What causes premature beats?
Normal people will have premature beats. But patients with cardiac neurosis and organic heart disease are more likely to occur. Emotional excitement, tension, fatigue, indigestion, excessive smoking, drinking alcohol or strong tea can all cause seizures, or there is no obvious inducement. The toxic effects of digitalis, barium, quinidine, sympathomimetic drugs, chloroform, cyclopropane anesthetic, potassium deficiency, heart surgery or cardiac catheterization can all be caused. Coronary heart disease, advanced mitral valve disease, heart disease, myocarditis, hyperthyroidism heart disease, mitral valve prolapse and so on are often prone to premature beats.
It can be produced in many ways.
(1) Abnormal impulse formation caused by autonomic abnormality (1) Under certain conditions, such as Weidensky phenomenon, when sinus impulse reaches ectopic pacing point, the threshold potential of this point decreases and the slope of diastolic depolarization changes, causing premature beats. ② The membrane permeability of diseased atria, ventricles or Purkinje fibers changed to different ions, which made the fast-reaction fibers become slow-reaction fibers, and the diastolic depolarization accelerated automatically, and the self-discipline was enhanced, leading to premature beats.
The sinus impulse reaches the ectopic pacing point, which makes the threshold potential level move down, so the diastolic depolarization of ectopic pacing point reaches the threshold potential before the basal rhythm pacing point, causing premature beats.
(2) reentry phenomenon-annular reentry or focal micro-reentry, if the reentry path is the same, the premature beat mode is the same; If the conduction velocity during reentry is the same, the pairing time of premature beat and previous beat is fixed.
(3) Parallel contraction
Triggered activity
What are the manifestations of premature beats and how to diagnose them?
(1) History and symptoms: Due to the different sensitivity of patients, they may feel no obvious discomfort or only palpitation, precordial discomfort or cardiac arrest. Asking about the history of hypertension, coronary heart disease, cardiomyopathy and rheumatic heart disease is helpful to understand the causes of premature beats and guide treatment. Pay attention to asking if you have a recent history of cold, fever and diarrhea, which is helpful to judge whether you have acute viral myocarditis. The application of digitalis, antiarrhythmic drugs and diuretics sometimes induces premature beats.
(2) Physical examination found that in addition to the positive signs of the original basic heart disease, an early heartbeat can be found in the regular heart rhythm, followed by a longer interval (compensatory interval). The early appearance of the first heart sound enhancement and the second heart sound attenuation may be accompanied by the weakening or disappearance of this pulse.
(3) Auxiliary examination: ECG has diagnostic significance for premature beats. Atrial premature beat is an early QRS wave, which is preceded by abnormal P wave and followed by incomplete compensation period. QRS waveform is basically consistent with normal QRS waveform. The early QRS wave of nodal premature beats is consistent with the normal QRS wave, and there is no P wave before, and the compensation period is complete. QRS wave is wide and deformed in the early stage of ventricular premature beats, and the compensation period is complete. 24-hour Holter can record the frequency, regularity and therapeutic effect of premature beats in detail. Suspected myocarditis can be examined by blood myocardial enzymes. Cardiomyopathy and some patients with coronary heart disease can be found by echocardiography. Long-term use of diuretics and suspected digitalis poisoning should determine blood electrolytes, and if necessary, determine blood digitalis concentration.
What tests should be done for premature beats?
Physical examination can find that there are premature beats between basic heart rhythms, and then the interval is very long. The heart sounds of atrial premature beats are similar to the basic heart rhythm. Most of the first heart sounds of atrial premature beats are enhanced or alleviated, and the second heart sounds are inaudible. The pulse of radial artery caused by premature beats is weak or invisible, resulting in pulse loss. When the premature beat is binary or ternary, an interval can be heard after every 2 or 3 heartbeats. Premature beats inserted between two basic heartbeats are called inserted premature beats. Auscultation can be to connect heartbeats three times faster than the basic heartbeat. Electrocardiogram:
First, atrial premature beats.
Second, premature beats in atrioventricular junction.
Third, ventricular premature beats. QRS complex appeared prematurely with abnormal morphology, and the time was mostly ≥0. 12 seconds. The direction of T wave is opposite to the main wave of QRS syndrome, and the S-T segment shifts with the direction of T wave. There is no related P wave before it, and there is a complete compensation interval. Ventricular premature beats can occur between two sinus beats, forming inserted ventricular premature beats.
Fourth, multi-source premature beats.
Five, parallel rhythm premature beats. The pattern of ventricular premature beats is helpful to diagnose myocardial infarction.
