Clin. RadioL (1976) 27, 483--488

T H E S U B C L A V I A N S T E A L S Y N D R O M E

S. BLOCH, M. O R E L O W I T Z and J. D A N Z I G E R

From the Department of Radiology, Princess Nursing Home, Esselen Street, Hillbrow 2001, Johannesburg, South Africa

THE subclavian steal syndrome is a well-recognised clinical entity in which a stenosis or complete obstruction of a subclavian artery is present proxi- mal to the origin of the vertebral artery. The blood pressure in the affected subclavian and vertebral arteries is then lower than in the other arteries supplying the brain, resulting in retrograde blood flow down the vertebral artery on the side of the subclavian obstruction. This syndrome was apparently first noted by Contorni in 1960. Reivich et al. (1961) published a report of two cases, in whom retrograde flow was seen in the left vertebral artery, Since then, many articles have appeared reporting similar findings; the largest group being 168 cases reported by Fields et al. (1972) collected over a period of 12 years from the Central Registry of Texas extracted f rom a total of 6534 cases with extravascular occlusive disease.

We were prompted to carry out this report on

seven patients since they illustrated the bizarre clinical presentations, the extensive collateral cir- culations and some radiological pitfalls.

CASE REPORTS

The clinical data of the seven patients are sum- marised in Table 1.

DISCUSSION

In this syndrome, the main collateral pathways are the opposite vertebral and basilar arteries in the presence of complete or partial occlusion of the subclavian artery (Figs. 1a, ~, 2A, B). Other collateral channels, although not always seen angiographically, do exist (North et al., 1962).

Ipsilateral collateral pathways can take place through:

TABLE 1 CLINICAL DATA

Case Sex Age Symptoms

1 F 57 Vertigo. Binocular vision

2 M 58 Headaches. Vertigo

3 F 65 Vertigo. Numb left hand

4 M 53 Focal fit involving left upper limb

5 F 55 Blackouts. Vertigo. Numb left hand

6 M 59 Syncopal attacks. Pain right arm

7 F 47 Headaches. Vertigo

Blood pressure

Right Left

145/80 105/80

180/90 110/80

145/70 80/60

140/90 100/80

150/95 120/95

? ?

135/90 120/85

I Radial pulses

Right Left

Good Weak

Good Weak

Good Weak

Good Weak

Good Weak

Poor Good

Good Good

Site of obstruction

LSA

LSA

LSA

LSA

LSA

RSA distal to origin of vertebral

Nil

Degree of obstruction

Partial

Complete

Complete

Complete

Partial

Complete by ligation

Nil

LSA = left subclavian artery. RSA = right subclavian artery.

483

484 CLINICAL RADIOLOGY

FIG. 1 Arch aortography with subtraction, showing:

Good filling of all the great arteries excluding the left vertebral and subclavian arteries.

B. A film taken 1 sec later demonstrating filling of the left vertebral and subclavian arteries by retrograde flow with a complete obstruction at the origin of the left subclavian artery (~').

F~6. 2 A. Arch aortography demonstrating in the arterial phase an

incomplete obstruction immediately distal to the origin of the left subclavian artery (~') with non-filling of the left vertebral artery.

B. A delayed film showing retrograde filling of the left vertebral and subclavian arteries.

THE S U B C L A V I A N STEAL SYNDROME 485

FIG. 3 Arch aortography with subtraction, demonstrating:

A. Early arterial phase: a complete obstruction of the right subclavian artery immediately distal to the origin of the right vertebral artery 1. Faint retrograde filling is seen in deep cervical arteries 2.

B. Two seconds later: a plexus of collateral arteries is seen in the right upper cervical region 1 with retrograde filling of the ascending 2 and deep cervical arteries 3 and distal subclavian artery 4.

c. Right common carotid angiogram: there is non-filling of

31

the ascending and deep cervical arteries. The superior thyroid artery 1 and the thyroid plexus of vessels 2 are well filled. There is retrograde filling of the inferior thyroid artery 3. Note the bullet fragment adjacent to the inferior thyroid artery 4.

