Upper Extremity Arteries

Normal and Variant Anatomy

The arterial blood supply of the upper extremities begins with the subclavian artery on the left and the brachiocephalic (also known as the innominate) artery on the right. The left subclavian artery arises directly from the aorta, while on the right the brachiocephalic artery bifurcates into the right common carotid and subclavian arteries (see Fig. 5-1 ). The subclavian arteries are defined as the segment of vessel between the aortic arch or brachiocephalic artery bifurcation and the lateral border of the first rib. The subclavian artery exits the thoracic cavity between the anterior and middle scalene muscles, and then passes between the clavicle and first rib ( Fig. 6-1 ). The typical diameter of the subclavian artery is 7-10 mm. The subclavian arteries provide blood to the upper chest, the arms, and the central nervous system (through the vertebral artery).

The internal mammary arteries are constant vessels that arise from the anterior inferior aspect of the subclavian arteries just opposite or slightly distal to the vertebral arteries. These vessels course anteriorly and medially along the inner surface of the chest wall. The internal mammary arteries are important potential sources of collateral blood supply in cases of thoracic or abdominal aortic obstruction (via the anterior anastomoses with the intercostal arteries in the former, and the inferior epigastric arteries in the latter). The internal mammary arteries can provide collateral supply to bronchial arteries as well.

The other named branches of the subclavian arteries are highly variable in origin, but relatively constant in presence. The vertebral arteries arise from the superoposterior surface of the subclavian arteries and are discussed in Chapter 5 . The thyrocervical trunk arises just distal to the internal mammary arteries from the superior surface of the subclavian artery, often lateral to the vertebral artery. This vessel is subject to enormous variability, but is typically the origin of the inferior thyroidal, superficial cervical, and suprascapular arteries. Only slightly more than 50% of individuals have this classic anatomy. Independent origins of one or more of these vessels from the subclavian artery are common. The next major branch of the subclavian artery is the costocervical trunk, which gives rise to the deep cervical, supreme intercostal (highest thoracic), and occasionally the anterior spinal (radiculomedullary) arteries ( Fig. 6-2 ). The supreme intercostal artery contributes to the blood supply of the first through third ribs. This anatomy is found in approximately 80% of individuals, with the most common variants being independent origins of the two branches.

The axillary artery begins at the lateral margin of the first rib, extending to the lateral margin of the teres major muscle tendon. Thus a portion of the axillary artery is located quite medial to the anatomic axilla. The branches of the axillary artery are highly variable in origin. These are the superior thoracic artery (to the anterior portions of the first through third intercostal spaces); the lateral thoracic artery (to the lateral chest, with a prominent mammary branch in women); the thoracoacromial artery (with branches to the clavicle, the acromion, and deltoid); the subscapular artery, which gives rise to the thoracodorsal artery (supplying the musculature along the lateral margin of the scapula); and the scapular circumflex artery (supplying the muscles of the back deep to the scapula). The last branch of the axillary artery is the circumflex humeral artery, which supplies the humeral head and the surrounding soft tissues. All of the axillary and subclavian artery branches (exclusive of the vertebral artery) have potential anastomoses with each other that become evident in the presence of occlusive disease or vascular tumors. Of great importance, the radial, ulnar, and median nerves lie in close proximity to the axillary artery. Contained in a sheath of connective tissue along with the artery, these neural structures are at risk for compression by even a small amount of bleeding within the sheath after axillary artery punctures.

The brachial artery begins lateral to the teres major muscle tendon (see Fig. 6-1 ). Variants of the brachial artery proper are uncommon, but include a small accessory branch to the radial artery (persistent superficial brachial artery, 1%-2%) and duplication (0.1%). The profunda brachialis artery is usually the first major branch of this vessel, traveling with the ulnar nerve in a posterolateral course around the humerus ( Fig. 6-3 ). This vessel supplies the muscular structures of the posterior aspect of the upper arm, as well as collateral supply around the elbow. There are many unnamed muscular branches of this artery, but those that anastomose to muscular branches distal to the elbow joint are termed collateral vessels . These variable vessels are named after the forearm vessel to which they collateralize (e.g., ulnar collateral artery).

