heart block in the elderly
Introduction
Introduction to heart block in the elderly The cardiac conduction system is composed of sinus node, atrioventricular node, atrioventricular velocity (His beam), left and right bundle branches and branches thereof. It plays the role of cardiac pacing and conduction impulse to ensure the atrial ventricular co-systolic contraction. Impulsive conduction can occur in any part of the heart conduction system, such as between the sinus node and the atrium, called sinus block; between the atrium and the ventricle, called atrioventricular block; Intraventricular block; located in the ventricle, called indoor conduction block. basic knowledge The proportion of illness: 22% of the probability of being over 50 years old Susceptible people: the elderly Mode of infection: non-infectious Complications: syncope, sudden death
Cause
The cause of heart block in the elderly
(1) Causes of the disease
Age is an important factor affecting the incidence of heart block, especially in the elderly with organic heart disease, the gender itself has little effect on the conduction block, a small number of congenital atrioventricular block Family genetic predisposition, the majority of sinus conduction block is seen in organic heart disease, common sinus and coronary heart disease in the elderly, atrioventricular block is mainly seen in various causes of left atrial hypertrophy or enlargement, such as rheumatic heart Disease, mitral stenosis and primary cardiomyopathy, also common in acute and chronic ischemia of atrial muscle, atrial infarction and hyperkalemia or quinidine and other drugs, in addition, atrial muscle due to fibrosis, fat infiltration or Degenerative lesions such as amyloidosis, intraventricular conduction block, especially coronary heart disease.
(two) pathogenesis
1. Sick sinus syndrome: related to sick sinus syndrome, see elderly arrhythmia.
2. Intraventricular block: refers to the impulse of sinus node in the atrial conduction time prolonged or interrupted, divided into two types of incomplete and complete conduction block.
(1) Incomplete intraventricular conduction block: mainly seen in various causes of left atrial hypertrophy or enlargement, such as rheumatic heart disease, mitral stenosis and primary cardiomyopathy, also common in acute and chronic atrial muscle Ischemia, atrial infarction and hyperkalemia or quinidine and other drugs, in addition, atrial muscle due to fibrosis, fat infiltration or amyloidosis and other degenerative diseases, can also cause prolonged conduction time in the room.
(2) Complete intraventricular block (ie atrial separation): refers to complete blockade of the left and right heart chambers, or complete conduction between a part of the atrium and other parts, at this time on either side of the atrium or The two parts of the lateral atrium are controlled by a single pace point.
At heart block, atrioventricular block (AVB) is one of the most common blockades, which means that atrial conduction is caused by one or more sites in the atrioventricular conduction system. When the ventricle is delivered, there is a phenomenon that the conduction is delayed, or some or even all of it cannot be transmitted. There are also some functional atrioventricular block, which is a transient change and does not belong to the pathological pathological disorder.
3. The pathological basis of atrioventricular block The atrioventricular block most of them have the pathological basis of organic heart, generally divided into two categories:
(1) Congenital atrioventricular block: This type is more common in children. It is a conduction block that is found at birth or shortly after birth. It can be caused by aging in the elderly, and the symptoms are aggravated due to aging of the conductive tissue. The stagnation site is mostly in the atrioventricular junction, the QRS complex is normal, and the ventricular rate is 45-80 beats/min, which is more common in congenital heart disease or due to poor development of the conduction system.
(2) Acquired atrioventricular block: acute and chronic two kinds of atrioventricular block.
1 acute atrioventricular block: common disease because of acute myocardial infarction and myocarditis, due to anatomical reasons, inferior myocardial infarction is easy to merge with atrioventricular block, transient, self-recovery; anterior wall myocardial infarction caused by the room Ventricular block, mostly low block, permanent, difficult to recover, the mechanism of atrioventricular block in inferior myocardial infarction may be related to the following comprehensive factors:
A. Atrioventricular node is temporarily ischemic and hypoxic.
B. Local potassium ion accumulation.
C. Increased vagal tone.
D. Edema of the atrioventricular node after infarction and inflammatory infiltration lead to the occurrence of conduction block.
E. Negative conduction of ischemic metabolites leads to cardiac arrest, and atrioventricular block caused by viral myocarditis is not easy to disappear.
2 chronic atrioventricular block: the most common cause is idiopathic bundle branch fibrosis, in addition to chronic myocardial ischemia, cardiomyopathy, conduction system calcification, etc., the nature of idiopathic bundle branch fibrosis is the conduction system Gradually fibrosis, many patients have left ventricular hypertrophy or focal scar, but the myocardial is basically unaffected, therefore, the disease is characterized by atrioventricular conduction disorder rather than heart failure.
Prevention
Elderly heart block prevention
Heart blockage in the elderly should be clear, cause active treatment, and severe symptoms associated with clinical syncope, bradycardia or cardiac arrest. The pacemaker must be placed immediately.
