Andy Rodriguez

First Degree Heart Block

• Not a true block
• Conduction delay at AV node
• All impulses are conducted to ventricles
• PRI will be >0.20 consistently across the strip

Second Degree Heart Block

• Intermittent
• Some get through and some don’t
• pathology can be in AV node or below in Bundle of His
• pathology is often blended with other blocks
• Mobitz Type I (Wenckebach)
• Impulses encounter progressive delays at the AV node until one impulse is blocked completely
• PRI starts getting progressively longer and then dropped QRS
• All conducted QRSs present are tight, <0.12 and preceded by a P wave
• Mobitz Type II
• Can be regular or irregular, depending on conduction ratio
• Usually a Brady rhythm
• More than one P wave for every QRS
• PRI constant on conducted beats can be >0.20
• QRS <0.12
• Conduction Ratios
• 2:1, 3:1, etc. two P waves for every conducted QRS

Third Degree Heart Block (Complete Heart Block)

• All impulses generated by Sinus node are being blocked by AV node
• Separate Sinus and Ventricular Pacemakers –
• Complete disassociation between P waves and QRSs
• Regular
• Rate depends on whether its junctional or ventricular
• P waves, normal and upright, more P waves than QRS
• PRI – no relationship between P waves and QRS , occasional superimposed on QRS
• QRS width depends on whether its junctional or ventricular

Heart blocks are best diagnosed using a 12 Lead EKG Machine. This and other used medical equipment can be found easily online.