Atrioventricular BlockAtrioventricular block occurs frequently when the conduction system presents an idiophatic fibrosis. Av block in fact is a deficiency at the conductor level between atria and the ventricles. Idiopathic fibrosis and sclerosis of the conduction system cause AV block in about 50%.
There are 3 degrees of atrioventricualar block . The first degree is has almost no symptoms and in general it requires no treatment. But when this condition is caused by drug use or by another heart problem it requires further investigations. The first degree of Av block is common for athletes and young patients. A clue in this situationmay be more than 20 seconds of PR interval.
The second degree of Av block has two types. Mobitz 1 (or type 1) is more common in young and athletic patients. The PR interval is prolonged progressively with dropped beats until the atrial impulse is not conducted and the QRS complex is dropped. Treatment is necessary only if the block causes bradycardia with obvious symptoms . In this case, the treatment will be a pacemaker insertion. The second degree is pathologic, the problem generally occurs in the bundle branches. In 20% case it can appear in the His. The symptoms are not likely to appear. If they appear though, the patient may experience presyncope, and syncope, light-headedness. The difference between Mobitz 1 and Mobitz 2 are hard to make because 2 P waves are not conducted in a row.
The third type of Av block is appears when the atria and ventricles have no electrical communication and P waves and QRS complexes have no connection . The heart block is complete. A ventricular pacemaker helps keeping the cardiac function. T he risk of asystole-related syncope and death is higher when low escape rhythms appear. In general the majority of patients require a pacemaker. If the block is caused by use of drugs, it’s important to stop the drug effect. Block caused by acute inferior MI usually reflects AV nodal dysfunction and may resolve alone after several days. Immediate transvenous pacemaker insertion is needed when the block is caused by anterior MI and it reflects extensive myocardial necrosis involving the His-Purkinje system. Most patients that suffer from this third type of Av block need a permanent pacemakerearly in life .
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