Cardiac CT examination
1. Cardiac CT examination (contrast-enhanced cardiac CT examination)
A common cardiac CT examine is a contrast-enhanced CT that using an iodine contrast medium. The indications for contrast-enhanced CT examine encountered in routine practice are shown Table 1 .
Several multicenter studies reported that the sensitivity of the test is about 85-90% and the specificity is about 96-98% compared to invasive cardiac catheterization. Characteristic is the high negative predictive value, which is often reported to be about 93-100%. This means that if cardiac CT is normal, we can be confident that there is no coronary artery disease. In fact, for cardiovascular doctors who handle the heart, this ability to conclude is a big attraction.
Taking advantage of this feature of cardiac CT, the usefulness of cardiac CT in patients with acute chest pain, whose chest suddenly hurts and differentiation from acute myocardial infarction becomes a problem. A multicenter study of 1,000 patients with acute chest pain in the United States has reported the effectiveness of the first diagnostic method using cardiac CT. According to the results of comparison between the method using cardiac CT (501 patients) and the conventional diagnostic method without cardiac CT (499 patients), both the length of hospitalization and the rate of direct discharge from the emergency room are shorter in the cardiac CT group. It has been reported that myocardial infarction and heart failure do not increase after discharge. Based on these research results, it is recommended that you first have a heart CT scan when your chest suddenly hurts.
In summary, we show the characteristics of cardiac CT, its advantages and disadvantages, and its contrast with other coronary angiography-capable examinations ( Table 2 ).
2. Coronary artery calcification score (non-contrast-enhanced cardiac CT examination)
Coronary artery calcification is considered a sensitive marker of arteriosclerosis, and adding a coronary artery calcification score to conventional risk factors may allow more accurate prediction of the risk of coronary artery disease. It has been reported. Coronary artery calcification scores can be taken with a small amount of X-ray exposure without the need for iodine contrast media, and there are many reports of clinical usefulness. In addition, it can be easily confirmed visually, and it is easy for patients to understand the pathological condition.
However, it is also true that 3.5% of patients with symptoms without coronary artery calcification have significant stenosis on cardiac CT, and coronary artery lesions can be detected only by the calcification score. It is also true that it is impossible to make a complete diagnosis. However, patients with a calcification score of <100 have a heart disease event of 0.4% per year, which is considered unlikely to be associated with coronary artery disease.
Recent studies have also reported that coronary artery calcification scores are more capable of detecting coronary artery disease than traditional arteriosclerosis markers and risk factors because they look directly at the coronary arteries. In addition, the most researched American Institute of Health has published data on coronary artery calcification scores for multiple races by age and gender. Using these data, it is possible to estimate the relative degree of calcification of individual patients in the average distribution in Asians.
It is possible to grasp the position of arteriosclerosis of one's coronary arteries among Asians of the same age and gender, which will lead to prevention of future progression of arteriosclerosis. .. There is also data that people with a coronary calcification score of 100 or higher should consider drug treatment with antiplatelet drugs, and those with a coronary calcification score of 400 or higher should be retested within 2-3 years.
3. Coronary plaque imaging by cardiac CT
A major feature of cardiac CT is that it is possible to obtain information on coronary plaque, which was not possible with conventional cardiac catheterization ( Table 2 ). Other coronary angiography to date has only shown the lumen of the blood vessel through which blood is flowing to determine if the blood vessel is thin. However, coronary CT can image atherosclerotic plaques that have accumulated on the walls of blood vessels.
A typical case of coronary plaque is shown (above). Because of the chest pain that I felt while exercising for 2 hours, I visited a nearby practitioner and was referred to the hospital for a cardiac CT examination. Coronary CT shows a moderate stenosis in the left anterior descending artery (A). In the detailed observation image (B) of the same site, atherosclerotic plaque with low CT value can be seen around the moderately stenotic lesion (B). The entire vessel dilates due to plaque accumulation, showing the compensatory enlargement characteristic of vulnerable plaques. In the orthogonal cross section (C), the presence of atherosclerotic plaque can be seen surrounding the white-looking vascular lumen. After that, although the patient underwent cardiac catheterization, the patient was not treated with a coronary stent because of moderate stenosis, and the patient was followed up with strict control of cholesterol and blood pressure.