The terminal branches of the brachial artery are the radial, ulnar, and interosseous arteries ( Fig. 6-4 ). Anomalous high origins of the radial or ulnar artery from the brachial or axillary arteries are present in 15% and 3% of patients, respectively. These variants are potential sources of confusion during upper extremity angiography if the catheter is unknowingly placed distal to an anomalously high origin ( Fig. 6-5 ). The forearm arteries supply the adjacent muscles and (usually only the radial and ulnar arteries) continue into the hand. The interosseous artery divides into an anterior and posterior branch. In fewer than 2% of individuals, the interosseous artery may continue into the hand as the median artery ( Fig. 6-6 ).

The classic arterial anatomy of the hand is comprised of two complete palmar arcades, both of which receive contributions from the radial and the ulnar arteries ( Fig. 6-7 ). The more proximal arcade, the deep palmar arch, is primarily supplied by the radial artery. The more distal arcade, the superficial palmar arch, is supplied primarily by the ulnar artery. Variations of this anatomy are so prevalent that the classic anatomy of two complete interconnected arcades is present in fewer than 50% of patients ( Table 6-1 ). These variants are the rule rather than the exception.

The blood supply to the fingers is derived from the paired palmar metacarpal and common palmar digital arteries that originate from the deep and superficial palmar arches, respectively. These arteries join at the interdigital webspace to form the paired proper palmar digital arteries of the fingers. The radial artery is usually the dominant blood supply to the thumb and the second digit, while the ulnar artery supplies the fourth and fifth digits. The third digit may be supplied by either artery. The dominant blood supply to the fingers varies with the arch anatomy.

Key Collateral Pathways

The potential collateral routes around a subclavian artery origin stenosis or occlusion are numerous, in that they include all of the branches of the subclavian and axillary artery. One pattern, subclavian steal, describes retrograde flow in the ipsilateral vertebral artery ( Fig. 6-8 ; see Fig. 3-11 ). Subclavian steal is associated with arm pain or central neurologic symptoms in a third of patients. Symptoms may be exacerbated with use of the arm ( Box 6-1 ). Bilateral subclavian steal is uncommon.

Steal physiology can affect other vessels in the upper extremity. Proximal occlusion of the brachiocephalic artery origin can result in retrograde flow down the right common carotid artery as well as the right vertebral artery. Reversal of flow can occur in smaller subclavian artery branches such as the thyrocervical trunk and the internal mammary artery. In patients with cardiac bypass surgery based on an internal mammary artery, proximal subclavian stenosis can cause a steal phenomenon involving the internal mammary artery that presents as angina ( Fig. 6-9 ).

Axillary artery occlusion is usually well tolerated because of the rich potential collateral pathways around the scapula and humerus. Frequently, the subscapular artery assumes a dominant role in reconstituting the distal axillary artery. In addition, the intercostal arteries can provide collateral blood supply to the upper extremity through anastomoses with the vessels of the chest wall, such as the lateral thoracic artery. Occlusion of the distal brachial artery results in collateral supply from the profunda brachialis artery high in the arm and around the elbow through the radial and ulnar collateral arteries to radial and ulnar recurrent arteries.

Occlusion of either the radial or ulnar artery is well tolerated by the fingers as long as one or both arches are intact. When the deep and superficial arches are incomplete or absent, acute occlusion of a forearm artery may result in severe digital ischemia. Over time, collateral supply can develop from the opposite forearm vessel or the interosseous artery.

Imaging

Ultrasound examination of the upper extremity arteries distal to the clavicle is relatively straightforward. Standard duplex color-flow ultrasound techniques can be used for the peripheral vessels. A high-resistance triphasic waveform is normal in the upper extremity except in the fingers, which are biphasic. Pulse volume recordings of the fingers can be used to assess digital perfusion ( Fig. 6-10 ). The superficial location of these vessels facilitates visualization with ultrasound. Medial to the clavicle, the vessels dive deep into the mediastinum, beyond the reach of surface probes. To fully evaluate the subclavian artery origins and brachiocephalic artery, a transesophageal probe is needed. However, even with this technique the origins of the arteries may not be completely visualized.

