Intracoronary thermography: does it help us in clinical decision making?

The concept of the "vulnerable" plaque has recently emerged to explain how quiescent atherosclerotic lesions evolve to cause clinical events. The morphologic and immunologic determinants specific for the vulnerable plaque have been reported: a large lipid core (>or=40% plaque volume) composed of free cholesterol crystals, cholesterol esters, and oxidized lipids impregnated with tissue factor; a thin fibrous cap depleted of smooth muscle cells and collagen; an outward (positive) remodeling; inflammatory cell infiltration of fibrous cap and adventitia (mostly monocyte-macrophages, some activated T cells, and mast cells); and increased neovascularity. Despite the large amount of information regarding the morphological characteristics of remote lesions, we lack studies with functional assessment of non-culprit lesions. Coronary thermography is a technique for functional assessment of coronary atherosclerotic plaques. Several catheter designs have been proposed. There are catheters with thermistor(s) and wires with thermal sensors at the distal tip. All designs have several advantages and disadvantages. Despite the current limitations of coronary thermography, we gained important pathophysiological and clinical information regarding the vulnerability of atheromatic plaques. It has been documented both experimentally and clinically that increased heat generation is associated with increased macrophage concentration within the plaque. The correlation between local inflammatory involvement and local heat generation has also been observed with the peripheral inflammatory markers such as C-reactive protein. Whether systemic treatment, with agents such as statins or interventional techniques, such as drug-eluting stents, will have an impact on stabilizing vulnerable plaques need to be determined in future studies. In conclusion, although there are several techniques for evaluating morphologically atheromatic plaques, thermography is a promising method for the functional assessment of vulnerable plaque and has been introduced into clinical practice, with a good predictive value for clinical events in patients with increased temperature in the atherosclerotic plaque.