tenosis of the subclavian artery is an interesting finding, which is often overlooked both on clinical visits (history and physical) and on cardiac catheterization and angiography. In a nutshell, the ostial or proximal narrowing of the subclavian artery severely diminishes the forward flow from the aorta into the distal subclavian creating a pressure gradient in which the subclavian pressure distal to the blockage is quite low. Symptoms directly due to this pressure drop are most often exertional arm claudication (heaviness), but occasionally, if pressure is low enough, resting arm pain and/or finger ulcerations may occur. Physical exam should show a clearly reduced pressure in the affected arm. In this case the pressure in the right arm was 170/90, in the left arm 70 by palpation.
Patent branches of the subclavian, vertebral and internal mammary arteries, which exit distal to the stenosis may demonstrate reversed flow (ie: flow backwards toward the subclavian rather than away toward the intended vascular bed). This is referred to as a “steal,” and, when severe enough in capturing flow from the ipsilateral vertebral artery (especially in conjunction with disease in the contralateral vertebral), may result in significant dizziness during arm exercise due to the siphoning or stealing of flow away from the posterior circulation of the brain. Rarely, in conjunction with significant carotid disease, pre-syncope or syncope may occur.
Similarly, the internal mammary artery, another subclavian branch that gives blood supply to the chest wall, may provide a pathway for reversed flow into the distal subclavian. The stakes are upped when the internal mammary artery has been used for an in situ bypass graft to a coronary artery as in this patient. In this scenario, flow reversal from the coronary artery through the mammary to the distal subclavian may result in angina during left arm exertion as in this patient’s paddleball games.
We have seen two other patients within the past year who demonstrated subclavian stenoses on exam and angiography prior to planned internal mammary artery bypass grafting for coronary disease. One patient had sustained clavicular traumatic fracture earlier in life, and the other was a multivascular patient with widespread bruits in the neck. The first patient was found to have a severe subclavian stenosis which we stented prior to off-pump multivessel bypass the following day including an in situ IMA graft to the LAD. The second patient showed a severe left internal carotid artery stenosis as well as the subclavian stenosis. Because of his severe generalized vascular disease, we performed carotid stenting followed by subclavian stenting, and then a minimally invasive coronary bypass using the internal mammary to the LAD.
Both of these patients would have been ill-served by the coronaries-only approach to angiography, and would either not have had the carotid and subclavian stenoses recognized pre-op (potentially resulting in stroke and/or failure to relieve angina) or would have been considerably delayed by the pace of the Doppler studies and MRAs which would have been recommended had the angios not been done at the time of the coronary angiography.
J.R. Wilentz, M.D., NY Interventional Cardiology