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The number of patients with ischemic heart disease (myocardial infarction and angina pectoris) is estimated at more than 700,000, accounting for approximately 5% of all deaths in Japan. In myocardial infarction, the coronary arteries that supply blood to the heart muscle (myocardium) become completely blocked, which can lead to sudden death. We summarize the symptoms of ischemic heart disease, test methods for diagnosis, and measures for early detection.

Ischemic heart disease is a condition in which the coronary arteries that supply blood to the myocardium become narrowed or blocked, resulting in poor blood flow to the myocardium and oxygen deficiency in the myocardium. A narrowed coronary artery is angina pectoris, and a blocked coronary artery is a heart attack. According to a patient survey conducted by the Ministry of Health, Labor and Welfare, the number of patients with ischemic heart disease is about 720,000 (as of 2017), and the number of male patients is higher than that of males and females. It is also said to account for about 5% of all deaths in Japan. The main cause of ischemic heart disease is arteriosclerosis, which is said to be easily caused by lifestyle factors such as hypertension, dyslipidemia, diabetes, lack of exercise, and smoking.

In angina pectoris, although the coronary arteries are narrowed, they are not completely blocked, so myocardial cells do not die, and angina is not immediately life-threatening. When symptoms such as strong squeezing pain and a feeling of pressure appear, they are often precursors of myocardial infarction. Patients may not even be aware that they have symptoms. Especially in the case of the elderly, it seems that there are many cases where the symptoms are overlooked as a result of aging. In some cases, people with diabetes may not feel the pain of angina pectoris due to the effects of neuropathy, which is one of the complications. Most angina pectoris occurs during activity, but spasms of the coronary arteries can occur at rest, resulting in an angina attack.

Myocardial infarction is a condition in which the coronary arteries are blocked, depriving the heart muscle of oxygen, and can lead to sudden death. More than 30,000 people die from myocardial infarction each year, and it is one of the three major causes of death in Japan. When it develops, symptoms such as strong chest pain and pressure accompanied by cold sweat and nausea appear. Chest pain lasts more than 30 minutes. Once myocardial infarction occurs, the mortality rate is said to be as high as 30%.

Common symptoms of ischemic heart disease include chest pain and pressure, nausea, and shortness of breath, as well as pain in the side, arms, and shoulders. It is especially important to see a doctor as soon as possible if you experience chest pain or chest pain.
Tests for early detection of ischemic heart disease include the following:

①トレッドミル運動負荷心電図検査:
症状の現れていない時に心電図を確認しても変化がありません。そこで、症状が現れている状況を再現するために運動の負荷をかけ、心筋の酸素の需要を高めて虚血状態を誘発し、その際の心電図の変化を観察します。負荷は動くベルトコンベアーの上を歩行することで行い、運動負荷をかける前後の心電図と合わせて、運動中の心電図、血圧を確認します。この検査で、心電図に異変が見られた場合には、労作時狭心症を疑います。

②ホルター心電図検査:
狭心症の症状は数分で消失してしまうため、症状が出現した際の心電図がとりづらいという難点があります。そこで、持ち運びができる携帯型の心電図を24時間装着して観察することで、どのタイミングで異常な心電図が出るかを調べます。異常な心電図が出たのが労作によるものなのか、安静時に起こっていたものかの判別が可能です。

③心筋シンチグラム検査:
放射線を微量に発生する薬剤を体内に注射して心筋への取り込みを計測します。心筋がどれくらい虚血状態なのか、また心筋がどれくらい弱ってしまっているかの評価ができます。使用される薬剤は半日ほどで自然に消失するほど微量なので、体に害が出ることはありません。

④Cardiac CT examination:
A contrast agent is injected into the body and photographed, and the stenosis of the coronary arteries is examined in 3D images. Compared to the conventional mainstream cardiac catheterization, it is a test that places less burden on the body. However, since the contrast medium is excreted through the kidneys as urine, caution should be exercised in patients with renal dysfunction.

⑤ Cardiac MRI examination:
A magnetic force is used to image the coronary arteries by computer analysis of the signals from the body's hydrogen atoms. There is no exposure to X-rays and the examination can be performed without using a contrast agent, making it suitable for patients with renal failure or contrast agent allergies.

⑥Echocardiography (echo):
Ultrasound waves are applied directly to the heart in the chest and an image is projected. The heart is cut into slices to examine the shape of the heart and blood vessels and the flow of blood. Heart movement abnormalities and changes in diastolic capacity may be observed. Ultrasound is harmless and painless.

⑦ Coronary angiography (cardiac catheterization) examination:
A thin, soft tube called a catheter with a diameter of 1 to 3 mm and a length of 1 m is inserted from the base of the foot or wrist, advanced to the coronary arteries of the heart, a contrast medium is injected, and moving images are taken with X-rays. Although an invasive technique, it allows direct visualization of vascular occlusions and narrowings that contribute to ischemic heart disease. In addition, if the examination reveals narrowed areas in the coronary arteries, treatment to widen the arteries may be performed.

If ischemic heart disease is suspected, electrocardiography, diagnostic imaging and examinations are performed, and coronary angiography is performed. The leading cause of death in Japan is malignant neoplasm <cancer>, followed by heart disease (heart failure, ischemic heart disease). The important thing is early detection at the stage of angina pectoris before myocardial infarction occurs. If you feel any discomfort in your body, we recommend that you see a doctor as soon as possible.