Temperature distribution in atherosclerotic coronary arteries: influence of plaque geometry and flow (a numerical study).

Intravascular coronary thermography is a method that may detect vulnerable, atherosclerotic plaques and is currently evaluated in a clinical setting. Active macrophages or enzymatic heat releasing processes in vulnerable plaques may act as heat sources. To better understand the parameters of influence on thermographic measurements, numerical simulations have been performed on a model of a coronary artery segment containing a heat source. Heat source parameters and flow were varied to study their influence on temperatures at the lumen wall. Maximal temperature differences at the lumen wall increased when the source volume increased and they differ with the source geometry. The simulations showed that blood flow acts as a coolant to the lumen wall. Blood flow decreased maximal temperatures depending on the source geometry, source volume and the maximal flow velocity. Influence of flow was highest for circumferentially extended sources, up to a factor 3.7, and lowest for longitudinally extended sources, down to a factor 1.9. When cap thickness increased, maximal temperatures decreased and the influence of flow increased. This study shows that correct interpretation of intravascular thermographic measurements requires data on the flow and on the morphologic characteristics of the atherosclerotic plaque.

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