Equine Arrhythmias

Flowchart nodes

• Heart Rate

• Bradycardia

• Tachycardia

• Dropped Beats

• No dropped beats

• S4 heard

• S4 not heard

• 2' AV block

• 2' SA block

• HR <20

• 3' AV block

• V irreg rhythm

• Regular rhythm

• occ extra beat

• S4 not heard

• Atrial fibrillation

• compensatory pause after extra beat?

• Ventricular tachycardia

• VPC

• APC

• Supraventricular tachycardia

• Mobitz type 1 is non-pathogenic reg -irreg, Type 2 is pathogenic, irreg-irreg

• Whole complex is missed, insignificant unless HR <20

• AVN disease, inflamm or degenerative, K imbalance, or digoxin

• causes an exercise intolerance because HR fails to increase

• QRS without P

• Tx: correct elec imbalance or underlying cause. If there is an inflam stimulus, consider corticosteroids. Phenytoin in chronic cases (Na channel blocker

• P with no QRS

• systolic murmur common from V contraction while AV valve open

• Large atria with carcadian movement of impulses, or high vagal tone cuase refractory period to be different in different cells

• non pathological, exercise resolves, but may be recursor to AF

• Ventricular atopic beats

• Tx if HR >100, there are runs, or R on T phenomenon. Procainamide infusion, Lidocaine infusion with MgSO4

• Cardioversion therapy for Atrial fibrillation

• Less successful conversion if >6 duration, underlying cardiac disease exists. Poorer prognosis if there is a pathological murmur with volume overload, if HR >55, or previous treatment was unsuccessful

• Oral boluses of Quinidine Sulphate: 22mg/kg via stomach tube q2hr, max 5 doses. Vagolytic and prolongs AP so increases the refractory period.

• Risk severe ventricular tachycardia if Vs start responding to every AF Other Signs of toxicity include depression, D+, colic, muzzle swelling, weakness, laminitis, hypotension and collapse leading to death Managing SEs: Stop dosing, give mineral oil to decrease further absorption. NaHCO3 to increase protein binding of QS, Lidocaine IV for VT tx if rate >100bpm, MgSO4 if Tsordes de pointes develops (Ca channel blocker so staibilises membranes)

• Electric Shock therapy Can be attempted under GA if unresponsive to medical therapy. Use echo examination to determine suitability

• Non-Pathological Dysrrhythmias 2'AV block, Sinus Block, Sinus arrhythmia, APC, VPC (1 or 2 in 24hr) Pathological Dysrrhythmia 3' AV block, Sinus Bradycardia, AF, APC, VPC, VT