Successful Stent Delivery and Symptom Resolution With Novel Bare Metal Stent Implantation in Challenging Patients

Although the use of drug-eluting stents (DES) in percutaneous coronary intervention (PCI) has increased markedly in the last decade, the need for extended dual antiplatelet therapy (DAPT) limits the use of these devices in certain patients.¹ Bare metal stents (BMS) may be more appropriate for patients with high bleeding risk or other features that suggest advantages to shorter duration of DAPT (i.e., 30 days vs 6-12 months).² 

Since their introduction for clinical use, BMS have undergone continued development, and advanced BMS technologies are now available. One example is the NIRxcell™ Coronary Stent System (Medinol), a cobalt-chromium BMS with unique features that promote excellent long-term outcomes and facilitate placement in challenging anatomies. These features include a unique cell structure, a spring tip delivery system, and a design that combines wide and narrow struts for radial strength and conformability. 

Here, we discuss our experience with the NIRxcell stent in two challenging cases, a male with an acute coronary syndrome (ACS) and multiple comorbidities, and a female with complicated coronary anatomy and a history of medical non-compliance. 

Case One: Right Coronary Artery Sub-Total Occlusion in ACS 

Presentation and history 

A 76-year-old man with a history of peripheral arterial disease (managed with right carotid endarterectomy), hypertension, hyperlipidemia, obstructive sleep apnea, and non-Hodgkin’s lymphoma (NHL) presented to our office complaining of rapidly progressive to resting angina pectoris. 

Prior to presentation at our office, the patient’s NHL became clinically aggressive. Evaluation by computed tomography (CT) scan identified involvement of multiple right pelvic structures, including the iliac artery, vein, and ureter. The patient had a right-sided nephrostomy tube placed to treat obstructive uropathy and chemotherapy was planned. The onset of chest pain occurred before chemotherapy was started. 

Management 

On presentation with unstable angina, the patient was admitted and treated with IV heparin and nitroglycerin. Cardiac catheterization was planned, and the potential use of a BMS was discussed based on the presence of active lymphoma, indwelling nephrostomy tube, high bleeding risk, and questionable ability to maintain DAPT for more than 30 days. 

In the catheterization lab, a subtotal occlusion of the right coronary artery (RCA) was identified (Figure 1). A 7 French Judkins right (JR)4 guide catheter (Boston Scientific) was inserted through left common femoral access. The target lesion was crossed with a Hi-Torque Pilot 50 guidewire (Abbott Vascular) and, after crossing the lesion, exchanged for an Asahi Prowater guidewire (Abbott Vascular) (Figure 2). Pre-dilatation (Figure 3) was performed with a 2.5 x 15 mm Emerge balloon (Boston Scientific). A 3.0 x 33 mm NIRxcell stent was placed across the lesion. The stent was expanded with balloon inflation to 16 atmospheres (atm). Post-dilation was performed with a 3.25 x 20 mm NC Emerge balloon (Boston Scientific). After completion of the procedure, angiographic appearance of the stent was excellent, with restoration of TIMI-3 flow (Figure 4). 

Follow-up 

Following PCI, the patient reported no angina. He completed a 1-month course of DAPT (aspirin 325 mg qd and clopidogrel 75 mg qd). Following completion of DAPT, he maintained daily aspirin 325 mg and underwent chemotherapy for NHL. The nephrostomy tube was removed following chemotherapy. Six months post-PCI, the patient has had no recurrence of angina. 

Case Two: LCX Subtotal Occlusion 

Presentation and History 

A 68-year-old female with a history of multiple transient ischemic attacks (TIA), hypertension, hyperlipidemia, type 2 diabetes, and gastroesophageal reflux disease presented to the emergency department (ED) with resting chest pressure and diaphoresis. A previous cerebrovascular accident left her with residual left-sided weakness. Due to a history of multiple TIAs, the patient had lost the capacity for independent decision-making, and a family member had power of attorney (POA) over healthcare decisions. The patient also had a history of non-compliance with medical therapy. 

