Equine Arrhythmias

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