Cardiac arrhythmia diagnosis and treatment in dogs

Cardiac arrhythmias are abnormalities of the heart's electrical system that cause it to beat too fast, too slow, or irregularly. Some are benign and incidental; others cause syncope (fainting), exercise intolerance, or sudden death. Specialist veterinary cardiologists use ECG, echocardiography, and 24-hour Holter monitoring to diagnose arrhythmias accurately and decide when and how to treat them.

What it is

The most clinically significant arrhythmias in dogs include: atrial fibrillation (AF) — chaotic atrial activation causing an irregularly irregular rhythm, common in large breeds and secondary to structural heart disease; ventricular tachycardia (VT) — a fast, life-threatening rhythm originating in the ventricles, most dangerous in Dobermanns with DCM; bradyarrhythmias and complete heart block — where the heart beats too slowly, often requiring a pacemaker; and sick sinus syndrome — intermittent pauses causing syncope, common in Miniature Schnauzers. Pacemaker implantation is available at specialist cardiology centres for bradyarrhythmias.

When it's needed

• Syncope (fainting) or collapse episodes requiring diagnosis
• Irregular heart rhythm detected on examination — Holter monitoring to quantify and classify
• Atrial fibrillation — rate control with digoxin and/or diltiazem; cardioversion in select cases
• Symptomatic ventricular tachycardia — antiarrhythmic therapy (sotalol, mexiletine, amiodarone)
• Complete heart block or sick sinus syndrome causing clinical signs — pacemaker implantation
• Monitoring of Dobermanns with DCM for arrhythmia burden

Procedure summary

Diagnosis: ECG at rest, 24-hour ambulatory Holter monitor, echocardiogram. Treatment is predominantly medical — specific antiarrhythmic drugs chosen based on arrhythmia type. Pacemaker implantation (transvenous or epicardial) is a surgical procedure performed under general anaesthesia, typically taking 1–2 hours, and available at specialist cardiology centres. Implantable loop recorders are increasingly used for intermittent syncope investigation.

Recovery

Medical management of arrhythmias is lifelong with regular Holter monitoring to assess response. Pacemaker implantation: 48–72 hours hospitalisation post-implant; most dogs recover to near-normal function within 2–4 weeks. Pacemaker battery typically lasts 5–12 years depending on model and pacing percentage.

Common questions