Nongated CT Coronary Calcium Predicts Postoperative Risk
- Information from preoperative non-ECG-gated chest CT scans, obtained for purposes unrelated to cardiac risk stratification, may allow more accurate risk prediction for postoperative adverse clinical events after major noncardiac surgery.
- Methods of determining coronary artery calcification burden from nongated chest CT scans show excellent inter-reader reliability, indicating that inclusion of these data may be a useful and cost-effective tool to improve preoperative cardiovascular risk assessment.
Does the severity of coronary artery calcification (CAC) observed on non-ECG-gated chest computed tomography (CT) imaging obtained during a 1-year preoperative period provide preoperative information on risk of postoperative major clinical events (MCE) after major noncardiac surgery (NCS)?
Patients ≥45 years of age undergoing major inpatient NCS between 2016–2020 at one of four academic medical centers were retrospectively identified, and all who had undergone non-ECG-gated chest CT within a 12-month period prior to surgery were included. Exclusion criteria included previous coronary revascularization or valve prosthesis. From these non-ECG-gated CT scans, severity of calcification in each of three major epicardial coronary arteries (left main-left anterior descending, left circumflex, and right coronary artery) was determined based on the length of calcium visualized, and in each vessel an ordinal score was assigned (0 = no CAC seen; 1 = mild, 1-24% vessel involved; 2 = moderate, 25-29% of vessel involved; and 4 = severe, with ≥50% of vessel involved). Estimated coronary calcification burden (ECCB) was calculated by summation of the ordinal score from all three vessels, and clinically relevant thresholds were chosen for further analysis. Revised Cardiac Risk Index (RCRI) score was calculated for each subject. The primary outcome was all-cause mortality or myocardial infarction within 30 days of surgery. The ability of RCRI versus ECCB to discriminate risk was determined by receiver operating characteristic (ROC) curve model comparison. To assess pragmatic feasibility, a sample of 100 studies (50 contrast and 50 noncontrast) was reviewed by two nonradiologist physicians to estimate inter-reader reliability.
Among 24,939 screened subjects, 2,554 qualified for inclusion, with 48% having noncontrast and 52% contrast-enhanced scans. Calcification in ≥1 vessel, of mild or greater severity, was observed in 60.3%. Mild or greater calcification was observed in all three coronary arteries in 22.8%. The primary outcome occurred in 5.2% of patients. Subjects with any CAC had significantly higher risk of the primary outcome versus subjects with no CAC (6.8% vs. 2.9%; p < 0.0001). MCE increased with higher ECCB (0 = 2.9%, 1-2 = 3.7%, 3-5 = 8.0%, and 6-9 = 12.6%; p < 0.0001). Addition of ECCB to RCRI improved prediction of MCE versus RCRI alone (C-statistic 0.712 vs. 0.675; p = 0.018). Inter-rater reliability of ECCB adjudication among nonradiologist physicians in the sample in 100 randomly chosen subjects = 0.96 (0.94, 0.98).
A positive correlation was observed between MAE after NCS and advanced CAC burden (ECCB) observed on non-ECG-gated chest CT obtained within 1 year of surgery. This relationship was consistent across all RCRI strata and improved the RCRI’s discrimination of risk.
Approximately 10% of patients aged ≥45 years undergoing major NCS had pre-existing nongated chest CT scan imaging within 1 year of surgery that provided more discriminative risk stratification beyond RCRI alone. Low ECCB, even in the setting of higher RCRI categories, may identify patients in whom extensive preoperative cardiovascular testing may not be indicated.
Keywords: Acute Coronary Syndrome, Computed Tomography, Diagnostic Imaging, General Surgery, Plaque, Atherosclerotic, Risk Assessment
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