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Hemodynamic consequences of carotid-carotid bypass for innominate artery stenosis
S W Oweida1, D N Ku, A G Justicz
1Department of Surgery, Emory University School of Medicine, Atlanta, GA.
Insights
Carotid-carotid bypass surgery can reverse blood flow in the critical segment of the carotid artery during high-grade innominate artery stenosis. This flow reversal may impact emboli, influencing stroke risk.
Area of Science:
- Vascular Surgery
- Cerebrovascular Disease
- Hemodynamics
Background:
- Carotid-carotid bypass is a surgical option for innominate artery atherosclerotic lesions.
- The necessity of excluding innominate plaques from cerebral circulation remains debated.
Purpose of the Study:
- To characterize hemodynamic alterations in the right common carotid artery's critical segment after carotid-carotid bypass.
- To determine flow direction in the critical segment and its implications for emboli originating from the innominate artery.
Main Methods:
- A canine model (six mongrel dogs) was used to simulate carotid-carotid bypass.
- Innominate artery stenosis was quantitatively altered, and flow in the critical segment was measured using an electromagnetic flowmeter.
Main Results:
- Low-grade innominate artery stenosis resulted in prograde flow in the critical segment.
- High-grade stenosis led to complete flow reversal.
- Stenoses between 57% and 67% showed flow values around 10 +/- 24 ml/min with mean flow reversal.
Conclusions:
- Carotid-carotid bypass causes complete flow reversal in the critical segment with high-grade innominate artery stenosis.
- Flow in the critical segment oscillates even near zero, indicating non-stagnant, bidirectional movement.
- Theoretical analysis suggests arm exercise could increase retrograde flow in the critical segment.
Abstract:
The carotid-carotid cervical bypass is one surgical option for symptomatic atherosclerotic lesions of the innominate artery. Controversy exists regarding the necessity of surgically excluding the innominate plaque from the cerebral circuit. A canine study was instituted to characterize the hemodynamic alterations that occur in the right common carotid artery proximal to the bypass graft, termed the critical segment. The direction of flow in the critical segment determines whether emboli originating in the innominate may be propelled cranially despite a patent bypass graft. Six mongrel dogs underwent placement of an autogenous arterial crossover graft as a carotid-carotid bypass. A stenosis of the innominate artery was quantitatively altered, and an electromagnetic flowmeter measured the magnitude and direction of flow in the critical segment at three levels of diameter reduction in the innominate artery. For low-grade stenoses, flow in the critical segment was always prograde. For high-grade stenoses, the flow was always reversed. Stenoses between 57% and 67% yielded flow values of 10 +/- 24 ml/min, and it was in this range that mean flow reversal was found to occur. Even when the mean flow was near zero in the critical segment, flow was not stagnant but oscillated in antegrade and retrograde directions throughout the cardiac cycle. These data indicate that a carotid-carotid bypass causes complete flow reversal in the critical segment when there is high-grade stenosis in the innominate artery. Theoretical analysis of the hemodynamic circuit indicated that arm exercise would augment retrograde flow in the critical segment.(ABSTRACT TRUNCATED AT 250 WORDS)