Vascular Laboratory

The noninvasive Vascular Laboratory at UMMHC was established in 1976. The laboratory has experienced steady growth since its inception. On the University Campus, the lab is located on the A level in the Cardiovascular Center. On the Memorial Campus, the lab is located on the 1st Floor, South Side. The laboratories are ICAVL approved facilities that perform over 16,000 hemodynamic studies each year. These include duplex carotid evaluation, transcranial Doppler examinations, peripheral arterial and venous studies, visceral vascular studies and graft surveillance.

The laboratory provides outpatient and inpatient testing from 7:30 AM to 4:30 PM daily. A technologist is available on call for emergency studies from 10 AM to 1 PM on weekends and holidays.

Vascular Studies Available:

• Carotid duplex scan
• Transcranial Doppler (TCD) ultrasonography
• Ankle/Brachial index (ABI)
• Segmental Doppler Pressures and Pulse Volume Recordings
• Arterial Stress Testing
• Arterial duplex color-flow scanning
• Venous Duplex scan
• Visceral Vascular Evaluations
• Duplex Scan of Abdominal Vessels
• Abdominal aorta/iliac arteries
• Inferior vena cava/iliac veins
• Renal arteries
• Mesenteric arteries (celiac axis/superior mesenteric artery)
• Portal/Hepatic venous flow

Scheduling Examinations

Requests for inpatient studies are transmitted to the Vascular Laboratory through the inpatient order entry system.

All outpatient studies may be scheduled in the through the Central Scheduling Department at 508 334-9900. Every effort will be made to accommodate requests for urgent studies. Referring physicians are informed of critical test results by telephone.

Description of Vascular Studies:

Extracranial Carotid

Carotid duplex scanning provides real time B-mode ultrasound images of the carotid bifurcation in combination with color Doppler and pulsed Doppler spectral analysis of flow through the extracranial common carotid artery, the proximal external carotid artery and the proximal internal carotid artery. The vertebral artery is assessed in the mid cervical region to detect abnormalities in vertebral flow, including flow reversal caused by a subclavian steal syndrome. Indications for carotid duplex scanning include stroke, transient ischemic attack (TIA), amaurosis fugax, carotid bruit, follow-up of previously detected carotid stenosis (to evaluate for disease progression) and follow-up of carotid endarterectomy or carotid artery stenting. Other indications less likely to be associated with significant carotid artery stenosis include dizziness, syncope and diplopia.

Interpretation of carotid duplex ultrasonography is based upon a combination of the grey scale and Doppler spectral waveform analysis of flow velocities. Standard categories of percent diameter stenosis have been developed: Normal, 1-29% stenosis, 30-49% stenosis, 50- 69% stenosis, 70-79% stenosis, 80-99% stenosis, and Occlusion.

Intracranial

Transcranial Doppler (TCD) sonography provides Doppler spectral waveform analysis of intracranial arterial flow through the Circle of Willis. Two "acoustic windows" (transtemporal and transoccipital) are used to obtain measurements of blood flow velocity through the middle cerebral artery, the anterior cerebral artery, the posterior cerebral artery, the vertebral arteries, the basilar artery, and the intracranial internal carotid artery. TCD studies are used most often to detect the presence of vasospasm following subarachnoid hemorrhage (SAH) or following surgical repair of intracranial arterial aneurysms. Less commonly, TCD may be used to detect the presence of intracranial arterial stenosis or to evaluate patterns of collateral flow in patients with carotid artery stenosis.

Peripheral Arterial

Ankle/Brachial index (ABI)/Segmental Doppler pressure measurements in combination with Pulse Volume Recordings document the presence of hemodynamically significant arterial occlusive disease in the lower extremities. Normally, the ratio of the systolic pressure at the ankle divided by the brachial systolic pressure (ABI) will be 1.0 or higher. The ABI will decrease with increasing levels of arterial insufficiency. Segmental pressure measurements will help to determine the level(s) of significant occlusive disease. Segmental pressures are measured at the high thigh, above knee, calf, and ankle levels. In patients with arterial wall calcification, most often secondary to diabetes, pressure measurements may be falsely elevated or unobtainable. In these cases, Pulse Volume Recordings provides additional information regarding the presence and location of hemodynamically significant arterial occlusive lesions in the lower extremities.

Arterial Exercise Testing is useful in patients with arterial occlusive lesions that do not limit flow at rest. Peripheral vasodilation will occur during treadmill exercise. With normal arterial circulation the postexercise ankle pressure will remain normal. If a flow reducing arterial stenosis is present, the patient will develop claudication and there will be a fall in the postexercise ankle pressure measurements. A postexercise fall in ankle pressure will not be observed in patients with a nonvascular etiology to exercise induced leg discomfort.

Arterial duplex scan is indicated in patients suspected of peripheral artery aneurysms, pseudoaneurysms (following femoral or brachial artery catheterization), or arteriovenous communications. Duplex scanning is also useful in the follow up of leg bypass grafts and arterial stents to detect the presence of stenosis following surgical or endovascular intervention. As with carotid duplex ultrasonography, Doppler velocity measurements are an important component of arterial duplex scanning. Increased flow velocities are noted at the site of an arterial stenosis.

Peripheral Venous

Venous duplex scanning combines real time B-mode images with color Doppler and spectral Doppler recordings to detect thrombosis of the deep and superficial veins in the upper and lower extremities. Normally, the veins of the extremities will compress when pressure is applied with the ultrasound transducer. In the presence of venous thrombosis, the vessel will become dilated and incompressible. Intralumenal echoes noted on the real time images are consistent with the presence of thrombus within the vein.

Indications for performing a venous duplex scan include limb pain and swelling. Hospitalized patients at high risk for developing venous thrombosis may benefit from venous duplex scanning to detect the presence of asymptomatic proximal leg vein thrombosis. Venous duplex imaging is also used to document the presence of venous valvular incompetence in patients with varicose veins or a history of venous thrombosis, and to determine the adequacy of superficial veins prior to peripheral vascular /coronary bypass surgery.

Visceral Vascular Studies

Abdominal duplex imaging has traditionally been used to document the presence of aneurysmal disease involving the abdominal aorta and iliac arteries, and thrombosis of the inferior vena cava and iliac veins. More recently, duplex scanning has been demonstrated to be of value in the evaluation of flow to the major organs in the abdomen. Evaluation of renal artery flow is indicated in patients with symptoms of renovascular hypertension. The celiac axis, superior mesenteric artery, and inferior mesenteric artery may be examined in patients with symptoms of mesenteric insufficiency ("intestinal angina"). Evaluation of the portal/hepatic veins is useful in patients suspected of portal hypertension/thrombosis or other vascular disorders of the liver. To limit the presence of abdominal gas, all patients undergoing abdominal duplex scanning are required to fast for six hours prior to the examination.

For Additional Information:

Vascular Lab

University Campus 774-443-3464
Memorial Campus 508-334-6219

Karen Saia, RVT, RN
Manager of the Vascular Laboratory-Memorial Campus
508-334-6236

Denise Kush, RVT
Chief Technologist, Vascular Laboratory-University Campus
774-442-6473