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Arterial investigations invariably aim at demonstrating sites of disease and suitability for intervention. The choice of investigation is mainly determined by the clinical findings i.e. the symptoms and severity of the disease.
The Hand Held Doppler The hand held Doppler is a very useful investigative tool. The machine is capable of detecting blood flow in arteries deep under the skin, even when the pulses cannot be felt. An ultrasound wave is directed at an artery and reflected back again. The receiving signal is picked up and the change in frequencies between the two signals is then converted into an audio signal, which is usually heard as a pulsatile sound. It is a very simple, quick investigation.
The hand held Doppler is used to measure the Ankle Brachial Pressure Index (ABPI). This index is very useful in quantifying the reduction in blood flow due to arterial disease. In normal individuals, the blood pressure in the legs is slightly higher than that in the arms. Dividing the blood pressure in the legs by that in the arms will therefore give a value higher than one (the ABPI). When the leg arteries are narrowed, the blood pressure in the affected leg becomes less than that in the arm. In this case, the ABPI will be less than one. When the ABPI is less than 0.5 (normal is 0.9 to 1.2), the leg is potentially critically ischaemic.
Duplex Imaging Duplex scanning uses two different types of ultrasound, B-mode and Doppler. The first creates an image of the vessels and the second measures the flow. The machine is, therefore, able to look directly at the flow of blood through a vessel, measuring its speed and direction. It also looks for any narrowing or blockages of the arteries.
Arteriography Arteriography involves the injection of a radio-opaque dye (contrast) into the arteries and at the same time taking x ray pictures of these arteries. This allows examiner to identify areas of narrowing or complete occlusion with ease. This is a more invasive investigation and is associated with a small complication rate including clotting, bruising and very rarely an allergy to the dye involved. |
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