PCI of the Right Coronary Artery via or under Struts of Stents
Protruding into the Aorta

The ostium of the right coronary artery (RCA) is not a tubular structure . Hence, sizing, positioning and flaring the stent in the ostium of the RCA demands considerable skill, and occasionally will not yield optimal results. At least mild protrusion (1–3 mm) of the RCA ostial stent into the aorta is required in order to ensure ostial coverage. Exact positioning may be difficult, and can be enhanced by certain maneuvers. Some operators will also flare the proximal portion of the stent to allow easy repeat catheter access to the treated vessel. Occasionally, especially with short ostial stents, “stent migration” into the aorta has been reported. The encounter of a stent protruding from the ostial RCA into the aorta may subject the interventionalist to a considerable diagnostic and interventional challenge. Stent protrusion may cause difficulty in subsequent imaging of the RCA or during reinterventions (due to inability to obtain guiding catheter support or pass the guidewire through the stent’s central lumen).

Case 1. A 53-year-old female was hospitalized with acute coronary syndrome accompanied by ischemic electrocardiographic (ECG) changes of the inferior wall and troponin-I rise. Six months prior, the patient underwent percutaneous coronary intervention (PCI) of the RCA. That procedure was complicated by a long spiral dissection extending from the ostium of the RCA to the distal RCA (just proximal to the posterior descending and posterior left ventricular bifurcation).

She was treated with 4 overlapping stents (only 1 of these was drug-eluting). Subselective right coronary sinus contrast injection showed that the proximal half of the proximal RCA stent (bare-metal stent) was protruding into the aorta. There was 90% diffuse in-stent restenosis with thrombus in the proximal half of the proximal stent and 80% in-stent restenosis at the more distal stent (Figure 1). Selective coronary angiography of the left coronary artery revealed that the left system was unchanged and essentially disease-free.

Proper engagement of the RCA ostium could not be executed with an array of diagnostic and interventional catheters. We made subselective use of an Amplatz Right-2 guiding catheter and a 0.014 inch PT-2 wire (Boston Scientific, Natick, Massachusetts) to pass through one of the cells at the protruding segment of the proximal stent and advance into the distal part of the RCA (Figure 1B). A 2.5 x 15 mm Maverick balloon (Boston Scientific) was positioned at the stent cell and inflated at 8 atm to ensure a safe passageway toward the RCA ostium (Figure 1C).

Subsequently, balloon angioplasty was performed with the same balloon to both distal and proximal lesions. A second series of predilatations were executed with a 3.0 x 15 Maverick balloon. Next, a 3.0 x 23 mm Cypher stent (Cordis Corp., Miami, Florida) was advanced into the proximal lesion and deployed at 14 atm (Figure 1D). After final postdilatation employing 4.0 x 12 mm Quantum Maverick balloon (Boston Scientific) at 14 atm, satisfactory angiographic results were obtained (Figure 1E). Six-month follow up was uneventful.

Case 2. An 81-year-old female with a past history of diabetes mellitus, hypertension and hyperlipidemia was brought by the emergency medical services with acute inferoposterior and right myocardial infarction, complicated by hypotension and complete atrioventricular block resulting in syncope. Cardiac catheterization revealed a proximal RCA occlusion. During cardiac catheterization, the patient, while being supported by intra-aortic balloon pumping and transvenous pacing, suffered from numerous episodes of ventricular tachycardia and fibrillation, alternating with complete heart block. The patient’s systolic blood pressure dropped to 30 mmHg and she was subjected to repeated small dosages of adrenaline and noradrenaline superimposed on a high-dose dopamine drip. Emergency PCI was attempted during cardiopulmonary resuscitation with a 6 Fr LIMA-curve guiding catheter and a Hi-Torque Balance 0.014 inch guidewire (Guidant Corp., Indianapolis, Indiana). The wire was brought into the distal RCA. During direct stent deployment (Cypher 3 x 18 mm), the patient made a violent move, causing retraction of the guiding catheter, guidewire and stent. The stent was suboptimally deployed into the ostial RCAprotruding > 5 mm into t h e aorta, and was underexpanded. The distal portion of the proximal RCA lesion was not covered by the stent.

The patient’s violent movement resulted in the loss of both guiding catheter and wire positions. The RCA closed again distal to the stent. We attempted to engage the guiding catheter into the RCA, but the catheter was sitting underneath the protruding stent (Figure 2B). Attempts to thread a guidewire through the partially deployed stent were unsuccessful. We were able to advance 2 Whisper 0.014 inch wires (Guidant) underneath the stents’ struts (Figure 2C).

Using sequential inflations with Maverick balloons (initially 2 x 15 mm, and later 3 x 15 mm), we were able to crush the Cypher stent and make a track for a 3 x 20 mm Liberté stent (Boston Scientific) that was deployed at 20 atm in the proximal RCA (Figure 2D). A second Liberté stent (2.75 x 32 mm) was brought to the mid RCA lesion (Figure 2E) and deployed (Figure 2F) at 16 atm.

Finally, high-pressure (16 atm) inflations were executed with a 3.5 x 12 mm balloon at the proximal RCA to secure the crushing of the protruding Cypher stent. We reestablished flow (TIMI grade 3) in the RCA (Figures 2G and 2H). The patient’s hospital course was uneventful, and she was discharged home 4 days after her admission.

Discussion. A protruding ostial RCA stent is a challenging problem during interventions. Most protrusions can be approached using nonconventional vascular access, unusual catheters, and subselective guiding catheter position, followed by “remote-control” wiring. A double-wire method has also been used for that purpose. When these attempts fail, wiring the artery through the protruding stent struts and creating a new orifice at the side of the stent remains a valid option. This method was described only by Burstein in a single case report. Occasionally, especially with underdeployed underexpanded or undersized stents, wiring through the stent lumen may be difficult to achieve. In those situations, crushing the stent (in its partial or full length) by sequential balloon dilatations and later by a second stent will yield a new stent lumen with a stent crushed underneath. This method should probably be reserved for life-threatening emergencies and only after more conventional methods have failed. There are no large series in which the safety consequences of a coronary stent crushed under another coronary stent has beenassessed. The few reports describing crushing an embolized or underdeployed stent under another coronary stent or covered stent yielded favorable outcomes. The authors have used this method before (to treat 3 patients with stent embolization within the coronary tree), without any early or late adverse events.

References

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