Vet Approved Guide: Dog Arrhythmia – Types, Causes & 2025 Care Strategies 🐶🐾 

By Dr. Duncan Houston BVSc

Arrhythmia in dogs refers to an irregular heartbeat: too fast, too slow, or uneven rhythm. It ranges from harmless to life-threatening—early recognition and intervention can make all the difference. 🛡️

⚠️ Common Types of Arrhythmias

• Sinus arrhythmia: normal variation with breathing—usually benign.
• Boxer cardiomyopathy (ARVC): inherited ventricular arrhythmia in Boxers, Bulldogs; can cause collapse & sudden death.
• Atrial fibrillation: serious fluttering of atria—common in large breeds like Great Danes, Dobermans.
• Ventricular premature complexes (VPCs): extra beats from ventricles—may vary in significance.
• Atrioventricular (AV) block & Sick sinus syndrome: blocked or erratic signals causing slow or paused heartbeats—seen in older small breeds.
• Ventricular fibrillation: chaotic rhythm—an emergency requiring immediate defibrillation.

🧬 Why Arrhythmias Happen

• Genetic predisposition: ARVC in Boxers, inherited ventricular rhythm issues.
• Heart disease: valve dysplasia, cardiomyopathy, myocarditis.
• External factors: infections, toxins, trauma, electrolyte imbalances, anemia, and heartworms.
• Nervous system effects: vagal stimulation from other diseases.

👀 Signs to Watch For

• “Fluttering” or irregular heartbeat
• Exercise intolerance, panting, coughing, swollen belly.
• Weakness, cold or pale extremities, collapse.
• Sudden collapse or death in severe cases (e.g., ventricular fibrillation).

🩺 Diagnostic Approach

• Physical exam & stethoscope detection of arrhythmia.
• Blood tests: CBC, chemistry, electrolytes, and infectious disease screening.
• Electrocardiogram (EKG/ECG): measures rhythm on the spot.
• Holter monitor: 24-48h portable EKG to catch intermittent issues.
• Echocardiogram & chest X‑rays to check heart structure/function.

🛠️ Treatment Plans

• No treatment for benign sinus arrhythmia or mild cases.
• Medications:
  • Atrial fibrillation: diltiazem, digoxin, atenolol.
  • Ventricular arrhythmias: sotalol, amiodarone, mexiletine, procainamide.
  • Bradyarrhythmias/blocks: atropine acutely, theophylline, propantheline.
• Pacemaker: implanted for severe AV block or sick sinus syndrome.
• Cardioversion: emergency electrical shock for ventricular fibrillation.
• Treat underlying disease: infections, toxins, anemia, and heartworm.

📈 Prognosis & Outlook

• Prognosis depends on arrhythmia type and underlying cause.
• Benign sinus rhythms mean normal life expectancy.
• Mediated arrhythmias with meds or a pacemaker often have good control.
• Atrial fibrillation with heart disease and uncontrolled rates may have poorer survival.
• Ventricular fibrillation requires immediate intervention; survival depends on rapid care.

🛡️ Prevention & Monitoring

• Regular vet exams and heart screenings for predisposed breeds.
• Holter monitoring to track changes under treatment.
• Prompt treatment of infections, toxins, anemia, and heartworm.

📱 Vet-Approved Support Tools

• Ask A Vet: 24/7 advice on symptoms, medications, and when to seek emergency care. 

🎯 Final Thoughts

Arrhythmias in dogs vary widely—from harmless to life-threatening. Recognizing symptoms and obtaining timely diagnostics are key. Most dogs manage well with tailored treatment and monitoring. If you notice irregular heartbeats, fainting, or exercise intolerance, consult your vet promptly—especially in predisposed breeds like Boxers, Great Danes, and senior dogs. 🐾

For expert support and reassurance, download the Ask A Vet app today. 📲🐶