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January 15, 2020
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Elevated pulmonary vascular resistance increases mortality risk after heart transplant

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Even with lower pulmonary artery pressures, elevated pulmonary vascular resistance is associated with worse survival after heart transplant, according to a recently published study.

Whereas pulmonary hypertension was previously defined as a mean pulmonary artery pressure (mPAP) of at least 25 mm Hg, the definition was revised at the 6th World Symposium on Pulmonary Hypertension to lower the mPAP threshold to greater than 20 mm Hg in the setting of pulmonary vascular resistance greater than three Wood units.

“How this definition impacts World Health Organization group 2 pulmonary hypertension (pulmonary hypertension due to left heart disease), and specifically the relevance of lower pulmonary artery pressures in the hemodynamic assessment of cardiac transplant candidates, is largely unknown,” Todd C. Crawford, MD, from the division of cardiac surgery at Johns Hopkins University School of Medicine, and colleagues wrote.

Using the United Network for Organ Sharing database, the researchers identified adults who underwent heart transplantation from 1996 to 2015 and categorized them as having mPAP less than 25 mm Hg or mPAP of 25 mm Hg or greater. Primary outcomes included survival at 30 days and 1 year, which was conditional on survival at 30 days.

From 1996 to 2015, 32,465 patients underwent heart transplantation. Of these, 38% had mPAP less than 25 mm Hg and 62% had mPAP of 25 mm Hg or greater. Among those with lower mPAP, the median age was 55 years and the median pulmonary vascular resistance was 1.5 Wood units.

Even with lower pulmonary artery pressures, elevated pulmonary vascular resistance is associated with worse survival after heart transplant, according to a recently published study.
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Among patients with lower mPAP, pulmonary vascular resistance was still linked to an increased risk for death at 30 days after transplant (HR = 1.16; 95% CI, 1.05-1.27) after adjustment for recipient-, donor- and transplantation-related confounders. However, it remained unassociated with 1-year conditional mortality (HR = 1.03; 95% CI, 0.94-1.12).

Additionally, an absolute increase in 30-day mortality of 1.9% was noted with pulmonary vascular resistance of three Wood units or greater among patients with mPAP less than 25 mm Hg, which was similar to that observed among patients with pulmonary vascular resistance of three Wood units or greater and higher mPAP.

“In conclusion, increasing pulmonary vascular resistance in heart transplant recipients with mPAP < 25 mm Hg is associated with statistically significantly worse early survival after transplantation, and clinicians should not be reassured by normal or near normal pulmonary pressures alone,” the researchers wrote. “The absolute increase in risk may not be prohibitive and is similar in magnitude to other comorbid conditions in heart transplantation, but should be considered in the overall assessment of candidacy.”

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They also noted that these findings lend support to the change in definition of pulmonary hypertension that now incorporates lower pulmonary pressures in the setting of elevated pulmonary vascular resistance. – by Melissa Foster

Disclosure s : Crawford reports he received funding from the Hugh R. Sharp Endowed Fellowship. Please see the study for all other authors’ relevant financial disclosures.