February EMS Training: AV Blocks & Pacing Used with permission of Silver Cross EMS System

Goals Review different heart blocks found when completing an EKG Identify how to differentiate between different heart blocks Review transcutaneous pacing equipment and how to pace a patient Identify any other relevant treatments for patients with a heart block 2

Cardiac Rhythm of the Month AV Blocks 3

Review - AV Junction 4 AV Junction = AV Node and Bundle of His Pacemaker cells located throughout AV Junction

Review - Functions of AV Node 5 Backup pacemaker for SA Node Creates delay between atrial and ventricular depolarizations Physiologic block for rapid supraventricular rhythms

Degrees of AV Blocks First Degree - Delay in conduction Second Degree - Some impulses blocked Third Degree - All impulses blocked 6

First Degree AV Block An abnormal slowing of AV Junction conduction 7

First Degree AV Block ECG Criteria Rate - Dependent on underlying rhythm – Interpretation must include underlying rhythm Rhythm - Dependent on underlying rhythm P-Waves - Normal morphology with one P- Wave for each QRS PRI - >.20 seconds and constant QRS - Dependent on underlying rhythm 8

First Degree AV Block Clinical Significance Not usually detrimental and often resolves when ischemia corrected Must consider entire patient 9

Second Degree AV Blocks Type I – Also called “Wenckebach” – Also called Mobitz I Type II – Also called Mobitz II 10

Second Degree AV Block, Type I Intermittent block in which AV conduction gradually slows until an impulse is blocked “Long, longer, longer, drop! Long, longer, longer, drop!” 11

Second Degree AV Block, Type I ECG Criteria Rate - Atrial rate unaffected but ventricular rate is less than atrial rate Rhythm - Atrial rhythm usually regular. Ventricular rhythm is irregular with more P- Waves than QRS Complexes. P-Waves - Unaffected with more P-Waves than QRS Complexes PRI - Progressively increases for consecutively conducted P-Waves until QRS Complex is dropped QRS - Unaffected 12

Second Degree AV Block, Type I Etiology Often caused by increased parasympathetic tone or drug effect Can be caused by MI 13

Second Degree AV Block, Type I Clinical Significance Usually transient with good prognosis Can reduce cardiac output due to bradycardia 14

Second Degree AV Block, Type II Intermittent block in which not all P-Waves are conducted to ventricles but there is no progressive prolongation of PRI “Extra” p-waves. 15

Second Degree AV Block, Type II Etiology Usually due to MI or other organic heart disease Rarely the result of increased parasympathetic tone or drug effect 16

Second Degree AV Block, Type II Clinical Significance Poorer prognosis than Type I Usually requires pacemaker Frequently develops into Complete Block 17

Second Degree AV Block, Type II ECG Criteria Rate - Atrial rate is unaffected but ventricular rate is less than atrial Rhythm - Atrial rhythm regular, Ventricular irregular with more P-waves than QRS Complexes P-Waves - Normal morphology with more P- Waves than QRS Complexes PRI - Constant for consecutively conducted P- Waves QRS - Usually wide but may be narrow if block is at His level or above 18

Second Degree AV Block, Type II Example 19

Third Degree AV Block 20 Complete blockage of impulse conduction through AV Junction Results in “AV dissociation” (very very bad thing) P’s and QRS’s “march to their own drummer”

AV Dissociation 21 No relationship between P-waves and QRS complexes

Third Degree AV Block Etiology 22 MI Increased parasympathetic tone Drug toxicity

Third Degree AV Block ECG Criteria 23 Rate - Atrial > 60, Ventricular based on escape Rhythm - Atrial and ventricular regular P-Waves - Normal PRI - No association between P-Waves and QRS complexes (P’s and QRS’s are divorced and do their own thing) QRS - Narrow if intranodal, Wide if infranodal

Transcutaneous Pacing (TCP) 24 Non-invasive electrical therapy for symptomatic bradycardias/complete heart blocks Fast to set up Reasonably reliable

TCP Equipment 25 Give the patient Versed if they are awake, per SMO Set milliamps (adjustable 0-200mA typical) – Start low if they are awake, and high if they are out. Set rate to 70. Similar controls across brands Be familiar with your equipment!

Typical TCP Controls 26

Assess Electrical and Mechanical Capture 27 Electrical – Displayed on monitor Mechanical – Pulse