Abstract 6117: Significance of Flow Aliasing in the Proximal Left Coronary Artery on Transthoracic Color Doppler Echocardiography in Patients with Unstable Angina
Background: Noninvasive coronary flow velocity reserve (CFVR) measurement by transthoracic Doppler echocardiography (TTDE) has been validated and utilized at the bedside. However, because this method requires pharmaceutical provocation, it has some risk especially for patients suspected of acute coronary syndrome. Color aliasing of coronary flow on TTDE in the short axis (SAX) view at the aortic root level suggests that flow acceleration produced by stenosis is occasionally observed during screening in patients with chest pain. The aim of this study was to investigate the clinical significance of flow aliasing on TTDE in the SAX view at the aortic root in patients with unstable angina.
Methods: Patients (n=104) with unstable angina were evaluated. Proximal left coronary flow was sought in the SAX view at the aortic root level under color Doppler guidance at a color velocity range of ±19 cm/sec. When detected coronary flow showed color aliasing, the color velocity range was gradually raised until color aliasing nearly disappeared. Then, the color baseline was shifted until color flow showed isovelocity. AHA segment 6 on the coronary angiogram obtained within 24 hours was defined as the proximal left anterior descending artery (LAD).
Results: Color aliasing was observed in 49 of 104 patients. In 14 of these 49 patients, there was significant stenosis (≥50% luminal reduction) in the left main coronary artery (LMCA) and 25 had significant stenosis in the proximal LAD. In patients with flow aliasing, a cut-off value of isovelocity ≥33.0 cm/sec predicted significant coronary stenosis with a sensitivity of 90%, specificity of 80%, positive predictive value of 95%, and negative predictive value of 67%. In all 104 patients, the cut-off value predicted significant coronary stenosis with a sensitivity of 60%, specificity of 96%, positive predictive value of 95%, and negative predictive value of 66%.
Conclusion: Detection of flow aliasing by TTDE in the SAX view is a promising method for noninvasive diagnosis of LMCA and proximal LAD stenosis. This method may be useful for expeditious risk stratification and decision making in patients with unstable angina.