Small Animal Cardiology - PDF

Auscultation of Heart Rate and Rhythm 166 Slow Heart Rate Fast Heart Rate Slow, irregular Slow, regular Fast, irregular...

Auscultation of Heart Rate and Rhythm 166 Slow Heart Rate Fast Heart Rate Slow, irregular Slow, regular Fast, irregular Fast, regular Pronounced sinus Sinus bradycardia Intermittent SVPCs Sinus tachycardia arrhythmia Complete heart block Paroxysmal SVT Sustained SVT Intermittent sinus (Ventricular escape Atrial fibrillation (excluding A fib) arrest rhythm) Intermittent VPCs Sustained VT Sick sinus syndrome Atrial standstill with Paroxysmal VT High-grade 2⬚ heart escape rhythm block R/O: Underlying causes of ectopic rhythms (Box 12-1) R/O: Disorders of excess vagal tone versus SA, AV node, or other conduction abnormality Treat arrhythmia if: More than 30 ectopic complexes per minute Common Cardiac Arrhythmias Give atropine: 0.04 mg/kg IV, reassess ECG in Paroxysms or sustained VT >130 bpm 20 minutes; normalization of Paroxysms or sustained SVT >160-180 bpm heart rate (>125 bpm) and Multiform VPCs rhythm suggest excess vagal SV or V arrhythmias in the presence of myocardial failure tone Breeds at risk for sudden death (Dobermans, Boxers) Clinical signs of hypotension VPCs close to the T wave of the proceeding complex (R-on-T phenomenon) Figure 12-3. An algorithm for differential cardiac rhythm diagnoses by auscultation. SVPC, Supraventicular premature complex; SVT, supraventicular tachycardia; VPC, ventricu- lar premature complex; VT, ventricular tachycardia. Table 12-1. The Classic Four Types of Antiarrhythmic Drugs Class Channel Effects Examples Use or Comments IA Sodium, block Quinidine, procainamide Supraventricular and ventricular rhythms; inexpensive IB Sodium, block Lidocaine, mexiletine, tocainide Ventricular rhythms; affinity for diseased or ischemic muscle tissue IC Sodium, block Flecainide, propafenone Markedly inhibits Na2+ channels; rarely used II Beta receptor, block Atenolol, propanolol, Supraventricular rhythms using the AV metoprolol, sotalol node (i.e., atrial fibrillation); some ventricular rhythms III K+ repolarizing, block Amiodarone, sotalol, bretylium Broad-spectrum class, supraventricular and ventricular rhythms Miscellaneous drug class, multiple mechanisms noted (i.e., sotalol) IV Calcium, block Diltiazem, verapamil Supraventricular rhythms using the AV Common Cardiac Arrhythmias node (i.e., atrial fibrillation) 167