Electrocardiography. How to obtain an ECG. The Cardiac Conduction System. The Cardiac Conduction System 10/14/2015

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1 Electrocardiography Sarah Lehman, VMD Resident in Cardiology, CVCA The Veterinary Forum presented by The LifeCentre October 18, 2015 The Cardiac Conduction System The Cardiac Conduction System How to obtain an ECG Right lateral recumbency, legs perpendicular Every time, same way Exception = standing in giant breeds 1

2 How to obtain an ECG Lead Placement White on the right; snow over grass; smoke over fire; Christmas trees on the knees Minimize artifact with lead placement and spray with alcohol or use conductive gel How to obtain an ECG ECG Machine Settings Paper speed: 25 vs. 50 mm/sec. Sensitivity: 5 vs. 10 vs. 20 mm/mv Filter: On vs. Off Which leads: I, II, III, avr, avl, avf The 6 lead system (-) I avf (+) (-) RA (-) LA RA The 6 lead system I avf LA II III II III avl avr avl avr (+) LL (+) LL 2

3 1) Determine heart rate 1) Determine heart rate Know your paper speed Instantaneous rate used if the R-R interval is consistent 50 mm/s 3000/number of small boxes 25 mm/s 1500/number of small boxes Average rate used when the rhythm is irregular # of complexes in 6 sec. x 10 or 3 sec. x 20 BicPen rule 2) Determine Regularity Are the complexes regular, occasionally irregular, regularly irregular or irregularly irregular? 3) P and QRS relationship Find what you think are P waves Find what you think are QRS complexes P for every QRS? QRS for every P? 3

4 3) P and QRS relationship 4) P wave morphology Are P waves regularly associated with each QRS complex and vice versa? 4) P wave morphology 5) PR interval Wandering pacemaker P mitrale wide P pulmonale tall Dogs: sec Cats: sec 5 x 0.04 = 0.2 sec 25 mm/s: each small box = 0.04 sec 4

5 5) QRS complex morphology Causes of Arrhythmias Influences of the Autonomic Nervous System Increased Sympathetic and Parasympathetic Tone Cardiac Causes Extracardiac Causes Normal RBBB LBBB Does An Arrhythmia Need To Be Treated? Could the arrhythmia result in clinical signs? Could it lead to or worsen signs of CHF? Could it lead to sudden death? Is there evidence of cardiac disease? Sinus Rhythm 5

6 Bradyarrhythmias 12yo FS Min. Schnauzer Sick Sinus Syndrome Treatment of Bradyarrhythmias Permanent Transvenous Pacemaker Atropine 0.04 mg/kg IM/SQ; 0.02 mg/kg IV Glycopyrrolate: mg/kg IV/IM/SQ Levsin (L-Hyoscyamine): mg/kg PO 8-12hr Propantheline: mg PO 8-12hr Theophylline: 5-10mg/kg 8-12hr Terbutaline: 0.2 mg/kg 8-12 hr Isoproterenol: ug/kg/min IV 6

7 Tachyarrhythmias Tachycardias Arising from the Atria: Atrial fibrillation Tachycardia Wide QRS Narrow QRS Ventricular or SVT with aberrancy Sinus Tachycardia Afib/Flutter Atrial/junc. SVT Tachycardias Arising from the Atria: Atrial flutter Tachycardias Arising from the Atria: Supraventricular tachycardia 7

8 Control of Atrial/Junctional arrhythmias Suppress atrial ectopy and/or impair conduction through AV node Digoxin mg/kg BID Diltiazem mg/kg TID Atenolol mg/kg BID Sotalol 1-2 mg/kg BID Ventricular arrhythmias Ventricular arrhythmias Control of Ventricular Arrhythmias: Parenteral vs. Oral treatment Lidocaine: 2-4 mg/kg IV slow bolus CRI ug/kg/min Procainamide: 5-15 mg/kg over 2 minutes CRI ug/kg/min Amiodarone 5mg/kg IV slow*; high risk of side effects Tapering PO dose (5-10mg/kg q hr) Sotalol: 1-2 mg/kg PO q12 hr Atenolol: mg/kg PO q12hr Mexiletine: 6-8 mg/kg PO q8-12 hr 8

9 Feline ECG Treatment of feline tachyarrhythmias Lidocaine 0.25 mg/kg IV slow Sensitive to neurotoxic effects have midazolam ready Atenolol: mg/kg PO q12-14hr Sotalol: 1-2 mg/kg PO q12hr Procainamide: mg/kg PO q8hr 10 yo MN Labrador Post-op splenectomy Accelerated Idioventricular Rhythm (AIVR) Common in post-op GDV and splenectomy patients Ventricular rhythm with heart rate of Typically uniform, consistent coupling, no R-on-T May alternate with sinus rhythm of similar rate Often no obvious hemodynamic consequence No treatment needed in most cases 9

10 7yo MN Boxer Syncopal Episodes ARVC Singlet VPCs (LBBB) Aggressive triplet Treatment: Echo Holter Sotalol vs. Mexiletene 10yo FS Cavalier King Charles Sp. Echo: Mitral Valve Disease Shiver artifact Ventricular Bigeminy 10

11 6yo FS Great Dane Coughing, incr. RR, ascites: CHF Recheck 2 weeks later Sinus tachycardia SVT, LBBB, VPCs Questions? Thank you! Sarah Lehman, VMD sarah.lehman@cvcavets.com 11