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狭心症 I：はじめに
定義と症状：狭心症（狭心症発作）は、心筋虚血によって引き起こされる胸痛または不快感です。心筋虚血は、心臓の筋肉が酸素を豊富に含む血液を十分に受け取れなくなったときに発生します。通常、胸部に圧迫感、絞られるような感じ、または押し潰されるような感覚として現れ、肩、腕、首、顎、または背中に放散することがあ…
狭心症、または狭心症は、心筋が酸素が豊富な血液を十分に摂取する心筋虚血によって引き起こされる胸痛または不快感です。
通常、胸を圧迫したり、圧迫したり、押しつぶしたりしているように感じられ、多くの場合、肩、腕、首、顎、または背中に放射状に広がります。
狭心症の主な原因はアテローム性動脈硬化症であり、プラークの蓄積が冠状動脈を狭くし、心筋への酸素が豊富な血液供給を減らします。
その他の要因には、冠状動脈のけいれん、微小血管疾患、および左心室肥大や頻脈などの心筋酸素要求量を増加させる状態が含まれます。
狭心症の一因となる危険因子には、高血圧、高脂血症、喫煙、糖尿病、肥満、ストレス、運動不足、貧しい食生活、加齢、冠状動脈疾患の家族歴などがあります。
狭心症の病態生理学は、心筋の酸素供給と供給の間の不均衡によるものです。
身体活動やストレスが増加すると、冠状動脈が狭くなるため、心臓の酸素需要が制限された供給を超え、虚血や狭心症の痛みを引き起こします。
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Q1: What is angina and what does it feel like?
Angina, or angina pectoris, is chest pain or discomfort caused by myocardial ischemia, when the heart muscle receives insufficient oxygen-rich blood. It typically feels like pressing, squeezing, or crushing sensations in the chest and may radiate to the shoulders, arms, neck, jaw, or back.
Q2: What causes angina to develop?
The primary cause of angina is atherosclerosis, where plaque buildup narrows the coronary arteries, reducing oxygen-rich blood flow to the heart muscle. Contributing factors include coronary artery spasms, microvascular disease, and conditions that increase myocardial oxygen demand, such as left ventricular hypertrophy or tachycardia.
Q3: How does myocardial ischemia lead to anginal pain?
Angina results from an imbalance between the heart muscle's oxygen supply and demand. During increased physical activity or stress, the heart's demand for oxygen surpasses the restricted supply due to narrowed coronary arteries, leading to ischemia and anginal pain. This oxygen deficit triggers chest discomfort.
Q4: What physical and emotional factors trigger angina?
Physical activity such as walking, running, or climbing stairs increases the heart's workload and oxygen demand. Emotional stress can also increase heart rate and blood pressure, raising oxygen demand. Narrowed coronary arteries cannot deliver sufficient oxygen-rich blood to meet these increased demands, triggering angina.
Q5: What are the main risk factors for developing angina?
Risk factors include hypertension, hyperlipidemia, smoking, diabetes, obesity, stress, physical inactivity, poor diet, increasing age, and family history of coronary artery disease. These factors contribute to atherosclerosis and narrowing of coronary arteries, significantly increasing the risk of developing angina symptoms.
Q6: How do healthy coronary arteries differ from those affected by coronary artery disease?
In a healthy state, coronary arteries can dilate to increase blood flow and meet increased oxygen demand during physical activity or stress. In coronary artery disease, narrowed coronary arteries limit the ability to increase blood flow during increased oxygen demand, leading to ischemia and angina.
Q7: What role do microvascular disease and coronary artery spasms play in angina?
Microvascular disease affects small blood vessels in the heart, reducing blood flow and causing angina. Coronary artery spasms cause sudden, temporary narrowing of coronary arteries, also reducing blood flow and oxygen delivery. Both conditions contribute to myocardial ischemia and anginal symptoms in susceptible patients.