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Identification of internal carotid artery stenosis in coronary artery bypass candidates
Insights
Detecting internal carotid artery stenosis in asymptomatic bypass candidates is challenging. Combining carotid auscultation with duplex ultrasound significantly improves accuracy for identifying significant stenosis, aiding preoperative decisions.
Area of Science:
- Vascular Surgery
- Diagnostic Imaging
- Cardiology
Background:
- Identifying internal carotid artery (ICA) stenosis in neurologically asymptomatic patients undergoing coronary artery bypass grafting (CABG) is clinically significant but challenging.
- Preoperative assessment aims to prevent perioperative stroke by identifying high-risk individuals.
Purpose of the Study:
- To evaluate the diagnostic accuracy of carotid auscultation (bruits) and noninvasive duplex ultrasonography (DUS) with Fast Fourier Transform (FFT) spectral analysis for detecting significant ICA stenosis (≥50% diameter reduction) in CABG candidates.
- To determine the optimal noninvasive strategy for selecting patients who would benefit from preoperative carotid arteriography.
Main Methods:
- Correlation of carotid arteriograms with carotid bruits in 422 vessels.
- Assessment of noninvasive duplex scan with FFT spectral analysis.
- Application of Bayes' theorem to calculate predictive values based on the prevalence of significant stenosis (6%) in this population.
Main Results:
- Carotid bruits demonstrated a sensitivity of 79% and specificity of 65% for detecting ≥50% ICA stenosis.
- Duplex scan with FFT spectral analysis achieved 90% sensitivity and 90% specificity.
- Individually, carotid bruits were incorrect 87% of the time, and DUS was incorrect 64% of the time in predicting stenosis.
Conclusions:
- Neither carotid auscultation nor duplex scanning alone provides sufficient predictive value for determining the necessity of preoperative carotid arteriography.
- Limiting duplex scanning to patients with a carotid bruit significantly increases the predictive value to 92% with minimal increase in undiagnosed patients.
- A combined approach of duplex scanning in patients with a carotid bruit is recommended for preoperative evaluation in CABG candidates.
Abstract:
Identification of stenotic internal carotid arteries in neurologically asymptomatic coronary artery bypass candidates is difficult. We correlated carotid arteriograms with carotid bruits in 422 vessels and demonstrated a sensitivity of 79% and a specificity of 65% with regard to the bruit's identification of vessels with a 50% or more reduction in angiographic diameter. The noninvasive duplex scan, used in conjunction with Fast Fourier Transform spectral analysis, had a sensitivity and a specificity of 90% in this same regard. Since there is only a 6% incidence of significant internal carotid stenosis in bypass candidates, Bayes' theorem used in conjunction with our findings showed that a carotid bruit was an incorrect predictor of internal carotid stenosis 87% of the time. The duplex scan was somewhat better, but still inaccurate 64% of the time. Thus neither parameter alone has a high enough predictive value to determine whether preoperative carotid angiography is necessary. However, if one limits duplex scanning to patients with a carotid bruit, the predictive value is raised to 92%. At the same time, there is minimal increase in the number of undiagnosed patients. Thus far this combined approach is recommended for preoperative evaluation of patients scheduled for coronary artery bypass.