OVERVIEW OF CARDIOVASCULAR DISEASES AND THE
INTERVENTIONAL MEDICAL DEVICE MARKET
Cardiovascular diseases generally refer to conditions that affect the circulatory system, which consists of the heart, blood vessels and neurohumoral tissues that regulate blood circulation. Cardiovascular diseases are leading causes of death and disability in China and globally, while hypertension is considered as one of the most common risk factors that can lead to various serious cardiovascular diseases. However, currently there are limited effective treatments for such diseases. In recent years, interventional therapies are developing rapidly for the treatment of these diseases, and are progressively replacing traditional therapies such as invasive surgeries and drugs, because they generally involve shorter procedure time and minimal invasiveness, cause fewer post-procedural complications, enable faster recovery, and relieve the patients from long term use and potential side effects of medications.
Coronary Artery Disease
Coronary artery disease (CAD), also known as ischemic heart disease, is a type of cardiovascular disease that develops due to the narrowing or blockage of the coronary arteries, usually caused by atherosclerosis. Atherosclerosis is the buildup of plaque on the inner walls of the arteries. When the blood lipid content is high, cholesterol and other substances are prone to deposit on the artery wall and form plaque. These plaque buildups can cause artery stenosis, which can substantially interfere with blood flow and generate lesions. CAD is one of the most common types of organ diseases caused by atherosclerosis.
Treatment for Coronary Artery Disease
CAD is considered to be one of the most serious diseases, because of its high incidence and mortality rates. Currently, treatments for CAD are generally divided into four categories: medication, coronary artery bypass grafting (CABG), percutaneous coronary intervention (PCI) and stem cell transplantation. The medication approach is used to manage the risk factors associated with CAD, such as hypertension, high cholesterol, high blood lipids and diabetes, therefore it can only help alleviate the patients’symptoms, but cannot prevent CAD from progressing to severe CAD. If severe CAD is not treated by redirecting blood flow or widening the coronary arteries through surgeries or interventional procedures, patients will experience worsening symptoms, which can lead to death. Both CABG and PCI can effectively treat CAD and are the two mainstream treatment methods recommended by physicians. CABG is an open-heart surgery, in which an artery or vein taken from elsewhere in the body is stitched in place to reroute blood around the blocked artery. However, not all patients can withstand open-heart surgeries. For patients with inoperable CAD, or with high surgical risks, PCI offers them a viable alternative with minimal invasiveness. In addition, because PCI procedures require shorter hospitalization time, enable faster recovery, and are relatively cheaper than CABG procedures, PCI procedures have also become increasingly popular among intermediate to low surgical risk CAD patients.
Overview of PCI
PCI is used primarily to open a narrowed or blocked coronary artery and restore arterial blood flow to heart tissue, without requiring open-heart surgery. In patients with a restricted or blocked coronary artery, PCI may be the best option to re-establish blood flow as well as to prevent angina (chest pain), myocardial infarctions (heart attacks) and death. The PCI procedure consists of two parts: angiography and treatment. After the puncture through the radial or femoral artery, an angiography catheter is inserted into the blood vessel and is guided to the coronary sinus with the help of an angiography guidewire. By injecting a radiocontrast agent, the blocked part of the coronary artery can be identified under X-rays. Then a micro-guidewire is passed through the guiding catheter to the narrowed coronary artery. A balloon catheter is then placed into the blocked part through the guiding catheter on the micro-guidewire, and is inflated to compress the blockage against the artery wall. After the blocked part is opened up and the blood flow returns to normal, the balloon catheter is withdrawn. Certain devices such as coronary stents can be placed in the artery to keep the blood vessel open.
Since the conduct of the world's first successful PCI procedure in Zurich, the interventional treatment for CAD has undergone more than 40 years of development, and the treatment methods evolved from PTA balloons to bare-metal stents (BMS), to drug-eluting stents (DES), and further to bioresorbable scaffolds (BRS). Compared with PTA balloon, BMS can provide sufficient mechanical support to keep the artery open and to prevent recoil, thereby reducing the chance of restenosis. Compared with BMS, DES can further reduce the chance of restenosis, thanks to the anti-proliferation drug eluted on the stents. However, treatment solutions using BMS or DES leave the stents in the human bodies, but actually, once the vessel has healed, it no longer needs a stent to keep it open. The retention of the stent not only hinders the recovery of blood vessel elasticity, but also increases the risk of thrombosis. Leaving a permanent metal implantation inside the human body may also necessitate lifelong medication, hinder further surgery, impair X-ray imaging, and interfere with computer tomography (CT) and magnetic resonance imaging (MRI) e xaminations. All the aforementioned limitations led to the idea of creating new devices that are able to provide mechanical support when needed and then disappear completely from the vessel, allowing its natural healing and avoiding the risks associated with permanently leaving a foreign object in the vessel. The diagram below shows the evolvement trends of PCI treatment and coronary artery scaffold, and the advantages and drawbacks of the different products: