I'm 27 and mom of four. I've been diagnosed with a 2nd degree av block. anyone know anything about this.

Background: 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. Electrocardiographically, some P waves are not followed by a QRS complex. Second-degree AV block is composed of 2 types: Mobitz I or Wenckebach block, and Mobitz II.

The Mobitz I second-degree AV block is characterized by a progressive prolongation of the PR interval, which results in a progressive shortening of the R-R interval. Ultimately, the atrial impulse fails to conduct, a QRS complex is not generated, and there is no ventricular contraction. The PR interval is the shortest in the first beat in the cycle, while the R-R interval is the longest in the first beat in the cycle.

The Mobitz II second-degree AV block is characterized by an unexpected nonconducted atrial impulse. Thus, the PR and R-R intervals between conducted beats are constant.

Pathophysiology: Mobitz type I block is caused by conduction delay in the AV node in 72% of patients and by conduction delay in the His-Purkinje system in the remaining 28%. The presence of a narrow QRS complex suggests the site of the delay is more likely to be in the AV node. However, a wide QRS complex may be observed with either AV nodal or infranodal conduction delay.

In Mobitz type II block, the conduction delay occurs infranodally. The QRS complex is likely to be wide, except in patients where the delay is localized to the bundle of His.

Frequency:

In the US: In the United States, the prevalence of second-degree heart block in young adults is reported to be 0.003%. However, the rate is significantly higher among trained athletes, occurring in 2.4% of athletes undergoing routine ECGs.

Mortality/Morbidity: Mobitz type I second-degree AV block is localized to the AV node, and thus is not associated with any increased risk of morbidity or death, in the absence of organic heart disease. In addition, when the block is localized to the AV node, no risk of progression to a type II second-degree block or complete heart block exists. However, when a Mobitz type I block occurs during an acute myocardial infarction, mortality is increased. Mobitz type II blocks do carry a risk of progressing to complete heart block, and thus are associated with an increased risk of mortality. Mobitz I blocks localized to the His-Purkinje system are associated with the same risks as type II blocks.