Implantation of metal stents

When balloon angioplasty was the only intracoronary treatment option, there were two fundamental problems that reduced the efficacy of percutaneous therapy. One was the acute or sub-acute occlusion of the treated artery, which occurred in 5-7% of treated patients, leading to infarction and the need of a new urgent catheterism or surgery. The other was the incidence of re-stenosis of the treated plaque, either due to adverse vascular remodelling with vasoconstriction or due to excessive neointimal proliferation during scarring, which occurred in around 30-40% of patients.

Implantación de stents metálicos

The metal stent arose in the early 1990s, significantly reducing these percentages of sub-acute occlusions and re-stenosis. Stents forced an acute remodelling of the treated vessel. As a support for the vascular wall, the metal stent forced the vessel to remain open after being expanded with a balloon, and also prevents vasodilation. At the same time, a metal endoprosthesis was inserted with radial force to secure and compress the treated plaque. Intraluminal reconstruction was better, but it added a new problem to be solved, as the thrombogenic tendency of the metal had to be counteracted. With appropriate management with antithrombotic drugs in patients treated with stents, subacute occlusion was reduced to 1-2%, increasing the success rate and reducing the incidence of re-stenosis to 25-30%. In this case, re-stenosis was always secondary to excessive proliferation in response to the scarring process.

Treatment with stents was further developed and strategies were designed to fix an arterial segment in any anatomic position. Stents were developed for bifurcations, for chronic and acute occlusions, for long lesions or small vessels, for the treatment of acute infarction or unstable angina, and for locations not previously approached, such as life-threatening left main coronary artery (LMCA) lesions. Imaging techniques were also developed for intracoronary flow that taught us previously unknown aspects, such as inappropriate apposition to the arterial wall. All this led to better supports and improved outcomes.

Inert metal stents are still used today, largely in patients who are unable to maintain a prolonged (more than 1 month) antithrombotic regimen, or have comorbidities or pending surgeries. In this case, it is estimated that a layer of neoendothelium has already covered the legs of the stent if it is not medicated. What was learnt from inert metal stents was very useful for the subsequent development of drug-eluting stents. There was parallel progress in our knowledge of vascular physiopathology and rheology, the anatomy of plaques, their content and numerous other aspects that continue to improve treatment with stents.