Myocardial perfusion reserve is low in heart transplant patients and is related to exercise capacity

Heart transplant (HTx) patients are known to be at risk of coronary microvascular dysfunction as well as having decreased exercise capacity. The aim of this study was to investigate if microvascular function in HTx patients differs from healthy controls and is related to objective measures of exercise capacity.

Twenty-nine HTx patients (51 ± 15 years, 34% women) and 26 healthy controls (57 ± 10 years, 38% women) underwent CMR. Quantitative myocardial perfusion maps were acquired using single-bolus (0.05 mmol/kg), dual-sequence perfusion mapping at adenosine stress and at rest. In addition, all HTx patients performed a maximal cardiopulmonary exercise test with gas-exchange analysis for objective assessment of exercise capacity. Heart transplant patients had lower stress myocardial perfusion (2.9 ± 0.8 vs 3.4 ± 0.8, p = 0.03) and lower myocardial perfusion reserve (MPR) (2.7 ± 0.7 vs 3.8 ± 1.2, p < 0.001) compared to healthy controls. Furthermore, MPR in HTx patients was correlated with maximal workload (R² = 0.25, p = 0.016), O₂ pulse (R² = 0.21, p = 0.026), peak O₂ consumption (VO₂ peak) (R² = 0.25, p = 0.015) and O₂ consumption (VO₂) at the anaerobic threshold (AT) (R² = 0.27, p = 0.011).

Microvascular function as assessed by quantitative CMR perfusion mapping is lower in HTx patients than in healthy controls and is partly related to objective measures of exercise capacity.