1, the concept of premature beats
Premature beat is also called premature beat, also called premature beat, abbreviated as premature beat. It is an early ectopic heartbeat, which can be divided into sinus, atrium, atrioventricular junction and ventricle according to its origin, of which ventricle is the most common, followed by atrium, and sinus premature beats are rare. Premature beats are a common ectopic rhythm. It can occur on the basis of sinus rhythm or ectopic rhythm (such as atrial fibrillation). It can occur occasionally or frequently, or irregularly or regularly after each or several normal beats, forming biphasic or biphasic premature beats.
2. Pathological factors of premature heart beats
Normal people can have premature beats, but patients with cardiac neurosis and organic heart disease are more likely to have them. Emotional excitement, tension, fatigue, indigestion, excessive smoking, drinking 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 cause coronary heart disease. It can be produced in many ways.
(1) abnormal impulse formation caused by abnormal self-discipline; 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, leading to premature beats; ② The membrane permeability of diseased atria, ventricles or Purkinje fibers changed to different ions, which changed the fast-reaction fibers into slow-reaction fibers, accelerated diastolic depolarization, enhanced self-discipline and led to premature beats.
Weidensky phenomenon indication
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-circular reentry or focal micro reentry, if the reentry route is the same, the premature beat pattern 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
Clinical manifestations of premature heart beats
Premature beats can be asymptomatic, but there are also feelings of palpitations or cardiac arrest. Frequent premature beats can cause fatigue, dizziness and other symptoms (caused by decreased cardiac output), which can induce or aggravate angina pectoris or heart failure in patients with original heart disease. Arrhythmia can be found by auscultation, and there is a long compensatory interval after premature beats. Most of the first heart sounds of premature beats are enhanced, and most of the second heart sounds are weakened or disappeared. When premature beats are two or three laws, a long interval can be heard after every two or three heartbeats. Premature beats inserted between two normal heartbeats can be characterized by three consecutive heartbeats. Pulse palpation can find intermittent pulse loss.
Diagnosis of premature beats
(1) Medical history and symptoms: Due to different sensitivities 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 beats are early QRS waves, with abnormal P waves before them and incomplete compensation period after them. QRS waves appearing in the early stage of nodal premature beats are consistent with normal QRS waves, and there is no P wave before them, and there is a complete compensation period. 24-hour Holter can record the frequency, regularity and therapeutic effect of premature beats in detail. Suspected myocarditis, blood myocardial enzymes can be checked. Cardiomyopathy and some patients with coronary heart disease can be found by echocardiography. Long-term use of diuretics, suspected digitalis poisoning, blood electrolytes and digitalis concentration should be determined when necessary.
3. Treatment of premature heart beats
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- 100mg can be injected intravenously until the premature beats disappear or the total amount reaches 250mg. After the arrhythmia is corrected, 1-3mg 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. The oral medicine can be selected from:
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 Beta 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.
4, premature beat diet conditioning
Dietotherapy for premature beats (for reference only, please consult your doctor for details):
Formula 1: tremella 15-30g, lean pork 200g, jujube 10. * * * stew in a pot and add salt to taste with the meal.
Recipe 2: lotus seed meat and sugar in moderation, boiled. You can also grind steamed cakes and make breakfast in the morning, 50- 100g each time.
5. Preventive nursing of premature heart 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.
6, premature beat inspection method
Physical examination shows that premature beats are sandwiched between basic heart rhythms, followed by a long interval. 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 weakened, and the second heart sounds are inaudible. The pulsation of radial artery caused by premature beats is weak or undetectable, resulting in pulse loss. When premature beats are binary or ternary rhythms, an interval can be heard after every two or three heartbeats, and premature beats are inserted between two basic heartbeats.
Electrocardiogram:
First, atrial premature beats.
Second, premature beats in atrioventricular junction.
3. Ventricular premature beats, with QRS complex of premature beats, with abnormal shape, time more than or equal to 0.12 seconds, T wave and QRS complex main wave in opposite directions, S-T segment shifted with the direction of T wave, and there was no related P wave before, and there was a complete compensation interval. Ventricular premature beats can occur between two sinus beats, forming inserted ventricular premature beats.
