Ophthalmic artery flow reversal and pressure reducing carotid stenosis.

BACKGROUND

In the United States (US), 80,000 strokes annually are attributed to carotid stenosis among the 140,000,000 people over age 40 years old. More than 300,000 people in the US have severe carotid stenosis. Most of those people have normal cerebral perfusion pressure to each portion of the brain because the circle of Willis (coW) provides collateral connection between the basilar artery and the two carotid arteries. In those cases, a reduction in flow through one carotid artery does not affect brain perfusion. However, about 75,000 people with severe carotid stenosis also have a disconnected coW resulting in a pressure reducing carotid stenosis and regional reduced cerebral perfusion pressure. Currently, in standard medical care, every carotid stenosis is treated aggressively without considering whether the coW is connected. Currently, the 240,000 patients reporting transient ischemic attack (TIA) and 550,000 additional patients suffering unheralded stroke are evaluated for carotid artery stenosis after the event resulting in 160,000 carotid stenoses diagnosed. Fewer than 10,000 strokes are prevented annually by 104,000 carotid revascularizations by endarterectomy or stent. Carotid stenosis contributes to 40,000 cases of cognitive impairment and dementia. The United States Preventive Services Task Force (USPSTF) recommends against carotid stenosis screening, although patients might benefit from medical treatment for atherosclerotic artery stenosis. A complete ultrasonic cerebral arterial examination in specialty care includes Doppler measurements from carotid, ophthalmic, and cerebral arteries. Could ophthalmic artery (OA) direction measurement alone in primary care be used for effective screening for pressure reducing carotid stenosis? The aim of this analysis is to determine whether OA flow reversal (OAr) is a specific marker of pressure reducing carotid stenosis indicating elevated risk of preventable stroke and/or cognitive deficit.

METHODS

This analysis of 21,106 cerebro-arterial examinations compared simple measurements [OA flow direction, carotid bruit (CBr) auscultation, bilateral arm blood pressure (BP)] to carotid artery Doppler measurements [peak systolic velocity (PSV) greater than 230 cm/s, or occlusion].

RESULTS

OAr had a 12.5% sensitivity for carotid stenosis, 43.9% sensitivity for carotid occlusion, and 99.4% specificity for carotid obstruction.

CONCLUSIONS

The purpose of the carotid artery examination is to predict whether therapy will provide benefit to the patient. Doppler detection of OAr can be a primary care screening method for pressure reducing carotid obstruction with high specificity that might discover some of the 1% of people who have pressure reducing carotid stenosis. These people might benefit from anti-atherosclerotic medical therapy in primary care. With 6 months of medical treatment, OAr might normalize to forward flow indicating improved cerebral perfusion pressure. In addition, 2% of people have carotid occlusion. These people might be at risk for stroke during systemic hypotension. They might be spared cerebral dysfunction by more careful BP control in primary care or during surgery.