Cardiac arrhythmia (Canine) — NAVLE Prep

Quick anchor

Trigger

Irregular rhythm, pulse deficits, syncope, or collapse

First step

Ask whether the patient is hemodynamically stable

Confirm

ECG pattern, not auscultation alone

Trap

Do not treat every isolated ectopic beat like VT

Exam core — read this first

Unstable arrhythmia → poor perfusion, weakness, syncope, or collapse means emergency action

ECG matters → the board expects rhythm classification before final treatment choice

Big buckets → tachyarrhythmias, bradyarrhythmias, and incidental ectopy behave differently

Underlying disease → DCM, electrolyte problems, drug effects, and systemic illness often drive the rhythm

Pattern recognition

Core pattern

Irregular rhythmPulse deficitsWeakness / syncope / exercise intolerance

Supporting clues

Known cardiomyopathyBoxer or DobermanElectrolyte disturbanceDrug exposureVery slow or very fast heart rate

NAVLE trigger: The key board move is deciding whether the arrhythmia is causing instability or is an incidental finding that still needs workup.

Decision core — what NAVLE actually asks

Fast rhythm with collapse or poor pulses

→ Treat as an unstable tachyarrhythmia and stabilize immediately while ECG-guided therapy proceeds

Ventricular ectopy in a stable dog

→ Confirm rhythm, look for myocardial/systemic disease, and decide whether therapy is actually needed

Marked bradyarrhythmia with syncope

→ Think high-grade AV block / severe conduction disease and pacemaker-level reasoning

Key interpretation

ECG

Definitive

Best way to classify the rhythm

Pulse deficits

Important clue

Mechanical output does not match every beat

Atrial fibrillation

Very irregular

Often with structural heart disease

Ventricular tachycardia

Potentially unstable

Wide-complex fast rhythm needs respect

AV block

Markedly slow

Syncope raises urgency

Electrolytes / myocardium

Check both

Arrhythmia often reflects broader disease

⚠ ECG pattern plus patient stability drives the answer. An irregular heartbeat alone is not enough to choose therapy correctly.

Treatment

Step 1

Stabilize the unstable rhythm patient and use ECG-guided antiarrhythmic or electrical therapy as indicated

Treat the dangerous rhythm, not just the monitor.

Step 2

Address underlying myocardial or systemic disease

Many canine arrhythmias are secondary, not isolated primary problems.

Step 3

Pacemaker reasoning for severe symptomatic bradyarrhythmias

High-grade conduction disease is often not a drug-only problem.

NAVLE traps — where students lose marks

Sinus arrhythmia can be physiologic in dogs

Do not overcall every irregular rhythm as disease.

Stable VPCs are not managed the same way as unstable VT

The perfusion status determines urgency.

Auscultation cannot fully classify the rhythm

The board expects ECG confirmation.

Syncope with profound bradycardia should trigger AV block thinking

That is a pacemaker-style clue, not just “monitor and see.”

Differentials — how to separate these on NAVLE

Fast separator: The exam is usually asking whether you are dealing with incidental irregularity, unstable tachyarrhythmia, or severe bradyarrhythmia.

Rhythm problem	Heart rate	Perfusion clue	Key separator
Unstable tachyarrhythmia	Fast	Collapse / weak pulses	Immediate stabilization
Ventricular premature complexes	Usually near-normal overall	May be stable	ECG ectopy without continuous VT
Atrial fibrillation	Rapid irregularly irregular	Often structural heart disease	No organized atrial activity
High-grade AV block	Very slow	Syncope / weakness	Bradyarrhythmia / pacemaker logic
Sinus arrhythmia	Variable but physiologic	Usually normal patient	Normal canine rhythm variation

30-second revision

Question 1Stable or unstable rhythm?

Question 2Tachyarrhythmia, bradyarrhythmia, or incidental ectopy?

Best testECG

Brady syncope clueAV block thinking

Critical trapIrregular rhythm alone does not equal emergency

Practice questions

Pre-built NAVLE-style · Cardiac arrhythmia

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Q1Recognition

A dog with collapse, weak pulses, and a very rapid wide-complex rhythm on ECG most likely has which problem?

Q2Next best step

What is the most important first decision in a canine arrhythmia case?

Q3Diagnostic logic

Which test most directly classifies a canine arrhythmia?

Q4Bradyarrhythmia clue

A dog with recurrent syncope has a profoundly slow heart rate and evidence of conduction failure. Which long-term concept is most appropriate?

Q5Trap question

Which statement about canine arrhythmias is most accurate?