complete atrioventricular block
Introduction
Introduction to complete atrioventricular block Complete atrioventricular block, also known as third-degree atrioventricular block, means that due to an abnormal decrease in the conduction capacity of a part of the atrioventricular conduction system, all agitation from the atria cannot be transmitted down and cause complete atrioventricular separation. This is the most high degree of atrioventricular block. 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. basic knowledge Sickness ratio: 0.1% Susceptible people: over 50 years old Mode of infection: non-infectious Complications: syncope A-Syst Syndrome Sudden Death Syndrome Heart Failure Cerebral Embolism Arrhythmia
Cause
Complete atrioventricular block
Disease factor (88%)
Complete atrioventricular block is common in patients with coronary heart disease, especially in patients over 50 years old. The incidence of complete atrioventricular block in acute myocardial infarction is 1.8% to 8%, and that in Fuwai Hospital is 2.6%. The incidence of acute inferior myocardial infarction is 2 to 4 times higher than that of anterior myocardial infarction, and occurs mostly 1 to 4 days after onset. The duration can vary from several seconds to several days. Complete atrioventricular block occurs in the next In the wall, there is a first- or second-degree type I atrioventricular block before the occurrence of complete atrioventricular block; in the anterior wall infarction, before or after the occurrence of second degree II Type of atrioventricular block or right bundle branch block, a small number of patients from the beginning of the infarction showed complete atrioventricular block.
Other factors (12%)
In recent years, it is believed that many chronic or persistent complete atrioventricular block is caused by bilateral bundle fiber fibrosis of unknown cause. There is reported Lev disease (ie, left cardiac sclerosis, also known as cardiac stent disease, Interventricular sepsis or idiopathic bundle branch blockade, or bundled sclerosing degenerative disease) and Lenegre disease (also known as idiopathic bilateral bundle branch fibrosis, or indoor conduction system degeneration) 42% of the causes of complete atrioventricular block, ranking first, other such as dilated cardiomyopathy, 15% have complete atrioventricular block, viral myocarditis third degree block is not uncommon, usually temporary Occasionally, it can also become the initial manifestation and sudden death of patients with acute myocarditis. Acute rheumatic fever is more common, followed by second degree, third degree rare, in addition, such as congenital malformation, cardiac surgery, trauma, various infections. Myocarditis, cardiomyopathy, etc. can also lead to permanent complete atrioventricular block, due to drug poisoning, electrolyte imbalance, but most of the temporary complete atrioventricular block.
Pathogenesis
The mechanism of complete atrioventricular block is that the pathological absolute refractory period of the atrioventricular junction is extremely prolonged, occupying the entire cardiac cycle, and all atrial agitation falls within the absolute refractory period of the atrioventricular junction. All atrial agitation is blocked in the junction area and can not be transmitted to the ventricle. The ventricle is controlled by the chamber junction area or ventricular pacemaker point, forming an escape rhythm or ventricular escape rhythm, or atrioventricular conduction in the atrioventricular junction area. The system is interrupted by anatomical atrioventricular conduction due to surgical injury or congenital malformation, resulting in complete atrioventricular block.
Prevention
Complete atrioventricular block prevention
1. Active treatment of the primary disease, timely control, elimination of causes and incentives is the key to prevent the occurrence of this disease.
2. Familiar with the anatomy of the conduction system and strict ECG monitoring during cardiac surgery can reduce the incidence of this disease.
3. For patients with complete atrioventricular block, different measures are taken according to the block position and the rate of ventricular rate, such as slow ventricular rate, heart rate <40 times / min, and QRS wide and deformed, atrioventricular block The site is below the His bundle and has poor response to the drug. An artificial cardiac pacemaker should be placed to prevent the occurrence of cardio-cerebral syndrome.
4. Diet has a section, daily life is always, emotional comfort, work and rest, avoiding evil, appropriate physical exercise to enhance physical fitness.
Complication
Complete atrioventricular block complication Complications syncope A-S syndrome sudden cardiac death syndrome heart failure cerebral embolism arrhythmia
Complete atrioventricular block due to slow ventricular rate, may appear syncope, A-S syndrome, sudden cardiac death, heart failure, cerebral embolism and other complications.
1. Syncope According to statistics, cardiac irritation occurred in 19%.
2. A-S syndrome patients with complete atrioventricular block are more likely to develop this disease, especially the ventricular rate is below 35 ~ 40 times / min, ventricular beats intermittent time is too long or low pace pacing point no escape, As the cardiac output is significantly reduced, resulting in a drop in blood pressure, the brain blood cortical dysfunction caused by minimal blood flow in the brain tissue can not be maintained and A-S syndrome occurs.
