F&E Arrhythmia 5

First-Degree AV block - ECG PR interval

Prolonged, constant PR interval (>0.20 s).

First-Degree AV block - Common drug causes

beta blocker, diltiazem, verapamil, digoxin.

Second-Degree AV block Mobitz type I (Wenckebach) - ECG QRS complex

Narrow QRS.

Second-Degree AV block Mobitz type I (Wenckebach) - ECG PR interval characteristic

progressive increase in PR interval.

Second-Degree AV block Mobitz type I (Wenckebach) - Site of block

The site of the block is usually within the AV node.

Second-Degree AV block Mobitz type I (Wenckebach) - Associated drug intoxication

digitalis, beta blockers.

Second-Degree AV block Mobitz type I (Wenckebach) - Management

Usually transient, no therapy required

Second-Degree AV block Mobitz type II - Site of block

The site of the block is within the His-Purkinje system.

Second-Degree AV block Mobitz type II - ECG PR interval characteristic

Fixed PR interval (i.e., no progressive lengthening).

Second-Degree AV block Mobitz type II - ECG conduction characteristic

occasional dropped beats.

Second-Degree AV block Mobitz type II - ECG block patterns

2:1, 3:1, or 4:1 pattern.

Second-Degree AV block Mobitz type II - Progression risk

may progress suddenly to complete AV block.

Second-Degree AV block Mobitz type II - Treatment

permanent pacemaker is indicated.

Third-Degree AV block (Complete Heart Block) - Conduction status

Complete failure of conduction from atria to ventricles.

Third-Degree AV block (Complete Heart Block) - ECG P and QRS relationship

no correspondence between P waves and QRS complexes.

Third-Degree AV block (Complete Heart Block) - Treatment

Permanent pacemaker is indicated.

Left bundle branch block (LBBB) - ECG QRS duration

QRS duration > 120ms (wide).

Left bundle branch block (LBBB) - ECG V1 characteristic

Dominant S wave in V1.

Left bundle branch block (LBBB) - ECG characteristic pattern

"W" in V1 and "M" in V6 pattern is characteristic of (LBBB).