[ECG manifestations]
The ECG of premature beats is characterized by one or more P-QRS complexes earlier than the basal heart rate.
(1) The P wave of atrial premature beats appeared early, and its shape was different from the basic rhythm. The P-R interval was > > 0. 12s. QRS wave is the same as sinus rhythm, sometimes slightly widened or deformed. The corresponding changes of ST and T wave are called ventricular differential conduction, which needs to be differentiated from ventricular premature beats. Early abnormal P' wave can be seen in front of abnormal QRS complex of atrial premature beats, accompanied by differential conduction in ventricles. There may be no QRS wave after early abnormal P' wave, which is called atrial premature beat block. It should be differentiated from sinus arrhythmia or sinus stasis. If the abnormal early P' wave is found on the ST segment or T wave of the previous heartbeat, it can be diagnosed as atrial premature beat block. The impulse of atrial premature beats often invades the sinus node, which depolarizes in advance, and the sinus node spontaneously depolarizes and restarts according to the original cycle, forming an incomplete compensation interval, and occasionally a complete compensation interval after atrial premature beats.
(3) The QRS complex of ventricular premature beats appeared early and its shape was abnormal. The time limit is mostly > > 0. 12s. The main wave directions of T wave and QRS wave are opposite, ST shifts with T wave, and there is no P wave before. When ventricular premature beats occur near the bundle branch, QRS complex may not widen. Most ventricular premature beats have fully compensated intervals. When the basal heart rate is slow, ventricular premature beats can be inserted between two sinus beats to form inserted ventricular premature beats. Occasionally, the retrograde P' wave from ventricular premature beats to atrium often appears on the ST segment of ventricular premature beats.
Atrial and ventricular premature beats can be divided into two types according to the relationship with the basic rhythm, taking ventricular premature beats as an example:
1. Pairing means that all premature beats are at a fixed distance from the QRS wave before them, which is more common.
2. The parallel premature contraction does not appear in pairs with the previous QRS complex, but there is a fixed law between them. The relationship between the longest premature beat and the shortest premature beat is an integer multiple, and ventricular fusion waves often appear.
Experimental research shows that the above rules can be changed due to sinus or ectopic impulses, so that the conduction in the protective afferent block area is slowly reduced, and subthreshold potential is generated at the distal end of the block, which affects the spontaneous depolarization of abnormal impulses in parallel rhythm and makes them be suppressed in advance, delayed or completely, which is called paracystole of electrical tension modulation.
Atrial or ventricular premature beats are sometimes produced by more than two ectopic pacing points. Electrocardiogram shows two or two premature beats with different forms and unequal pairing intervals, which are called multi-source premature beats. Two or more consecutive premature beats are called continuous bursts and short bursts of tachycardia respectively.
What diseases are premature beats easily confused with?
The normal beating of the heart originates from the sinoatrial node. If it originates from other parts of the heart, it is medically called premature beat. Premature beats can be divided into sinus, atrial, nodal and ventricular, of which ventricular is the most common, followed by atrial and sinus is rare. Among the ectopic heart rhythms seen in clinic, premature beats are the most common, which can be divided into functional and pathological types. Functional premature beats generally do not require special treatment. Pathological premature beats need to be treated in time, otherwise it may cause serious consequences and even life-threatening. Therefore, not only doctors, but also ordinary people should understand and master the knowledge of distinguishing functional and pathological premature beats, and make judgments in time, which is of great significance to the prevention and treatment of diseases.
(1) functional premature beats
It is not uncommon in young adults, and most of them can't find pathological reasons. It is often caused by mental stress, overwork, smoking, alcoholism, drinking strong tea and coffee. It usually appears when quiet or before going to bed, and the premature beats disappear after exercise. Functional premature beats generally do not affect health. After a period of time, most of these premature beats will heal without treatment, so there is no need for treatment. But at ordinary times, we should pay attention to the combination of work and rest, avoid excessive tension and fatigue, stay optimistic, live a regular life, don't overeat, and take appropriate physical exercise every day.
(2) Pathological premature beats
When suffering from myocarditis, coronary heart disease, rheumatic heart disease, hyperthyroidism heart disease, mitral valve prolapse and digitalis poisoning, premature beats often occur. This is a pathological premature beat, which is common in the following situations: it is common in the elderly or children; The number of premature beats increased after exercise; People diagnosed with heart disease; In addition to premature beats, ECG examination often has other abnormal ECG changes. For pathological premature beats, we should attach great importance to it, go to the hospital for ECG examination in the morning, and use drugs under the guidance of doctors. If severe and frequent premature beats occur, it is best to be hospitalized for observation and treatment.
