Third-level atrioventricular block (AV block), also known as complete heart block , is a medical condition in which nerve impulses produced in the sinoatrial node (SA node) in the cardiac atrium spread to the ventricle.
Because the drive is blocked, the pacemaker accessory in the lower chamber will usually activate the ventricle. This is known as escape rhythm . Because the pacemaker is also actively independent of the impulses produced in the SA node, two independent rhythms can be recorded on the electrocardiogram (EKG).
- P wave with regular P-to-P interval (in other words, sinus rhythm) represents the first rhythm.
- The QRS complex with regular R-to-R intervals represents a second rhythm. The PR interval will vary, since the hallmark of complete heart block is the lack of a clear relationship between the P waves and the QRS complex.
Patients with three-level AV block usually have severe bradycardia (low abnormally measured heartbeat), hypotension, and occasionally, hemodynamic instability.
Video Third-degree atrioventricular block
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Many conditions can cause a third-degree heart block, but the most common cause is coronary ischemia. Progressive degeneration of the heart's electrical conduction system can lead to a third-degree heart block. This can be preceded by first-level AV blocks, second-level AV blocks, bundle block blocks, or bifascicular blocks. In addition, acute myocardial infarction may present with a third level AV block.
An inferior myocardial infarct wall can cause damage to the AV node, leading to a third-degree heart block. In this case, the damage is usually temporary. Studies have shown that the third level heart block in the setting of inferior infarction myocardial infarction usually heals within 2 weeks. The escape rhythm usually comes from an AV junction, resulting in a complex and narrow escape rhythm.
An anterior myocardial infarct wall may damage the heart's distal conduction system, leading to a third-degree heart block. This is usually extensive, permanent damage to the conduction system, requiring permanent pacemaker to be placed. The escape rhythm usually comes from the ventricle, resulting in a complicated escape rhythm.
Third-level heart block may also be congenital and has been associated with maternal lupus. It is thought that maternal antibodies can cross the placenta and invade the heart tissue during pregnancy. The cause of congenital three-level heart block in many patients is unknown. Studies show that the prevalence of congenital third-level heart block is between 1 in 15,000 and 1 in 22,000 live births.
Hyperkalemia in those with previous heart disease and Lyme disease may also result in third-degree heart block.
Maps Third-degree atrioventricular block
Prognosis
The prognosis of patients with complete heart block is generally poor without therapy. Patients with 1 and 2-degree heart block are usually asymptomatic.
Treatment
Treatment in emergency situations ultimately involves the speed of electricity. Pharmacological management of suspected beta-blocker overdose can be treated with glucagon, calcium channel overdose treated with calcium chloride and digitalis toxicity treated with digoxin immune fab.
Third-level AV blocks can be treated using a dual-chamber pacemaker. This type of device usually listens to the pulse from the SA node through the lead in the right atrium and sends the pulse through the lead to the right ventricle at the right delay, pushing both right and left ventricle. Pacemakers in this role are usually programmed to establish a minimum heart rate and to record the atrial flutter and atrial fibrillation events, two common secondary conditions that may accompany the third-degree AV block. Because pacemaker correction in third-degree blocks requires full-time ventricular racing, potential adverse effects are pacemaker syndrome, and may require the use of a biventricular pacemaker, which has a third tin addition placed in a vein in the left ventricle, which is more coordinated than both ventricles.
The Joint Resuscitation and Resuscitation Council (UK) 2005 Guide states that atropine is a first-line treatment especially if there are bad signs, namely: 1) heart rate & lt; 40 bpm, 2) systolic blood pressure & lt; 100 mm Hg, 3) signs of heart failure, and 4) ventricular arrhythmias that require suppression. If this fails to respond to atropine or there is a potential risk of asystole, a transvenus pacemaker is indicated. Risk factors for asystole include 1) previous asystole, 2) complete heart block with wide complex, and 3) ventricular pause for & gt; 3 seconds. Mobitz Type 2 AV Block is another indication for pacing.
Like other forms of heart block, secondary prevention may also include drugs to control blood pressure and atrial fibrillation, as well as lifestyle and dietary changes to reduce risk factors associated with heart attacks and strokes.
See also
- Pacemakers
- Cardiac conduction system of the heart
- Electrocardiogram (ECG)
- The atrioventricular block
- First level AV block
- Second degree AV block
References
External links
- RN.ORG Nursing Resources
Source of the article : Wikipedia
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