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All about heart block first degree heart block second degree heart block third degree or complete heart block causes of heart block symptoms of heart block diagnosis of heart block treatments for heart block arrhythmias (abnormal heart rhythms) {bundle branch block cardiac arrhythmia atrial fibrillation atrial flutter supraventricular tachycardia sick sinus syndrome ventricular arrhythmias ventricular tachycardia ventricular fibrillation heart block Brugada syndrome long QT syndrome short QT syndrome Wolff-Parkinson-White syndrome (WPW syndrome)}

What is second degree heart block?

Second degree heart block is a disease of the electrical conduction system of the heart. If this term is used without a qualifier, it is usually assumed to be regarding disease of the atrioventricular node (AV node). However it is possible to have a second degree heart block involving the sinoatrial node (SA node) as well. In this condition, some signals from the atria

don't reach the ventricles. This causes "dropped beats." On an electrocardiogram, the P wave isn't followed by the QRS wave, because the ventricles weren't activated. There are two distinct types of second degree heart block, called type 1 and type 2. The distinction is made between them because type 1 second degree heart block is considered a more benign entity than type 2 second degree heart block.

Type 1 second degree heart block, also known as Mobitz I heart block or Wenckebach phenomenon, is a disease of the AV node. Mobitz I heart block is characterized by progressive prolongation of the PR interval on the electrocardiogram (EKG) on consecutive beats followed by a blocked beat (dropped QRS complex). After the dropped QRS complex, the PR interval resets and the cycle repeats. One of the baseline assumptions when determining if an individual has Mobitz I heart block is that the sinus rhythm has to be regular. If the sinus rhythm is not regular, there could be alternative explanations as to why the P wave wasn't followed by a QRS complex.

Type 2 second degree heart block, also known as Mobitz II heart block is a disease of the distal conduction system. This is also known as Infrahisian block because the level of block is below the bundle of His. Mobitz II heart block is characterized on a surface EKG by a fixed PR interval with a droped QRS complex after a certain number of P waves. For instance, for every 4 P waves, there are only 3 QRS complexes. Since there is no lengthening of the PR interval, the PR interval does not reset after the dropped QRS complex.

More information on heart block

What is heart block? - Heart block is a disorder of the heartbeat. Heart block is common in elderly people as their hearts have undergone degenerative changes.
What's first degree heart block? - First-degree heart block, or first-degree AV block, is when the electrical impulse moves through the AV node more slowly than normal.
What's second degree heart block? - Second degree heart block is a disease of the electrical conduction system of the heart. There are two distinct types of second degree heart block.
What's third degree or complete heart block? - Third degree heart block, also known as complete heart block, is a disease of the electrical system of the heart.
What causes heart block? - Heart block has a variety of causes. It can sometimes be a result of a congenital defect. It can also occur after a heart attack or as a result of myocarditis.
What are the symptoms of heart block? - The main symptom associated with heart block is fainting (syncope). Second degree heart block may not cause symptoms.
How is heart block diagnosed? - Heart blocks can be diagnosed with a test called an electrocardiogram (ECG), which measures the heart's electrical activity.
What're the treatments for heart block? - First-degree heart block requires no treatment even when it is caused by heart disease. A temporary pacemaker may be used in an emergency.
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