The non-invasive Vascular Laboratory is a specially designed unit with equipment and personnel to accurately diagnose diseases of the vascular system. Non-invasive testing as the name implies, allows patients to be examined in a manner that is safe, pain free and risk free. These tests are used to diagnose or confirm known or suspected vascular disorders and can determine the severity of the problem and the need for intervention. State-of-the-art colour duplex ultrasound has brought the Vascular Laboratory to the forefront in the diagnosis of vascular disease. Duplex ultrasound examinations are frequently used as the sole investigation prior to surgical intervention, hence, non-invasive vascular diagnostic services demand close collaboration between clinical scientists and vascular surgeons.
A full range of investigations are available in the laboratory including, colour duplex imaging, continuous wave Doppler, plethysmography and exercise testing. Colour duplex imaging combines real-time b-mode imaging, pulsed wave Doppler and colour, allowing simultaneous visualisation of the blood vessels and blood flow velocity data. Continuous wave Doppler is used to detect the presence or absence of blood flow (for example, to quantify the blood circulation to the legs when sitting and when exercising). Plethysmography is used to detect and measure changes in blood volume using a light /pressure sensor. Exercise testing is often included in an examination to assess tolerance limitation and symptoms brought on by exercise. These tests can be used after surgery to measure the magnitude of improvement in blood flow or can be used to document the durability of a treatment or compare one treatment to another (e.g. Angioplasty V’s Bypass). In this way, the Vascular Laboratory contributes to clinical research and quality in patient care through outcome assessments.

Tests carried out in the Vascular Laboratory include:

Segmental Pressure Measurement:
This examination is used to determine the presence, severity and level of arterial disease in the upper and lower extremities. Indications for this examination include leg pain while walking (claudication), lower extremity rest pain, non-healing foot/leg ulcers, tissue loss/gangrene. This examination is performed using high quality Doppler Ultrasound with specialized pressure cuffs that together accurately measure blood flow to the limbs.
Toe pressures are also measured (particularly in diabetics) using photoplethysmography (PPG). Arterial pressure measurements provide safe, reliable, reproducible methods for the assessment of peripheral arterial disease. Data obtained from these procedures can prove useful in documenting the status of the circulation pre & post surgical intervention.

Exercise Testing:
It is possible for patients with peripheral arterial disease to have normal ankle/brachial indices (ABI’s) at rest, yet have symptoms of intermittent claudication (calf pain) upon exercise. In these cases, stressing of the peripheral musculature is required to identify if the symptoms are in fact being caused by ischaemia. ABI’s are performed post exercise and compared with resting values. The most common method of exercising the patient is using a treadmill. A drop in ABI post exercise is indicative of disease and the magnitude of the drop is related to the degree of obstruction.

Arterial Duplex:
The ability of arterial duplex to identify disease of the upper/lower extremity, differentiate between stenosis/occlusion, identify multiple/tandem stenoses or multisegment disease as well as the classification of percentage stenosis make it an invaluable tool in Vascular Surgery. Colour duplex provides a means of imaging stenoses/occlusions in a vessel, many of which are marked for the surgeon prior to angioplasty/bypass. Arterial duplex can be used to identify aneurysms of the upper and lower extremity and pseudoaneurysms.

Graft Surveillance:
Duplex is crucial for evaluating the patency of bypass grafts and long-term graft surveillance. The clinical scientist can determine if a vein graft or prosthetic graft is open, closed or narrowed in any way. If a significant narrowing is visualised within the graft or at the graft anastomoses, immediate action can be taken by the vascular surgeon before the graft stops functioning. The Vascular Laboratory plays an important role in the follow-up of dialysis access grafts in patients with renal impairment. These grafts are subject to wear and tear by being utilized several times a week for dialysis. Duplex ultrasound can be used to image scar tissue/thrombus that may have developed in the fistula that can hinder the flow of blood in the device and hamper the dialysis process.


Aortic Duplex:
Abdominal aortic aneurysms are caused by progressive weakening of the aortic wall, which results in dilatation of the vessel. Aneurysms will grow progressively larger and can eventually rupture causing death if they are not diagnosed and treated. Duplex plays an important role in screening patients with abdominal aortic aneurysm (AAA). Patients are usually asked to fast prior to having this investigation. Maximum diameter measurements of the abdominal aorta are measured. Positive scans are referred automatically to the vascular surgeon who will decide if intervention is required.

Carotid Duplex:
Carotid ultrasound is the most common method of screening patients with cerebrovascular disease (ie narrowing or blockages in the main arteries to the brain, thus increasing risk of TIA/Stroke). Carotid ultrasound uses technology to detect and quantify atherosclerotic plaque within the carotid vessels. The force of arterial blood passing over a carotid plaque can send unstable particles to the brain. These particles lodge in the smaller vessels in the brain shutting off blood flow to the brain tissue, thus causing strokes.
Duplex ultrasound provides vital information about the type and stability of the plaque in these arteries, which directly correlates with risk of stroke to the patient. This information is used to determine which patients should or should not undergo Carotid Endarterectomy/ Carotid Artery Stenting (stroke prevention surgery).

Venous Duplex:
Venous duplex is used to image the deep and superficial venous systems of the upper and lower limbs. It is used to assess the competency of deep and superficial veins in patients that present to the Laboratory with varicose veins and leg ulcers. It is particularly useful in the detection of deep venous thrombosis where a physician suspects that a patient may have a blood clot (usually in the arm or leg). Duplex is often performed prior to leg bypass surgery where a suitable superficial vein (usually GSV) is mapped as a conduit.

Research:
Vascular clinical scientists are actively involved in clinical research with the vascular surgeons. This is usually incorporated into the day-to-day workload of the laboratory. Most technologists will be given the opportunity to produce and publish research in their area of interest.