Positive remodeling and napkin ring sign involving the right coronary artery
Presentation
Chest pain.
Patient Data
CORONARY ANATOMY: The coronary arteries arise normally. The right coronary is dominant.
CORONARY CT ANGIOGRAM:
Left main: Bifurcates into the LAD and LCX. Plaque and/or stenosis: none.
Left anterior descending: Plaque and/or stenosis: atherosclerotic plaque with mild stenosis (25-49%) in the proximal and mid LAD.
Left circumflex: Plaque and/or stenosis: none.
Right coronary artery: Gives off a patent posterior descending artery and a patent posterior left ventricular branch. Plaque and/or stenosis: Predominantly noncalcified long-segment atherosclerotic plaque causing moderate stenosis (50-69%). There is positive remodeling and a "napkin ring sign": these are features of vulnerable plaque at high risk of rupture and subsequent thrombosis. There is also a predominantly noncalcified plaque in the distal segmental with mild stenosis (25-49%).
Right coronary catheter angiogram shows only mild narrowing of the mid-RCA in the area of positive remodeling visible on the CT angiogram.
Positive vessel remodeling
In positive remodeling, plaque accumulates in and expands the vessel wall outwards, often without significant luminal narrowing.
Napkin ring sign
A napkin ring sign is present when plaque with a lower density core has a thin, high attenuation peripheral ring. The high attenuation ring does not need to completely surround the plaque, but must be <130 HU, i.e. less than the attenuation of calcium.
Case Discussion
Four features of so-called vulnerable plaque, atherosclerotic lesions at high risk of rupture and subsequent thrombosis, have been described: 1) positive remodeling, 2) low attenuation plaque, 3) the napkin ring sign, and 4) spotty calcium. These features may be present without significant vessel narrowing with preserved myocardial blood flow and absent symptoms until the vulnerable plaque suddenly ruptures. Because of the preserved myocardial blood flow, these lesions may not be detected on a stress test, nuclear medicine studies, or catheter angiography since these methods don't depict the vessel wall. Intravascular ultrasound, coronary CTA, and magnetic resonance imaging are the best techniques for evaluating the vessel wall and detecting these vulnerable plaque features.
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