• The only "Plum" book is Plum and Posner's Diagnosis and Treatment of Stupor and Coma (a human neurology textbook)
• There are no veterinary-specific titles (no Plumb's, no veterinary pharmacology, no small animal medicine)

Furosemide — Plumb's Veterinary Drug Handbook

Dog

Cat

Note: Cats are more sensitive to furosemide than dogs — use the lower end of the dosing range and monitor closely for dehydration and electrolyte imbalances (especially hypokalemia).

Dilated Cardiomyopathy (DCM) in Dogs

A Comprehensive Review from Multiple Authoritative Sources

1. Definition

"Dilated cardiomyopathy is characterized by progressive cardiac dilation and contractile (systolic) dysfunction, usually with concurrent hypertrophy; regardless of the cause, the clinicopathologic patterns are similar." — Robbins & Kumar Basic Pathology, 10th ed., p. 371

2. Epidemiology and Breed Predisposition

Wess G. Screening for dilated cardiomyopathy in dogs. J Vet Cardiol. 2022; PMID: 34732313

3. Etiopathogenesis

A. Genetic / Hereditary Causes

• PDK4 (pyruvate dehydrogenase kinase 4) — Doberman Pinschers; one of the first canine DCM genes discovered
• Titin (TTN) — Doberman Pinschers; titin mutations account for ~25% of familial cases in humans and are increasingly recognized in dogs; titin spans the sarcomere, connecting Z and M bands, limiting passive stretch range
• Striatin (STRN) — associated with the arrhythmogenic form in Boxers (a desmosomal gene)
• Dystrophin — X-linked DCM; dystrophin physically couples intracellular cytoskeleton to the extracellular matrix (ECM)
• Desmin, Lamin A/C — cytoskeletal and nuclear envelope genes causing conduction abnormalities concurrent with DCM

"It is most often caused by loss of function mutations affecting cytoskeletal proteins or proteins that link the sarcomere to the cytoskeleton." — Robbins & Kumar Basic Pathology, 10th ed., p. 371

Fig. 9.24 — Myocyte proteins mutated in DCM (red) and HCM (blue). Titin mutations are the most common cause of hereditary DCM. — Robbins & Kumar Basic Pathology, 10th ed.

Shen L, Estrada AH, Meurs KM et al. A review of the underlying genetics and emerging therapies for canine cardiomyopathies. J Vet Cardiol. 2022; PMID: 34147413

Gaar-Humphreys KR et al. Genetic Basis of Dilated Cardiomyopathy in Dogs and Its Potential as a Bidirectional Model. Animals (Basel). 2022; PMID: 35804579

B. Nutritional / Dietary Causes — Taurine and Carnitine Deficiency

• Taurine deficiency is strongly implicated in DCM in Golden Retrievers, Cocker Spaniels, and other breeds, particularly those fed grain-free, legume-rich (pea- or potato-based) diets
• In 2018, the FDA issued an alert linking grain-free diets to DCM in breeds without known genetic predisposition
• Affected dogs show enlarged LV diameters, reduced systolic function, and increased ventricular premature complexes — many improve or fully recover with dietary change + taurine supplementation, suggesting reversibility
• Proposed mechanisms include: impaired bile acid metabolism due to high legume fiber content, altered gut microbiota, reduced taurine absorption from high-pulse diets
• L-carnitine deficiency has also been associated with DCM in Boxers and Cocker Spaniels

Mornard L, Brasileiro ACM, Marcondes-Santos M. Role of Diet as a Predisposing Factor for Dilated Cardiomyopathy in Dogs: A Narrative Review. Vet Sci. 2025; PMID: 41295744

C. Infectious / Inflammatory

• Viral myocarditis (parvovirus, enteroviruses, adenovirus) can progress to DCM
• Sequential myocardial injury depletes functional cardiomyocytes → replacement fibrosis → systolic dysfunction
• Chagas disease (Trypanosoma cruzi) is an important cause in endemic regions (southern US, Latin America)

