Technical Aspects

Once vascular access has been selected and gained, a diagnostic catheter is selected based on the angulation involved and the need for coaxial support.

From a femoral or brachial access, a simple JR4 or IMA catheter may suffice for guiding a wire through a stenotic lesion; an occlusion, especially approached from the arch, may need the additional backup support offered by a VTK, Amplatz, or Simmons shaped catheter. Great care must be used with such aggressive catheter shapes to avoid disrupting aortic plaque. When tempted to use them, brachial access should at least be considered as an alternate approach. Appropriate wire selection may include an 0.018- to 0.035-inch transition wire, a Wholey wire, or other similar metallic wire for stenosis, but a hydrophilic straight or angled wire will be necessary to cross most occlusions. Careful fluoroscopic guidance with road map support (if available) is necessary to ensure wire passage safely into the lumen beyond the occlusion. Care must be taken, especially with hydrophilic wires, to avoid propagating a dissection plane, either toward the vertebral artery or into the aorta retrogradely. Although helpful in infrainguinal revascularization, a subintimal approach in brachiocephalic disease is best avoided.

In occlusive disease, once the hydrophilic wire is free in the distal lumen, it is advisable to pass a diagnostic catheter (hydrophilic if necessary) through the occlusion, then remove the wire and confirm luminal placement by blood aspiration and gentle injection of contrast medium. A stiff exchange-length guidewire is then advanced through the catheter for completion of the procedure.

Although there is no conclusive evidence in favor of primary stenting for subclavian and brachiocephalic artery lesions, most operators treat these lesions by stenting in preference to angioplasty alone.

Once guidewire access across the lesion has been achieved, one has the choice of whether or not to predilate before stent placement. Predilation has several advantages, including better visualization of the lesion length, especially of the distal stent landing point, proof of distensibility (especially in calcific lesions), and the ability to visually confirm correct balloon size. The main disadvantages are the possibility of propagating a dissection and, in theory, relieving the subclavian gradient enough to restore antegrade vertebral flow and lose the inherent protection against vertebral embolization retrograde flow provides. There is controversial evidence from a small study done over 20 years ago that restoration of antegrade flow may take several minutes,¹⁴ perhaps owing to chronic ischemic vasodilation in the arm. In our experience, however, restoration of antegrade flow in the vertebral artery occurs immediately on relief of the pressure gradient across the lesion, either with aggressive predilation or stenting. There is some evidence that direct stenting (i.e., without predilation) may be associated with a lower restenosis rate as well.¹⁰ In general, we gently predilate occlusions with undersized balloons to allow some antegrade flow for better visualization, and primary stent most stenoses that are not heavily calcified.

As is the case with most aortic branch vessel disease, most subclavian disease is ostial or near ostial. This includes the right subclavian artery, where typically the lesion is at the brachiocephalic bifurcation. In general, these lesions have a high degree of resistance to dilation and subsequent recoil; accordingly, balloon-expandable stents are generally preferred to self-expanding stents or angioplasty alone.9,10

When positioning the stent, it is important to fully cover the lesion, but every attempt should be made to leave the ostium of the common carotid, internal mammary, and/or vertebral artery uncovered. One should be mindful, especially if predilation was not performed, that the vertebral or IMA may not be visible owing to reversed blood flow. If any of these ostia become compromised, rescue angioplasty with or without coronary-sized stent placement should be considered. In the case of the ostial right subclavian artery, consideration may be given to placing an additional guidewire in the proximal right common carotid artery in the event the ostium is severely compromised when the stent is deployed.

Many cases of stent migration before deployment in the lesion have been reported.7,12 This usually arises from either the stent edge catching in the lesion during attempted passage through the lesion, or the rear of the stent catching on the guiding catheter during attempted stent withdrawal if the stent cannot be passed across the lesion. In both instances, the stent may be loosened (“skimmed”) off the balloon and left free on the wire. Although there are several methods available to rescue this event, including safely deploying the stent in a more proximal vessel,⁷ this situation is best avoided. Stents that are factory rather than hand mounted may be more resistant to skimming, and the risk can be eliminated entirely by readvancing the dilator and sheath through the lesion before the stent is advanced. In this way, the stent can be positioned while it is still protected inside the sheath, which can subsequently be withdrawn, and the exposed stent deployed. Especially when using 6F guiding sheaths, the potential for distal embolization is minimized.

Finally, after stent deployment, repeat angiography to assess optimal sizing should be undertaken, and postdilation can be performed if necessary, aiming for no more than a 1 : 1 balloon size–to-vessel ratio.

Figures 34-1 to 34-6 illustrate various aspects of the interventions discussed.