ABSTRACT: Stent underexpansion is a catastrophic complication of stent implantation that can usually be treated with high-pressure balloon dilatation. We report a case of emergency, unprotected distal left main coronary artery stenting, in which the left main stent remained under-expanded in spite of multiple high-pressure balloon inflations, cutting balloon angioplasty, and angioplasty using one buddy wire. The stent eventually expanded after balloon angioplasty using a double buddy wire technique.
J INVASIVE CARDIOL 2007;19:E355–E358
Key Words: balloon angioplasty; coronary artery stents; complications
Case Report. A 74-year-old male developed a non-ST-segment elevation acute myocardial infarction after open surgical repair of a 9.5 cm abdominal aortic aneurysm; his peak serum troponin-T and CK-MB concentrations were 2.38 ng/mL and 28.9 ng/mL, respectively. Because of recurrent episodes of rest angina, he underwent diagnostic coronary angiography that demonstrated severe, distal left main coronary artery (LMCA) disease (Figure 1A) and a chronic total occlusion of the mid-right coronary artery (Figure 1B). His left ventricular ejection fraction, as determined by echocardiography, was 35%. He was offered coronary artery bypass graft surgery, but declined. He subsequently developed angina, intermittent sinus arrest and cardiogenic shock. He was emergently intubated and transferred to the cardiac catheterization laboratory for emergency percutaneous coronary intervention (PCI) of the unprotected LMCA.
An intra-aortic balloon pump and a temporary pacemaker were inserted and capture was verified. Anticoagulation was achieved using 7,000 units of unfractionated heparin and a loading dose of 600 mg of clopidogrel. The LMCA was engaged with a 7 Fr 3.5 XB guide catheter (Cordis Corp., Miami Lakes, Florida). An Asahi Soft (Abbott Vascular, Abbott Park Illinois) and a Balance Middleweight (Abbott Vascular) guidewire were advanced into the left anterior descending (LAD) and the left circumflex (LCX) coronary arteries, respectively. Intravascular ultrasound of the distal LMCA lesion revealed severe circumferential calcification (Figure 2).
The proximal circumflex was predilated with a 2.0 mm x 12 mm Voyager Rx balloon (Abbott Vascular). The distal LMCA and proximal LAD stenosis was predilated with a 2.5 mm x 20 mm Voyager Rx balloon and a 3.0 mm x 12 mm Voyager Rx balloon inflated up to 12 atm with apparent complete expansion of each balloon. To achieve as complete a revascularization as possible in the presence of cardiogenic shock, we elected to use a T-stenting technique to prevent occlusion of the severely stenotic ostial circumflex artery. A 2.5 mm x 18 mm Cypher™ stent (Cordis) was implanted at 16 atm in the ostium of the LCX with good angiographic success (Figure 3). Next, a 3.0 mm x 18 mm Cypher stent was implanted in the distal LMCA in the proximal LAD with an inflation pressure of 16 atm. However, the distal LMCA stent remained underexpanded (Figure 4).
To expand the LMCA stent, we performed several balloon inflations using the following compliant and noncompliant balloons: Voyager and Powersail (Abbott Vascular) and Maverick and NC Ranger (Boston Scientific Corp., Natick, Massachusetts) in several diameters (2.5 mm, 2.75 mm and 3.0 mm) and lengths (8 mm, 9 mm, 13 mm and 15 mm). Each balloon was inflated up to 30 atm, but the stent remained underexpanded. A 2.5 mm x 10 mm Cutting Balloon Ultra (Boston Scientific) inflated up to 10 atm was also unsuccessful in expanding the stent. With each balloon inflation, the patient developed hypotension and transient electromechanical dissociation, occasionally requiring cardiopulmonary resuscitation.
