Coronary artery disease in a zero calcium score patient: questioning the reliability of CAC in high-risk individuals

Background/Synopsis

Coronary calcium score (CAC) is a non-invasive test that measures calcified plaque in the coronary arteries. It is often used to improve risk assessment in patients with a borderline 10-year ASCVD risk (5-7.5%) or with a strong family history of ASCVD. A CAC score of 0 has a high negative predictive value (95%-99%) and is reassuring. While CAC detects calcified plaques, it cannot identify non-calcified, potentially unstable plaques, which could contribute to acute coronary syndromes. This limitation is important in patients who are symptomatic despite a zero score.

Objective/Purpose

To evaluate the predictability of CAC in risk assessment of CAD in patients with high clinical risk.

Methods

A 47-year-old female with a history of hypertension, preeclampsia, and antiphospholipid syndrome presented with intermittent chest pain for weeks. Her echocardiogram and Holter monitoring were negative for CAD. She had no history of venous thromboembolism or smoking, but has a family history of SCAD, CABG, MI, and CVA. Initial ECG, troponin, and CAC score (0) were normal. LDL was 81, triglycerides 160, and ASCVD risk 0.8%. No further diagnostic test was pursued. However, she subsequently developed typical chest pain. ECG showed anterolateral STEMI, though troponins remained negative.

Results

PCI with left heart catheterization was done and showed non calcified plaque in proximal LAD with an 80% stenosis. A drug eluting stent was inserted, and she was treated with dual antiplatelet therapy and high intensity statins.

Conclusions

This case highlights the limitations of over-relying on CAC for risk assessment. While a CAC=0 has a high predictive value (95-99%) for obstructive CAD, the “power of zero” applies to asymptomatic patients and does not reliably exclude CAD risk in symptomatic younger patients.

Complementary functional tests could have helped make the correct diagnosis such as cardiac stress test, with sensitivity and specificity of 68% and 77% or Sestamibi Scintigraphy with a sensitivity and specificity of 92% and 68%. Coronary Computed Tomography Angiography (CCTA) with a sensitivity of 96% and NPV of 99% for excluding severe (≥ 70%) coronary stenosis could have been considered. This case highlights the importance of applying the correct diagnostic test when evaluating patients with chest pain. This is particularly important in women who are less likely to have coronary calcification and often have a lower calculated ASCVD risk score.