The new definition of pulmonary hypertension has demonstrated validity in a study recently published in CHEST, which showed an association between elevated pulmonary vascular resistance (PVR) and increased risk for mortality within 30 days of heart transplant. This risk can be sustained even with lower pulmonary arterial pressures.

This retrospective study included 32,465 adult participants (mean age, 55 years), all of whom were given primary heart transplants. Of these, 62% (n=20,208) had pretransplant mean pulmonary arterial pressure (mPAP) of ≥25 mm Hg, while 38% (n=12,257) had mPAP <25 mm Hg.

Researchers identified participants using the United Network for Organ Sharing Scientific Registry of Transplant Recipients, and all received first-time cardiac transplants in the period between 1996 and 2015. Potential risk factors for mortality within 30-day and 1-year periods among the group with mPAP <25 mm Hg were investigated using univariable analysis. Associations between these risk factors and PVR were examined using multivariable Cox proportional hazards models. The Kaplan-Meier method was then used to compare 30-day survival probability between mPAP <25 mm Hg and ≥25 mm Hg groups.

Compared with the mPAP ≥25 mm Hg group, patients with mPAP <25 mm Hg had significantly higher mean cardiac output (4.8±1.5 L/min vs 4.3±1.5 L/min; P <.01). The group with mPAP <25 mm Hg had a mean PVR of 1.5 Wood units (WU) (interquartile range [IQR], 1-2.2 WU), which was lower than those in the mPAP ≥25 mm Hg group. Individuals in the mPAP ≥25 mm Hg group had increased risks for both 30-day (hazard ratio [HR], 1.17; 95% CI, 1.05-1.31; P <.01) and 1-year mortality (HR, 1.20; 95% CI, 1.12-1.29; P <.01).

Although an independent association was not identified between PVR and conditional 1-year mortality, it was identified between PVR and 30-day mortality (HR, 1.16 per 1-WU increase; 95% CI, 1.05-1.27; P <.01) after controlling for confounders. A similar survival rate for 30-day mortality was observed between mPAP <25 mm Hg with PVR ≥3 WU (93.5%; n=514) and mPAP ≥25 mm Hg with PVR ≥3 WU (94.8%; n=6953).

Study limitations included a lack of data on incidence of right ventricular failure, the retrospective design, bias, and the effect of varied hemodynamic data interpretations and practice patterns on results.

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The researchers concluded that “increasing [PVR] in heart transplant recipients with mPAP <25 mm Hg is associated with a statistically significantly worse early survival after transplantation.” The researchers further indicated that pulmonary pressures near normal or normal should not be assumed to indicate low risk. PVR ≥3.0 WU may correlate with lower 30-day survival rates among at-risk individuals. By accounting for decreased PAPs with elevated PVR, the new definition of pulmonary hypertension appears to strengthen prognostic power in practice.

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

Reference

Crawford TC, Leary PJ, Fraser C III, et al. Impact of the new pulmonary hypertension definition on heart transplant outcomes: expanding the hemodynamic risk profile [published online August 22, 2019]. CHEST. doi:10.1016/j.chest.2019.07.028