Introduction to Electrocardiography & Dysrhythmias Janet Smith, RN, MPH

Objectives To gain a basic knowledge of cardiac electrophysiology To understand the representations of the cardiac cycle on the ECG To master techniques used for learning the characteristics of the different dysrhythmias To learn measurement and count techniques essential for dysrhythmia interpretation

Definitions Tachycardia Bradycardia Intrinsic Firing Rate Isoelectric Line Rate of > 100 Rate if < 100 The normal firing rate for the rhythm of a certain pacemaker The baseline of a rhythm where no electrical activity is present

Definitions Depolarization Repolarization Refractory period The complete electrical firing of the cells of the heart The time during which the cells recharge after depolarization The time during the repolarization when cells rearm

Definitions PR Interval The distance between the beginning of innervation of the sinus node to the beginning of ventricular depolarization

Cardiac Conduction

Cardiac Conduction R P T Q S

Cardiac Conduction ST Seg. Q R S PR .12 - .20 s <.12 s

EKG Paper Measures time – horizontal in seconds Measures amplitude – vertical in milliamps Uses the Metric system Is very good for accuracy

EKG Paper 1 mm .04 sec. .2 sec.

Rate Measurement 300 divided by number of big blocks between R – R interval (must be a regular rhythm) i.e. 300/4 = 75

Rate Measurement 300 150 100 75 60 50 43 37 33 30 Memorization and counting backward between R – R interval (must be regular)

Dysrhythmia Characteristics

Normal Sinus Rhythm Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Regular 60-100 BPM Upright/Normal .12-.20 s (120-200 ms) .04-.12 s (40-120 ms)

Sinus Bradycardia Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Regular < 60 BPM Upright/Normal .12-.20 s (120-200 ms) .04-.12 s (40-120 ms)

Sinus Tachycardia Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Regular > 100 and < 160 BPM Upright/Normal .12-.20 s (120-200 ms) .04-.12 s (40-120 ms)

Sinus Dysrhythmia Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Irregular 60-100 BPM Upright/Normal .12-.20 s (120-200 ms) .04-.12 s (40-120 ms)

Sinus Arrest Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Irregular Normal - slow Upright/Normal .12-.20 s (120-200 ms) .04-.12 s (40-120 ms)

Premature Atrial Contractions Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Irregular (PACs);Non-compensatory Depends on underlying rhythm Upright/Normal .12-.20 s (120-200 ms) .04-.12 s (40-120 ms)

(Paroxysmal) Atrial Tachycardia Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Regular > 150-250 BPM Upright/Normal .12-.20 s (120-200 ms) .04-.12 s (40-120 ms)

Supraventricular Tachycardia Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Regular > 150-250 BPM Indiscernible None seen .04-.12 s (40-120 ms)

Atrial Flutter Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Atrial: Regular; Ventr.: Varies Atrial: 250-300; Ventr.: Varies Big F-Waves – Saw tooth pattern Normally constant – may vary .04-.12 s (40-120 ms)

Atrial Fibrillation Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Irregularly irregular ventricular Atrial: 350-750; Ventr.: Varies Little F-Waves – no pattern No discernable P waves .04-.12 s (40-120 ms)

Junctional Rhythm Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Regular 40-60 BPM Inverted – prior to or after; absent < .12s if present .04-.12 s (40-120 ms)

First Degree AV Block Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Regular; can be irregular Usually 60-100 BPM; Rhythm dep. Upright/Normal > .20 s (200 ms); Constant .04-.12 s (40-120 ms)

Second Degree AV Block (Type I) Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Atrial: Reg.; Ventr.: Regularly irreg. Atrial: Normal; Vent.: Norm./Slow Normal: extra P waves Not constant; Lengthens - drops beat Usually .04-.12 s (40-120 ms)

Second Degree AV Block (Type II) Classical Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Atrial: Reg.; Ventr.: Regular or irreg. Atrial: Normal; Ventricular: Slow Normal; extra P waves Constant on conducted beats Usually .04-.12 s (40-120 ms)

Second Degree AV Block (Type II) Variable Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Atrial: Reg.; Ventr.: Regular or irreg. Atrial: Normal; Ventricular: Slow Normal; extra P waves Constant on conducted beats Usually .04-.12 s (40-120 ms)

Third-Degree AV Block Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Atrial & Ventricular: Regular Atrial: Normal; Vent.: 40-60; < 40 Normal: extra P waves No Atrial/Ventricular Relationship <.12 s (120 ms) Junct.;> .12 Ventr.

Pacemaker Rhythm Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Paced: Reg.; Demand: Irregular Varies with pacemaker rate May be present No relationship > .12 s (120 ms);Ventricular

Premature Ventricular Contractions Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Irregular (PVCs); Compensatory Depends on underlying rhythm None on premature beat None on PVCs > .12s (120 ms) on PVC

Ventricular Tachycardia Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Usually Regular 100-250 BPM If present, not associated None > .12s (120 ms)

Ventricular Fibrillation Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Chaotic;no set rhythm;fine/coarse None Absent No discernable; medium F-waves

Asystole Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: No electrical activity No electrical rhythm Absent

Idioventricular Rhythm Rate: P Waves: P-R Interval: (Q)RS Complex: Usually Regular 15-40 BPM None > .12 s (120 ms);exaggerated

TIME FOR SOME PRACTICE

REMEMBER!!! Use a systematic approach Go through all the steps Take your time! Compare with your characteristics list Interpret the dysrhythmia

Atrial Flutter Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Irregular 70 Big F (Flutter) Waves .20 s Normal; .04-.12 s

Sinus Dysrhythmia Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Irregular 60 BPM Normal; upright .16 s Normal

Third Degree Heart Block Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Regular 37 BPM Normal; upright; extra Non-constant; No relationship Normal

Sinus Tachy with PVCs (UF) Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Irregular (due to ectopics) 110 BPM Present underlying; none ectopics .16 s Normal; .16 for ectopics

Sinus Arrest Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Regularly Irregular; loses complexes 40 BPM Normal; upright .16 s Normal

Sinus Rhythm with PAC Rhythm: Rate: P Waves: P-R Interval: (Q)RS Complex: Irregular (due to ectopics) 60 Normal; upright; present for ectopic .18 s; .14 s for ectopic Normal for all complexes

Sinus Rhythm with V-Tach Rate: P Waves: P-R Interval: (Q)RS Complex: Irregular (due to ectopics) 80 BPM Normal; upright – none for ectopics .14 s; none on ectopics Normal; .14 s on ectopics

Acute Anterior MI

Summary You need to learn the definitive characteristics Use a complete, systematic approach to dissect the rhythm Take your time Mistakes are made when steps are skipped Practice! Practice! Practice!