Computed tomography angiography (CTA) of the upper extremity vessels is an excellent modality for evaluation of the axillosubclavian arteries, especially within the mediastinum. CTA requires the patient to breath-hold, with a short delay after injection of contrast. As a general rule, a noncontrast scan should be obtained before contrast injection. Thick collimation is appropriate for the noncontrast scan. Thinner effective collimation (sub 1 cm) should be used for the contrast-enhanced scan. The area of coverage should include the proximal neck to the hand for complete upper extremity studies. A very important technical consideration is the route of administration of contrast. Contrast injected into an upper extremity vein remains extremely dense on CT scan before it reaches the central circulation. This causes streak artifacts that degrade image quality, particularly across the great vessel origins. The arm opposite the side of interest should therefore be used for contrast administration. The vessels can be evaluated using simple postprocessing techniques such as reformatting.

The upper extremity arteries are well suited for evaluation with magnetic resonance angiographic (MRA) techniques. Gadolinium-enhanced three-dimensional (3-D) acquisitions provide excellent images of the arch and proximal portions of the upper extremity arteries ( Fig. 6-11 ). Acquisitions oriented in the coronal plane can include both the arch and the upper extremity vessels to the shoulder. An important pitfall is signal loss due to susceptibility artifact from adjacent veins caused by undiluted gadolinium injected in an upper extremity vein (see Fig. 3-17 ). As with CTA of the upper extremities, contrast should be injected into the extremity opposite the side of clinical interest. Imaging arteries of the arm and hand can be accomplished with either contrast-enhanced or noncontrast acquisitions. Small coils can be used to maximize image detail ( Fig. 6-12 ).

Angiographic studies are usually performed from a femoral arterial approach, but retrograde access from axillary, brachial, or radial arteries can be used. Documentation of the upper extremity pulses (axillary, brachial, radial, and ulnar arteries) in both arms, the carotid pulses, and bilateral brachial artery blood pressure measurements should be confirmed before inserting a catheter, even when the problem is unilateral. Subclavian artery aneurysms may be palpable as a pulsatile mass in the supraclavicular fossa, although a tortuous but normal-caliber artery may feel similar.

The complete angiographic study of the upper extremity involves visualization of all arteries from the aortic arch to the tips of the fingers. Anything less risks missing important pathology. Exceptions to this rule should be made only after careful analysis of the clinical scenario and of the patient. For each injection it is essential to ensure that there is satisfactory overlap of coverage with the preceding injection so that the extremity is imaged in its entirety.

An arch aortogram in the left anterior oblique (LAO) projection will profile the origins of the great vessels (see Fig. 6-8 ). To open the brachiocephalic artery bifurcation, filming in the right anterior oblique (RAO) projection is necessary (see Fig. 5-1 ). The pigtail catheter should be positioned in the ascending aorta just proximal to the brachiocephalic artery origin. Specific injection and exposure rates are listed in Table 6-2 . To select the subclavian arteries, the pigtail catheter is exchanged for a 5-French 100-cm length catheter with a gentle angle at the tip, such as Davis or H-1 (see Fig. 2-10 ). Arteries that arise from the arch at an acute angle can be selected with a Simmons-2 (right subclavian) or Simmons-1 (left subclavian). With the tube angled to show the arch in an LAO projection, the catheter is positioned in the aorta proximal to the great vessel origins. The catheter is then turned so that the tip points toward the head and is slowly withdrawn until it pops up into a great vessel origin. Leading with 1 cm of soft guidewire (e.g., Bentson) minimizes the risk of vessel trauma. In older patients there is frequently enough calcification at the ostia of the great vessels to provide a fluoroscopic landmark. A gentle test of contrast (no air bubbles!) can be used to identify the vessel. The subclavian artery can be selected using almost any atraumatic guidewire, such as a 3-J long taper or an angled hydrophilic guidewire. If the guidewire passes into the neck toward the head, it may be in a vertebral artery or, on the right, in the common carotid artery. When selecting the right subclavian artery, remember that the origin is usually posterior to the right common carotid artery (see Fig. 5-1 ).

