ANGIOGRAPHIC FINDINGS IN SYMPTOMATIC PATIENTS WITH EVIDENCE OF ISCHEMIA BY PET/CT PERFUSION IMAGING BUT WITH ZERO CORONARY ARTERY CALCIUM

Therapeutic Area

ASCVD/CVD Risk Assessment

Background

Coronary artery calcium (CAC) is a strong, incremental predictor of coronary artery disease (CAD) risk. In contrast, the absence of CAC portends a low but not zero risk, which has been ascribed to non-calcified, “soft” plaques. However, other pathologies in CAC=0 patients (pts) are possible, including spontaneous coronary artery dissection, microvascular disease, coronary anomalies, etc. We sought to determine the spectrum and frequency of angiographic findings in symptomatic pts with ischemia on stress PET/CT who had zero CAC.

Methods

The Intermountain nuclear medicine and hospital electronic medical record databases were searched for CAC=0 pts undergoing stress positron emission tomography (PET/CT) between 2/1/2014 and 7/1/2022. We defined PET abnormality with ischemic burden (IB) >=10% as definite, IB >0<10% as equivocal, and IB=0 as normal. We defined severe and moderate CAD as >=70% and 50-69% stenosis, respectively. Pts were followed for coronary interventions and major adverse cardiovascular events (MACE) over 1.1 +/- 0.9 y.

Results

Of 59,639 total PET/CT studies, 4284 (7.2%) had CAC=0 and no prior history of CAD. Of these, 28 with adequate quality PET (0.65%) had IB >=10% (NPV 99.3%). Table 1 summarizes demographics across IB categories. Coronary angiography (n=21) or coronary CT angiography (n=5) was performed within <90 days in 25 (89%) of IB>=10% pts (Table 2). Severe CAD was present in 11, moderate in 1, mild in 4, and none in 9. Thus, 14 (56%) with positive PET (IB>=10%) of 25 angiographic cases were not explained by severe CAD, suggesting possible microvascular dysfunction. Revascularization was indicated in only 10 (PCI in 6, CABG in 4) of the 28 IB>=10% pts (35.7% of IB>=10%, 0.23% of CAC=0 pts); follow-up MACE occurred in 2 (7%) with IB>=10% (repeat revascularizations) vs 1.6% of others (p=NS).

Conclusions

In this large stress PET/CT experience, IB >=10% in pts with CAC=0 was rare. The majority were not explained by obstructive CAD. However, given the rare possibility of severe CAD or other pathologies, such as microvascular angina, a zero CAC score should be interpreted in the context of clinical judgement in deciding whether to proceed with additional testing such as stress PET.