Prognostic value of the pre-transplant diastolic pulmonary artery pressure–to–pulmonary capillary wedge pressure gradient in cardiac transplant recipients with pulmonary hypertension

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Background

Although the transpulmonary gradient (TPG) and pulmonary vascular resistance (PVR) are commonly used to differentiate heart failure patients with pulmonary vascular disease from those with passive pulmonary hypertension (PH), elevations in TPG and PVR may not always reflect pre-capillary PH. Recently, it has been suggested an elevated diastolic pulmonary artery pressure–to–pulmonary capillary wedge pressure gradient (DPG) may be a better indicator of pulmonary vascular remodeling, and therefore, may be of added prognostic value in patients with PH being considered for cardiac transplantation.

Methods

Using the United Network for Organ Sharing (UNOS) database, we retrospectively reviewed all primary adult (age > 17 years) orthotropic heart transplant recipients between 1998 and 2011. All patients with available pre-transplant hemodynamic data and PH (mean pulmonary artery pressure ≥ 25 mm Hg) were included (n = 16,811). We assessed the prognostic value of DPG on post-transplant survival in patients with PH and an elevated TPG and PVR.

Results

In patients with PH and a TPG > 12 mm Hg (n = 5,827), there was no difference in survival at up to 5 years post-transplant between high DPG (defined as ≥3, ≥5, ≥7, or ≥10 mm Hg) and low DPG (<3, <5, <7, or <10 mm Hg) groups. Similarly, there was no difference in survival between high and low DPG groups in those with a PVR > 3 Wood units (n = 6,270). Defining an elevated TPG as > 15 mm Hg (n = 3,065) or an elevated PVR > 5 (n = 1,783) yielded similar results.

Conclusions

This large analysis investigating the prognostic value of DPG found an elevated DPG had no effect on post-transplant survival in patients with PH and an elevated TPG and PVR.

Section snippets

Data source

UNOS provided Standard Transplant Analysis and Research (STAR) files with donor-specific data from December 1988 to June 2011. The data set included prospectively collected metrics from all patients who underwent thoracic transplantation in the United States. The current study was granted an exemption by the Johns Hopkins Institutional Review Board because none of the investigators had access to data sets containing protected health information.

Study design

We retrospectively examined all primary, adult

Cohort statistics

From December 1988 to June 2011, 43,494 patients aged > 17 years underwent primary OHT. After excluding 18,041 patients without complete hemodynamic data and 8,642 patients without PH (mPAP < 25 mm Hg), the final study cohort consisted of 16,811 patients.

ROC curve analyses

When considering all patients with PH (mPAP ≥ 25 mm Hg), DPG, TPG, and PVR all had poor ability to discriminate survivors from non-survivors, as evidenced by the AUC values near 0.5 (Table 1). The optimal cut points for DPG in those patients

PH with an elevated TPG and elevated PVR

In 4,419 patients with a TPG > 12 mm Hg and PVR > 3 WU and in 1,290 with a TPG > 15 mm Hg and PVR > 5 WU, there was no difference in survival between low and high DPG groups at up to 5 years post-OHT (Table 4).

Discussion

In OHT candidates with PH, determining the non-reversible component is vital for proper patient selection and good outcomes. Recent studies have suggested the dPAP-to-PCWP gradient may be useful in this regard,4, 6 but this has not been confirmed by large, multicenter studies. Using the UNOS database, we show that the DPG does not meaningfully delineate risk among patients with elevated TPG and PVR undergoing OHT.

An elevated TPG or PVR does not always reflect irreversible pulmonary vascular

Disclosure statement

This study received funding from the National Heart, Lung, and Blood Institute (Grants 1R01 HL114910-01 and L30 HL110304).

None of the authors has a financial relationship with a commercial entity that has an interest in the subject of the presented manuscript or other conflicts of interest to disclose.

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