Severe stenosis or total occlusion of the left subclavian artery may lead to myocardial ischemia and angina. The pathophysiology parallels that of subclavian steal syndrome. In the presence of severe subclavian artery stenosis flow of internal mammary artery (IMA) may be reversed leading to cardiac ischemia. This rare phenomenon is called coronarysubclavian steal syndrome (CSSS). The problem is often neglected in the differential diagnosis of recurrent angina. Same steal phenomenon may work for an other branch of subclavian artery for example vertebral artery and leads to vertebrobasilar insufficiency.
Coronary angiography demonstrated an occlusive disease of the left anterior descending artery (LAD) and the right coronory artery, but circumflex artery was free of a stenotic lesion.The left IMA was patent and filled by LAD in retrograde fashion. The arch aortgraphy and selective left subclavian arteriography demonstrated a proximally total occlusion of the subclavian artery. Selective arteriography to the right common carotid artery revealed 90% obstruction at very proximal of the right internal carotid artery and spontaneous visualization of the left vertebral artery short after radiopague was injected into the innominate artery (Figure 1).
Figure 1: (a) Coronary angiography demonstrated retrograde filling of the left IMA from LAD.
Figure 1: (b) Selective left subclavian arteriography revealed total obstruction.
Total cerebral blood flow significantly decreases in patients with subclavian steal syndrome in which the neurologic symptoms come out. Subclavian steal phenomenon can be more likely to cause significant neurologic symptoms in patients with disease in other arteries supplying the brain. This patients neurologic findings can be attributed to internal carotid stenosis and contralateral subclavian obstruction presenting together and enhancing their effects to steal blood of the brain.
Subclavian stenosis or occlusion can be diagnosed by ultrasonography or more recently by magnetic resonans imaging [3]. It is utmost important to diagnose subclavian stenosis before bypass surgery. Bilateral upper extremity blood pressure measurements are an excellent screening tool for detecting the presence of subclavian artery stenosis. A blood pressure difference of more than 20 mmHg is highly suggestive of subclavian artery stenosis [4]. However the absence of difference in extremity blood pressure does not exclude the presence of subclavian artery stenosis because the frequent occurance of innominate, bilateral subclavian, and diffuse atherosclerotic occlusive disease in these patients [5]. When screening for subclavian artery stenosis it is advocated ultrasonographic duplex scanning with hemodynamic measurements before and after exercise to be more reliable than the assessment for discrepancy in upper extremity blood pressure. This method is also effective for documenting patency after an interventional procedure [6].
After the presence of CSSS is ascertained there are various treatment modaities. Treatment of CSSS is directed towards treating the subclavian artery stenosis. Successful correction with relief of symptoms has been accomplished by carotid subclavian bypass [7], angioplasty [8], or atherectomy [9] of the subclavian artery. Before deciding the type of interventional procedure it is exceedingly important to visualize the arch vessels in order not to omit an other stenotic lesion in this multicircular system. This will help us to fully comprehend the pathophysiology and determine the right strategy.
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