Management

On presentation to the ED, the patient was treated with intravenous (IV) nitroglycerine and heparin. Her chest pain resolved, but laboratory studies identified elevated cardiac enzymes on three separate samples. An echocardiogram was performed, which showed preserved left ventricular function, aortic sclerosis without stenosis, and a new area of infero-lateral hypokinesis. An attempt was made to wean the IV nitroglycerine, but the patient experienced recurrent chest pain. After discussion with the patient’s POA, catheterization was planned. 

On catheterization, the patient had three-vessel coronary artery disease: a 100% RCA occlusion, collateralized from the left-sided system; subtotal occlusion of the second obtuse marginal branch (OM2) of the left circumflex artery (LCX), which was determined to be the vessel responsible for infarct (Figure 5); and a 70% stenosis of the mid left anterior descending artery (LAD). Based on cardiothoracic surgical evaluation, the patient was not considered a candidate for coronary artery bypass grafting. After discussion with the team and the patient’s POA, angioplasty of the LCX (OM2) was performed. A BMS was selected based on the patient’s history of medical non-compliance and concern that she could not complete long-term DAPT. 

To perform PCI, a 6 French Extra Backup (EBU) 3.5 guide catheter (Medtronic) was inserted through right common femoral artery access. The LCX (OM2) lesion was crossed with a Pilot 50 wire. Pre-dilatation was performed with a 1.5 x 8 mm Emerge balloon. To further increase vessel lumen, additional pre-dilatation was performed with a 2.0 x 15 mm Emerge balloon. The guide wire was then exchanged for a Prowater wire. Bare metal stents were placed in a distal-to-proximal fashion: a 2.5 x 20 mm NIRxcell stent was placed first and overlapped with a more proximal 2.75 x 28 mm NIRxcell stent (Figure 6). Post-placement dilatation was performed with a 2.75 x 20 mm NC Emerge balloon. Final angiography revealed re-establishment of TIMI-3 flow with the stents providing an excellent visual result, including optimal scaffolding and vessel conformance, with a smooth appearance (Figure 7). 

Follow-up

Following placement of the two NIRxcell stents, the patient reported no angina and was rapidly weaned from IV medications. She maintained DAPT (aspirin 325 mg and clopidogrel 75 mg) for 1 month and remains on daily aspirin 325 mg. At seven months post-PCI, she has reported no recurrence of cardiac symptoms.

Discussion 

The cases discussed above illustrate the benefits of the NIRxcell stent in high-risk patients. In both cases, patient characteristics indicated a preference for a short course of DAPT following PCI based on bleeding risk, need for post-PCI chemotherapy, and/or risk for non-compliance with medical therapy. 

Increased risk factors for bleeding clearly suggest the need to minimize DAPT and therefore, bleeding risk.² However, adherence to long-term DAPT is a significant consideration following PCI. One systematic review found that adherence to DAPT following coronary stenting was high at 30 days, but declined by 12 months.³ In patients managed with DES, studies have demonstrated that early discontinuation of DAPT is the most powerful predictor of stent thrombosis.^4,5 Therefore, minimizing the duration of DAPT should be considered in patients at risk for medical non-compliance. The use of BMS may be appropriate for such patients. 

Features Supporting Use of NIRxcell in Appropriate Patients 

At our institution, the main reasons supporting our selection of the NIRxcell stent were its reported trial outcomes and unique manufacturing process, which allows for improved efficiencies. Other advantages to this stent system emerged with use, including excellent deliverability, conformance to vessel architecture, and superior scaffolding. 

Most importantly, the NIRxcell stent has demonstrated low target lesion revascularization rates (TLR) in clinical trials.^6-8 As illustrated in Figure 8, TLR rates with NIRxcell at 9 months post-PCI were in the single digits and lower than rates reported with other BMS.^9–11 These data must be interpreted with caution, as they are not derived from head-to-head studies. 

