What is high risk? Redefining elevated pulmonary vascular resistance index in pediatric heart transplantation

Currently, pulmonary vascular resistance index (PVRI) >6 WU × m(2) (indexed units) is generally considered a contraindication to isolated orthotopic heart transplantation (OHT). However, this has been questioned in the literature.

A retrospective review was performed on all patients <18 years old who underwent primary OHT for cardiomyopathy. Data were collected with regard to demographics, pre-operative hemodynamics, need for pre-operative mechanical circulatory support, vasodilator reactivity and 30-day mortality (30dM). A receiver operating characteristic (ROC) curve was used to establish an optimal threshold. Uni- and multivariate logistic regressions were performed to assess the influence of PVRI on 30dM.

Complete data were available for 158 cardiomyopathy patients <18 years of age, who underwent primary OHT between June 1984 and November 2010. The ROC curve yielded a threshold of 9.290 indexed units. Four of 19 patients (21.1%) with PVRI >9 died in the first 30 days. In patients with PVRI <9, there was only 1 death among 139 patients (0.7%). Odds of mortality increased incrementally with PVRI as a continuous variable, with an odds ratio (OR) of 1.35 per indexed unit (95% confidence interval 1.12 to 1.63). PVRI was dichomotomized (PVRId) using the previously established threshold and revealed an increasing risk of mortality, OR 36.80 (95% confidence interval 3.86 to 350.90), with a PVRI of >9 indexed units.

Using a PVRI >6 as a contraindication to isolated OHT may be too restrictive. Patients with PVRI ≤9 do not appear to be at increased risk of early mortality. In patients with PVRI >9, 30-day survival was 78.9% in this study. This represents a viable alternative to heart-lung transplantation.