New index predicts mortality in bridge-to-heart-transplantation patients

A novel, cross-validated scoring system accurately predicted morality in patients on mechanical circulatory support as a bridge to heart transplantation, researchers wrote in JACC: Heart Failure.

Using the United Network for Organ Sharing database, the researchers developed a risk index — transplantation risk index in patients with mechanical circulatory support (TRIP-MCS) — for such patients to predict 1-year mortality after orthotopic heart transplantation.

Lily E. Johnston, MD, MPH, and colleagues analyzed 6,036 patients (mean age, 51.2 years; 18.3% women) who underwent orthotopic heart transplantation after being on mechanical circulatory support between 2000 and 2013. They randomly assigned the population to the derivation cohort (80%) or the validation cohort (20%). They reported that 1,556 patients died during the study period, for an incidence rate of 7.33 deaths per 100 person-years.

After screening approximately 50 variables, Johnston, from the Bloomberg School of Public Health, Johns Hopkins University, and colleagues devised a 75-point scoring system from nine recipient variables and four donor variables.

Predictive variables

The nine recipient variables that best predicted 1-year mortality were age older than 60 years, BMI of at least 25 kg/m², ICU admission at time of transplantation, required preoperative mechanical ventilation, any dialysis since listing, estimated glomerular filtration rate (eGFR) less than 50 mL/min/1.73 m², bilirubin more than 1 mg/dL, recently treated infection and non-left ventricular assist device circulatory support, they wrote.

They determined that the four donor variables best predicting 1-year mortality were age older than 40 years, sex mismatch with recipient, ischemic time more than 4 hours and eGFR less than 50 mL/min/1.73 m².

Mean score in the validation cohort was 14.4 (range, 0-57), which was similar to the derivation cohort’s mean score of 14.5 (range, 0-60), according to the researchers.

Johnston and colleagues determined that each 1-point increase in the TRIP-MCS score corresponded to an 8.3% increase in odds of death at 1 year (OR = 1.08; 95% CI, 1.06-1.11).

When the researchers stratified patients by TRIP-MCS score indicating low risk (0-10), intermediate risk (11-20) or high risk ( 21), they found that in the validation cohort, predicted 1-year mortality was 8.6% in the low-risk group, 12.8% in the intermediate-risk group and 31% in the high-risk group.

“This score may serve to add structure to shared decision-making conversations between patients and providers by quantitating the short- and midterm risks of transplantation,” Johnston and colleagues wrote. “From society’s perspective, organs remain a scarce resource, and it may be reasonable to question the utility of performing transplantation in a stable, or especially high-risk, [mechanical circulatory support] patient.”

Effect not yet known

In a related editorial, Jennifer A. Cowger, MD, MS, from the department of cardiovascular medicine, St. Vincent Heart Center, Indianapolis, wrote that the area under the curve for the model was 0.66, which “suggests modest model discrimination exists.”

“The utility of the TRIP-MCS can only be known once it has been applied prospectively to patients and the impact of delayed transplantation on wait-list mortality and post-transplantation survival has been scrutinized,” Cowger concluded. – by Erik Swain

Disclosure: The researchers and Cowger report no relevant financial disclosures.