Coronary CTA is more and more widely used in clinical practice due to its convenience and accuracy. You must have seen the following films in clinical practice.
Indications
First, we need to clarify the indications and inapplicability of coronary CTA:
Applicable situations
1. Used to rule out coronary heart disease
(1) Patients with a low possibility of coronary heart disease such as atypical symptoms
(2) There is precordial discomfort but other examination methods do not support coronary heart disease
(3) Acute chest pain with positive myocardial injury markers but negative ECG
2. Exclude coronary heart disease and examine coronary artery grafts before non-cardiac surgery.
3. For examination of coronary artery anomalies
Not applicable
1.Health check-up
2. Patients with confirmed or highly suspected coronary heart disease
3. There is severe calcification in the coronary arteries (Agatston calcium score > 400)
4. Evaluate whether there is in-stent restenosis
5. Patients who cannot use contrast media due to allergies or other conditions
6. Qualification and quantification of coronary plaques
7. Detection and evaluation of myocardial survival and myocardial perfusion
Coronary related anatomy
The next most basic and important part is to understand the general anatomy of the coronary arteries:
The coronary arteries arise from the left and right coronary sinuses.
Under normal circumstances (non-mutated):
The left coronary sinus generally gives off the LM (left main branch), and the LM branches into the LAD (left anterior descending artery) and LCX (left circumflex artery);
The main branches of LAD are D1 (angular branch) and D2 (second angular branch);
The main branch of LCX is OM1 (branch obtuse);
Sometimes LM also sends out Ramus (intermediate branch).
The right coronary sinus gives off the RCA (right coronary branch).
The main branch of the RCA is the PDA (right posterior descending artery).
imaging mode
One thing that needs to be understood is that all CTA images are the same. They are all injected with iodine contrast agent intravenously, and then scanned through thin layers. The final difference lies in the image post-processing on the workstation. Generally speaking, there are three imaging modes for image post-processing, respectively. They are surface imaging, surface reconstruction, and coronary probe mode. These three different post-processing modes are the different graphics at the beginning of this article.
Surface imaging (VR) can display the surface contours of the heart and coronary arteries, but can only observe large contours such as the origin and shape of the coronary arteries, but cannot see stenosis.
Surface reconstruction : look at designated blood vessels and look at stenosis
Coronary Probe: Combined with Surface Reconstruction, Look at Cross Sections
Influencing factors
After learning to read images, we must also be aware of the conditions that may affect the quality of coronary CTA images:
1. Patients with impaired consciousness and unable to cooperate;
2. Patients with severe arrhythmia;
3. Patients with uncontrollable rapid heart rate;
4. Patients who cannot cooperate with breathing;
5. Patients with metal implants in or near the heart;
6. Severely obese patients.
There are several major misunderstandings in judging the degree of stenosis:
1. Positive plaque remodeling:
The plaque grows outward to form positive remodeling. Because the plaque is large, the lumen appears narrow, which is often mistaken for lumen stenosis. Coronary angiography shows no obvious stenosis of the lumen.
2. Severe calcification:
Because coronary CTA can amplify the components of very high-density calcified plaques and conceal the true size of the lesions, resulting in misjudgment of the degree of luminal stenosis, it is often misjudged as severe stenosis.
3. Cross-layering artifacts:
Due to poor breath-holding or arrhythmia, a step-like misalignment artifact appears, which manifests as a sudden disconnection of blood vessels in the long axis, and is often misjudged as vascular stenosis.
