Loss of atrium assisting pump to ventricular contraction

Introduction Atrioventricular block refers to impulsive blockage during atrioventricular conduction. Divided into two categories of incompleteness and completeness. The former includes first- and second-degree atrioventricular block, the latter also known as third-degree atrioventricular block, and the block can be in the atria, atrioventricular node, His bundle and double bundle. At the time of complete atrioventricular block, the temporal relationship between the atrium and the ventricle is separated, and the atrial pumping of the ventricular contraction is lost, resulting in a decrease in cardiac output. Patients with complete atrioventricular block are more than 50 years old, and complete atrioventricular block is more temporary in young patients. More male patients than females. Symptoms and hemodynamic changes in complete atrioventricular block depend on the degree of ventricular rate slowdown and myocardial pathology and functional status. At the time of complete atrioventricular block, the temporal relationship between the atrium and the ventricle is separated, and the atrial pumping of the ventricular contraction is lost, resulting in a decrease in cardiac output. In congenital complete atrioventricular block, the ventricular rhythm point is often above the atrioventricular bundle bifurcation, the ventricular rate is faster, and can increase with physical activity. Myocardial function is better, and cardiac output is easy to increase, so these patients often have no obvious symptoms. In patients with acquired complete atrioventricular block, most of them may be asymptomatic at rest or have a feeling of palpitations. In physical activity, you may have heart palpitations, dizziness, fatigue, chest tightness, and shortness of breath. If the ventricular rate is too slow, especially if the heart has obvious ischemia or other pathological changes, or complicated by extensive acute myocardial infarction or severe acute myocarditis, the symptoms may be severe, heart failure or shock may occur, or the brain may be insufficiently supplied. And the reaction is slow or blurred, and then developed into syncope (incidence rate of up to 60%), A-S syndrome. Due to the increase in diastolic ventricular filling and stroke volume, a widening of the pulse pressure difference and a mild to moderate heart enlargement may occur. The clinical manifestations of complete atrioventricular block in acute myocardial infarction have its characteristics: the degree of hemodynamic disorder in acute myocardial infarction depends on the location of the infarction, the rate of conduction block, and the pace of ventricular paceps. Site and ventricular rate. Inferior wall infarction complicated by third-degree atrioventricular block, if the first or second degree of Ventricular type atrioventricular block gradually developed, the ventricular rate is not too slow, can not cause clinical deterioration. Conversely, most anterior wall infarctions with third-degree atrioventricular block may present with hypotension, shock, and severe left heart failure. Regardless of the infarction of the anterior or inferior wall, if the QRS wave is suddenly widened, the ventricular rate is too slow, and the third-degree atrioventricular block below 40 beats/min is susceptible to ventricular arrest or ventricular tachycardia. Ventricular fibrillation. The anterior wall is twice as likely to have a complete atrioventricular block as the inferior myocardial infarction. However, when the inferior wall combined with right ventricular myocardial infarction complicated by complete atrioventricular block, the right ventricle to the left ventricle filling effect is reduced, and the cardiac output is further reduced, hemodynamic disorder is aggravated, and the mortality rate is significantly increased. Complete atrioventricular block complicated by acute myocardial infarction is mostly temporary, and only a few patients will never recover after infarction. The slow rate of the central electrocardiogram and the widening of the QRS wave are particularly prone to syncope or heart failure. The first heart sounds of patients with complete atrioventricular block are sometimes different, sometimes loud, such as firing, because the relationship between atrial and ventricular contraction times often changes.

Cause

Pay attention to the cause of atrioventricular block, whether there is organic heart disease, whether to take antiarrhythmic drugs for a long time or a large amount, whether there is cardiac surgery, inflammation, electrolytes and acid-base imbalance, etc., whether there is excessive vagal tone, Carotid sinus syndrome.

1 Myocardial inflammation is most common for a variety of reasons, such as rheumatic, viral myocarditis and other infections.

2 vagus nerve excitement, often manifested as transient atrioventricular block.

3 drugs: such as digitalis and other antiarrhythmic drugs, most of the discontinuation of the drug, atrioventricular block disappeared.

