Heart transplant patients with mild-to-severe coronary artery calcifications (CAC) have a greater probability of developing obstructive cardiac allograft vasculopathy (CAV), a form of coronary heart disease shown to limit long-term survival.
In a study conducted in Spain, researchers determined that at five years post-transplant, patients who presented with mild-to-severe risk, based on their level of CAC, showed almost two and a half times greater probability to develop CAV than patients with either no or minimal risk.
"The prognostic value of CAC to predict the risk of developing heart disease has been well described, but the clinical significance of CAC burden in heart transplant patients is less known. We wanted to study the value of CAC and its relationship with the development of CAV in this patient population," said presenter Alejandra Garcia Baizán, MD, a radiology resident at Clinica Universidad de Navarra in Spain.
From June 2007 to December 2017, Dr. Baizán and her colleagues prospectively recruited 117 heart transplant patients undergoing coronary CT angiography (CCTA) to evaluate the patient's potential of developing CAV. The presence of CAC in each patient was determined using the Agatston score which quantifies the extent of CAC detected by an unenhanced low-dose CT scan.
Five patients were excluded because of the presence of stents. Those remaining were then divided into two groups according to basal CAC burden: those with absence of or minimal risk (0-10) and those with mild-moderate-severe risk (>11). The researchers analyzed differences in the degrees of CAC and CAV.
Correlation Found Between CAC and CAV
Nearly 77 percent of the patients showed no or minimal risk. However, approximately 23 percent were classified as having mild-to-severe risk. After a median follow-up period of 46 months, the researchers noted a significant association between basal CAC and the presence of obstructive (≥ 50 percent) CAV.
"At five years, obstructive CAV occurred in 15.8 percent of patients with no or minimal risk and in 37.6 percent of those with mild-to-severe risk. The hazard ratio was 2.4 for patients with a basal CAC score greater than 11," Dr. Baizán said.
"We did not expect such a huge difference between presenting with an initial Agatston score and the probability of developing significant stenosis at five years," she said.
The results of the study suggest there may be opportunity for clinicians to more proactively evaluate and care for heart transplant patients before they develop significant CAV.
Dr. Baizán noted, "Considering the results, and the fact that heart transplant patients may develop renal insufficiency, and therefore may not be suitable for surveillance with coronary CT angiography, we consider it worthwhile to have at least one CAC evaluation performed in order to determine the risk of developing coronary stenosis in the future."
Understanding the prognostic value for heart transplant patients, Dr. Baizán suggested one approach may be CAC quantification and coronary CT angiography performed in the same setting. "This would provide useful information not only to detect clinically non-symptomatic CAV but also allow for follow-up with this patient population in a non-invasive way."
"Of course, this imaging approach requires state-of-the-art CT equipment to obtain diagnostic image quality of all coronary segments as well as to maintain minimum radiation dose levels," she added.