (PVR) of ≥2.2 Wood units could identify the risk of mortality and heart failure (HF) in patients undergoing a right heart catheterization (RHC), expanding the clinical continuum of risk from the standard 3.0 Wood units that is used in clinical practice. The study was published in Lancet Respiratory Medicine.

Patients who underwent an RHC in the US Veterans Affairs healthcare system between 2007 and 2016 were enrolled in this retrospective cohort study. Only inpatients and outpatients with data for a complete RHC and ≥1 year of follow up were included in the analysis (N=40,082). The time to all-cause mortality comprised the primary outcome. An RHC cohort from Vanderbilt University Medical Center (1998-2016; n=3699) was used to validate the mortality hazard ratio (HR) in the primary cohort. Additionally, the researchers examined the association between PVR and outcomes.

The median age of the primary cohort was 66.5 years, and the median follow-up period for these patients was 1153 days. This cohort included patients with a HF history (57.9%) and a history of chronic obstructive pulmonary disease (33.3%). In the validation cohort, the median age was 60.4 years, and the median follow-up period was 1752 days.


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The all-cause mortality hazard for PVR, when modeled as a continuous variable, increased at approximately 2.2 Wood units, which the investigators suggested “is well below the PVR associated with the disease state in clinical practice.” In a comparison between PVR of ≥2.2 Wood units with <2.2 Wood units, the adjusted HR for mortality in patients with a mean pulmonary artery pressure (mPAP) of ≥19 mm Hg and pulmonary artery wedge pressure (PAWP) of ≤15 mm Hg was 1.71 (95% CI, 1.59-1.84; P <.0001). In these same patients, the adjusted HR for HF hospitalization was 1.27 (95% CI, 1.13-1.43; P =.0001).

In the validation cohort, a total of 2870 patients had a mPAP of ≥19 mm Hg. Patients with a mPAP of ≥19 mm Hg and with PVR of ≥2.2 Wood units and a PAWP of ≤15 mm Hg had an adjusted HR for mortality of 1.81 (95% CI, 1.33-2.47; P =.0002).

Limitations of this study were its retrospective nature, the inclusion of mostly men in the primary cohort (96.7%), and the use of cohorts from a single country, which may limit generalizability of the findings.

Nonetheless, these results “suggest that reconsidering the hemodynamic parameters that define pulmonary hypertension in patients with cardiopulmonary disease is warranted.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Maron BA, Brittan EL, Hess E, et al. Pulmonary vascular resistance and clinical outcomes in patients with pulmonary hypertension: a retrospective cohort study. Lancet Respir Med. Published online July 27, 2020. doi:10.1016/S2213-2600(20)30317-9