Clinical Utility of SPECT in the Heart Transplant Population: Analysis from a Single Large-Volume Center.

BACKGROUND Survival after heart transplant has greatly improved, with median survival now over 12 years. Cardiac allograft vasculopathy (CAV), has become a major source of long-term morbidity and mortality. Single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is used for CAV surveillance, but there is limited data on its prognostic utility. METHODS We retrospectively identified patients undergoing SPECT MPI for CAV surveillance at a single, large-volume center. Images were assessed with semi-quantitative visual scoring (summed stress score [SSS] and summed rest score [SRS]) and quantitatively with total perfusion defect (TPD). RESULTS We studied 503 patients (mean age 62.5, 69.3% male) at a median of 9.0 years post-transplant. During mean follow-up of 5.1 ± 2.5 years, 114 (22.6%) patients died. The diagnostic accuracy for significant CAV (ISHLT grade 2 or 3) was highest for SSS with an area under the curve (AUC) of 0.650 and stress TPD (AUC 0.648), with no significant difference between SSS and stress TPD (p=0.061). Stress TPD (adjusted hazard ratio 1.07, p=0.018) was independently associated with all-cause mortality, while SSS was not (p=0.064). The prognostic accuracy of quantitative assessment of perfusion tended to be higher compared to semi-quantitative assessment, with the highest accuracy for stress TPD (area under the receiver operating curve 0.584). CONCLUSIONS While SPECT MPI identified a cohort of higher risk patients, with quantitative analysis of perfusion demonstrating higher prognostic accuracy. However, the overall prognostic accuracy was modest and alternative non-invasive modalities may be more suitable for CAV surveillance.