Upper Limb Arterial Doppler - Part 2

Subclavian Artery Thrombosis and Stenosis

One of the most common conditions which involves large arteries is thrombosis stenosis of the subclavian artery and thrombosis.

Stenosis of the subclavian artery very often presents with subclavian steal or the vertebral steal, so as an example of a thrombosis in the left subclavian artery with a vertebral steal happening on the same side with a reversal of flow in the vertebral artery as compared to the carotid artery.

Another example, this patient has a subclavian artery thrombosis in its proximal end, and there's a reversal of flow in the vertebral artery.

The same patient has a stenosis in the left subclavian artery, and that is what is known as a partial reverse steal in the right vertebral artery.

This partial steal waveform is very often referred to as a funny bunny waveform.

This patient, again has a subclavian artery thrombosis at the origin, and there is a reversal of flow in the vertebral artery throughout telling us that there is a complete steal, yet another patient now with a complete occlusion of the subclavian artery origin with the thrombus, with a complete reversal of flow in the vertebral artery suggesting that there is a steal,

the subclavian artery may be affected not only at its origin, but along its mid or distal portion.

Any is a thrombus in the distal portion of the subclavian artery, but the diagnosis comes up in the mid or proximal portion of subclavian artery.

What we see here is a quick systolic upstroke and multiple small peaks in the diastolic telling us that this is a high resistance flow, and if you look at a distal waveform, there is a dampened waveform because of the thrombus in the distal subclavian artery.

Thoracic Outlet Syndrome

Definition

Compression syndrome is another common thing we have to talk about in the upper limb arteries.

It's a complex of signs and symptoms caused by compression of vital neurovascular structures at the thoracic outlet region, pain, numbness, tingling, weakness, and other disorders in the upper extremity.

The compressed neurovascular structures in descending frequency include the brachial plexus, subin vein, and the artery compression usually occurs as a result of congenital or acquired changes in the surrounding fibro aous and fibromuscular structures.

Thoracic outlet syndrome is the most misunderstood, overlooked, and misdiagnosed condition.

Spaces Involved

The thoracic outlet cooperation syndrome could potentially happen at three spaces.

One is this colony triangle.

Second is the costo clavicle space,

and the third is a pectoral is minus space.

Etiological Factors

The etiological factors could be because of soft tissue lesions or boney lesions.

Soft tissue lesions include S scaley muscle hypertrophy, OID ligament injuries, or compression because of OID ligament and at a level of the minor muscle,

the bony lesions could be a cervical rib, first rib abnormalities, long C seven transverse process or clavicle abnormalities.

Symptoms

So the symptoms in thoracic outlet could be neural or they could be vascular, or very often we have a combination of neural and vascular symptoms.

The neural symptom could be peripheral or they can be symptom symptomatic like NARS phenomena.

Vascular symptoms could be because of arterial problems like loss of pulsations, claudications, or they could be because of venous involvement like pain edema, venous distension, collateral veins, or very often even thrombosis.

Diagnostic Tests

See the test, which is commonly done for thoracic outlet syndrome is known as at absences test.

The at absences test is basically a clinical test, which is performed by holding the patient's arm down and checking the radial pulse while the patient inhales deeply and keeps his head extended and turn towards the involvement extremity.

If the patient has a thoracic outlet syndrome, this action results in arbitration or decrease of the radial pulse.

As I said, this is a clinical test, but we can use it with Doppler where we replace the hand, which is holding the pulse with an ultrasound probe.

We have another test, which is known as neck tilting test.

This is similar to absences test.

However, here the patient tilts the head away from the affected side.

We have other tests like OG clavicle compression test where the examiner depresses the patient's shoulder,

or we have a hyper AB test where the patient is in a sitting position with the shoulders hyper abducted and rotated externally.

This is one of my favorite tests to look out for thoracic outlet syndrome.

We can modify this test by what is known as a rose test where we ask the patient to do exercises with the fingers.

So what do we see? This is a subclavian artery address showing a tri SIC waveform.

After an hyperabduction maneuver, we see that there is no flow happening in the subclavian artery, so this is a positive screening test for thoracic outlet syndrome.

Another patient on the left side, there is a good flow in the subcate artery.

At rest. After hyperabduction, we see that there is no flow in the subcate artery,

and if you look at a radial artery again, at rest we have got good flow, but after an hyperabduction maneuver, there is no flow in the radial artery suggesting that this patient has a thoracic outlet syndrome.

As I said, sometimes the veins can get affected.

This patient, for example, has normal flow in the artery subclavian artery, but if you look at the subclavian vein, at rest we have normal velocities.

But after doing the maneuver, there is narrowing of the vein, and this is shown on doppler as very high velocities, so veins can also get affected.

Some years back, we did a study with one of my colleagues, Dr. Raju Ani, and published it in the General AL ultrasound, and we found out that patients could have both arterial as well as venous involvement.

As I said, Doppler is a screening test for thoracic outlet syndrome.

If you feel that a patient really has a thoracic outlet, then this has to be confirmed with more definitive tests like an angiography or a CT angiography.

And in CT angiography, they very often do what is known as a Langs manoa to find out if the patient has a thoracic outlet syndrome.