Napkin-ring sign (heart)

The napkin-ring sign is a feature of high-risk coronary artery atherosclerotic plaque on CT coronary angiogram (coronary CTA). It has been shown to possess a high predictive value in predicting future cardiac events and is considered one of the imaging correlates of an unstable plaque.

It is not to be confused with the napkin ring sign of the bowel (apple core sign).

Radiographic features

The sign refers to a rupture-prone plaque in a coronary artery, comprising a necrotic core covered by a thin cap (cap thickness <65 μm), also referred to as so-called thin-cap fibroatheroma.

While the cap itself is too thin to be depicted by non-invasive imaging techniques including CT, the necrotic core may be visible on thin sections (<0.6 mm) of modern coronary CTA.

The napkin-ring sign represents a cross-section of a coronary artery showing luminal narrowing by a low attenuating eccentric structure (also called circumferentially extensive necrotic core), that is surrounded by a thin ring-like hyperattenuating rim and may represent indirect evidence of the aforementioned thin, vulnerable cap .

Treatment and prognosis

The napkin-ring sign has recently been shown to be associated with future cardiac events presenting as culprit lesion in acute coronary syndrome .