3. Sudden cardiac death 20% to 30% of sudden cardiac death is arrhythmia or cardiac arrest.
4. Heart failure Complete atrioventricular block due to the loss of atrioventricular sequential contraction, resulting in a significant decrease in cardiac output; combined with the original heart disease, easy to induce heart failure.
5. Complete embolization of cerebral embolism can cause blood flow disorder, easy to form a wall thrombus, and once it falls off, it forms a cerebral embolism.
Symptom
Complete atrioventricular block symptoms Common symptoms Atrial-to-ventricular contraction... Twitching bradycardia, cerebral palsy, ischemia, sudden death, atrioventricular block, sudden cardiac death
1. Clinical manifestations : Patients with complete atrioventricular block are more than 50 years old. In young patients, complete atrioventricular block is more temporary, and more male patients than females.
Symptoms and hemodynamic changes in complete atrioventricular block depend on the degree of ventricular rate slowdown and myocardial lesions and functional status. When complete atrioventricular block, the atrial and ventricular phases are separated, atrial The loss of the auxiliary pump for ventricular contraction results 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 follow physical strength. Increased activity, better myocardial function, easy to increase blood output, so these patients often have no obvious symptoms, in patients with acquired complete atrioventricular block, most of them can be asymptomatic at rest, or have heart palpitations Feeling, during physical activity, there may be palpitations, dizziness, fatigue, chest tightness, shortness of breath, such as ventricular rate is too slow, especially if the heart has obvious ischemia or other lesions, or complicated by extensive acute myocardial infarction or severe acute myocarditis, Symptoms can be severe, heart failure or shock may occur, or the brain may be unresponsive or ambiguous due to insufficient blood supply to the brain, and then develop into syncope (incidence rate of up to 60%), A-S S syndrome, diastolic ventricular filling volume due to increased stroke volume, there may be widened pulse pressure and mild to moderate heart expansion.
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 pacemakers. The location 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, in most patients with anterior wall infarction complicated by third-degree atrioventricular block, hypotension, shock, and severe left heart failure may occur. Regardless of anterior or inferior wall infarction, if the QRS wave is suddenly widened, the ventricular rate is too slow, lower than Third-degree atrioventricular block of 40 times/min is prone to induce ventricular arrest or ventricular tachycardia or ventricular fibrillation. The anterior wall has a higher mortality rate than inferior myocardial infarction complicated with complete atrioventricular block. 2 times, but 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, the mortality rate Significantly increased, complete atrioventricular block complicated by acute myocardial infarction is mostly temporary, and only a few patients will never recover after infarction.
The rate of central electrocardiogram is slow, and the widening of QRS wave is 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.
2. Clinical classification
(1) Congenital complete atrioventricular block: most coexist with congenital heart disease, associated with atrioventricular node, His bundle and its bundle branch hypoplasia or defects, when combined with complex cardiac malformations, escape rhythm The QRS wide-width malformation and QT interval prolongation suggest a poor prognosis. Most patients with congenital complete atrioventricular block are asymptomatic, but some patients may have syncope in the future and need to place a pacemaker. A few may die suddenly. The response of the beat to the atropine and the recovery time of the atrioventricular escape escape can help to estimate the possible 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 In 10% of cases, the block can be in the His bundle, 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 damage is often irreversible. Need to place a pacemaker, the original Xi-Pu system lesions, in the application of certain antiarrhythmic drugs, especially drugs that inhibit sodium fast channel, such as lidocaine, procainamide, propiamine, can Two or three degrees of He-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, the original left In patients with bundle branch block, complete atrioventricular block may be caused by right bundle branch block during right heart catheterization. In most cases, bundle branch injury caused by cardiac catheterization is temporary. Recovery after hours, RF or DC ablation When the speed arrhythmias, when close to the AV node ablation catheter also can produce complete atrioventricular block.
(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 Disease and conduction system fibrosis (Lenegre disease) can lead to chronic progressive aggravation of bundle branch and branch block, mitral and aortic valve ring calcification, degenerative changes, stenosis, calcified bicuspid aortic valve Can also cause severe atrioventricular block, and mainly involving the proximal end of the His bundle, other diseases, such as sarcoidosis, rheumatoid arthritis, hemochromatosis, hereditary neuromuscular disease, syphilis, thyroid disease (hyperthyroidism Chronic complete atrioventricular block can cause chronic complete atrioventricular block, which tends to be permanent and often requires an artificial cardiac pacemaker.
