Vet Guide 2025: Spotting & Treating Ventricular Fibrillation in Dogs 🩺

By Dr. Duncan Houston BVSc

💡 What Is Ventricular Fibrillation?

Ventricular fibrillation (V‑fib) is a chaotic, life‑threatening arrhythmia where the heart’s ventricles quiver ineffectively, stopping blood flow and causing sudden cardiac arrest.

On ECG, it appears as rapid, irregular waveforms without organized QRS complexes—often called a “quivering baseline”.

🚩 Who’s Affected & Why?

• Can occur at any age, but more often in older dogs or those with preexisting heart disease.
• Common causes:
• Severe ventricular tachycardia that degenerates to V‑fib.
• Myocarditis, cardiomyopathy (e.g. Boxer ARVC), or heart valve disease.
• Electrolyte imbalances, toxins, anesthetic complications, shock, hypoxia.
• Also triggered by surgical manipulation or electrosurgery during procedures like pericardiectomy.

👀 Clinical Signs & ECG Recognition

• Sudden collapse, loss of consciousness, and pulselessness—a veterinary emergency.
• ECG: chaotic rapid waves, no discernible P‑QRS‑T complexes.
• Often preceded by sustained ventricular tachycardia—wide, abnormal QRS complexes >180 bpm.

🏥 Emergency Management & Defibrillation

1. Immediate CPR

• Begin chest compressions and assisted ventilation immediately, following RECOVER guidelines.
• Continue until the defibrillator is ready or ROSC (return of spontaneous circulation) occurs.

2. Electrical Defibrillation

• Definitive treatment—deliver shock as soon as possible to restore organized rhythm.
• If no defibrillator is available, a precordial thump may sometimes help—but it's rarely effective.
• Best outcomes occur when defibrillation is delivered within 3 minutes of arrest.

3. Post‑Resuscitation Care

• Hospitalized in ICU with continuous ECG, BP monitoring, and oxygen support.
• Treat underlying causes (e.g., myocarditis, electrolyte imbalances, toxins).
• Provide supportive care: IV fluids, ventilation support, antiarrhythmics as needed.

🩺 Long‑Term Management & Prevention

1. Antiarrhythmic Medications

• Sotalol, mexiletine, β‑blockers or amiodarone for dogs with recurrent ventricular arrhythmias.
• Holter monitoring is used to optimize medication efficacy and dosage.

2. Address Underlying Disease

• Treat or manage myocarditis, cardiomyopathy, ischemia, and electrolyte disturbances.
• Monitor and manage surgical or procedural risks in at-risk dogs.

3. Regular Monitoring

• Periodic ECG and Holter studies to detect arrhythmic patterns early.
• Monitor electrolytes, cardiac enzymes, and organ function regularly.

📈 Prognosis & Outcomes

• V-fib is fatal if untreated—death usually occurs within minutes.
• Immediate CPR + defibrillation can save lives—but overall prognosis is guarded.
• Long-term survival depends on preventing recurrence with medication and addressing underlying issues.
• After surgery-related V-fib, mortality can be high—14 of 16 dogs died in one pericardiectomy study.

🚫 Prevention Strategies

• Screen breeds predisposed to arrhythmias (Boxers, Bulldogs, GSDs) periodically.
• Manage underlying cardiac disease early to prevent ventricular ectopy.
• Ensure balanced electrolytes in critically ill patients.
• Use caution during surgical procedures—minimize electrosurgical manipulation in at-risk hearts.

🏡 Ask A Vet App for Home Support

• 🗓 Medication reminders for antiarrhythmics, electrolytes, and follow-up labs.
• 📊 Home logs of pulse rate, collapse episodes, exercise tolerance.
• 📸 Video uploads of breathing patterns, syncopy events for remote review.
• 🔔 Alerts for collapse, weakness, rapid breathing, or heart rhythm changes.
• 📚 Guides on CPR basics, ECG interpretation, pre/post-op care, arrhythmia triggers.

🔑 Key Takeaways

• Ventricular fibrillation is an emergency—causes cardiac arrest within minutes.
• Immediate CPR + defibrillation is essential to restore circulation.
• Post-arrest care and treating the underlying disease are key to survival.
• Guarded prognosis; chronic antiarrhythmics and monitoring help prevent recurrence.
• Ask A Vet app aids with home tracking, medication management, and remote monitoring.

🩺 Final Thoughts ❤️

In 2025, prompt recognition and treatment of ventricular fibrillation—via modern defibrillation and critical care—can offer dogs a second chance at life. Long-term survival depends on identifying root causes, sustained medical therapy, and proactive monitoring. With support tools like the Ask A Vet app, pet owners can stay engaged in managing arrhythmia risk, ensuring timely care and better outcomes for their pups. 🐾✨

Visit AskAVet.com and download the Ask A Vet app to set medication reminders, record syncopy episodes, upload home ECG/trending data, schedule vet visits, and stay connected with your veterinary cardiologist—right from your phone. 📲