1Types

Sinus rhythm with acute inferior infarction complicated by Type I A-V block manifest in the form of 5:4 Wenckebach periods; R-P/P-R reciprocity.

Sinus tachycardia with complete A-V block and resulting junctional escape

Blocks that occur within the atrioventricular node (AV node) are described as AV nodal blocks.

Blocks that occur below the AV node are known as infra-Hisian blocks (named after the bundle of His).

Blocks that occur within the left or right bundle branches are known as bundle branch blocks.

Blocks that occur within the fascicles of the left bundle branch are known as hemiblocks.

Clinically speaking, most of the important heart blocks are AV nodal blocks and infra-Hisian blocks.

Sinus rhythm(rate = 100/min) with 3:2 and 2:1 Type II A-V block;RBBB

A heart block can be a blockage at any level of the electrical conduction system of the heart (shown in the diagram on the right).

Blocks that occur within the sinoatrial node (SA node) are described as SA nodal blocks.

1.1 SA nodal blocks

The SA nodal blocks rarely give symptoms. This is because if an individual had complete block at this level of the conduction system (which is uncommon), the secondary pacemaker of the heart would be at the AV node, which would fire at 40 to 60 beats a minute, which is enough to retain consciousness in the resting state.

Types of SA nodal blocks include:

SA node Wenckebach (Mobitz I)[1]

SA node Mobitz II

SA node exit block

In addition to the above blocks, the SA node can be suppressed by any other arrhythmia that reaches it. This includes retrograde conduction from the ventricles, ectopic atrial beats, atrial fibrillation, and atrial flutter.