Extra-period contraction

Introduction Premature beats, also known as "pre-systolic contraction", "external contraction", "premature beat" refers to the heart beat caused by ectopic pacemakers in advance, which is the most common arrhythmia. According to the different origin of the premature beat, it is divided into atrial, ventricular and knot. Among them, ventricular premature beats are the most common, followed by atrial and less common. Premature beats can be seen in normal people, or in patients with structural heart disease, can also be seen in quinidine, procainamide, digitalis or tincture poisoning; hypokalemia; cardiac surgery or cardiac catheterization on the heart Mechanical stimulation, etc.

Cause

In the pulsation of the heart, if the function of the sinus node is not perfect, or the excitability of the atrioventricular node is strengthened, the impulse is first transmitted when the impulse of the sinus node has not been transmitted, which may cause contraction other than normal contraction of the ventricle.

ECG can distinguish between atrial, borderline and ventricular premature contractions:

(1) Pre-atrial contraction:

The atrial ectopic P wave that appeared before the first phase was different from the sinus P wave.

The 2P-R interval is prolonged in the normal range (>0.10 s) or in the interfering PR interval.

3 The QRS wave after the ectopic P wave is the same as the sinus QRS wave. If there is differential conduction, the QRS wave shape is mutated. If the ectopic P wave occurs too early, the atrioventricular junction area is still in the absolute refractory period, then the P wave After that, no QRS wave is called a pre-atrial contraction that has not been transmitted.

4 compensation intervals are mostly incomplete.

(2) Premature contraction before contraction:

The QRS wave that appeared before the first phase has the same morphology as the sinus QRS wave.

2 retrograde P wave PII, III, aVF inverted PaVR upright retrograde P wave can appear before QRS wave, its PR interval is <0.10s; if after QRS wave, RP interval is <0.20s; can also be embedded in QRS wave Medium, without retrograde P waves.

3 compensation intervals are mostly complete.

(3) ventricular premature contraction:

1 QRS wave appearing in advance, without P wave before it.

The QRS wave widening before the 2nd stage (elderly >0.12s; infants and young children>0.10s) is opposite to the T wave direction. For example, the pacing point is close to normal in the vicinity of the atrioventricular bundle.

The 3 compensation interval is complete.

In the same lead of the electrocardiogram, the pre-systolic contraction morphology is different, and the inter-trial interval is different, which is the polymorphic pre-contraction. After each interval of sinus beats, a pre-contraction is called the second law. After every 2 sinus fluctuations, a pre-contraction is triad and so on. The fourth and fifth pre-contraction contraction is 5 times per minute. The above is called pre-systolic contraction, and 5 or less is sporadic.

(1) Healthy children: pre-contraction is common in healthy children or non-organic heart disease, caused by overwork, mental stress, biliary tract infections of the gastrointestinal tract or autonomic nervous disorders. Some can't find obvious causes.

(2) Children with heart disease: Children with heart disease are more prone to premature contraction, such as rheumatic heart disease, various myocarditis, primary cardiomyopathy, congenital heart disease and heart failure. Long QT syndrome, mitral valve prolapse and left ventricular false chord often have ventricular premature contractions.

(3) drug poisoning: digitalis drug poisoning often occurs ventricular premature contraction. Other drugs such as quinidine adrenaline sputum poisoning.

(4) hypokalemia and hypoxia: hypokalemia and hypoxia can also cause premature contraction.

(5) Others: Pre-contraction often occurs during cardiac catheterization, cardiac surgery, and anesthesia.

Polymorphism in pairs or consecutive three ventricular premature contractions, more common in children with severe heart disease.

an examination

Related inspection

Electrocardiogram

1. ECG performance:

(1) ventricular premature contraction grading: according to conventional electrocardiogram and 24h dynamic electrocardiogram examination, ventricular premature contraction can be divided into 6 levels:

Electrocardiograph

Level 0: No contraction before the period.

Grade 1: Pre-contraction <2 times/min or <30 times/h.

Level 2: Pre-contraction > 2 times / min or > 30 times / h.

Level 3: Polymorphism pre-contraction.

Grade 4 A: contraction before the contraction or 2 consecutive contractions.

Grade 4 B: There are more than 3 contractions before the continuity period.

Level 5: R wave falls on the T wave, that is, the ventricular premature contraction occurs in the vulnerable period of the ventricle, which may cause ventricular tachycardia or ventricular fibrillation.

(2) Benign pre-contraction: ventricular premature contractions in healthy children are equal in morphologically consistent intervals, most of which belong to grade 1 and grade 2, occasionally grade 4 A, do not cause ventricular tachycardia, benign Contraction before the period.

(3) Complex ventricular premature contraction: pleomorphic pairing occurs or three consecutive and R wave falls on the T wave. Premature contraction is complicated ventricular premature contraction, and ventricular tachycardia may occur. Found in patients with structural heart disease. Complex ventricular premature contractions should be further examined for 24h dynamic ECG cardiac catheterization and cardiovascular angiography to obtain more detailed cardiac hemodynamic changes and morphological changes to understand mild myocardial disease.

(4) Myocardial injury type: conventional electrocardiogram examination attention to myocardial injury ST-T wave changes, ventricular hypertrophy voltage standard and QT interval measurement corrected QT interval should be <0.44s.

2. Ventricular premature contraction grading (Lown classification method): Low is classified according to the ventricular premature contraction detected during the monitoring of patients with acute myocardial infarction (Table 2). Clinically, it is sometimes simple to call more than 6 pre-systolic contractions. It is a premature contraction, and 6 or less is an episode contraction.

3. Pre-systolic grading: According to Kleiger's atrial pre-systolic grading standard, the atrial pre-contraction is divided into six levels.

Differential diagnosis

The symptoms of extra-systolic contraction need to be identified as follows.

1 Various heart diseases can cause premature beats, but premature beats are more common in heart diseases such as rheumatic heart disease, coronary sclerosing heart disease, myocarditis and cardiomyopathy.

2 Emotional stress, excitement, anxiety, excessive smoking, heavy drinking, drinking tea, and even constipation can cause premature beats.

3 other non-cardiac diseases, such as hyperthyroidism, anemia target=_blank> anemia, hypokalemia, fever, etc., can also trigger premature beats.

The material in this site is intended to be of general informational use and is not intended to constitute medical advice, probable diagnosis, or recommended treatments.