An additional Balance Middleweight guidewire (Abbott Vascular, Illinois) was advanced into the LAD, but subsequent balloon inflations with noncompliant 2.5 and 3.0 balloons (inflated up to 30 atm) did not expand the LMCA stent. After a second buddy guidewire, a Cougar LS (Medtronic Inc., Minneapolis, Minnesota) was advanced into the LAD (total of 3 guidewires in the LAD), inflation of a 2.75 mm x 15 mm Powersail balloon up to 25 atm expanded the LMCA stent (Figure 5). Subsequent “kissing” balloon inflations were performed within the LMCA and the LCX (Figure 6), resulting in a well-expanded LMCA stent with residual ostial stenosis of the LCX (Figure 7). Intravascular ultrasonography revealed a well-expanded LMCA stent (Figure 8).
The patient’s clinical status gradually improved with removal of the intra-aortic balloon pump and the temporary pacemaker in the first 24 hours after PCI. He was subsequently extubated and was discharged from the hospital without recurrent angina 2 weeks later.
Discussion. Our case demonstrates for the first time the use of a double-buddy wire technique to expand an underexpanded coronary artery stent.
Stent underexpansion is a rare complication of stent implantation that is usually due to severe vessel calcification. Stent underexpansion may result in stent thrombosis or may limit coronary flow. Full expansion of the LMCA stent was crucial for our patient with cardiogenic shock, whose myocardial perfusion was critically dependent on unimpeded flow through the LMCA.
Stent underexpansion may be best prevented rather than treated. Adequate preparation of a coronary artery lesion before stenting is the best way to prevent underexpansion. This is especially true in our patient who had severe distal LMCA calcification. Although the LMCA lesion was predilated, the incomplete balloon expansion was not seen until after stent implantation. In severely calcified lesions, predilatation with a larger balloon might provide important insight into the lesion resistance to expansion; if the lesion is resistant, additional predilatation and/or other plaque debulking strategies should be used before a stent is deployed.
Stent underexpansion can be corrected by: (a) high-pressure balloon angioplasty; (b) cutting balloon angioplasty; (c) laser, (d) “stentablation”, i.e., rotational atherectomy within the underexpanded stent; and (e) angioplasty using 1 (or > 1, as in our case) buddy wires.
High-pressure balloon inflations should be the first step to treat stent underexpansion, using balloons of different diameters, both compliant and preferably noncompliant. The balloon should be shorter than the stent to avoid injury of the nonstented vessel segment. However, high-pressure balloon inflation does carry the risk of vessel rupture or perforation.
Laser angioplasty while flushing with contrast may result in vapor formation and local arterial trauma due to acoustic injury that has been reported to facilitate stent expansion.1 However, laser angioplasty may not be available in many catheterization laboratories.
Rotational atherectomy has been successfully used to expand an underexpanded stent (“stentablation”),2–4 but may result in stent material or plaque embolization, and could damage the stent, making it necessary to implant an additional stent.3
Use of a single buddy wire5–7 and of a cutting balloon8 has been reported to help with expansion of an underexpanded stent, but the use of a cutting balloon inside a stent may be complicated by fracture of the cutting balloon blade,9 stent strut avulsion10,11 and balloon entrapment.12
Two buddy wires have been used to facilitate stent advancement in a coronary lesion13 or to advance a left ventricular lead in cardiac resynchronization therapy.14 Our case demonstrates that 2 buddy wires may succeed in expanding an underexpanded stent, even when a single buddy wire has failed. The mechanism is likely similar to the mechanism of cutting balloon angioplasty (focusing force from the balloon expansion within the stent, leading to fracture of the calcified ring within the vessel wall).8 However, cutting balloon angioplasty had previously failed in our case. Although complete stent expansion in our patient was most likely due to the use of 2 buddy wires, it could also have resulted from the repeated high-pressure balloon inflations.
In summary, balloon dilatation with 2 (or possibly more) buddy wires is a simple, low-cost and widely-available technique to treat underexpanded stents.
Acknowledgements. We gratefully acknowledge the contribution of Michele Roesle, RN, for her assistance with manuscript preparation.
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