FIG. 4 Arch aortography with subtraction. Multiple stenotic areas are seen in the proximal portion of the left subclavian artery (~ ) . There is non-visualisation of the left vertebral artery.

486 CLINICAL RADIOLOGY

(a) The external carotid artery to the occipital artery and then by reversal of blood flow through the ascending or deep cervical arteries.

(b) The external carotid artery and superior thyroid artery to the inferior thyroid artery where flow is reversed.

(c) The external carotid artery to the occipital artery, and finally by reversal of flo w in muscular branches to the vertebral artery.

Some of these collateral pathways are seen in case 6. These occured after ligation of the right subclavian artery distal to the origin of the vertebral artery following a bullet injury (Fig. 3A, B). In this case, it was concluded that blood was being 'stolen' f r o m t h e distal vertebral artery via muscular branches into the ipsilateral ascending and deep cervical arteries and then flowing in a retrograde direction to the right subclavian artery. This view was further strengthened by an observation that no such retrograde filling of these collateral vessels occurred from branches of the external carotid artery during direct percutaneous carotid angio- graphy (Fig. 3c), and is thus put forward as a vari- ant of the usual subclavian steal syndrome to account for the patient's syncopal attacks. The common carotid angiogram demonstrated retrograde col- lateral filling of the inferior thyroid artery via a normal prograde flow in the superior thyroid artery and thyroid plexus of vessels from the ipsilateral external carotid artery (Fig. 3c).

Reivich et al. (1961) demonstrated that a reduc- tion of 10 % in the systemic arterial blood pressure within the subclavian artery will reverse the blood flow within the vertebral artery.

Sammartino and Toole (1964) showed that a 50 % reduction in the size of the lumen of the sub- clavian artery was needed to produce the necessary 10% reduction in blood pressure. Stenotic or obstructive lesions may exist in the subclavian artery without reversal of flow in the vertebral artery. This may be due to either a sufficient collateral supply or a stenosis that is below 50 %.

An awareness of this syndrome is essential for radiographic diagnosis. Arch aortography may, for example, demonstrate areas of stenosis in the proximal part of the left subclavian artery with non-filling of the left vertebral artery and the diag- nosis of unilateral vertebral artery occlusion mis- takenly made (Fig. 4). In patients presenting with the above radiographic picture and clinical findings suggestive of a subclavian steal syndrome, vertebral angiography on the normal side is essential to

demonstrate masked retrograde flow down the contralateral vertebral artery (Fig. 5A, ~).

If vertebral angiography, irrespective of the method, is initially carried out on the side of the lesion, abnormal retrograde flow in the ipsilateral vertebral artery may be transiently altered by the countercurrent of forceful injection, thus masking retrograde flow on this side. This is a relatively uncommon pitfall (Simon et al., 1962).

With direct injection into the vertebral artery one often sees partial reflux down the opposite vertebral artery. According to Scatliff et al. (1965) this will occur normally in 32 % of cases with this procedure and should not be mistaken for the subclavian steal syndrome.

Occasionally vertebral angiography by the selec- tive subclavian, retrograde axillary or brachial routes can produce a transient retrograde flow in the contralateral vertebral artery, in spite of the absence of obstruction to the contralateral subclav- ian artery (Shockman, 1964) (Fig. 6A, a). Two possible explanations for this phenomenon are offered :

1. The end-hole of the catheter may impinge against the wall of the artery and be occluded. The greatest part of the pressure and contrast medium will then be delivered via a catheter side-hole directly into the vertebral artery on injection. This then falsely creates a gradient between the basilar and proximal contra- lateral vertebral arteries. The same result may occur when a catheter without side-holes

FIG. 5 Same patient as in Fig. 4.

A. Right vertebral angiogram via the right axillary route, demonstrating good filling of the right vertebral artery. Note the unusual filling of a radicular artery 1 and brnnches of the thyro-cervical trunk 2. The former appears to be a collateral artery supplying the distal left vertebral artery 3.

