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.

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UPDATED 6/15/09

Sinus Blocks, Pauses and Arrest

• In all cases, no P, QRS or T wave present – Impulse is blocked a SA node and Atria are never depolarized.
• Sinus Block – Always a multiple of underlying P-P interval. can be more than one missing complex
• Sinus Pause – Not a multiple of P-P interval. Shorter than three times the P-P
• Sinus Arrest – Same as pause but more than 2 missing complexes (consecutive)

Andy Rodriguez

Ventricular Rhythms

• Impulse is generated in the ventricles. Generally recognized by wide QRS complex, >0.12

Premature Ventricular Contraction (PVC)

• Regular – ectopics will interrupt
• Rate – depending on underlying rhythm
• No P wave before PVC
• Wide QRS >0.12
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Compensatory Pause

• Allows for heart pick up its rhythm again after a PVC, resumes normal rhythm as was before PVC
• 2x R-R
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Interpolated

• R-R stays the same and PVC is between normal R-R
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Types of PVCs

• Unifocal – One focus generating the extra beat, generates PVCs that look exactly the same
• Multifocal – Multiple foci generating extra impulses. generates PVCs that look different

R on T Phenomenon

• PVC hits during or end of T wave, can cause Vfib if hits just right
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PVC Couplets

• Two PVCs in a row
• May be unifocal or multifocal

PVCs in a run or Run of PVCs

• More than three PVCs in a row
• Also called a “run of vtach”

PVC Groupings

• 1:1 Ratio – Bigeminy (every other is a PVC)
• 2:1 Ratio – Trigeminy (every third is a PVC)
• 4:1 Ratio – Quadgeminy (every fourth is a PVC)

Ventricular Tachycardia

• Usually Regular – can be slightly irregular
• Rate of 150 – 250 (Less than 150 is slow VT, greater than 250 V flutter)
• No P waves
• PRI – None
• QRS- wide and bizarre >0.12
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Ventricular Fibrillation

• Multiple foci firing in an uncoordinated fashion
• Grossly irregular
• Wide QRS – Fibrillating
• No pulse
• Shockable Rhythm
• Most lethal rhythm
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Idioventricular Rhythm

• Regular rate at 20-40 BPM (above 40 -120 called an accelerated idioventricular rhythm)
• No P waves
• No PI
• QRS wide and bizarre
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Asystole

• Absence of any electrical activity