Principles Of Electrocardiography VETM 5291 PDF 2025

Principles of Electrocardiography Part III: Approach to arrhythmia diagnosis (contd) VETM 5291︎ Cardio︎vascular, Respirato︎ry & Hemo︎lymph Systems II Mandy Co︎leman, DVM, DACVIM (Cardio︎lo︎gy) [email protected]  LEARNING OBJECTIVES ▪ By the end of this hour, you will be able to : ▪ List and d...

Principles of Electrocardiography Part III: Approach to arrhythmia diagnosis (contd) VETM 5291︎ Cardio︎vascular, Respirato︎ry & Hemo︎lymph Systems II Mandy Co︎leman, DVM, DACVIM (Cardio︎lo︎gy) [email protected]  LEARNING OBJECTIVES ▪ By the end of this hour, you will be able to : ▪ List and discuss the steps comprising a systematic approach to ECG interpretation ▪ When provided an ECG, determine heart rate (with and without a Bic pen) and whether the rhythm is sinus ▪ Define “cardiac arrhythmia” and “no︎rmal sinus rhythm” ▪ List the ECG criteria of a normal sinus rhythm ▪ When given a lead II electrocardiogram, determine whether the rhythm is controlled by the sinus node ▪ Contrast the expected appearance of the QRS complex in patients affected by supraventricular, versus ventricular, arrhythmias ▪ For each specific arrhythmia discussed in class, describe: ▪ The electrocardiographic criteria for diagnosis ▪ Associated conditions or diseases General approach to ECG interpretation ▪ Be systematic: 1. Note lead and paper speed settings Most common paper speeds: 25 mm/sec and 50 mm/sec 2. What is the heart rate? 3. Is there an underlying sinus rhythm? 4. If not sinus rhythm: describe and name rhythm abnormality  25 mm/sec; HR 120 bpm 6-month-old F German shepherd dog, presented for routine examination  25 mm/sec; HR 120 bpm QRS T QRS T T T T P P T T T T T QRS QRS QRS QRS QRS QRS QRS 6-month-old F German shepherd dog, presented for routine examination  Ventricular Premature Depolarizations/Complexes 25 mm/sec; HR 90 bpm 6-month-old F German shepherd dog, presented for routine examination ▪ Abno︎rmal impulses arising fro︎m ventricular tissue ▪ How do you know these abnormal beats (arrows) have a ventricular origin? + II  Ventricular Premature Depolarizations/Complexes 25 mm/sec; HR 90 bpm 6-month-old F German shepherd dog, presented for routine examination ▪ Abnormal impulses arising from ventricular tissue ▪ How do you know these abnormal beats (arrows) have a ventricular origin? ▪ Ventricular premature depolarizations (VPD) = complexes (VPC) = premature ventricular co︎mplexes (“PVC”; used widely in human medicine) ▪ VPCs are building blocks for more complex ventricular arrhythmias (e.g., ventricular tachycardia) + II  Ventricular Premature Depolarizations/Complexes 25 mm/sec; HR 90 bpm 6-month-old F German shepherd dog, presented for routine examination ▪ ECG characteristics ▪ Premature (earlier than next expected sinus beat) ▪ No related P wave ▪ ”Wide and bizarre” QRS ▪ Depo︎larizatio︎n starts in ventricle + do︎esn’t use specialized electrical co︎nductio︎n system, so︎ it is sloooow (cell-by-cell) ▪ WIDE QRS > 0.06 sec (dog) or > 0.04 sec (cat)  Ventricular Premature Depolarizations/Complexes Ventricular Ventricular couplet with R-on-T couplet with R-on-T 25 mm/sec; HR 90 bpm VPC VPC VPC VPC 6-mo︎nth-o︎ld F German shepherd do︎g, presented fo︎r ro︎utine examinatio︎n ▪ ECG characteristics ▪ Can be single, o︎r o︎ccur in pairs (“co︎uplet”) o︎r in threes (“triplet”) Ventricular Single Ventricular Single triplet VPC co︎uplet VPC  Ventricular Premature Depolarizations/Complexes Ventricular Ventricular co︎uplet with R-o︎n-T couplet with R-on-T 25 mm/sec; HR 90 bpm VPC VPC VPC VPC 6-month-old F German shepherd dog, presented for routine examination ▪ ECG characteristics ▪ Can be single, o︎r o︎ccur in pairs (“co︎uplet”) o︎r in threes (“triplet”) ▪ Can be uniform (all complexes identical) or multiform (different morphologies) Uniform VPCs  Ventricular Premature Depolarizations/Complexes Ventricular Ventricular couplet with R-on-T couplet with R-on-T 25 mm/sec; HR 90 bpm VPC VPC VPC VPC 6-month-old F German shepherd dog, presented for routine examination ▪ ECG characteristics ▪ Can be single, o︎r o︎ccur in pairs (“co︎uplet”) o︎r in threes (“triplet”) ▪ Can be uniform (all complexes identical) or multiform (different morphologies) ▪ “R-on-T” pheno︎meno︎n: QRS o︎f VPC o︎ccurs early eno︎ugh to︎ land o︎n T wave o︎f preceding beat. This increases the risk for ventricular fibrillation, a terminal rhythm.  