Heart Block is a condition in which there is failure in the conduction of electrical impulses from the naturalpacemaker (Sinoatrial node) through the heart, which can lead to a slowing of the pumpaction.In some cases, a pacemaker is implanted to treat the abnormally slow heartbeat that may result from this condition. Third degree heart block , also known as complete heart block , is a disease of the electrical system of the heart , in which the impulse generated in the top half of the heart (typically the SA node in the right atrium ) does not propagate to the left or right ventricles. Thus, the ventricles beat very slowly—less than 50 beats per minute and sometimes as slowly as 30 beats per minute. Third-degree heart block is a serious arrhythmia that can affect the heart's pumping ability. Fatigue, dizziness, and fainting are common. When the ventricles beat faster than 40 beats per minute, symptoms are less severe.
A heart block denotes a disease in the electrical system of the heart. In this condition, the electrical signals that stimulate heart muscle contractions are partially or totally blocked between the upper chambers (atria) and the lower chambers (ventricles). Electrocardiographically, some P waves are not followed by a QRS complex. However, the disorder also occurs in people with rheumatic fever, sarcoidosis that affects the heart, or other structural heart diseases. Heart rate and rhythm are normal, and there may be nothing wrong with the heart. Certain heart medicines such as digitalis can slow conduction of the impulse from the atria to the ventricles and cause first-degree AV block. In second-degree heart block, only some electrical impulses reach the ventricles.The heart may beat slowly, irregularly, or both. Some forms of second-degree heart block progress to third-degree heart block.This condition is less common than Type I, but is generally more serious.
Heart block occurs when there is an interruption in the electrical conduction of the heart.First-degree heart block, or first-degree atrioventricular (AV) block, is defined as prolongation of the PR interval on the ECG to more than 200 msec. First-degree heart block rarely causes any symptoms or problems, and well-trained athletes may have this. Medications can contribute to the condition. No treatment is generally necessary for first degree heart block. Second-degree heart block, or second-degree atrioventricular (AV) block, refers to a disorder of the cardiac conduction system in which some atrial impulses are not conducted to the ventricles. This signal spreads across the muscles of these chambers, making them contract, squeezing blood into the ventricles or lower chambers. Third degree heart block is when the electrical signals don't travel between the upper and lower chambers of the heart. It's most common in adults with heart disease, and can have serious complications, such as heart attack, if it's not treated with a pacemaker. This means they do beat and pump blood, but at a slower rate and more inefficiently than if by an impulse from the upper chambers.
Causes of Heart Block
The common Causes of Heart Block :
- Mobitz I block can occur in infants and young children with structural heart disease (eg, tetralogy of Fallot) and in individuals of any age following valvular surgery (especially mitral valve).
- Class Ic antiarrhythmics (eg, flecainide, encainide, propafenone)
- Mobitz I block can occur in individuals with high vagal tone, such as athletes or young children.
- Heart attack
- Coronary artery disease
- Valvular heart disease (disease of the heart valves).
- Sinus node disease
- Coronary thrombosis (sudden blockage in the heart blood vessels)
- Myocarditis (inflammation of the muscle in the wall of the heart)
- Drugs (especially those drugs that increase the refractory time of the AV node, thereby slowing conduction)
Symptoms of Heart Block
Some are common Symptoms of Heart Block :
- Syncope (fainting)
- shortness of breath
- Slow heartbeat
- palpitations (when you notice the irregular heartbeat)
- Lightheadedness or dizziness
- fainting or light-headedness Dizziness or feeling light-headed.
- Palpitations, which can be skipping, fluttering or pounding in the chest
Treatment of Heart Block
- If the patient is symptomatic, standard advanced cardiac life support (ACLS) guidelines for bradycardia, including the use of atropine and transcutaneous pacing, is indicated.
- Patients with suspected myocardial ischemia should be treated with an appropriate anti-ischemic regimen.
- A temporary pacemaker may be used in an emergency until a permanent one can be implanted.
- Treatment may include adjusting the medications or in certain cases, such as Mobitz type II block and complete heart block, a pacemaker may be necessary.
- This treatment involves using drugs such as streptokinase or tissue plasminogen activator to dissolve blood clots and increase the flow of blood to the heart.
- Some institutions recommend insertion of a transvenous pacemaker for all new Mobitz type II blocks, although this practice varies greatly from institution to institution.