# Characterizing the Mechanical Performance of a Bare-Metal Stent with an Auxetic Cell Geometry
## 1 Introduction  
Diseases, including atherosclerosis, hypertension, diabetes, genetic defects, and aging, result in alterations in the mechanics of arteries, such as the development of artery blockage, contraction, twisting, elongation, tortuosity, kinking, and curving. These changes cause several cardiovascular diseases, such as coronary heart disease and peripheral artery disease, which reduce the ability of the heart to pump enough blood within the vessels and arteries, leading to heart failure. Coronary artery disease occurs from plaque build-up on an artery's inner surface, which becomes significantly narrowed and blocked in advanced stages of the disease [1; 2; 3; 4; 5; 6]. This process consisting of the hardening of the arteries is called atherosclerosis. About 17.6 million people in the United States suffer from narrow heart vessel disease, causing 450,000 deaths each year due to heart attacks caused by fully obstructed arteries. Balloon angioplasty followed by the placement of a stent is the most common therapy used to open these blocked arteries [7; 8; 9; 10; 11]. This procedure utilizes a catheter to place a stent in blood vessels narrowed by plaque build-up. It was first introduced to reduce the risks of elastic recoiling and restenosis while strengthening the artery wall so it remains open [12]. The chances of restenosis reduced to 25% in stenting procedures while compared to angioplasty [13]. Early permanent metal stents were known as first-generation bare-metal stents. In 1986, the first metal stent was implanted into a human coronary artery. These bare metal stent almost eliminated the chances of an artery collapsing, but had other issues. Subsequently, first-generation drug-eluting, and second- and third-generation biodegradable polymer-based drug-eluting stents were developed [11; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22]. Drug-eluting stents also reduced early and delayed complications with stenting, as well as restenosis rate by 80% [23]. Bioresorbable vascular scaffolds are also being developed. This category of stents disappears after treating diseased blood vessels by creating a thin and all-natural cell layer inside the artery [24]. In this second-and third-generation drug-eluting stent era, a large body of evidence has demonstrated a significant improvement in coronary stent safety and efficacy in most clinical situations [25]. However, the bare-metal stent (BMS) still remains an option for percutaneous coronary intervention (PCI). Particularly for patients who cannot complete the recommended duration of dual antiplatelet therapy because of noncompliance, the avoidance of cardiac surgery, or increased risk for bleeding, especially if the accused lesion is present in large coronary vessels, PCI is recommended. It is suggested for patients who are at high risk of bleeding that the duration of dual antiplatelet therapy be reduced to a minimum of one month with BMS placement or three months with a drug-eluting stent [26]. These first-generation BMS are considered most effective in preventing acute occlusion and reducing late restenosis, and 20% of patients in the USA and 19.6% of patients in Australia are treated with BMS implantation every year [12; 13; 27; 28; 29]. Over the past 40 years, research and clinical trials in this regard have resulted in different stent designs comprising diverse materials include metals, metal alloys, platinum, polymer, plastics, coated or uncoated in balloon-expandable and self-expandable forms. Depending on the appropriate choice of a stent depends on the patient's symptoms--the local deposition of plaque, fatty substances, and the potential side effects [12; 18; 30; 31]. During the last decade, the quantity and quality of life of patients suffering from heart attacks due to arterial blockages have improved immensely through stent implantation interventions, which are a suitable replacement for surgery. However, there are still patients suffering from stent failure, thrombosis, or restenosis.