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CTA shown capable of identifying features of plaque disruption
Madder R. Circ Cardiovasc Imaging. 2011;doi:10.1161/CIRCIMAGING.110.957282.
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Researchers performing CTA analysis in patients with unstable angina reported that the imaging modality was able to delineate features of plaque disruption that are specific markers of invasively detected complex plaque, including ulceration and intra-plaque dye penetration.
Identifying features indicative of complex ruptured plaque, the researchers wrote, may have considerable clinical implications.
“Furthermore, recent observations suggest that plaque characterization by CTA can identify patients at risk for clinical events, as well as specific ‘vulnerable’ plaque features of lesions that underlie such events,” they said. “The present findings are consistent with and support this concept.”
The study included patients with unstable angina who underwent CTA, as well as subsequent invasive coronary angiography within 30 days. After exclusion for prior revascularization, inadequate CTA imaging quality and chronic total occlusions, the final population included 60 patients.
Overall, 295 lesions that caused more than 25% diameter stenosis were detected with CTA. Among them, 109 (37.1%) had features of disruption, which included intra-plaque dye penetration (n=80; 27.2%) and ulceration (n=53; 18%).
According to researchers, compared with non-disrupted lesions, plaques with either feature of disruption were more voluminous (313 ± 356 mm3 vs. 118 ± 93 mm3; P<.0001), more often positively remodeled (94.5% vs. 44.3%; P<.0001), contained more low attenuation plaque (99 ± 161 mm3 vs. 19 ± 18 mm3; P<.0001) and were more often complex by invasive coronary angiography (57.8% vs. 8.1%; P<.0001).
Madder and colleagues demonstrate CTA can identify features of vulnerable plaque related to plaque disruption. As compared with nondisrupted plaques, the disrupted plaques were more frequently associated with greater lesion volume, low attenuation volume, a greater positive remodeling index, and ulceration and intra-plaque dye penetration. Of interest, among the 60 patients, 35 had disrupted plaques in more than one area, and 15 plaques with CTA features of disruption occurred in vessels with a calcium score of zero. The ability to diagnose CTA plaque disruption was reduced in calcified lesions, resulting in greater interobservor variability.
The paper raises an important clinical question: Should CTA be used more often to identify vulnerable plaques noninvasively in lower-risk patients with an unstable angina presentation that might not be considered at the time for urgent coronary revascularization to prevent subsequent cardiac events? This proof-of-concept study suggests that trials to address this question might be feasible, although very high-quality studies and expertise are required to assess plaque disruption; more than half of the unstable angina patients screened for the Madder study had to be excluded for uninterpretable studies. The PROMISE (Prospective Multicenter Imaging Study for Evaluation of Chest Pain) trial, scheduled to enroll at least 10,000 participants at low to intermediate risk for coronary artery disease and follow them for approximately 2.5 years, might shed some light on this issue. Other studies would be needed to address the scientific question of whether or not coronary revascularization reduces cardiac events in patients with unstable angina and CTA-identified vulnerable plaque(s).
– Bernard R. Chaitman, MD
Cardiology
Today Editorial Board member
Disclosure: Dr. Chaitman reports no relevant financial disclosures.
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