Carotid Plaque Ultrasound Sharpens Stress Echo CAD Risk Assessment in Prospective Study

Liam Davenport

April 18, 2017

LONDON, UK — Taking a few extra minutes to perform carotid-artery ultrasound alongside stress echocardiography in patients with suspected coronary artery disease (CAD) offers incremental prognostic value that could aid in primary prevention, say UK researchers, based on their single-center but large and prospective study[1].

Combining the two ultrasound techniques to assess all at once for both myocardial ischemia and carotid arterial plaque burden better predicted the subsequent risk of a major adverse event in patients with suspected CAD than either imaging technique alone.

The current research, published online April 12, 2017 in JACC: Cardiovascular Imaging, builds on observational studies suggesting that supplementing risk-factor assessment with ultrasound assessment of carotid intima-media thickness (CIMT) can significantly improve clinical CAD risk stratification.

However, its value in actual practice is less well established. The current study may be its first successful demonstration in a large prospective study, according to the authors, led by Dr Shahram Ahmadvazir (Imperial College and Royal Brompton Hospital, London, UK).

"In patients with suspected stable angina but without known CAD, simultaneous stress echocardiography and carotid ultrasound provided incremental prognostic value" and carry "prognostic importance and implications for primary prevention," they write.

The addition of carotid ultrasound to stress echo "is a very simple procedure," senior author Dr Roxy Senior (Imperial College and Royal Brompton Hospital) told heartwire from Medscape. "It takes about an extra 3 to 4 minutes only to get those images."

Although the current findings have shown the prognostic value of the combined techniques, they do not indicate whether, by using it to guide aspirin and statin therapy, outcomes will be altered, Senior observed.

"Having said that, now there are at least a few papers that have shown that it does . . . so the evidence is accumulating that if there is atherosclerosis, then a preventive therapy like aspirin and statins do influence outcomes," he said.

"My take on this would be that, yes, we need to do a study to prove it. But I think logic states—and the evidence is already there with computed tomography data—that if there's plaque and it gets treated with aspirin and statins, they reduce myocardial infarctions," compared with treatment guided by functional testing only, he said.

 He and his colleagues recruited 591 patients with recent-onset suspected stable angina and no previous history of CAD; both imaging tests were performed simultaneously.

Stress echocardiography included either a standard treadmill test or a dobutamine stress test, with the result defined as "abnormal" in the presence of a wall-thickening abnormality in at least two consecutive segments. Carotid plaque was defined as a focal structure encroaching into the arterial lumen by ≥0.5 mm or a distinct area of carotid intima-media thickness ≥50% greater than the adjacent wall or >1.5 mm in thickness.

The team also determined the pretest probability (PTP) of CAD, a composite factor that included the known CAD risk factors of chest-pain characteristics (such as whether it is new-onset), age, gender, diabetes mellitus, hyperlipidemia, and smoking status.

Follow-up data was available 580 participants, of whom 46% were male; their mean age was 59 years.

Over a mean follow-up of 1117 days, there were 40 major adverse cardiac events (MACE), comprising 12 deaths, nine nonfatal MIs, and 19 unplanned coronary revascularizations. Over the same period, there were 32 MACE and 13 hard cardiac events (defined as cardiovascular mortality or nonfatal MI).

In multivariate analysis, predictors of MACE included PTP (P=0.001), results of stress echo (P<0.0001), and carotid plaque burden (P<0.0001). MACE were predicted by PTP (P=0.004), stress echo (P<0.0001), and carotid plaque burden (P<0.0001).

But carotid plaque burden was only the significant predictor of hard cardiac events (P<0.0001); stress echo as a predictor fell short of significant (P=0.06).

Patients negative for carotid plaque and a normal stress echo showed a MACE annual rate per year of 0.9%, which rose to 1.97% among those positive for plaque and normal stress echocardiography, 4.3% in patients with no plaque and abnormal stress echocardiography, and 9.7% those with both plaque and abnormal stress echocardiography (P<0.0001).

On hierarchical analysis, carotid plaque burden offered an incremental prognostic value over PTP and stress echo, while stress echo added prognostic value to PTP and carotid plaque burden (P<0.0001 for both).

Earlier data suggesting incremental benefit from the combination of tests for atherosclerosis and myocardial ischemia have been limited to patients undergoing single-photon-emission tomography (SPECT) or positron-emission-tomography (PET) with coronary computed tomographic angiography (CCTA), the group writes. "However, both combination modalities are costly, with a prohibitive ionizing radiation dose, and not widely available."

They continue, "This is the first study showing that contemporary stress echocardiography (harmonic imaging with contrast use where required) and simultaneous carotid ultrasound can not only provide similar prognostic information to the radiation-based techniques but were feasible in all patients, free of any ionizing radiation, significantly less costly, and ubiquitously available."

In an accompanying editorial[2], Dr Eugenio Picano (National Research Council Institute of Clinical Physiology, Pisa, Italy) and Dr Maria Chiara Scali (Nottola Hospital, Siena, Italy) write that translating the findings into clinical practice will take "additional cultural, technological, and scientific steps," including "appropriate education, training, and certification" for sonographers.

"The strict standardization of acquisition and analysis of carotid intima-media thickness and plaque imaging is required, possibly with the assistance of software controlling variability through semiautomated reading of wall thickness and plaque texture."

Interviewed, Senior disagreed that such steps are needed before the simultaneous use of the techniques can be introduced into clinical practice. Standardization to that degree "can be done, but if you are going to use [the imaging combination] practically, then just the presence of plaque is enough, as shown in this paper, to look at outcomes."

Senior discloses speaker fees/honorarium from Bracco and Philips. The coauthors report no relevant financial relationships, as do Picano and Scali.  

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