Premature beat

Japanese: 期外収縮 - きがいしゅうしゅく（英語表記）Premature beat

What is the disease?

A premature ventricular contraction is an electrical impulse that occurs before the natural heartbeat (timing) is expected, resulting in an extra heartbeat. Atrium ( Patience ) or Chamber ( Hat ) Premature contractions occurring from the junction Upper room ( Classroom ) This is called a premature contraction, and occurs when the muscle fibers below the bundle of His (the muscle fibers that transmit the impulse) Ventricle ( Classroom ) Premature contractions resulting from this are called ventricular premature contractions.

Premature ventricular contractions themselves are arrhythmias that can be left alone, but premature ventricular contractions can trigger Tachycardia ( Pest ) If this occurs or if there are severe symptoms due to premature ventricular contractions, treatment is indicated.

What is the cause?

It is often caused by abnormalities in the autonomic nervous system, but the cause is sometimes unclear. It can occur in healthy people as well as those with heart disease. Excessive alcohol consumption, lack of sleep, fatigue, stress, etc. can be triggers.

Physiologically, most premature contractions are Hyperactivity ( Autonomous vehicle ) arises in Mitral valve ( Soubouen ) It is thought that in some tissues, such as the pulmonary vein, the disease is caused by sudden activity. Regression shrinkage ( Recruitment ) This can also occur with re-entry.

How symptoms manifest

Symptoms of premature ventricular contractions vary, and their intensity varies depending on the patient's sensitivity. They are described as feeling a sudden heartbeat, a dizziness, or a feeling of uneasiness. When you notice such symptoms, if you check your pulse, it is often determined to be a premature ventricular contraction because there is no pulse. There is no difference in subjective symptoms between supraventricular and ventricular premature ventricular contractions.

The intensity of the symptoms depends on how long after the preceding heartbeat (the coupling period) the premature ventricular contraction occurs.

When a premature systole occurs with a long coupling period close to the time when the next normal heartbeat appears, the premature systole is hardly felt because there is no significant difference in the time of the appearance of the previous and next heartbeats. Conversely, a premature systole that occurs close to the leading heartbeat and with a short coupling period causes strong symptoms regardless of its origin.

Sensitive people are aware of a single premature ventricular contraction. However, people who generally experience 20,000 to 30,000 premature ventricular contractions a day are often unaware of symptoms caused by premature ventricular contractions, and are more aware of symptoms when there are hundreds to thousands of premature ventricular contractions a day. Even healthy people should not be surprised to experience premature ventricular contractions equal to their age.

Testing and diagnosis

Accurate diagnosis is made with an electrocardiogram. Supraventricular premature contractions are characterized by early appearance of QRS waves that are almost identical to those in sinus rhythm or basic rhythm. On closer inspection, ectopic P waves can be found before and after the preceding T wave. Ventricular premature contractions show a completely different QRS waveform than sinus rhythm, with no preceding P wave, Sinus rhythm ( Traffic law ) It appears earlier in the cycle.

The test involves a Holter monitor to check the frequency and form of premature ventricular contractions. The frequency of premature ventricular contractions is considered to be within the physiological range for the patient's age. Sporadic ( Sanpati ) Premature contractions, over 3,000 shots Frequent ( Frequency ) This is called a premature contraction.

To examine whether exercise increases or decreases the amount of calories burned, a treadmill exercise stress test is performed. Instead of the treadmill, the Master 2-stair stress test can also be used.

If exercise causes frequent premature ventricular contractions, you should refrain from exercising, as this may lead to tachycardia or sustained tachycardia due to a series of premature ventricular contractions. Conversely, if exercise eliminates premature ventricular contractions, there is no need to restrict exercise.

Treatment methods

There is no need to treat the single premature ventricular contraction itself, but if the symptoms are severe, antianxiety medication will be administered first. If symptoms persist, antiarrhythmic drugs will be used.

In general, because premature ventricular contractions are likely to occur due to increased automaticity, sodium channel blockers that suppress automaticity are administered. Any antiarrhythmic drug can be used for ventricular premature contractions, but the non-activating sodium channel blockers lidocaine and mexiletine are ineffective for supraventricular premature contractions.

