Coronary Artery Calcium Scoring by Computed Tomography and the GRACE Risk Score as Predictors of Obstructive Coronary Artery Disease in Patients with Non-ST Segment Elevation Acute Coronary Syndrome: A Comparative Study
Authors: Abadeer Maria Ashraf , Sallam Walid Mohamed , Onsy Ahmed Mohamed 
Published: August 2023

Abstract

Aim and objectives
The aim of our study is to enhance patient risk stratification which can potentially influence the treatment strategy. Our objective is to evaluate the correlation of the Global Registry of Acute Coronary Events (GRACE) risk score, the coronary artery calcium (CAC) score and their use combined with the extent and severity of obstructive coronary artery disease (CAD) in patients with non-ST-elevation acute coronary syndrome (NSTE-ACS).

Patients and Methods
This study included two hundred and two patients who presented with NSTE-ACS and were planned for coronary angiography in Ain Shams University hospitals during the period from September 2020 to February 2021. The GRACE score was calculated for all patients and they were divided into 3 groups according to the predicted in-hospital and post-discharge to 6 months mortality risk. Patients then underwent coronary artery calcium scoring (CACS) using computed tomography (CT) and were divided into 4 groups according to their Agatston score. Following invasive coronary angiography, patients were divided into 2 groups depending on whether or not there was at least one significant stenosis. Patients who had significant stenosis were then divided into 4 subgroups according to the number of vessels affected; one-vessel disease, two-vessel disease, multi-vessel disease and left main CAD. A receiveroperating characteristic (ROC) curve was plotted for the CAC score, the GRACE score and for the CAC score combined with the GRACE score. It was used to suggest a cut-off value for each score below which obstructive CAD can be excluded in patients presenting with NSTE-ACS.

Results
The CAC score and the GRACE score were significantly higher in patients with obstructive CAD detected on invasive coronary angiography. Both, the CAC score and the GRACE score positively correlated with the number of affected coronaries. It was also detected that a CAC score of zero had a highly significant relationship with the absence of significant stenosis on invasive coronary angiography (p value &lt;0.001). A CAC score of zero had a negative predictive value of 84.8% [95% Confidence Interval (CI): 72.4% to 92.2%], a positive predictive value of 73.7(95% CI: 69.3% to 77.7%), a sensitivity of 94.3 %( 95% CI: 88.5% to 97.7 %), and a specificity of 48.8% (95% CI: 37.4% to 60.2%). In addition, tested the use of zero CAC to exclude obstructive CAD in patients with low inhospital and post discharge mortality risk had a higher sensitivity, specificity, positive and negative predictive values. From the ROC curve, it could be concluded that the use of CACS in combination with the GRACE score improves the sensitivity, specificity, positive and negative predictive value in comparison to the use of the GRACE score alone.

Conclusion
CAC score as detected by CT is predictive of obstructive CAD and correlates with its extent or in other words, the number of affected coronaries. The low radiation dose and absence of contrast exposure in CACS make it an attractive candidate for the on-going research regarding the noninvasive tools for prediction of CAD. In addition to the role of GRACE score in predicting the risk of mortality in ACS, it can be also used to predict the severity and extent of obstructive CAD. It can be hypothesized that its combination with CAC score improves its reliability as a predictor of obstructive CAD.