What is the role of coronary angiography in the workup of coronary artery atherosclerosis?

Updated: Apr 09, 2021
  • Author: Sandy N Shah, DO, MBA, FACC, FACP, FACOI; Chief Editor: Yasmine S Ali, MD, MSCI, FACC, FACP  more...
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Answer

Coronary angiography was the first available in vivo assessment of the coronary arteries. In this technique, an iodinated contrast agent is injected through a catheter placed at the ostium of the coronaries. The contrast agent is then visualized through radiographic fluoroscopic examination of the heart.

Coronary angiography remains the criterion standard for detecting significant flow-limiting stenoses that may be revascularized through percutaneous or surgical intervention (as seen in the image below).

Coronary Artery Atherosclerosis. Cardiac catheteri Coronary Artery Atherosclerosis. Cardiac catheterization and coronary angiography in the left panel shows severe left anterior descending coronary artery stenosis. This lesion was treated with stent placement in the left anterior descending coronary artery, as observed in the right panel.

Quantitative coronary angiography (QCA) is used to perform computerized quantitative analysis of the entire coronary tree and has been widely employed in many trials of atherosclerotic progression and regression.

Coronary angiography has several limitations. Severity of stenosis is generally estimated visually, but estimation is limited by the fact that interobserver variability may range from 30-60%. The presence of diffuse disease may also lead to underestimation of stenoses, because the stenosed areas are expressed as a percent of luminal diameter compared with adjacent normal coronary segments, and, in diffuse disease, no such segments are noted. This usually occurs in diabetic patients, in whom coronary arteries are traditionally described as small-caliber vessels, when that appearance is actually due to the presence of diffuse symmetrical involvement of the entire vessel, as elucidated by IVUS studies.

One of the other limitations of coronary angiography is that only the vessel space occupied by blood is visualized. The actual extent of atherosclerotic plaque volume in the wall cannot be assessed with this technique.

Angiography does not provide information about plaque burden, which may be significant due to positive remodeling of the plaque, even when the degree of luminal obstruction is mild.

Because of the inherent limitations of coronary angiography, attention has been directed toward using physiologic approaches to determine the severity of coronary stenoses. The commonly used methods of measuring human coronary blood flow in the cardiac catheterization laboratory are Doppler velocity probes (for measuring CFR) and pressure wires (for measuring FFR). Although most current methods measure relative changes in coronary blood flow, useful information about the physiologic significance of stenosis, cardiac hypertrophy, and pharmacologic interventions can be obtained from these measurements.

Through the Prospective Multicenter Diagnosis of Ischemia-Causing Stenoses Obtained Via Noninvasive Fractional Flow Reserve (DISCOVER-FLOW) Study, Koo et al created a novel technique to noninvasively assess fractional flow reserve, using coronary CT angiograms (CTA). They analyzed 159 vessels in 103 patients. All patients underwent cardiac CTA, invasive angiography fractional flow reserve (FFR), and CT-FFR. FFR-CT and CTA were compared with invasive FFR as the criterion standard. In a per-vessel basis, the accuracy, sensitivity, specificity, positive predictive value, and negative predictive value were 84.3%, 87.9%, 82.2%, 73.9%, 92.2%, respectively, for FFRCT. For cardiac CTA stenosis, they were 58.5%, 91.4%, 39.6%, 46.5%, 88.9%, respectively. This technique, if widely available, may be immensely useful because CTA, although easily interpreted in terms of presence or absence of disease, can be difficult to interpret with regards to severity of disease. [47]


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