Several features of the NIRxcell system promote its good outcomes and ease of use, even in challenging anatomies. The stent features a unique cell geometry, which integrates advantages of both closed-cell and open-cell designs. The closed-cell stent design has several advantages. Studies have demonstrated that closed-cell stents are associated with superior angiographic outcomes compared to open-cell stents¹², and may better prevent restenosis by reducing plaque prolapse through the stent¹³. The closed-cell design also promotes smooth scaffolding on deployment in the vessel. The NIRxcell cell design (WiZeCell™) also enhances the stent’s conformability and deliverability, as do comparable open-cell designs.

Conformance to vessel architecture is important to support good outcomes and limit risk for complications, especially in tortuous vessels. Optimal stent conformance combines the radial strength required to maintain a large vessel lumen and sufficient flexibility to avoid straightening naturally curved vessels. Straightening vessels introduces risk for dissections of the vessel wall at the edges of the stent and poor angiographic results. The design of the NIRxcell stent combines wide and narrow struts, balancing conformance and radial strength (Figure 9). 

Failure of stent delivery is estimated to occur in 4% of PCIs. More than 90% of these failures are due to anatomic challenges, such as vessel tortuosity and/or calcification.¹⁴ Techniques to foster deliverability in these challenging lesions include using guiding catheters with good backup, use of buddy wires, and lesion preparation.¹⁵ The flexibility of the stent and maneuverability of the stent delivery system are also centrally important factors. As illustrated in the second case described above, the flexibility of the NIRxcell stent and the tapered spring tip of the catheter (Figure 10) provide excellent deliverability in challenging vessel anatomies, such as the LCX OM2 (Figure 5). The metal spring tip also creates a strong relationship between pressure on the shaft and movement of the device during delivery, balancing flexibility and feel. 

One other advantage of the NIRxcell stent delivery system is the use of a radio-opaque tip that allows the operator to observe the location and movement of the catheter during stent placement. 

Conclusion

The cases described above illustrate the utility of the NIRxcell stent for treatment of challenging patients who are not optimal candidates for DES. In these cases, the NIRxcell stent demonstrated good deliverability, flexibility and conformance to tortuous vessels, smooth scaffolding and good angiographic results, and good clinical outcomes up to 7 months post-PCI.

Bio

Dr. David Drucker is a Fellow of the American College of Cardiology and the Society of Coronary Angiography and Interventions. He is Board Certified in Cardiovascular Diseases, Interventional Cardiology and Cardiovascular CT Imaging and holds additional certification in Endovascular Medicine through the American Board of Vascular Medicine. Dr. Drucker serves as the Director of minimally invasive vascular therapy at Saint Mary Medical Center in Langhorne Pennsylvania. He has participated in multiple clinical trials of advanced catheter based treatment of coronary artery and peripheral vascular disease, including serving as the principle investigator of studies on carotid stents in the treatment of extracranial carotid artery disease. 

St. Mary Medical Center, a member of Trinity Health, is the most comprehensive medical center in the Bucks County region. St. Mary performs more than 3,000 catheterizations and more than 1,100 interventional radiology procedures annually, making it one of the busiest and most experienced labs in the region. St. Mary Medical Center is among the most successful hospitals nationwide in performing emergency angioplasty within the optimal time frame with an average of 43 minutes over the past 12 months, which is well below the nationally recommended 90-minute door-to-balloon time. 

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From Mercer Bucks Cardiology; Director, Minimally Invasive Vascular Therapy, Saint Mary Medical Center, Langhorne, Pennsylvania.

This case was published with support from Medinol.

Disclosure: Dr. Drucker is a consultant to the following companies: Boston Scientific Corporation, Medtronic, Abbott Laboratories, and Medinol. 

David Drucker, MD, can be contacted at ddrucker@mercerbuckscardiology.com