Complication
Complications of heart block in the elderly Complications
When the heart block is severe in the elderly, syncope, cardiogenic syndrome, and even sudden death can occur.
Symptom
Symptoms of heart block in the elderly Common symptoms The threshold of fatigue ventricular fibrillation reduces dizziness, incomplete internal block, sudden fatigue, shortness of breath, low blood pressure, no obvious pre-cardiac pulsatile hyperkalemia
Symptom
In addition to the effects of the original heart disease and cardiac function, the symptoms of atrioventricular block patients depend on the extent and location of the block.
(1) Asymptomatic: seen in one-time atrioventricular block, this type of prognosis is good, second-degree type I atrioventricular block, or some chronic intermittent atrioventricular block.
(2) Symptoms: When the second degree type II atrioventricular block is greater, if the proportion of blocked atrial waves is larger (such as 3:2 conduction in the atrioventricular), especially at high atrioventricular block, Symptoms of bradycardia, dizziness, fatigue, chest tightness, shortness of breath and decreased heart function due to decreased ventricular rate, the symptoms of third-degree atrioventricular block are more obvious, and the hemodynamic effects are dependent on the ventricular escape frequency. Fast and slow, III degree atrioventricular block in the upper part of the His bundle branch, has little effect on hemodynamics, although the patient is weak, dizziness during activity, but not syncope; occurs in His bundle The lower third-degree atrioventricular block below the fork has a significant effect on hemodynamics, and patients may experience syncope, cardiogenic hypoxia syndrome, and even sudden death.
(3) Atypical symptoms, some patients have some atypical symptoms, such as general malaise, fatigue or hypotension, etc., need further examination to confirm the diagnosis.
2. Signs
(1) Some patients with one-degree atrioventricular block may have no signs.
(2) Once atrioventricular block: physical examination can find that the first heart sound of the apex is weakened. This is due to the delay of ventricular contraction, which makes the blood filling in the heart relatively full. The atrioventricular valve has floated at a distance before closing. The position of the closing point is relatively close, so the leaflet tension is low when closed, and the vibration generated by closing is small.
(3) second degree atrioventricular block: Venturi type second degree atrioventricular block, cardiac auscultation has intermittent, but there is no premature beat before the interval, the first heart sound can change with the change of PR, two Degree II type atrioventricular block may have intermittent leakage, but the first heart sound intensity is constant, and when the atrioventricular is 3:2 conduction, the auscultation may resemble the second law of paired premature contraction.
(4) Third-degree atrioventricular block: its specific signs are slow and regular ventricular rate, accompanied by the first heart sound intensity, especially the first heart sound that can suddenly increase, that is, "cannon sound "The second heart sound can be normal or abnormally divided, such as atrial and ventricular contraction occur simultaneously, a large "A" wave appears in the jugular vein.
3. ECG and clinical significance
(1) sinus conduction block: Because the tissue around the sinus node can not cause the sinus node to stimulate the excitement as usual, so that the time to reach the atrium is prolonged or unable to reach, causing atrial and ventricular arrest, called sinus conduction Blocking, one, two, three degrees.
1 once atrioventricular block: because the surface electrocardiogram can not show the sinus node potential, it is impossible to establish the diagnosis of the first sinus block.
2 second degree atrioventricular block:
The A.I type, ie, the Wen's block, exhibits a progressive shortening of PP until a long PP interval occurs, which is shorter than twice the basic PP interval.
B. Type II block: This type is characterized by a gradual extension of the sinus node conduction time. The electrocardiogram shows a constant PP spacing before the leak, and the long PP spacing with atrial leakage is just a multiple of the short PP spacing.
3 third degree sinus block: the activation of all sinus node can not be transmitted into the atria, there is no sinus P wave on the electrocardiogram.
Clinical manifestations: The vast majority of sinus conduction block is seen in organic heart disease. The most common cause in the elderly is sick sinus and coronary heart disease. Once sinus conduction block has no clinical symptoms, second degree or more, right eye The influence of hemodynamics determines the severity of clinical symptoms. If the III degree sinus block is not escape rhythm, sudden cardiac arrest may occur.
(2) Intraventricular conduction block: When the sinus node is transmitted to the atrium, the conduction delay causes the P wave to broaden and increase.
1 incomplete intraventricular block:
The AP wave widening time limit is 0.12s, and the notch is obvious. It often appears as a P-wave setback and is high.
B. Intermittent high-point P wave occurs in the regular PP interval, which is not related to breathing. The cause of no lung disease is mostly due to right atrial block.
2 complete intraventricular block:
The AP wave disappears, the QRS complex is broad and deformed, and the T wave is symmetrical and towering.
B. The rate is slow, about 60 times/min.
C. Seen in hyperkalemia.
(3) Atrioventricular block: Atrioventricular block refers to the conduction disorder between the atrioventricular conduction system, which is a pathological phenomenon.
