CardioBrief

Updated with comments from Roger Blumenthal and Valentin Fuster]– CT angiography may be able to identify atherosclerotic lesions that are likely to develop ACS, according to an intriguing new study from Japan appearing in JACC. “When more effective therapies” for vulnerable plaques become available, the paper will “surely become a landmark in the effort to prevent acute coronary events,” writes Eugene Braunwald, in an accompanying editorial. PK Shah told CardioBrief the study “is a major step forward in our quest for identifying at risk subjects.”

The Japanese team analyzed the atherosclerotic lesions from angiograms of 1,059 patients to assess the presence of positive vessel remodeling (PR) and low-attenuation plaques (LAP). “These 2 features,” the authors write, “have been observed in the lesions that have already resulted in ACS, but their prospective relation to ACS has not been previously described.”

ACS developed in 10 out of 45 (22.2%) patients showing plaque with both PR and LAP, compared to 1 out of 27 (3.7%) patients with only one feature, and 4 out of 820 (0.5%) patients with neither. There were no events in the 167 patients with normal angiograms.

In his editorial, Noninvasive Detection of Vulnerable Coronary Plaques: Locking the Barn Door Before the Horse Is Stolen, Braunwald asks “How could detection of vulnerable plaques by CTA fit into the prevention scheme?” He notes that it is not “appropriate at this time to propose the use of CTA to detect vulnerable plaques in patient populations” like those in the study, since it would require repeat procedures every few years, imposisng an undue economic burden and radiation exposure.

“However,” Braunwald continues, “this field is still in its infancy, and it is safe to predict that the limitations noted in the preceding text will diminish in the next few years.” Braunwald cites improvements in CT technology, and mentions the “greater yield” of studying higher risk patients.

PK Shah provided the following comment to CardioBrief:

“This is a landmark tour de force  study that for the first time provides evidence that plaque characteristics gleaned from careful analysis of 64 slice CT coronary angio has the potential to identify a subset of high-risk plaques that lead to future risk of ACS: expansive remodeling, low attenuation, large plaque size and spotty calcification appear to be the features that predict a high risk of future ACS thereby confirming indirect inferences derived from autopsy studies identifying features of vulnerability. This brings us a step closer to the Holy Grail in this field but we are not quite there: 4 of 15 ACS cases could not be predicted by these high risk features and that may be a limitation of the criteria or those 4 may have resulted from processes other than plaque rupture i.e. plaque erosion. Furthermore the obvious limitations of CTA like radiation and contrast exposure continue to be potential barriers; it is also not clear methodologically how easy it would be in a non research clinical practice setting to extract the features that authors defined as indices of vulnerability. Finally it is disturbing that despite statin therapy, events occurred indicating that even if we were able to identify vulnerable subjects , we would need to have better therapies to prevent events that go beyond current therapies. Notwithstanding these limitation, this study is a major step forward in our quest for identifying at risk subjects”

Roger Blumenthal was less enthusiastic about the study. Here is his comment:

This is a very interesting research study and editorial. Our group has published several important studies using CTA. I am much less optimistic than Dr. Braunwald is that CTA will ever have a role in preventive cardiology.

There is a wealth of data that a simple coronary calcium scan can identify those at a high risk from those at very low risk of an event over the next 5 years. If one has advanced subclinical atherosclerosis for one’s age on the basis of calcium scoring or carotid IMT then one would intensify lipid lowering and blood pressure management and likely add aspirin.

There is no role for prophylactic PCI because we identify a potentially vulnerable plaque. There is a role for more aggressive risk factor modification if we identify a high hsCRP or an above average amount of subclinical atherosclerosis.

Clinicians need to remember the ABCs:

• Assessment of Risk
• Antiplatelet Rx
• Blood Pressure Management
• Chlolesterol Management
• Cigarette Cessation
• Diet/Wt Management
• DM prevention/management
• Exercise instruction
• EF assessment
• Family history implications

Valentin Fuster sent the following comment to CardioBrief:

“This study identifies a novel imaging biomarker as a powerful predictor of future ACS.  Many questions are left unanswered.  For example, whether the same predictive utility could be extrapolated to asymptomatic subjects at risk.  Moreover, trials will need to be conducted to address what is the optimal treatment strategy to follow once these “high-risk features” are identified in a patient.”

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