The subclavian and axillary arteries can usually be included on one image with the catheter tip positioned just beyond the origin of the vertebral artery. Non-ionic contrast should be used to minimize patient discomfort during the examination. An angled hydrophilic guidewire can then be used to select a more peripheral location. The brachial artery should be imaged with the catheter in the proximal axillary artery in order to avoid causing spasm or missing a high origin of a radial or ulnar artery. Once these anomalies have been excluded, the catheter can be positioned in the mid or distal brachial artery for angiography of the forearm or hand. The hand should be in anatomic position (palm up and hand flat on the table) for forearm angiography (see Fig. 6-6 ). Otherwise it can be extremely difficult to identify vessels in the forearm or hand. Selective angiography of the individual forearm arteries is best performed with small high-flow microcatheters, because these vessels are subject to spasm when manipulated.

The hand can be maintained in anatomic position (palm up) or placed completely flat with the fingers spread slightly for the hand angiogram (see Fig. 6-7 ). Since the digital arteries are small and numerous, magnification views and vasodilation are frequently necessary to obtain the best images. Vasodilation of the arteries of the hand can be induced by wrapping the hand in warm towels or having the patient hold a warm pack during the initial parts of the examination. Another effective method is reactive hyperemia with the blood pressure cuff on the upper arm. Intraarterial injection of a vasodilating agent (such as 200 μg of nitroglycerin) through the catheter just before injection of contrast can also be used (see Fig. 6-10 ). There are few radiographic images more distinctive and beautiful than high-quality magnification arteriograms of the human hand.

Vasospastic Disorders

Raynaud phenomenon (primary or secondary) is the most common cause of symptomatic upper extremity ischemia (see Box 1-5 ). More prevalent in cold climates, the classic presentation is onset of a white digit or digits in response to cold exposure, followed by transition to blue, then red. The duration of the attack may be up to 1 hour. Patients with Raynaud phenomenon usually have a normal baseline physical examination. Although rarely performed, angiography demonstrates reversible vasospasm (induced by cold and ameliorated by heat or vasodilators) (see Fig. 1-31 ). Patients with secondary Raynaud phenomenon (i.e., associated connective tissue disorders, atherosclerosis, and history of repetitive trauma) may have underlying fixed small vessel arterial obstruction.

The differential diagnosis of the fixed purple digit is broad, including acrocyanosis, frostbite, insect or snake bite, antiphospholipid antibody syndrome, and cholesterol embolization. In each of these cases, the lack of improvement with warming is a distinguishing characteristic to differentiate from primary or secondary Raynaud syndrome.

Chronic Ischemia

Symptomatic chronic ischemia of the upper extremities can be divided into small (hand) or large (wrist to arch) vessel etiologies ( Boxes 6-2 and 6-3 ). Atherosclerotic occlusive disease is the cause of approximately 5% of all cases of clinically evident upper limb ischemia. The muscle mass of the upper body is smaller than in the lower limbs and is used less vigorously (perhaps if we walked on all fours symptomatic upper extremity arterial disease would be more common). In addition, the collateral pathways are numerous and well developed at multiple levels. The most frequent etiology of chronic large vessel upper extremity occlusive disease is atherosclerosis. The risk factors for atherosclerotic disease of the upper extremity arteries are the same as everywhere else in the body. Patients are usually older, with other manifestations of atherosclerosis. Cramping or a tight feeling in the upper arm and forearm muscles with activity due to proximal arterial occlusive disease is considered true arm claudication. Rest pain and tissue loss are rare. When ulcerations occur, the fingers are usually most affected ( Fig. 6-13 ).

On physical examination, diminished pulses or a lower blood pressure in an arm may indicate the presence of proximal occlusive disease. The Allen test (compression of both the radial and ulnar artery to prevent blood flow to the hand followed by sequential release of the arteries and inspection of pattern of reperfusion) is a simple measure that gauges both the relative contributions of the radial and ulnar arteries to the hand and the degree of collateralization between the deep and superficial arches.

