Coronary computed tomography in heart transplant patients: detection of significant stenosis and cardiac allograft vasculopathy, image quality, and radiation dose

Cardiac allograft vasculopathy (CAV) is an accelerated form of atherosclerosis unique to heart transplant (HTX) patients. To investigate the detection of significant coronary artery stenosis and CAV, determinants of image quality, and the radiation dose in coronary computed tomography angiography (CCTA) of HTX patients with 64-slice multidetector CT (64-MDCT). Fifty-two HTX recipients scheduled for invasive coronary angiography (ICA) were prospectively enrolled and underwent CCTA before ICA with intravascular ultrasound (IVUS). Interpretable CCTA images were acquired in 570 (95%) coronary artery segments ≥2？mm in diameter. Sensitivity, specificity, and positive and negative predictive values of CCTA for the detection of segments with significant stenosis (lumen reduction ≥50%) on ICA were 100%, 98%, 7.7%, and 100%, respectively. Twelve significant stenoses were located in segments with uninterpretable image quality or vessel diameter <2？mm; only one was eligible for intervention. IVUS detected CAV (maximal intimal thickness ≥0.5？mm) in 33/41 (81%) patients; CCTA and ICA identified CAV (any wall or luminal irregularity) in 18 (44%) and 14 (34%) of these 33 patients, respectively. The mean estimated radiation dose was 19.0？±？3.4？mSv for CCTA and 5.7？±？3.3？mSv for ICA (P？<？0.001). CCTA with interpretable image quality had a high negative predictive value for ruling out significant stenoses suitable for intervention. The modest detection of CAV by CCTA implied a limited value in identifying subtle CAV. The high estimated radiation dose for 64-MDCT is of concern considering the need for repetitive examinations in the HTX population