4 various organic heart diseases such as coronary heart disease, rheumatic heart disease and cardiomyopathy.

5 high blood potassium, uremia and so on.

6 idiopathic conduction system fibrosis, degeneration, etc.

7 trauma, accidental injury during cardiac surgery or affecting atrioventricular conduction tissue can cause atrioventricular block.

an examination

Related inspection

ECG dynamic electrocardiogram (Holter monitoring)

1. According to medical history, clinical symptoms and signs.

2. ECG diagnostic criteria

(1) Find complete atrioventricular block in complete atrioventricular dislocation.

(2) According to the frequency of P (P', F, f) wave, the appearance phase and QRS morphology, time and frequency, P has no relationship with QRS, ventricular rate <60 times / min, preliminary identification of complete atrioventricular Disjointed is block-type, and there is interference, or block and interference coexist, mainly based on interference, or block-based. Most P waves can not be transmitted after a certain time after the T wave to the next P wave, and complete atrioventricular block can be diagnosed.

Laboratory examination: There is currently no relevant information.

Differential diagnosis

According to the typical ECG changes and according to the medical history, combined with clinical symptoms and signs is not difficult to make a diagnosis. In order to estimate the prognosis and determine treatment, it is necessary to distinguish between physiological and pathological atrioventricular block, atrioventricular bundle block and three-branch block, and the degree of block.

(1) Congenital complete atrioventricular block: Most of them coexist with congenital heart disease, and are associated with atrioventricular node, His bundle and his bundle branch dysplasia or defects. When combined with complex cardiac malformations, QRS broadening of the escape rhythm and prolongation of the QT interval, the prognosis is poor. Most patients with congenital complete atrioventricular block are asymptomatic. However, some patients may have syncope in the future and need to place a pacemaker, and a few may have sudden death. The response of the escape point to atropine and the recovery of atrioventricular escape stroke can help to estimate the likely symptoms and prognosis of the patient.

(2) Acute acquired complete atrioventricular block: Complete atrioventricular block caused by acute myocardial infarction, drugs, cardiac surgery, cardiac catheterization, and catheter ablation is often temporary. About 10% of cases are blocked in the His bundle, and the escape point is often located in the bundle-Pu's fiber. The frequency is <4 times/min, and it is not constant. The QRS wave is often wide and deformed. This type of injury is often irreversible and requires the placement of a pacemaker. In the original Xi-Pu system lesions, after applying some antiarrhythmic drugs, especially drugs that inhibit sodium fast channel, such as lidocaine, procainamide, and propiamine, second or third degree - Pu system block. Surgical treatment of aortic valve disease and ventricular septal defect, easy to damage the His bundle, the incidence of complete atrioventricular block after surgery is higher. In patients with a left bundle branch block, a complete atrioventricular block can be caused by a right bundle branch block during a right heart catheterization. In most cases, bundle branch injury due to cardiac catheterization is temporary and can be recovered in a few hours. When radiofrequency or DC ablation is used to treat tachyarrhythmias, complete atrioventricular block is also produced when catheter ablation approaches the atrioventricular node.

(3) Chronic acquired complete atrioventricular block: usually seen in a wide range of myocardial scar formation caused by different causes, especially arteriosclerosis, dilated cardiomyopathy and hypertension, idiopathic cardiac fibrosclerosis (Lev The disease and the fibrosis of the conduction system (Lenegre's disease) can lead to bundles and branching blocks that are progressively progressively aggravated. The mitral and aortic annulus calcification, degenerative changes, stenosis, and calcified bicuspid aortic valve can also cause severe atrioventricular block, and mainly involve the proximal end of the His bundle. Other diseases, such as sarcoidosis, rheumatoid arthritis, hemochromatosis, hereditary neuromuscular disease, syphilis, thyroid disease (hyperthyroidism or hypothyroidism) and atrioventricular metastases, can cause chronic complete atrioventricular Conduction block. These blocks tend to be permanent and often require an artificial cardiac pacemaker.

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