When there is a partial or complete interruption in the cardiac electrical conduction system
- Varies depending on the relationship between the P wave and the QRS complex
The location of the block and the resulting patients symptoms
First degree heart block
Caused by a delay in the conduction of an electrical impulse between the atria and the bundle of his.
- Occurs when there is a partial interruption or slowing in the conduction of an electrical impulse through the AV node
What can first degree heart blocks be caused by?
MI, and medication such as beta blockers
Second degree heart block type 1
Characterized by progressive lengthening of the PR interval until the loss of s QRS complex occurs.
- Interruption becomes longer with each impulse delaying the depolarization of the ventricles
What can cause a second degree type 1 heart block?
MI, infection, or drug toxicity
Second degree heart block type 2
Occurs when there is a intermittent interruption in the electrical conduction system near or below the AV node
- can occur in any rhythm that has P waves followed by a QRS complex
What can a second degree type 2 heart block be caused by?
MI, heart disease, or drug toxicity
Third degree heart block
Occurs when the electrical impulse is completely blocked between the atria and the ventricles.
- Atria and ventricles function independently as if they were two separate hearts
What causes 3rd degree heart blocks?
MI or severe heart disease
Bundle branch block
Interruption in the cardiac electrical conduction system of either the right or left bundle branch.
- Not a true block
What can cause a bundle branch block?
Heart disease or MI