A 52-year-old woman with a history of type 2 diabetes and chronic kidney disease (eGFR 35 mL/min/1.73 m²) is being evaluated for asymptomatic coronary artery disease (CAD). She has no chest pain but has multiple risk factors. Which investigation is most appropriate to assess the extent and severity of atherosclerotic plaque burden and guide further management without exposing her to iodinated contrast?

Explanation

## Investigation of Choice for Atherosclerotic Plaque Burden Assessment in CKD ### Why CAC Scoring is Correct **Key Point:** In patients with advanced chronic kidney disease (eGFR <45 mL/min/1.73 m²), coronary artery calcium (CAC) scoring by non-contrast CT is the preferred investigation to assess atherosclerotic plaque burden because it: - Avoids iodinated contrast (which can precipitate contrast-induced nephropathy in CKD) - Quantifies calcified atherosclerotic plaque - Provides prognostic information for CAD risk - Guides intensity of medical therapy and further investigation **High-Yield:** CAC scoring is particularly valuable in CKD because: - **No contrast required** — eliminates risk of contrast-induced acute kidney injury (CI-AKI) - **Prognostic power** — CAC score independently predicts cardiovascular events - **Risk stratification** — helps determine who needs further invasive or non-invasive testing - **Reproducible** — standardized Agatston scoring system ### Investigation Comparison in CKD with Asymptomatic CAD | Investigation | Contrast Required | CKD Safety | Plaque Visualization | Functional Assessment | Use in CKD | |---|---|---|---|---|---| | **CAC scoring** | **No** | **Excellent** | Calcified plaque only | No | **Preferred** | | CCTA | Yes (iodinated) | Risky in eGFR <45 | Yes (all plaque) | No | Contraindicated without precautions | | Stress echo | No | Excellent | No | Yes | Alternative if CAC inconclusive | | Invasive angiography | Yes (iodinated) | High risk | Yes (direct) | No | Reserved for symptomatic/high-risk | **Clinical Pearl:** CAC score of 0 has high negative predictive value (~99%) for obstructive CAD in asymptomatic patients, allowing safe deferral of further testing. A high CAC score (>400) indicates extensive atherosclerosis and warrants intensive medical therapy ± further imaging. **Warning:** Do NOT use iodinated contrast-based investigations (CCTA, invasive angiography) in CKD without adequate hydration, N-acetylcysteine, and metformin withholding. CAC scoring avoids this entirely. **Mnemonic: CAC in CKD** — **C**oronary **A**rtery **C**alcium in **C**hronic **K**idney **D**isease — non-contrast, safe, prognostic. [cite:Robbins 10e Ch 11; Harrison 21e Ch 297]