Coronary CT angiography and comparative effectiveness research prognostic value of atherosclerotic disease burden in appropriately indicated clinical examinations

Histopathologic characteristics of atherosclerotic coronary disease and implications of the findings for the invasive and noninvasive detection of vulnerable plaques

OBJECTIVES

The goal of this study was to identify histomorphologic characteristics of atherosclerotic plaques and to determine the amenability of some of these components to be used as markers for invasive and noninvasive imaging.

BACKGROUND

Rupture of the atherosclerotic plaques is responsible for the majority of acute coronary events, and the culprit lesions demonstrate distinct histopathologic features. It has been tacitly believed that plaque rupture (PR) is associated with angiographically minimally occlusive lesions.

METHODS

We obtained 295 coronary atherosclerotic plaques, including stable (fibroatheroma [FA]; n = 105), vulnerable (thin-cap fibroatheroma [TCFA]; n = 88), and disrupted plaques (plaque rupture [PR]; n = 102) from the hearts of 181 men and 32 women who had died suddenly. The hierarchical importance of fibrous cap thickness, percent luminal stenosis, macrophage area, necrotic core area, and calcified plaque area was evaluated by using recursive partitioning analysis. Because clinical assessment of fibrous cap thickness is not possible by noninvasive imaging, it was excluded from the second set of partitioning analysis.

RESULTS

Thickness of the fibrous cap emerged as the best discriminator of plaque type; the cap thickness measured <55 μm in ruptured plaques, and all FA were associated with >84-μm cap thickness. Although the majority of TCFA were found in the 54- to 84-μm thickness group, those with <54-μm thickness were more likely to show <74% luminal stenosis (area under the curve: FA, 1.0; TCFA, 0.89; PR, 0.90). After exclusion of cap thickness, analysis of the plaque characteristics revealed macrophage infiltration and necrotic core to be the 2 best discriminators of plaque types (area under the curve: FA, 0.82; TCFA, 0.58; PR, 0.72). More than 75% cross-section area stenosis was seen in 70% of PR and 40% of TCFA; only 5% PR and 10% TCFA were <50% narrowed.

CONCLUSIONS

This postmortem study defines histomorphologic characteristics of vulnerable plaques, which may help develop imaging strategies for identification of such plaques in patients at a high risk of sustaining acute coronary events.

Matching between regional coronary vasodilator capacity and corresponding circumferential strain in individuals with normal and increasing body weight

BACKGROUND

To define the relationship between regional coronary vasodilator capacity and myocardial circumferential strain at rest in normal weight, overweight, and obese individuals with normal global left-ventricular function.

METHODS AND RESULTS

Myocardial blood flow at rest and during pharmacologic vasodilation was measured with (13)N-ammonia PET/CT in mL/g/minute in normal weight control (CON, n = 12), overweight (OW, n = 10), and obese individuals (OB, n = 10). In addition, resting myocardial function was evaluated as circumferential strain (Єc, %) by MRI. Global myocardial flow reserve (MFR) did not differ significantly between CON and OW (2.98 ± 0.96 vs 2.70 ± 0.66, P = .290), whereas it declined significantly in OB (1.98 ± 1.04, P = .030). Further, global Єc (%) was comparable between CON, OW, and OB (-0.24 ± 0.03, -0.23 ± 0.02, and -0.23 ± 0.04) but it was lowest in OB when normalized to the rate-pressure product (NЄc: -0.31 ± 0.06, -0.32 ± 0.05, and -0.26 ± 0.08). When MFR of the three major coronary territories was correlated with corresponding Єc, a positive association was observed in CON (r = 0.36, P = .030), in OW (r = 0.54, P = .002), and also in OB when relating NЄc to coronary vascular resistance during pharmacologic vasodilation (r = -0.46, P = .010).

CONCLUSIONS

Higher coronary vasodilator capacity is related to corresponding regional circumferential strain at rest in non-obese individuals, while this is also observed for reduced MFR in obesity.