The prognosis for premature ventricular contractions is good. However, premature ventricular contractions can trigger fatal tachycardia. In such cases, premature ventricular contractions require treatment. Radiofrequency catheter ablation (column) is used to identify the origin of premature ventricular contractions. Cauterization ( Presentation ) There is something to do.

What to do if you notice an illness

Premature ventricular contractions themselves are benign arrhythmias and can occur to anyone. Therefore, if you are simply told that you have premature ventricular contractions, there are no restrictions on your daily life. However, if the symptoms are severe or they trigger tachycardia, treatment is necessary, so please visit a cardiologist.

Like other arrhythmias, premature ventricular contractions are aggravated by excessive alcohol consumption, lack of sleep, fatigue, and stress, so be sure to avoid these risks.

Kaoru Sugi

Source: Houken “Sixth Edition Family Medicine Encyclopedia” Information about the Sixth Edition Family Medicine Encyclopedia

Japanese:

どんな病気か

　期外収縮は、もともとの調律（タイミング）で心拍が生じると予想される時期より早期に生じる電気的な興奮のことを指します。そのため、余分な心拍が現れます。心房(しんぼう)あるいは房室(ぼうしつ)接合部から生じる期外収縮を上室(じょうしつ)期外収縮といい、ヒス束（刺激を伝える筋線維）より下部の心室(しんしつ)から生じる期外収縮を心室期外収縮といいます。

　期外収縮自体は放っておいてもよい不整脈ですが、期外収縮が引き金になって頻拍(ひんぱく)が起こる場合や、期外収縮による自覚症状が強い場合には治療の対象になります。

原因は何か

　自律神経の異常によって起こることが多いようですが、原因がはっきりしないこともあります。病的な心臓だけでなく健常な人にも生じます。アルコールの飲みすぎ、睡眠不足、疲労、ストレスなどが誘因になります。

　生理学的には、大部分の期外収縮は自動能亢進(じどうのうこうしん)で生じ、僧帽弁(そうぼうべん)や肺静脈などの発生組織によっては激発活動で生じると考えられています。また、場合によっては回帰収縮(かいきしゅうしゅく)（リエントリー）で生じることもあります。

症状の現れ方

　期外収縮の症状はさまざまで、患者さんの感受性によって強弱も違います。どきっとする、くーとする、もやもやするなどと表現されます。そのような症状を自覚する時に脈をみると、脈が抜けていることで期外収縮と判断されることが多いようです。上室期外収縮と心室期外収縮とでは、自覚症状の差はありません。

　自覚症状の強弱は、先行する心拍のあと、どのくらいの時間（連結期）で期外収縮が現れるかによって左右されます。

　次の正常心拍が現れる時期に近いタイミングで、長い連結期をもって期外収縮が現れる時には、前後の心拍の出現時間に著しい差はないために、期外収縮はほとんど自覚されません。逆に先行心拍に近く、短い連結期で生じる期外収縮は、起源がどこであっても、強く症状を感じます。

　敏感な人では1発の期外収縮を的確に自覚します。しかし、一般に期外収縮の出現数が1日に2万発、3万発あるような人は期外収縮による症状を自覚しないことが多く、むしろ1日数百発から数千発出現する場合に症状を強く自覚します。健常な人でも自分の年齢数くらいは期外収縮が現れてもおかしくありません。

検査と診断

　正確な診断は心電図で行います。上室期外収縮は、洞調律あるいは基本調律のQRS波とほぼ同一のQRS波が早期に現れます。よくみると先行T波の前後に異所性P波が見つかります。心室期外収縮は、洞調律の時とはまったく違うQRS波形を示し、先行するP波がなく、洞調律(どうちょうりつ)の周期より早期に現れます。

　検査は期外収縮の出現頻度と出現形態をみるために、ホルター心電図を行います。患者さんの年齢数くらいの出現は生理的な範囲と考えられます。1日3千発未満を散発性(さんぱつせい)期外収縮、3千発以上を頻発性(ひんぱつせい)期外収縮としています。

　運動によって増えるか、あるいは減るかを検討するために、トレッドミル運動負荷試験を行います。トレッドミルの代わりにマスター2階段負荷試験でも十分検討できます。

　運動をすると期外収縮が頻発する場合には、期外収縮の連続による頻拍や持続性の頻拍が生じる可能性があるので、運動はひかえるようにします。逆に、運動によって期外収縮がなくなる場合には、運動制限をする必要はありません。