NAVLE Cardiovascular

Canine Congestive Heart Failure (CHF): Complete NAVLE Study Guide

March 28, 2026 12 min read 38 views
Master canine congestive heart failure for the NAVLE. Covers ACVIM staging, MMVD vs DCM, furosemide dosing, pimobendan use, and the EPIC/QUEST trials — with 3 practice questions.

Canine CHF shows up on the NAVLE constantly, and it almost always comes down to three things: knowing your breeds, knowing your staging, and knowing your drugs. Get those right and you'll handle whatever question they throw at you.

The Two Main Causes

MMVD

Myxomatous Mitral Valve Disease

Breeds: CKCS, Poodles, Dachshunds, small breeds

Mechanism: Valve thickening → MR → LA enlargement

FS: Usually preserved (>25%)

~75% of canine cardiac disease

DCM

Dilated Cardiomyopathy

Breeds: Doberman, Great Dane, Boxer, Irish Wolfhound

Mechanism: Myocardium dilates → poor contractility

FS: Reduced (<25%)

Occult phase common in Dobermans

NAVLE Pearl The signalment alone points you to the answer. Small breed + mitral murmur + LA enlargement on rads = MMVD. Large breed + weak dilated heart + arrhythmias = DCM. Read the signalment before the question body.

ACVIM Staging — Know This Cold

The 2019 ACVIM Consensus Guidelines divided MMVD into four stages. The boards test whether you know when to start treatment — not just which drugs to use.

Stage Definition Treatment
A At-risk breed, no murmur yet None — monitor
B1 Murmur present, no cardiac remodeling None — monitor q12 months
B2 Murmur + remodeling: LA:Ao ≥1.6 and VHS ≥10.5 Start pimobendan (EPIC trial)
C Current or past CHF signs Furosemide + pimobendan + ACE inhibitor
D Refractory CHF Add spironolactone, CRI furosemide, O²

The EPIC trial (2016) changed everything for Stage B2. Before EPIC, you waited until CHF to start pimobendan. Now you start it in asymptomatic dogs with significant remodeling — it delays onset of CHF by about 15 months. That finding is highly testable.

Clinical Signs: Left vs Right-Sided

Left-Sided Failure

• Soft, moist cough (worse at night)

• Exercise intolerance

• Tachypnea, orthopnea

• Pulmonary crackles

Rads: perihilar pulmonary edema

Right-Sided Failure

• Ascites

• Pleural effusion (less common in dogs)

• Jugular venous distension

• Hepatomegaly, peripheral edema

Rads: hepatomegaly + ascites

NAVLE Tip Cough + exercise intolerance + rads showing LA enlargement and perihilar edema = left-sided. Ascites on the same dog = right-sided or biventricular. Know which direction the fluid goes.

Diagnostics

Thoracic radiographs — first step in respiratory distress. Look for cardiomegaly (VHS >10.5), left atrial enlargement on lateral view (the caudal cardiac waist disappears), and perihilar alveolar pattern for pulmonary edema.

Echocardiography — gold standard for staging. Gives you LA:Ao ratio, fractional shortening (FS), and confirms structural disease. FS <25% = systolic dysfunction in dogs.

NT-proBNP — rises with myocardial wall stretch. Useful to differentiate cardiac from respiratory dyspnea before echo is available. The QUEST trial validated its use in MMVD.

Holter monitor — 24h ECG. Standard Doberman DCM screening. >300 VPCs/24h = clinically significant.

Treatment Drugs at a Glance

Drug Class Dose Notes
Furosemide Loop diuretic 2–4 mg/kg IV acute; 1–2 mg/kg PO BID-TID Watch for hypokalemia
Pimobendan Inodilator 0.25–0.3 mg/kg PO BID Empty stomach — bioavailability drops 30% with food
Enalapril ACE inhibitor 0.5 mg/kg PO BID Monitor renal values + K+
Spironolactone Aldosterone antagonist 2 mg/kg PO SID Anti-fibrotic; Stage C/D
Digoxin Cardiac glycoside Target level 0.8–1.2 ng/mL Rate control in AFib; narrow TI
Classic NAVLE Trap Dog in acute pulmonary edema → furosemide IV is correct. Next question: what do you add for long-term management? Answer: pimobendan — not digoxin, not ACE inhibitor alone. Pimobendan is now the cornerstone of canine CHF management.

Prognosis

Stage B2 dogs started on pimobendan: median time to CHF onset ~3 years. Stage C with optimal therapy: median survival 9–12 months. Stage D: weeks to a few months.

Atrial fibrillation in a Doberman with DCM = emergency. Rate control with diltiazem or digoxin + aggressive diuresis. AFib significantly shortens survival in large breed DCM.

Quick Reference

  • MMVD = small breeds (CKCSs); DCM = large breeds (Dobermans)
  • Stage B2 criteria: LA:Ao ≥1.6 AND VHS ≥10.5 → start pimobendan (EPIC trial)
  • Acute CHF: furosemide 2–4 mg/kg IV + oxygen
  • Chronic: furosemide + pimobendan + ACE inhibitor ± spironolactone
  • Pimobendan: empty stomach, BID
  • Left CHF = pulmonary edema; Right CHF = ascites/JVD
  • NT-proBNP differentiates cardiac vs respiratory dyspnea
  • Holter monitor Dobermans: >300 VPCs/24h = significant
  • FS <25% = systolic dysfunction (DCM territory)

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