B. Delayed film, demonstrating retrograde filling of the left vertebral and distal subclavian arteries. The small arteries noted in (A) arising from the thyro-cervical branches appear to be collateral vessels supplying the left subclavian artery ( I' ).

A.

B.

FIG. 6 Selective catheterisation of the left subclavian artery with visualisation of the right vertebral and distal subclavian arteries by retrograde filling. Same case as (g). Arch aortography with subtraction, demonstrating simultaneous filling of both vertebral arteries and absence of any stenotic lesions in the in- nominate or right subclavian arteries, thus excluding the diagnosis of a subclavian steal syndrome.

THE S U B C L A V I A N STEAL S Y N D R O M E 487

488 CLINICAL RADIOLOGY

is p laced in the p rox ima l subclavian ar tery (Fig. 6A, B).

2. A m a r k e d b lood pressure d rop - 30/40 m m can occur with ao r tog raphy (Amundsen et al., 1956).

I t is therefore possible tha t a general fall in the b lood pressure is manifes ted locally in the sub- clavian ar tery and may exaggerate the gradient when the pressure at the ver tebro-bas i la r junc t ion is at a m a x i m u m due to the pressure injection. In this way a t rans ient reversal of flow is created in the oppos i te ver tebral artery. Therefore, if retro- grade flow is seen in a cont ra la te ra l vertebral ar tery, or one of the other ma jo r branches of the sub- clavian ar tery dur ing re t rograde axil lary or brachia l ar ter ial injection, the inject ion should be repeated to see whether this p h e n o m e n o n recurs. Once the injection is complete, the direct ion of flow in the contra la tera l ver tebral ar tery should be observed during later serial films t aken at shor t intervals. I t may thus be possible to differentiate actual f rom artefactual reversal of ver tebra l flow. In the la t ter case, the re t rograde flow should immedia te ly revert to a p rog rade flow, clearing towards the base of the skull. I f the a b n o r m a l direct ion of flow persists, this diagnosis should be considered.

Final ly, the impor tance of arch ao r tog raphy is again stressed, no t only to confirm the diagnosis of the subclavian steal syndrome, but to evaluate the arter ial ana tomy in this region since a sub- clavian obs t ruc t ion may only be par t of extensive generalised ar ter ia l disease. This in format ion is of value to the vascular surgeon in p lanning future

surgical ma na ge me n t as the extent of general ar ter ial disease in this region determines the flow of b lood to the brain.

Acknowledgement. - We wish to thank Mrs J. Sudlow for typing the manuscript.

REFERENCES

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CONTORNI, L. (1960). Circolo caIlaterale vertebravertebrale nella obliterazione dellarteria succlavia alla sue orgine. Minerva Chirurgica, 15, 268-271.

FIELOS, W. S. & LEMAK, N. A. (1972). Joint study of extra- cranial arterial occlusion_ VII. Subclavian steal - a review of 168 cases. Journal of the American Medical Association, 9, 1139-1143.

NORTH, R. R., FIELD, W. S., DE BAKEY, M. E. & CRAWFOR~, S. (1962). Brachial-basilar insufficiency syndrome. Neuro- logy, 12, 810-820.

PmLP, T., SAMUEL, E. & DUNCAN, J. G. (1963). Reversed vertebral artery blood flow in subclavian artery obstruction (subclavian steal). ClinicaI Radiology, 14, 310-316.

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SAMMARTINO, W. F. & TOOLE, J. F. (1964). Reversed vertebral flow. Archives of Neurology, 10, 590-594.

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SIMON, M., RABINOV, K. & HORENSTEIN, S. (1962). Proximal subclavian artery occlusion and reversed vertebral blood flow to the arm. Clinical Radiology, 13, 201-206.

SHOCKMAN, A. T. (1964). Retrograde vertebral artery flow as an artefact of technique_ American Journal of Roentgeno- logy, 91, 1258 1262.