Fourth, multi-source premature beats.
5. Parallel rhythmic premature beats and ventricular premature beats are helpful to diagnose myocardial infarction.
7. ECG manifestations of premature beats
The ECG of premature beats is characterized by one or more P-QRS complexes earlier than the basal heart rate.
(1) P wave of atrial premature beats appears early, and its shape is different from the basic rhythm. P-R interval > > 0. 12s, QRS wave is the same as sinus rhythm, sometimes slightly widened or deformed. Abnormal QRS waves with corresponding changes in ST and T waves are called ventricular differential conduction and need to be differentiated from ventricular premature beats. When atrial premature beats are accompanied by ventricular differential conduction, abnormal QRS complex can be seen before them. There may be no corresponding QRS wave after the abnormal P' wave appears in advance, which is called atrial premature beat block and needs to be differentiated from sinus arrhythmia or sinus arrest. If abnormal P' wave is found on the ST segment or T wave of the previous heartbeat, it can be diagnosed as atrial premature beat block. Atrial premature beats often invade the sinoatrial node, which depolarizes in advance, and the sinoatrial node spontaneously depolarizes and restarts according to the original cycle, forming an incomplete compensation interval, which is rare.
Atrioventricular junctional premature beats
(3) The QRS complex of ventricular premature beats appeared early with abnormal shape, and the time limit was mostly > > 0. 12s. The main wave direction of T wave is opposite to QRS wave, ST shifts with T wave, and there is no P wave in front, which leads to ventricular premature beats near bundle branches. QRS complex may not widen, and most of them have completely compensated intervals after ventricular premature beats. Ventricular premature beats may occur when the basic heart rhythm is slow.
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.
Paired ventricular premature beats are triad.
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.
Parallel contraction ventricular premature beats
There is no fixed matching time between premature beats and the previous heart, and late premature beats meet sinus excitement to form ventricular fusion waves (ⅱ6 hearts).
Experimental research shows that the above rules can be changed due to sinus or ectopic impulse, which slowly reduces the conduction of protective afferent block, produces subthreshold potential at the distal end of block, affects the spontaneous depolarization of abnormal impulse of parallel rhythm, and makes it early, delayed or completely suppressed, which is called electric tension current modulation parallel rhythm.
Atrial or ventricular premature beats are sometimes produced by more than two ectopic pacing points. Electrocardiogram shows two or two different forms of premature beats with unequal pairing intervals, which are called multi-source premature beats. Two or more consecutive premature beats are called continuous paroxysmal tachycardia and short paroxysmal tachycardia respectively.
8. Complications of premature beats
This disease can induce ventricular tachycardia, ventricular fibrillation and, in severe cases, sudden cardiac death.
1 ventricular tachycardia
Ventricular tachycardia refers to tachycardia composed of more than 3-5 wide and deformed QRS waves originating from the bifurcation of his bundle, which is similar to paroxysmal supraventricular tachycardia, but the symptoms are more serious, such as restlessness, pallor and shortness of breath in children, palpitation and precordial pain in older children, syncope, shock and congestive heart failure in severe cases, and the hemodynamic changes in patients with short onset time are relatively light. If the attack lasts more than 24 hours, there will be significant hemodynamic changes. Physical examination found that the heart rate increased rapidly, often above 150 beats/min, with regular rhythm and different heart sounds.
2. Ventricular fibrillation
It is caused by many intersecting reentrant electrical activity waves, and its ECG shows chaotic recording curve. VF can often be fatal unless it is defibrillated by direct current (it is difficult to defibrillate with chest thumping or antiarrhythmic drugs).
3. Sudden cardiac death
Sudden death is a clinical syndrome, which refers to the sudden and unexpected non-human death of people who seem to be healthy or whose condition has basically recovered or stabilized. Most of them occur within 1 hour after acute attack, and the longest is no more than 6 hours, mainly due to primary ventricular fibrillation, ventricular arrest or electromechanical separation, which leads to the sudden stop of effective systolic function of the heart.