Examine
Complete atrioventricular block
Electrocardiogram examination
(1) ECG characteristics of typical complete atrioventricular block:
1 Atrial (P) and ventricular (QRS) are each excited, irrelevant, complete atrioventricular separation, PR interval is not fixed, atrial rate is faster than ventricular rate.
2 atrial rhythm can be sinus rhythm, atrial tachycardia, atrial flutter or atrial fibrillation (Figure 1).
3 ventricular rhythm can be atrioventricular transfer escape rhythm (QRS wave normal), ventricular rate 40 ~ 60 times / min (Figure 1) or ventricular escape rhythm (QRS wide deformity), ventricular rate 20 ~ 40 times / min (Figure 2), the ventricular rhythm is generally ruled, but also irregular.
(2) A detailed description of a typical complete atrioventricular block ECG:
1 Atrial rate is faster than ventricular rate is one of the important features of complete atrioventricular septal separation caused by complete atrioventricular block, which can rule out other primary arrhythmias that can cause complete atrioventricular septum, such as: A. Complete atrioventricular separation due to slowing of the frequency of the sinus node; B. Complete atrioventricular separation caused by the frequency of the junction or ventricular frequency; C. Caused by sinus block Complete atrioventricular separation; D. Complete atrioventricular separation resulting from a combination of the three different causes described above.
2 Atrial rhythm is mostly controlled by sinus node, followed by atrial fibrillation.
3 Atrioventricular junction escape rhythm occurs in complete atrioventricular block because the block is located in the atrioventricular node, and the escape rhythm usually originates from the atrioventricular nodal (NH zone) and the His bundle. The lower part is characterized by a ventricular rate of 40 to 55 times/min from the lower part of the atrioventricular node or the upper part of the His bundle, occasionally slower or slightly faster, and the QRS wave is normal (narrow); complete His bundle In the internal block, the escape point is often located in the lower part of the His bundle, and the ventricular rate is mostly below 40 beats/min (30-50 times/min), and the QRS wave pattern is normal.
4 ventricular escape rhythm occurs in complete atrioventricular block, because complete block occurs under the His bundle (bilateral bundle level), ventricular escape rhythm usually originates from His bundle bifurcation The following bundles or branches can be originated from the peripheral Purkinje fibers, which are characterized by: the ventricular rate is mostly 25-40 times/min, even slightly faster, or slower to 15-20 times/min, the QRS wave is increased. Wide (>0.11s) and deformed.
The QRS wave of ventricular escape rhythm is like the left bundle branch block diagram, then the pacing point is located in the right bundle branch, the QRS wave is in the right bundle branch block pattern, and the ECG axis is not biased, then the pacing point is located in the left bundle branch. If the electrocardiogram axis is significantly left-biased, the pacemaker is located at the left posterior branch; if the motor axis is significantly right-biased, the pacemaker is located at the left anterior branch.
5 The ventricular rate of complete atrioventricular block is generally regular, but the escape rhythm can also be irregular. For ventricular escape rhythm or atrioventricular transfer escape rhythm, the difference of RR spacing is >0.12s, ie Can be diagnosed as ventricular arrhythmia.
6 If ventricular capture occurs, even if there is only one, it is not complete atrioventricular block, should be diagnosed as a high degree of atrioventricular block, so the ECG should be traced longer, and carefully observed.
7 There were reports of electrophysiological examination of patients with complete atrioventricular block. It was found that 36% of patients had atrial capture, QRS waves were retrogradely transmitted to the atria, and retrograde P-waves were present; in addition, 17% were concealed to In the atrioventricular junction (H wave after V wave), there are up to 20% of patients with reverse conduction in His bundles.
(3) Special types of complete atrioventricular block ECG:
1 The phenomenon of hooking in complete atrioventricular block: In complete atrioventricular block, the atrium is usually under the control of the sinus node, the atrial rate is faster, the ventricular rate is slower, but the two frequencies of the atria and ventricles Different rhythm points can cause obvious positive chronotropic effects, that is, the ventricular heart rate can be temporarily increased when the ventricle emits excitement, and sinus arrhythmia is generated. The PP interval with QRS wave on the electrocardiogram is less than the QRS. The PP interval is short, and the P wave after the QRS wave often comes early. It is called the temporal sinus arrhythmia. It is actually the positive chronotropic effect of the hook phenomenon (Fig. 3). At the end of the atrioventricular block, about 42% of the ventricular waves can significantly advance the subsequent sinus P wave, and about 54.5% of the ventricular waves make the subsequent P wave slightly or not constantly shortened, but also 3.5%. The ventricular wave can delay the subsequent P wave, and the most obvious positive variability in the third degree block often occurs in the P wave which occurs 0.3 to 0.4 s after the QRS wave, and the PP interval is the shortest. The sinus P wave that appears 0.6 to 1.0 s after the ventricular wave is often pushed back, and the PP interval is prolonged.