1 Once atrioventricular block (atrioventricular conduction delay): AP-R interval 0.21s (adult), B. The same patient PR interval dynamic change 0.04s (without significant changes in heart rate), C. The PR interval of the borderline heart rate was >0.16 s, and the DP-R interval exceeded the normal maximum value of the corresponding heart rate (Fig. 1).
Electrophysiological examination features:
2 patients with atrioventricular block patients with QRS wave is not widened, conduction delay occurs in the atrioventricular node, electrophysiological examination only AH time prolonged, and even HV prolonged, can also be manifested as once atrioventricular block, such as patients There is a degree of atrioventricular block, while there is a bundle branch block, conduction block occurs in any part of the conduction system, but HV prolongation is mostly seen in the left bundle branch block.
3 second degree atrioventricular conduction stagnation is divided into second degree type I and second degree type II atrioventricular block:
A. Second degree type I atrioventricular block (Wenshi phenomenon):
ECG performance: aP-R interval gradually extended until ventricular leakage occurred; the increase of bP-R interval decreased gradually, resulting in a gradual shortening of PR interval; c. The first PR interval after ventricular leakage was normal The second PR interval has the largest increment; d. The long PR interval with ventricular leakage is less than twice the short PR interval.
B. Second degree type II block (also known as Mohs type II): less common than Wen's phenomenon, the electrocardiogram is: P wave periodic sudden can not be transmitted and ventricular leakage, and all PR intervals before and after shedding It is constant, normal or prolonged, and the long PR interval with ventricular leakage is a multiple of the short PR interval.
Electrophysiological examination: patients with second-degree type I atrioventricular block, such as QRS wave does not widen, block usually occurs in the atrioventricular node, AH time gradually extended until there is a long gap, and occasionally the His bundle buck It can be seen that the H-wave splits gradually and gradually falls off. At this time, the first part of the A wave, without the second part of the H wave, the surface electrocardiogram can also identify that the conduction block occurs at the atrioventricular node or the His bundle. After atropine is given, the blockage of His bundle will be more severe, and after massage of the carotid sinus, the block of His bundle will be relieved. If it occurs above the block of the atrioventricular node, the stimulation result is just the opposite, if the atrioventricular conduction Blocking combined bundle branch block, block may occur in the atrioventricular node, 75% of cases block at the atrioventricular node, and 25% occur at the atrioventricular node.
4 third degree atrioventricular block (ie complete atrioventricular block)
ECG performance: 1 room rate is uniform, room rate is uniform, room rate (P wave)> room rate (QRS wave), room rate is usually below 60 times / min, P wave is completely unrelated to QRS wave, 2QRS wave group morphology It is related to the height of the block, the ventricular rhythm point is generally not widened, the frequency is 40~60 times/min, the performance is stable, the rhythm point is in the heart chamber, the QRS complex is wide and deformed, the frequency is low, 30~40 times/min, the performance is unstable. .
Examine
Elderly heart block
During each cardiac cycle, the heart is excited by the pacemaker, the atria, and the ventricle. With the changes in bioelectricity, various forms of potential change patterns (ECG) are extracted from the body surface by electrocardiograph. An electrocardiogram is an objective indicator of the process of cardiac excitability, transmission, and recovery. Complete intraventricular block is seen in hyperkalemia.
The HV extension occurs in the His bundle beam diagram when the three blocks are blocked.
Diagnosis
Diagnosis and differential diagnosis of heart block in the elderly
According to the typical electrocardiogram changes combined with clinical manifestations, it is not difficult to make a diagnosis. In order to estimate the prognosis and determine the treatment, it is necessary to distinguish between physiological and pathological atrioventricular block, atrioventricular bundle branch block and three-branch block, and resistance. The degree of stagnation.
The prolongation of PR interval or ventricular leakage in individual or a few heartbeats is caused by physiological blockade, such as premature atrial, borderline escape, bidirectional blockage of premature contraction, and ventricular capture. , repeated heartbeat, etc., prolonged ventricular premature contraction occult conduction caused by PR extension (impulse reversed to the end of the atrioventricular node, not transmitted to the atria, and therefore no reverse P wave); but the atrioventricular node tissue due to conduction impulse In the refractory period, the next impulsive conduction delay is also a physiological block, and the atrial rate of supraventricular tachycardia is more than 180 beats/min with atrioventricular block, and atrial fibrillation due to occult conduction. Irregular ventricular rhythm is caused by physiological block, and another manifestation of physiological block, interfering atrioventricular septum should be carefully identified from the atrioventricular septum caused by complete atrioventricular block. The atrial rate is close to the ventricular rate and the ventricular rate is mostly slightly higher than the atrial rate; the latter ventricular rate is slower than the atrial rate.