How to prevent premature beats?
First of all, keep a regular life and proper physical exercise, don't stay up late, don't watch TV or sit in front of the computer for a long time; Walking, playing Tai Ji Chuan and using some fitness equipment for fitness training will bring long-term benefits to your health.
Second, quit smoking and avoid drinking heavily, because smoking and drinking are the main inducing factors of coronary heart disease.
Third, to maintain emotional stability, we should straighten out the relationship between work, life and study. High emotional tension and fluctuation are the main causes of functional "premature beats".
Fourth, we should go to the hospital for physical examination regularly, and go to the hospital in time once we find palpitations and missed jumps.
What diseases can premature beats be complicated with?
This disease can induce ventricular tachycardia, ventricular fibrillation and, in severe cases, sudden cardiac death.
1 ventricular tachycardia
Ventricular tachycardia refers to tachycardia which originates from below the bifurcation of his bundle and consists of more than 3-5 wide abnormal QRS waves. Similar to paroxysmal supraventricular tachycardia, but the symptoms are more serious. The children were fidgety, pale and short of breath. Older children can complain about palpitations and precordial pain, and in severe cases, they can include syncope, shock and congestive heart failure. The hemodynamic changes of patients with short-term attack are mild, and patients with continuous attack for more than 24 hours can have obvious hemodynamic changes. Physical examination found that the heart rate increased rapidly, often above 150 beats/min, with different rhythm and heart sound intensity.
2. Ventricular fibrillation
It is caused by many intersecting reentrant electrical activity waves, and its ECG shows chaotic recording curve. Ventricular fibrillation is often fatal unless it is defibrillated by direct current.
3. Sudden heart death
Sudden death is a clinical syndrome. Refers to the sudden and unexpected non-human death of a person who seems to be healthy or whose condition has basically recovered or stabilized. Most of them occur immediately after acute onset 1 hour, and the longest is no more than 6 hours, mainly due to primary ventricular fibrillation, ventricular arrest or electro-mechanical separation, which leads to the sudden stop of the effective systolic function of the heart.
How should premature beats be treated?
The main purpose of treating ventricular premature beats is to prevent ventricular tachycardia, ventricular fibrillation and sudden cardiac death.
1. Ventricular premature beats will not increase the mortality of patients without heart disease. Asymptomatic isolated ventricular premature beats, regardless of their shape and frequency, do not need medical treatment.
Second, the primary disease should be treated for ventricular premature beats related to organic heart disease. For ventricular premature beats that need urgent treatment, lidocaine 50- 100 mg can be injected intravenously until the premature beats disappear or the total amount reaches 250mg. After the arrhythmia is corrected, 1-3 mg can be instilled every minute as needed, and it can be maintained by oral drugs after stabilization. Lidocaine takes effect within a few minutes after intravenous injection, lasting 15-20 minutes. The therapeutic dose has little effect on myocardial contractility, blood pressure, atrioventricular or indoor conduction. Side effects include dizziness and drowsiness. Large doses can cause convulsions, respiratory or cardiac arrest, and aggravate the original atrioventricular or indoor conduction block. Use with caution in patients with liver and kidney dysfunction or severe heart failure.
Third, ventricular premature beats caused by digitalis poisoning. In addition to drug withdrawal, intravenous injection of phenytoin sodium or intravenous drip of potassium chloride is often effective. We should actively eliminate the causes of premature beats caused by hypokalemia and correct hypokalemia.
Four, quinidine syncope or antimony treatment of ventricular premature beats, should immediately stop using quinidine or antimony. Oral drugs can be selected: ① Slow heart rhythm. ② Beta blockers. ③ digitalis; It is suitable for ventricular premature beats caused by heart failure rather than digitalis poisoning. ④ Procaine amide. ⑤ Amiodarone, diisopropyl pyrazine, propranolol, antongding, chlorphenazine, ethambutol, incamide, etc.
Five, atrial premature beats should be actively treated. Remove the inducement and choose the following drugs for treatment: ① β -adrenergic receptor blockers, such as propranolol. ② Verapamil. The above two drugs are contraindicated for patients with hypotension and heart failure. (3) digitalis is suitable for heart failure but not atrial premature beats caused by digitalis. Commonly used digoxin 0.25mg, 1 time/day. ④ Quinidine. ⑤ phenytoin sodium 0. 1g, three times a day. ⑥ Amiodarone. The treatment of atrioventricular junctional premature beats is the same as atrial premature beats. If it fails, you can try drugs for premature ventricular contractions.
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