2 complete atrioventricular block with slow escape rhythm: the frequency of atrioventricular transfer escape rhythm is less than 40 beats / min, ventricular escape rhythm frequency is less than 25 times / min, this situation reflects escape The self-discipline of heart rhythm is low, and it is easy to develop into A-S syndrome, ventricular fibrillation, and ventricular arrest (Fig. 4, 5).
3 complete atrioventricular block with faster ventricular rate: more common in young patients, congenital complete atrioventricular block, caused by digitalis poisoning, after the onset of A-S syndrome, ventricular rate Up to 100 times / min, and soon became slow.
4 Complete atrioventricular block with large T wave after syncope: T wave can be inverted or erect, more common after ventricular arrest, the first T wave is particularly high, and then gradually lower, may be caused by ventricular dysfunction The nerve is extremely excited or related to myocardial ischemia.
5 Complete atrioventricular block with room conduction: Complete atrioventricular block was previously considered to be a two-way block, and it is believed that the reverse conduction function is not necessarily present when the atrioventricular conduction system undergoes a forward conduction block. With the same degree of blockage, it can be seen on the electrocardiogram that the atrium captures the retrograde P-wave or the atrial fusion wave, and the RP-interval is relatively fixed, which can also make the sinus or atrial rhythm reform.
6 complete atrioventricular block with escape rhythm efferent block: in complete or high atrioventricular block, the ventricle is controlled by the escape rhythm, if this secondary pacing point occurs, block may lead to The cardiac arrest time is prolonged and rarely seen.
2. Electrophysiological examination features complete atrioventricular block The His-beam electrical map is used to locate the diagnostic criteria of the block (combined with the surface electrocardiogram).
(1) Complete AH block (atrioventricular node block): about 46% of complete atrioventricular block, His's beam electrogram shows no H wave after A wave, and H wave before V wave, The HV interval is constant, accompanied by a normal QRS wave on the surface ECG or an existing QRS wave.
(2) Complete BH block (Intrapulmonary bundle block): About 21% of complete atrioventricular block, His's beam diagram shows:
1 "split H wave", each A wave is followed by H wave, AH interval is constant, V wave is H' wave front, H'-V interval is also constant, but there is no fixed relationship between H and H' wave They represent the His bundle potential at the proximal and distal ends of the block, respectively.
2 There is H wave after A wave in the distal block of His bundle, and the AH interval is constant, but there is no H' wave in front of V wave, accompanied by normal or abnormal QRS wave on the surface electrocardiogram. If it is the latter, its time limit The morphology must be the same as the QRS complex before the complete atrioventricular block.
3 Complete HV block (bilateral bundle branch block under His bundle): about 33% of complete atrioventricular block, His's beam electrogram shows H wave after A wave, constant AH interval The V wave is completely unrelated to the AH wave. The surface electrocardiogram QRS wave widens the deformity without exception (in one side bundle branch block or indoor block type), and its morphology is different from the QRS wave shape that can perform atrioventricular conduction in the past. It is indicated that the retardation zone is below the His bundle branch, ie within the bundle system.
Diagnosis
Diagnosis and diagnosis of complete atrioventricular block
Diagnostic criteria
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 are compared, P has no relationship with QRS, ventricular rate is <60 times/min, and the complete atrioventricular compartment is initially identified. Disconnection is blocky, and there is interference, or block and interference coexist, mainly based on interference, or blockade. Most P waves are located after T wave and after the next P wave. Can not be passed down, can be diagnosed with complete atrioventricular block.
Differential diagnosis
Complete atrioventricular block should be identified with the following conditions:
1. Interfering complete atrioventricular dislocation and complete atrioventricular block showed atrial septal separation, PP rule, RR rule, PR no fixed relationship, the two identification points are as follows:
(1) The rate of interfering atrioventricular dislocation is greater than the room rate (ie, QRS waves are more than P waves), the room rate is generally faster, greater than 60 times/min, and the room rate is greater than the room rate (ie, P waves are more than QRS waves). The rate is slower, generally less than 60 times / min.
(2) The QRS wave of interfering atrioventricular dislocation is mostly supraventricular (normal), and the QRS wave is wide and deformed with complete atrioventricular block.
2. Complete atrioventricular dislocation - Interference and block coexisting ventricular rate between 60 and 100 beats / min, P wave occurring in the middle of diastole can not capture the ventricle, consider the complete compartment caused by the coexistence of two factors Out of touch.
