Obstructive Coronary Atherosclerosis in a Patient with a Calcium Score of Zero

A 62-year-old female with morbid obesity, hypertension, and hyperlipidemia presented to the emergency department for evaluation of atypical substernal chest pressure and shortness of breath. The symptoms had lasted 6 to 8 weeks with a crescendo pattern. An electrocardiogram on admission showed normal sinus rhythm without ischemic changes. The 0- and 3-hour cardiac enzymes (troponin I) were minimally elevated without a significant delta. Given the patient’s low GRACE score, we pursued an ischemia-guided strategy and performed a positron emission tomography (PET) scan. The patient underwent a standard rest-stress pharmacologic (regadenoson) PET with rubidium-82. The stress echocardiogram showed no ischemic changes, and the ejection fraction (EF) did not increase at peak stress (rest EF 70%, stress EF 67%). The perfusion images revealed a large, moderate to severe intensity, completely reversible perfusion defect in the basal to distal anterior and antero-septal segments that was suspicious for ischemia in the left anterior descending (LAD) coronary artery vascular territory (Figure 1A). Surprisingly, the patient’s calcium score (performed as a standard part of the PET exam) was zero (Figure 1B). This raised concern of a false positive perfusion study and prompted us to reinspect the technical aspects of image acquisition; however, no technical errors were identified. Myocardial blood flow analysis revealed abnormal flow augmentation in the LAD territory (peak stress flow in the LAD 1.3 mL/min/g; expected normal > 1.8 mL/min/g) and normal flow augmentation in the rest of the coronary vessels (Figure 1C). The PET scan was abnormal with 26% ischemia in the LAD vascular territory. The patient underwent coronary angiography, revealing a 90% proximal LAD lesion, which was treated with a (3.0 × 15) Resolute Onyx drug-eluting stent (Medtronic; Figure 1D and 1E). The remaining coronary arteries were free of atherosclerotic disease.

Figure 1