Atherosclerotic occlusive disease can occur anywhere in the upper extremity arteries, but is most often manifested clinically when it is located at the subclavian artery origins (see Figs. 6-8 and 6-9 ). The left subclavian artery is affected more often than the brachiocephalic artery or the right subclavian artery. Obstruction at the ostia of the left subclavian artery is the result of aortic plaque, a feature that impacts on the types and outcomes of interventions. Ostial stenosis of the right subclavian artery may also involve the right common carotid artery origin. Subclavian artery occlusive disease proximal to the vertebral artery frequently results in subclavian steal physiology (see Key Collateral Pathways and Fig. 6-8 ).

Atherosclerotic digital arterial occlusive disease is more prevalent than it is symptomatic. Abnormal digital arteries are often found in smokers, patients with renal failure, diabetics, and individuals who perform heavy manual work. Symptoms may be precipitated by creation of a proximal surgical dialysis access which effectively “steals” arterial blood from the hand or after placement of a radial arterial catheter in a patient with an occluded ulnar artery (see Fig. 7-31 ).

The subclavian artery origins are difficult to visualize with ultrasound, but abnormal waveforms and flow velocities in accessible portions of the vessel infer a proximal lesion. The vertebral arteries are easily interrogated, as are the extremity arteries distal to the clavicle. Detailed ultrasound evaluation of the intrinsic small vessels of the hand can be challenging, but digital pressures and waveforms provide useful information about hand and digital perfusion (see Fig. 6-10 ).

CTA and contrast-enhanced MRA are excellent modalities for evaluation of the occlusive disease of the subclavian artery origins. Retrograde flow in the vertebral artery due to a proximal subclavian stenosis is indistinguishable from antegrade flow on CTA and conventional contrast-enhanced MRA. Noncontrast two-dimensional time-of-flight phase contrast images or time-resolved contrast imaging (TRICKS) of the vertebral artery can provide information about directional flow. Neither CTA nor MRA is suitable for routine vascular imaging of the hand owing to limited resolution and small size of the vessels (see Fig. 6-12 ).

Conventional angiography remains the definitive imaging modality for evaluation of symptomatic chronic upper extremity ischemia. Arch aortography should always precede selective angiography. Magnification angiography is usually necessary to adequately evaluate the hand vessels.

Surgical access to the subclavian artery origins requires a thoracotomy. This permits direct transaortic endarterectomy or bypass with a graft arising from the ascending aorta. Alternatively, bypass from a more accessible inflow source such as either common carotid artery or the contralateral axillary artery is less rigorous for the patient and usually performed if the anatomy permits. In extreme situations, a common femoral to axillary artery bypass can be used. Thoracic sympathectomy may delay or prevent amputation in patients with intractable digital ischemia due to fixed occlusive disease.

The most frequent percutaneous intervention in chronic upper extremity arterial occlusive disease is stent placement in the subclavian and brachiocephalic artery origins (see Fig. 6-9 ). This procedure can be performed from either a femoral, brachial, or (for the brachiocephalic artery) even carotid artery access. The relationship of the stenosis to the origin of cerebral branches and the status of the other cerebral arteries are key considerations when planning the procedure. Occlusion of a vertebral artery origin by a dissection flap during subclavian artery angioplasty, although rare, could result in a stroke in a patient with poor intracranial collateral circulation. Common balloon sizes range from 6 to 10 mm in diameter in the subclavian and innominate arteries. Balloon-expandable stent placement is almost always necessary when the lesion involves the arterial ostium. Careful stent positioning is required in this location to avoid compression of the orifice of the common carotid artery on the right or protruding too far into the aorta on the left. Self-expanding stents can be used in more peripheral locations. However, stents should be avoided in the segment of the subclavian artery between the clavicle and the first rib, because they can be crushed by the bony structures. The technical success rate of subclavian and innominate artery angioplasty and stent placement is greater than 95%, with a complication rate (stroke and distal embolization) of less than 1%. There is relatively little information on the long-term patency of these procedures, but available results suggest excellent outcomes.