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Comparative Effectiveness of CT-Derived Atherosclerotic Plaque Metrics for Predicting Myocardial Ischemia
Hooman Bakhshi1, Zahra Meyghani1, Satoru Kishi1
1Department of Medicine, Division of Cardiology, Johns Hopkins University, Baltimore, Maryland.
Insights
Cardiac CT plaque metrics predict ischemia, but maximum stenosis is the main predictor. Other metrics like percent atheroma volume and vulnerable plaque show some value, especially when compared to SPECT imaging.
Area of Science:
- Cardiovascular imaging
- Radiology
- Cardiac computed tomography
Background:
- Coronary artery stenosis has a modest association with myocardial ischemia.
- Cardiac CT offers additional atherosclerosis metrics beyond diameter stenosis.
- These metrics may provide incremental value in predicting ischemia.
Purpose of the Study:
- To evaluate cardiac CT-derived atherosclerotic plaque metrics for predicting myocardial ischemia.
- To determine if plaque characteristics offer incremental predictive value beyond diameter stenosis.
Main Methods:
- Analysis of 873 coronary arteries from 356 patients in the CORE320 study.
- Assessment of myocardial perfusion defects using CT perfusion imaging (rest and adenosine stress).
- Evaluation of various plaque metrics including stenosis, calcium score, PAV, and vulnerable plaque characteristics.
Main Results:
- All plaque metrics were associated with reversible ischemia in univariate analysis.
- Maximum percent diameter stenosis was the only independent predictor in adjusted models.
- Percent atheroma volume and "vulnerable plaque" remained predictors when using SPECT as a reference.
Conclusions:
- Cardiac CT plaque metrics predict ischemia primarily through association with stenosis.
- No single metric provided significant incremental value over stenosis assessment alone.
- PAV and "vulnerable plaque" showed small incremental predictive value compared to SPECT.
Objectives:
This study sought to investigate the performance of various cardiac computed tomography (CT)-derived atherosclerotic plaque metrics for predicting provocable myocardial ischemia.
Background:
The association of coronary arterial diameter stenosis with myocardial ischemia is only modest, but cardiac CT provides several other, readily available atherosclerosis metrics, which may have incremental value.
Methods:
The study analyzed 873 nonstented coronary arteries and their myocardial perfusion territories in 356 patients (mean 62 years of age) enrolled in the CORE320 (Coronary Artery Evaluation using 320-row Multidetector Computed Tomography Angiography and Myocardial Perfusion) study. Myocardial perfusion defects in static CT perfusion imaging were graded at rest and after adenosine in 13 myocardial segments using a 4-point scale. The summed difference score was calculated by subtracting the summed rest score from the summed stress score. Reversible ischemia was defined as summed difference score ≥1. In a sensitivity analysis, results were also provided using single-photon emission computed tomography (SPECT) as the reference standard. Vessel based predictor variables included maximum percent diameter stenosis, lesion length, coronary calcium score, maximum cross-sectional calcium arc, percent atheroma volume (PAV), low-attenuation atheroma volume, positive (external) vascular remodeling, and subjective impression of "vulnerable plaque." The study used logistic regression models to assess the association of plaque metrics with myocardial ischemia.
Results:
In univariate analysis, all plaque metrics were associated with reversible ischemia. In the adjusted logistic model, only maximum percent diameter stenosis (1.26; 95% confidence interval: 1.15 to 1.38) remained an independent predictor. With SPECT as outcome variable, PAV and "vulnerable" plaque remained predictive after adjustment. In vessels with intermediate stenosis (40% to 70%), no single metric had clinically meaningful incremental value.
Conclusions:
Various plaque metrics obtained by cardiac CT predict provocable myocardial ischemia by CT perfusion imaging through their association with maximum percent stenosis, while none had significant incremental value. With SPECT as reference standard, PAV and "vulnerable plaque" remained predictors of ischemia after adjustment but the predictive value added to stenosis assessment alone was small.
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