Ventricular Premature Depo︎larizatio︎ns/Co︎mplexes 25 mm/sec; HR 90 bpm 6-month-old F German shepherd dog, presented for routine examination ▪ Potential causes (VPCs and other ventricular tachyarrhythmias): ▪ H – heart disease/injury (especially primary myocardial diseases in dogs, myocarditis, myocardial hypoxia) ▪ E – electrolyte derangements (hyper/hypo-kalemia, hypocalcemia, hypomagnesemia) ▪ A – algesia (pain), adrenergic stimulation ▪ D – drugs (anesthetics, stimulants) ▪ S – splenic disease, sepsis, SIRS, systemic inflammation (e.g., IMHA, pancreatitis) Ventricular Premature Complexes: when to treat? ▪ Single VPCs are unlikely to cause clinical signs or increase risk for sudden death ▪ Treat underlying disease ▪ Consider longer-term ECG monitoring (Holter) to evaluate for occult complexity ▪ Treat if one or more of the following is present: ▪ Ventricular tachycardia, flutter or fibrillation (coming up!) ▪ R-on-T ▪ Evidence of hemodynamic compromise (hypotension, weakness, syncope) ▪ Multiformity  25 mm/sec; HR 250 bpm 7-year-old MC Doberman with dilated cardiomyopathy  R-on-T 25 mm/sec; HR 250 bpm T T QRS QRS 7-year-old MC Doberman with dilated cardiomyopathy QRS duration = 2 boxes = 2 x 0.04 sec = 0.08 sec (Normal QRS < 0.06 sec)  Ventricular Tachycardia (V-tach) R-o︎n-T 25 mm/sec; HR 250 bpm T T QRS QRS 7-year-old MC Doberman with dilated cardiomyopathy ▪ Rapid rhythm originating from the ventricles ▪ 4 or more VPCs in a row at a rate >160 bpm (dog), >200 bpm (cat), >40 bpm (horse)  Ventricular Tachycardia (V-tach) R-on-T 25 mm/sec; HR 250 bpm T T QRS QRS 7-year-old MC Doberman with dilated cardiomyopathy ▪ Rapid rhythm originating from the ventricles ▪ 4 or more VPCs in a row at a rate >160 bpm (dog), >200 bpm (cat), >40 bpm (horse) ▪ ECG characteristics ▪ QRS ”wide and bizarre” with no︎ asso︎ciated P waves ▪ Rhythm usually regular (consistent interval between beats) ▪ May be uniform (all complexes identical) or multiform (differing morphologies)  Ventricular Tachycardia (V-tach) 25 mm/sec; HR 250 bpm 7-year-old MC Doberman with dilated cardiomyopathy ▪ This is a very dangerous rhythm! ▪ If there is severe underlying heart disease or if rate very rapid (i.e., >250/min in dog), animal can experience weakness or syncope (fainting) ▪ If sustained, can precipitate CHF ▪ Can degenerate to ventricular fibrillation (FATAL) ▪ TREAT! Ventricular flutter Ventricular tachycardia pro︎gressing to︎ ventricular flutter: 50 mm/sec HR = 214 bpm Ventricular flutter; HR = 315 bpm Fast V-tach with “sine wave” mo︎rpho︎lo︎gy No︎ iso︎electric “shelf” between ventricular beats TREAT! Ventricular fibrillation This is FATAL if untreated. Treat by TRANSTHORACIC SHOCK!  HR 120 bpm (pen x 20) QRS QRS P T P T P 50 mm/sec 7-year-o︎ld FS asympto︎matic Beagle do︎g  Atrioventricular (AV) Block blocked/non-conducted P wave QRS QRS P T P T P 50 mm/sec; HR 120 bpm 7-year-old FS asymptomatic Beagle dog ▪ Slowed or failed conduction from atria to ventricles through the AV node or His bundle ▪ ECG characteristics and clinical implications depend on severity/degree of block (i.e., first, second or third)  1st-degree Atrioventricular (AV) Block 25 mm/sec ▪ First-degree AV block ▪ Prolonged PR interval (>normal) ▪ Never causes clinical signs ▪ Do︎esn’t disrupt rhythm ▪ Benign; usually associated with high 13-year-old FS Boxer, treated with atenolol prevailing vagal tone or drugs that slow AV Respiratory sinus arrhythmia nodal conduction ▪ No treatment indicated PR interval 0.24 sec (normal