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First-degree AV block and Mobitz I second-degree block are often thought to be just normal, benign, conditions in people, and do not often result from a severe underlying condition. [1] Mobitz II second-degree block and third-degree AV block are not normal variants and are associated with an underlying condition. [9]
The atrioventricular block can be first degree or much more severe like a complete atrioventricular block (third degree). [5] [6] In addition, several changes in the ECG can be detected. [5] Other manifestations of the congenital heart block can be related to the impact of the maternal autoantibodies in the autoimmune-mediated CHB.
The cause of congenital third-degree heart block in many patients is unknown. Studies suggest that the prevalence of congenital third-degree heart block is between 1 in 15,000 and 1 in 22,000 live births. [citation needed] Hyperkalemia in those with previous cardiac disease [8] and Lyme disease can also result in third-degree heart block. [9]
There are three basic types of AV nodal block: First-degree AV block; Second-degree AV block. Type 1 second-degree AV block (Mobitz I), also known as a Wenckebach block [5] Type 2 second-degree AV block (Mobitz II), also known as a Hay block – due to a block in or below the bundle of His [5] Third-degree AV block (complete heart block)
First degree AV block does not generally cause any symptoms, but may progress to more severe forms of heart block such as second- and third-degree atrioventricular block. It is diagnosed using an electrocardiogram , and is defined as a PR interval greater than 200 milliseconds. [ 1 ]
If there is a blockage between the AV node and the SA node, the atria may not contract at all. [6] [7] Junctional rhythm can be diagnosed by looking at an ECG: it usually presents without a P wave or with an inverted P wave. Retrograde, or inverted, P waves refers to the depolarization from the AV node back towards the SA node. [8]
This may be caused by a slowed signal from the sinus node (sinus bradycardia), by a pause in the normal activity of the sinus node (sinus arrest), or by blocking of the electrical impulse on its way from the atria to the ventricles (AV block or heart block). Heart block comes in varying degrees and severity.
Bradycardia, also called bradyarrhythmia, is a resting heart rate under 60 beats per minute (BPM). [1] While bradycardia can result from various pathological processes, it is commonly a physiological response to cardiovascular conditioning or due to asymptomatic type 1 atrioventricular block.