With the rapid development of coronary CT, there is a growing awareness and recognition of it.
One of the things I often tell my patients is that there are only two ways to rule out the diagnosis of coronary artery disease.
One is coronary angiography: an interventional procedure in which a contrast catheter is sent to the heart and a stent can be placed, which is the “gold standard” for the diagnosis of coronary artery disease.
Second, is the coronary CT examination: is actually a special enhanced CT examination, as long as the image is clear, diagnosis is correct, the accuracy of the diagnosis of coronary heart disease up to 99%. Other than this, any other cardiac examination at present cannot exclude the diagnosis of coronary heart disease, like cardiac ultrasound, ECG, Holter, myocardial nuclear scan, clinical history, physical examination and so on.
So, does everyone need a coronary CT to rule out coronary artery disease? We cannot recommend this at this time, for reasons to be discussed later.
What kind of people need coronary CT?
1.People who have multiple risk factors for coronary heart disease: such as middle-aged and elderly men, postmenopausal women, long-term smoking history, long-term history of hypertension, diabetes, hyperlipidemia, long-term unhealthy lifestyle, long-term high workload, etc.
2, is the clinical symptoms or other examinations suspected of the possibility of coronary heart disease: such as various causes of chest pain, chest tightness, breath-holding, toothache, pinching sensation, subxiphoid pain, left upper arm discomfort, etc., and electrocardiogram, ultrasound, Holter and other examinations suspected of the possibility of coronary heart disease; third is the review after coronary stent implantation or bypass surgery. In the past, the review after stent implantation is required to do imaging again, which is painful and costly for patients and requires hospitalization and poor compliance, but now the application of coronary CT review is simple and convenient, and can be done on an outpatient basis, which greatly facilitates patients and is widely used in clinical practice.
What should I do if I find stenosis on coronary CT? First, I would like to clarify two issues.
1, is the coronary CT reported narrowing percent, but only a false number, is the result of the diagnosis of the doctor’s visual inspection, not a precise number, do not have to be too entangled in this number;
2, is that coronary CT tends to overestimate the degree of stenosis, that is, if you later do a coronary angiography, you will often find that the degree of stenosis diagnosed by angiography is less than the degree of stenosis of coronary CT, which is caused by the differences in different imaging methods, not that the results of CT are not accurate.
The results of coronary CT are divided into five categories.
1.No clear stenosis and plaque seen: This indicates that there is no atherosclerotic manifestation in the coronary vessels, the best result;
2, visible atherosclerotic plaque: stenosis <20%, this is early atherosclerotic changes, will not lead to myocardial ischemic changes, but remind us of the need to control the process of atherosclerosis with drugs;
3.Light luminal stenosis: 20-50% stenosis, which generally does not cause various symptoms of myocardial ischemia and does not suggest coronary angiography, and requires standardized drug treatment;
4.Moderate lumen stenosis: 50-70% stenosis, which is a critical lesion and may cause various symptoms of myocardial ischemia, it is generally recommended to perform functional examinations such as exercise plate test, loading myocardial nuclear or myocardial perfusion MRI to diagnose the presence of myocardial ischemia, and coronary angiography can also be performed directly to clarify the coronary stenosis, and more precise examinations such as pressure guidewire or intravascular ultrasound can be performed at the same time during the operation. The CT finding of moderate stenosis is often the most difficult to determine the treatment;
5, severe luminal stenosis: stenosis ≥ 70%, which is a sign of severe coronary artery disease, patients are generally advised to perform coronary angiography, which can also look for evidence of myocardial ischemia, which also includes completely occluded (100%) lesions in the coronary arteries, suggesting that stent surgery may be difficult.
Coronary CT will also indicate the nature of the plaque, which is generally divided into three types: calcified plaque, non-calcified plaque and mixed plaque.
Generally, non-calcified plaques and mixed plaques are more dangerous than calcified plaques and are more likely to cause an infarction, especially if the plaque is very low density, which requires a specialist to interpret.
What are the disadvantages of coronary CT? Or what are people’s concerns about coronary CT? I will discuss a few points to solve your doubts.
1. The problem of contrast agent. Coronary CT must be injected with iodine-containing contrast agent, a very small number of people will have allergic reaction to contrast agent, mainly including fever, rash, nausea and vomiting, the most serious will appear laryngeal edema, cardiogenic shock, etc. (the incidence is less than one in 10,000), so the coronary CT examination needs to be observed for a period of time before leaving. For patients with renal insufficiency, the application of iodine contrast agent needs to be cautious and strictly follow the doctor’s advice. Another point is that the iodine allergy test cannot accurately predict the occurrence of iodine allergy, and currently our hospital has routinely refrained from performing iodine allergy tests;
2. The problem of radiation dose. I often hear patients discuss that a coronary CT examination is equivalent to taking thousands of chest films and so on. With the advancement of technology, the radiation dose of coronary CT in our hospital is effectively controlled, similar to the ordinary lung CT scan, and the radiation dose can be controlled to the range of 20 chest films by special Flash scan mode;
3. The problem of heart rate. Previously, coronary CT required patients not to have arrhythmias, and ventricular rate was required to be below 60. Now, with the advancement of technology, the requirement of heart rate is becoming less and less. Through the application of intravenous esmolol and the development of Flash scan mode, our hospital is able to perform clear coronary imaging even for patients with rapid atrial fibrillation.
Coronary CT, although not currently recommended as a must for physical examination, is ideal for people suspected of having coronary artery disease, is noninvasive and accurate, and is relatively economical. The significance of coronary CT is not only in the diagnosis, but for us surgeons, coronary CT can provide more anatomical information and has an important guiding value for the treatment of difficult coronary lesions, vascular variants, congenital heart disease, etc.