112 Computed tomographic coronary angiography to screen for allograft vasculopathy after heart transplantation

Abstract

Objective To evaluate ComputedTomographic Coronary Angiography (CTA) as an alternative to Invasive Coronary Angiography (ICA) for the detection of Cardiac Allograft Vasculopathy (CAV). Background CAV is an important cause of late mortality after heart transplantation (HT). Because patients are often asymptomatic, surveillance ICA is performed in our institution. CTA is effective for the diagnosis of coronary disease in non-transplant patients, but few studies have been done after HT. Methods 117 HT patients, 1 to 24 years post transplant (mean=12 years SD± 6) underwent CT coronary artery calcification (CTCAC) followed by retrospective ECG gated coronary angiogram on a 64-slice scanner without the use of any β-blockers. Majority (89%) of patients had CTA within 24 h before ICA. The Agatston calcium score (CS) was calculated for all patients. The CTA images were systematically analysed for image quality and the presence of CAV (graded as significant if >50% luminal stenosis) using a fifteen coronary segments model by an independent investigator blinded to the results of ICA. Results CS ranged from 0 to 1681 (Mean=91.7±275). Out of 77 patients with absent CS, 3 had significant CAV on ICA. Despite a mean resting heart rate of 82 bpm SD±13 and body mass index of 27 kg/m 2 SD ±5, 81% of the CTA images were graded as excellent or satisfactory. For all the 1755 segments assessed by CTA irrespective of the image quality, CTA had sensitivity, specificity, positive and negative predictive values of 71%, 79%, 72% and 78% respectively for the detection of any CAV found by ICA. On a patient basis, CTA best performed in diagnosing CAV of more than 25% with sensitivity, specificity, positive and negative predictive values of 74%, 94%, 79%, and 92% respectively. None of the 61 patients with completely normal CTA had CAV on ICA. 83 (92%) out of 90 patients who responded to a patient survey preferred CTA to ICA as a screening test for CAV. Non-coronary cardiac and non-cardiac abnormalities were identified in 18% and 14% patients respectively. Conclusion The study shows that CTA compares favourably with ICA in detecting CAV in heart transplant recipients, and may be a preferable screening technique because of its non-invasive nature, patient preference and yield of additional information. One has to exercise caution in just using CS in these patients as significant CAV can be missed out.