Coronary Artery Occlusions Diagnosed by Transthoracic Doppler
Coronary Artery Occlusions Diagnosed by Transthoracic Doppler
Coronary artery occlusions are common in coronary disease, with up to a quarter to a third of patients referred for coronary angiography reported to have coronary occlusions. Occluded coronary arteries are associated with high incidence of cardiac events. The coronary arteries are interconnected by intramyocardial and epicardial collaterals. These preformed, small vessels have the potential to remodel and grow in response to ischemia, delivering blood by an alternative route to an ischemic territory. Coronary lesion severity, proximal lesion location, and duration of ischemia are major determinants for collateralization. Though collateral development starts early after the manifestation of ischemia, adequate collateralization may take several weeks. There is individual variability in the propensity to develop collaterals. Coronary collaterals may significantly mitigate the effects of severe stenoses or occlusions. A recent meta-analysis demonstrated a 36% mortality reduction in patients with high collateralization compared with patients with low collateralization.
Traditionally, coronary occlusions and collaterals have been assessed using selective coronary angiography. Though transthoracic Doppler echocardiography (TTE) cannot give a complete and panoramic view of the coronary arteries and collateral vessels, various findings by TTE are shown to diagnose occlusions and collaterals with a high degree of accuracy. Using TTE, a coronary occlusion may be detected by demonstrating retrograde flow in the arterial trunk, left circumflex marginal branches (CxMb), or septal perforating branches. Enhanced flow in elongated epicardial or intramyocardial vessels has been shown to represent collateral flow to an occluded coronary artery. Finally, accelerated anterograde flow velocities in septal perforating branches have been proposed to indicate collateral flow to an occluded artery. However, these TTE studies are few, and most studies have in limited patient cohorts used only one or two parameters to detect coronary occlusions and collateral flow. Furthermore, anterograde flow velocities in septal perforators with collateral supply to occluded coronary arteries have not been extensively evaluated.
The purpose of our study was twofold. First, to assess whether anterograde flow velocities in septal perforating branches could identify an occluded contralateral coronary artery. Second, to assess the feasibility and accuracy of demonstrating occlusions in the three main coronary arteries by the combined use of several parameters, each of which indicates collateral flow. Coronary angiography was used as the reference for coronary occlusions.
Background
Coronary artery occlusions are common in coronary disease, with up to a quarter to a third of patients referred for coronary angiography reported to have coronary occlusions. Occluded coronary arteries are associated with high incidence of cardiac events. The coronary arteries are interconnected by intramyocardial and epicardial collaterals. These preformed, small vessels have the potential to remodel and grow in response to ischemia, delivering blood by an alternative route to an ischemic territory. Coronary lesion severity, proximal lesion location, and duration of ischemia are major determinants for collateralization. Though collateral development starts early after the manifestation of ischemia, adequate collateralization may take several weeks. There is individual variability in the propensity to develop collaterals. Coronary collaterals may significantly mitigate the effects of severe stenoses or occlusions. A recent meta-analysis demonstrated a 36% mortality reduction in patients with high collateralization compared with patients with low collateralization.
Traditionally, coronary occlusions and collaterals have been assessed using selective coronary angiography. Though transthoracic Doppler echocardiography (TTE) cannot give a complete and panoramic view of the coronary arteries and collateral vessels, various findings by TTE are shown to diagnose occlusions and collaterals with a high degree of accuracy. Using TTE, a coronary occlusion may be detected by demonstrating retrograde flow in the arterial trunk, left circumflex marginal branches (CxMb), or septal perforating branches. Enhanced flow in elongated epicardial or intramyocardial vessels has been shown to represent collateral flow to an occluded coronary artery. Finally, accelerated anterograde flow velocities in septal perforating branches have been proposed to indicate collateral flow to an occluded artery. However, these TTE studies are few, and most studies have in limited patient cohorts used only one or two parameters to detect coronary occlusions and collateral flow. Furthermore, anterograde flow velocities in septal perforators with collateral supply to occluded coronary arteries have not been extensively evaluated.
The purpose of our study was twofold. First, to assess whether anterograde flow velocities in septal perforating branches could identify an occluded contralateral coronary artery. Second, to assess the feasibility and accuracy of demonstrating occlusions in the three main coronary arteries by the combined use of several parameters, each of which indicates collateral flow. Coronary angiography was used as the reference for coronary occlusions.