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Cardiac CT

1. Cardiac CT examination 

A common cardiac CT is a contrast examination using iodine contrast agent. The indications for cardiac CT encountered in daily practice are shown inTable1.

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Previous studies have reported that compared to cardiac catheterization, the cardiac CT has a sensitivity of about 85-90% and a specificity of about 96-98%. It is characterized by the lack of coronary artery stenosis and is often reported to be about 93-100%. This means that if the cardiac CT is normal, there is no coronary artery disease. In fact, the establishment of this ability is the main attraction of cardiologists who treat the heart. Of course, even for anxiety patients with sudden cardiac death, the guarantee that "almost certainly will be fine" will provide a great sense of security.

Taking advantage of this characteristic of cardiac CT, the practicality of cardiac CT has recently attracted attention among patients who cause acute chest pain. The chest pain and the myocardial infarction is a problem. A study of 1,000 patients with acute chest pain in the United States showed the effectiveness of the first diagnostic method using cardiac CT. The first comparison between the method using cardiac CT (501 patients) and the method not using cardiac CT (499 patients) showed that the rate of direct discharge from the emergency room was shorter in the cardiac CT group. It is reported that after discharge from hospital, myocardial infarction or heart failure did not increase. Based on the results of these studies, it is recommended that a cardiac CT scan be performed first when there is sudden chest pain.


Here was introduced a heart CT scan of a 37-year-old man with severe stenosis found in the left coronary artery branch (Figure 14). This patient with mild hypertension and hyperlipidemia felt chest pressure and pain spread to his jaw as he walked. This patient was recommended to our hospital for CT. Heart CT images can be displayed in various ways, including three-dimensional color images (A) and black and white blood vessel images (B). Based on these 3D images, a whole curve of the coronary artery (C) can be displayed or stretched directly (D). As a result, the narrow blood vessel area can be observed by rotating 360 degrees like holding the blood vessel. The final diagnosis is made by cutting and observing the cross section of the thin part of the blood vessel (E). And you can see the narrowing of the blood vessel cavity or atherosclerosis. Therefore, for the accurate diagnosis of cardiac CT, it is important to use various 3D workstations and various image methods for diagnosis.

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In fact, we show a case of cardiac CT in a 37-year-old man who found a highly stenotic lesion (a site that was about to occlude) in the most important branch, the anterior descending branch of the left coronary artery (Fig. 14). Patients with mild hypertension and hyperlipidemia develop chest pressure and pain that spreads to the lower jaw when walking long distances, and a nearby practitioner suspects angina. , I was referred to the hospital for a cardiac CT examination. Various displays are possible for cardiac CT images, such as a three-dimensional three-dimensional color image (A) and a black-and-white image (B) that highlights only blood vessels. You can see that the blood vessels are thinning at the part of the arrow on the left anterior descending artery. Based on these 3D images, you can display the entire coronary artery with a curve (C) or straighten it (D). As a result, you can rotate the narrow part of the blood vessel 360 degrees and observe it as if you were picking it up. In the narrow area corresponding to the arrow in three dimensions, you can see the blood vessels narrowing and surrounding the arteriosclerotic plaque. Due to this plaque accumulation, the blood vessels themselves are also greatly swollen. It seems to be the compensatory expansion of blood vessels, which is characteristic of so-called vulnerable plaques. The final diagnosis can be made by cutting and observing an orthogonal cross section of a narrow part of a blood vessel (E). You can see that the vascular lumen has become quite narrow and the surrounding area is filled with arteriosclerotic plaque. In this way, for accurate diagnosis of cardiac CT, it is important to make a multifaceted diagnosis using various image reconstruction methods using a 3D workstation.

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More patients are receiving coronary stent treatment. According to the 2016 Cardiovascular Disease Survey, 230,000 patients receive stent treatment every year. In particular, the popularity of drug-eluting stents reduces intra-stent restenosis and improves the therapeutic effect. As a result, more and more cardiac CT examinations are used to evaluate in-stent restenosis. According to previous reports, using coronary stents of 3 mm or larger, good coronary CTA test results can be obtained, and cardiac CT is expected to be used to evaluate in-stent restenosis (Figure 15).

In summary, it shows the characteristics, advantages and disadvantages of cardiac CT and comparison with other coronary angiography examinations (Table 2).

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2. Coronary artery calcification score

Coronary artery calcification is considered to be a sensitive marker of arteriosclerosis, and it has been reported that the coronary artery calcification score can more accurately predict the risk of coronary artery disease. Coronary calcification scores can be imaged with low doses of x-ray exposure and no need for an Iodine contrast agent. In addition, it is easy to visually confirm, and it is easy for the patient to understand the condition (Fig. 16).

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However, it has been reported that 3.5% of patients with symptoms without coronary artery calcification have significant stenosis on cardiac CT. It is impossible to completely diagnose coronary artery lesions only based on the calcification score (Fig. 17).

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Recent studies have reported that coronary artery disease can be detected by simply observing the coronary arteries. In addition, research from the National Institutes of Health (NIH) has published data on coronary artery calcification scores in multi-ethnic groups by age and gender. Using this data, the relative degree of calcification in individual patients can be extrapolated within the Asian distribution (Figure 18).

In Asians of the same age and gender, the degree of arteriosclerosis can also be detected. In addition, there is data that for people with coronary artery calcification score of 100 or higher, it is best to consider the use of antiplatelet drugs for treatment, if the coronary artery calcification score is 400 or higher, you areneed to re-check within 2-3 years .

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3. Coronary plaque imaging by cardiac CT

A major feature of cardiac CT is that it is possible to obtain information on coronary plaque that could not be obtained by cardiac catheterization test (Table 2).

Other previous coronary angiography tests had only determined whether blood vessels are thin. However, with coronary CT, it is possible to image atherosclerotic plaque accumulated on the vessel wall. A typical case of coronary plaque is shown (Fig. 15).

The patient felt chest pain that lasted for two hours during exercise and was referred to a CVIC clinic by a nearby practitioner for a cardiac CT scan. Coronary CT showed a moderate stenosis in the left anterior descending branch (Fig. 15A). On a detailed observation image of the same place shows arteriosclerotic plaques with low CT values ​​around the moderate stenotic lesion (B). The entire blood vessel expands due to plaque accumulation, showing the compensatory expansion characteristic of vulnerable plaque.  

After that depending on this result ,did not undergo cardiac catheterization or coronary stent treatment, and was followed up by strict control of cholesterol and blood pressure.

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As mentioned above, the presence of large vulnerable plaques such as this case is suspected as one explanation for why myocardial infarction results from mild to moderate stenosis rather than from severe stenosis. At present, it is reported that compensatory expansion and small calcification are important along with large plaques with low CT values.

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