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Treatment of an iatrogenic subclavian artery dissection.

Christian Spies, David Fergusson.

Subclavian artery dissection is a rare complication of cardiac catheterization. The usual reason for entering this vessel is to access the origin of the left internal mammary artery (LIMA) when this has previously been used, or is being considered, as a bypass graft. We report an instance of such dissection occurring long after bypass surgery which had included a LIMA graft. Successful correction was achieved by angioplasty and stent placement, using a retrograde left brachial approach.

Editorial Comment:

Misadventures in the danger zone: Subclavian dissections.

Ian C. Gilchrist, MD, FSCAI, Pennsylvania.

Retrograde cardiac catheterization, during which wires and catheters are passed up the femoral to coronary arteries, carries little risk from iatrogenic dissection. Atherosclerotic plaques can be raised and limited dissections occur anywhere along the course to the coronary arteries. Fortunately, the systemic blood pressure and flow of the blood allow these minor retrograde transgressions to close without incident. When the iatrogenic dissection occurs in an antegrade fashion, a far different outcome can occur and the injury may behave more like a de novo aortic tear that progresses into catastrophic dissection. From the transfemoral approach, the danger zone for antegrade dissections exist when one directs a wire or catheter down a subclavian artery, for example, in pursuit of visualizing the internal thoracic artery. It is in this danger zone where one's equipment passes with the blood flow that any dissection has the potential to propagate into a disaster as the flow and pressure of the blood conspires to add insult to injury. For the transradialist, the subclavian region is passed retrograde so that the danger zone does not exist in this region. Instead, a danger zone for the radialist exists distal to the origins of the subclavians in the aorta. Those adventurous enough to attempt renal angioplasty and other noncardiac procedures via the radial approach need to pay notice in this region when passing antegrade.

Once prevention has failed, recognition is critical and a low threshold for concern should exist whenever passage in a danger zone is not as expected. Judicial use of contrast while minimizing poorly controlled injections into unknown pathology will often help to recognize the problem. Once a dissection with the potential for antegrade propagation is recognized, control of the true lumen becomes critical. If a wire can be passed antegrade and unequivocally within the true lumen, it can be used to maintain lumen control recognizing that repeated manipulation may also enhance the injury. Downstream entry into the arterial tree at a site distal to the dissection, such as the brachial or radial artery, is the optimal position to obtain. This preserves access into the true lumen and facilitates reconstruction if needed in the proximal portion of the subclavian. If in doubt, this position should be secured as soon as possible if the potential for the loss of distal pulse exists.

Driving the dissection's propagation will be the pulse pressure. Similar to the classic aortic dissection, it is logical to reduce the blood pressure if conditions permit as this will theoretically reduce the speed or likelihood of further extension. In the present case [[1]], an intra-aortic balloon pump was used to prevent secondary ischemia from reduced internal thoracic graft flow to the LAD. It could be argued that under some circumstances, the pulse augmentation produced by this devise might actually contribute to propagating dissection.

Once the true lumen has been controlled, unstable or occlusive flaps need to be sealed with a stent. Tamponading the entry site with prolonged balloon inflations may work under some situations. When concerns exist about interfering with critical blood flow down thoracic grafts or up a carotid artery, a stent will usually be needed to expeditiously seal the arterial flap. Once the proximal entry site is controlled, the extent of the dissection can be re-evaluated. In the case of subclavian dissection, the risk for compromise to the origins of branch vessels such as the internal thoracic branches needs to be considered. While closure of the entry site may be enough to conclude the misadventure, further work may at times be needed to protect the branch vessels. Controlling the true lumen early on from a site distal to the injury is critically important as it allows one to confidently consider the adequacy of the repair without the fear of inadvertently propagating a false lumen with misdirected balloon inflations.

Iatrogenic subclavian dissections during cardiac catheterization are rare but can occur on anyone's watch. Clearly prevention is the best advise as once this complication occurs, true experience is rare and the need for timely intervention may preclude time to ruminate on the best approach. Taking a moment to reflect on other's unfortunate experience can help to bridge the experience gap in one's practice and help to fortify ones knowledge for that day when it is your turn.

Catheterization and Cardiovascular Interventions, Volume 76 Issue 1, Pages 35 – 40.