Abdominal aortic calcification on routine preoperative computed tomography-A novel cardiovascular risk prediction tool in liver transplant patients

Abstract

Cardiovascular (CV) disease is a leading cause of postoperative mortality following liver transplantation (LT). The presence of abdominal aortic calcification (AAC) has been linked to CV events in the general population. We sought to investigate whether AAC on routine pre-transplant CT can improve the prediction of coronary artery disease, post-LT major adverse cardiovascular events (MACEs) or long-term mortality. Of 461 patients undergoing LT between 2010 and 2018, 318 were included in the analysis, among whom 81 had also undergone computed tomography coronary angiography. The extent of AAC was quantified with high AAC defined as a calcium score ≥500. High AAC was identified in 84/318 (26.4%) and demonstrated moderate correlation with coronary artery calcium score (CACS) ( r =0.52, p <0.001). Thirty-two MACE events occurred in 28 patients (8.8%) within 30 days. High AAC was a strong independent predictor of moderate-to-severe coronary disease on CT coronary angiography (OR 12.6, 95% CI 1.5-103.0, p =0.02). It was also associated with a significantly increased risk of 30-day MACE (OR 2.34, 95% CI 1.08-5.05, p =0.03) and long-term mortality (HR 2.45, 95% CI 1.18-5.06, p =0.02). Following multivariate analysis adjusting for pertinent CV risk factors, high AAC remained a strong independent predictor of MACE (OR 3.10, 95% CI 1.27-7.60, p =0.02). Addition of AAC to the Revised Cardiac Risk Index significantly improved model fit for predicting MACE outcomes ( p <0.01), while the absence of heavy AAC ruled out moderate-to-severe disease on CT coronary angiography with a negative predictive value of 97.0%. High AAC on routine CT scans was associated with a 3-fold increased risk of 30-day MACE post-LT and improved CV risk prediction compared to traditional indices. Quantification of AAC may offer a simple method of improving CV risk assessment in these patients.

Keywords: CT; abdominal aortic calcification; cardiac risk; liver transplantation; major adverse cardiovascular events.

Graphical abstract

FIGURE 1

Study flowchart. Abbreviations: CAD, coronary artery disease; CTCA, computed tomography coronary angiogram.

FIGURE 2

CT imaging of heavily calcified abdominal aorta (arrows) on coronal and sagittal imaging planes.

FIGURE 3

MACE outcomes stratified by AAC category. Abbreviations: AAC, abdominal aortic calcium score; ACS, acute coronary syndrome; AF, atrial fibrillation; CCF, congestive cardiac failure; MACE, major adverse cardiac event; VT/VF, ventricular tachycardia or ventricular fibrillation.

FIGURE 4

Kaplan–Meier survival estimates by AAC category. Abbreviation: AAC, abdominal aortic calcium score.

FIGURE 5

OR and 95% CIs for predicting MACE. Abbreviations: MACE, major adverse cardiovascular events; RCRI, revised cardiac risk index.