What are the risks of coronary artery stenosis? How to determine the degree of stenosis?

Author: Wang Huaibin, Chief Physician, Beijing Hospital

Reviewer: Zhang Haicheng, Chief Physician, Peking University People's Hospital

The coronary artery system mainly includes the left coronary artery and the right coronary artery. The right coronary artery divides into key branches such as the posterior descending branch and the posterior lateral branch. The left coronary artery divides into the left anterior descending branch and the left circumflex branch from the left main trunk, and is further divided into the intermediate branch, diagonal branch, obtuse marginal branch, etc. These branches may be affected by atherosclerosis.

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The left anterior descending artery is an important blood vessel in the coronary artery system, and its stenosis is crucial to myocardial blood supply. If the stenosis is less than 75%, myocardial blood supply can usually meet the demand, and drug treatment can be given priority at this time.

However, once the stenosis exceeds 75%, multiple factors need to be considered, such as the specific location of the stenosis, the diffuseness and degree of calcification of the lesion, the tortuosity of the blood vessels, the presence of aneurysms, and the patient's recent bleeding history (such as cerebral hemorrhage, positive fecal occult blood, etc.), to determine whether stent implantation surgery is suitable.

1. How to determine the degree of coronary artery stenosis?

Coronary angiography can usually effectively assess the degree of vascular stenosis and determine whether stent implantation is needed.

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When the imaging reference standard is difficult to determine, it may be necessary to further rely on functional indicators, the most representative of which is the coronary artery blood flow reserve fraction (FFR).

FFR measures the ratio between the maximum blood flow that a coronary artery can provide to a specific myocardial area when there is a stenotic lesion in the coronary artery and the maximum blood flow that can be achieved in the same myocardial area when the blood vessel is not stenotic. In short, it reflects the relative ability of the stenotic blood vessel to supply blood to the myocardium.

If the FFR value is greater than 80%, even if there is stenosis in the coronary artery, the blood vessel can still provide at least 80% of the normal blood flow to the myocardium. At this time, drug treatment can often alleviate the imbalance between blood supply and demand. On the contrary, if the FFR value is lower than 75%, it indicates that the blood supply is significantly insufficient, and revascularization may need to be considered, such as stent implantation or coronary artery bypass surgery. For cases where the FFR value is between 75% and 80%, clinicians need to carefully evaluate and make decisions based on multiple factors.

2. What are the risks for patients with coronary heart disease who need stent placement but do not do so?

After coronary angiography, if the doctor recommends stent placement, it indicates that the coronary artery stenosis is more serious. Coronary artery stenosis can affect the blood supply to myocardial cells and may lead to myocardial ischemia, which in turn causes symptoms such as chest tightness, shortness of breath, throat tightness, and angina pectoris.

If myocardial ischemia lasts for a long time, it may lead to myocardial cell necrosis, i.e. myocardial infarction, and may be accompanied by complications such as severe arrhythmias or cardiogenic shock. These complications may be fatal due to vascular spasm, plaque rupture and thrombosis.

Although adjusting lifestyle habits and taking medications can effectively slow the progression of coronary atherosclerosis, stabilize lipid plaques and prevent thrombosis, the possibility of reversing established vascular stenosis by relying solely on medications and lifestyle improvements is relatively small.

3. Is heart stent surgery safe?

After years of development, the technology of heart stent implantation is now quite mature and generally safe.

Usually, the radial artery or femoral artery is punctured, and then a guide wire is guided along the blood vessel to the aortic root and to the coronary artery lesion. After repeated exploration by rotational grinding or guide wire, balloon dilation is used at the stenosis site to expand the stenosis area, and a metal stent is placed to maintain blood vessel patency. The whole process causes relatively little trauma.

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Nevertheless, since stent implantation requires puncture, and the guidewire and catheter need to be advanced in the coronary artery, and balloon dilatation is required, these steps still involve certain trauma and risks. In rare cases, complications such as guidewire or catheter breakage, infection, arrhythmia, and even vascular perforation may occur. The risk of surgery is also related to factors such as the degree of calcification and tortuosity of the coronary artery and whether it is an emergency surgery.

In addition, the individual condition of the patient also affects the risk of surgery. The older the patient is, the lower the functional reserve of multiple organs. Patients with coronary heart disease often have other complications or comorbidities, such as chronic bronchitis, emphysema, or liver and kidney dysfunction, or even a history of cerebral infarction or cerebral hemorrhage, and multiple diseases such as hypertension and diabetes. These factors will increase the risk of surgery.

In general, heart stent implantation surgery has a low risk rate and high overall safety.