D. Toxic Causes

• Doxorubicin (anthracycline chemotherapy) — cumulative cardiotoxicity, dose-dependent
• Cobalt toxicity
• Alcohol metabolites (acetaldehyde) — relevant in humans, less so in dogs

E. Idiopathic

4. Pathological Anatomy (Morphology)

"The heart in DCM is characteristically enlarged (up to two to three times the normal weight) and flabby, with dilation of all chambers. Because of the wall thinning that accompanies dilation, the ventricular thickness may be less than, equal to, or greater than normal. Mural thrombi are often present and may be a source of thromboemboli." — Robbins & Kumar Basic Pathology, 10th ed., p. 372

• Markedly enlarged, globose, flabby heart
• All chambers dilated (biventricular involvement common in dogs)
• Ventricular wall thinning (despite overall heavy weight)
• Mural thrombi in atria or ventricles
• No significant valvular or coronary lesions

• Myocyte hypertrophy with enlarged, bizarre nuclei
• Attenuated, stretched, irregular myocytes (hallmark of end-stage DCM)
• Interstitial and replacement fibrosis — fingerprints of previous ischemic necrosis or resolved myocarditis
• In Dobermans: attenuated wavy fibers and fibrofatty replacement
• Canine breeds show distinct histopathological subtypes:
  • Fatty infiltration pattern (Doberman, Boxer) — similar to arrhythmogenic cardiomyopathy overlap
  • Fibrosis pattern — generalized fibrofatty replacement

Gaar-Humphreys KR et al. Animals (Basel). 2022; PMID: 35804579

5. Disease Staging

Wess G. Screening for dilated cardiomyopathy in dogs. J Vet Cardiol. 2022; PMID: 34732313

6. Clinical Presentation

Occult (Preclinical) Phase

• Dogs may be asymptomatic for months to years before overt CHF
• Detected only on screening (Holter, echo, biomarkers)
• Dobermans: mean occult phase of 3–4 years; sudden cardiac death can occur even in this phase
• Boxers: VPCs often precede systolic dysfunction

Overt (Clinical) Phase

• Exercise intolerance, weakness, lethargy
• Tachypnea, dyspnea (pulmonary edema)
• Cough (less common in dogs than in cats)
• Weight loss, muscle wasting (cardiac cachexia)

• Ascites
• Pleural effusion
• Jugular venous distension
• Hepatomegaly

• Syncope or collapse (VT, VF)
• Sudden cardiac death — particularly in Dobermans and Boxers

• Weak femoral pulses, pulse deficits
• Soft systolic murmur (secondary mitral regurgitation from annular dilation)
• S3 or S4 gallop sounds
• Arrhythmias on auscultation

7. Diagnosis

Electrocardiography (ECG / Holter monitoring)

• Atrial fibrillation — very common in Irish Wolfhounds and Great Danes; often the presenting rhythm in advanced disease
• Ventricular premature complexes (VPCs) — dominant in Boxers and Dobermans
• Holter criteria for Dobermans: >50 VPCs/24h (suspicious); >100 VPCs/24h (diagnostic threshold for occult DCM)
• Left bundle branch block pattern, sinus tachycardia, non-specific ST changes

Wess G. J Vet Cardiol. 2022; PMID: 34732313

Echocardiography

• Increased LV end-diastolic diameter (LVEDD) — >2 SD above BSA-corrected normal
• Decreased fractional shortening (FS) — <25% (normal 25–40% in dogs); severely reduced in DCM
• Decreased LV ejection fraction (EF) — <40% in end-stage (per Goldman-Cecil, p. 514)
• Increased E-point to septal separation (EPSS) — >6 mm suggests significant systolic dysfunction
• Biventricular dilation, mitral and tricuspid regurgitation (secondary)
• Left atrial enlargement (LA:Ao ratio >1.5–1.6)

• LVEDD >46 mm (females), >50 mm (males)
• LVESD >38 mm (females), >40 mm (males)

Goldman-Cecil Medicine, 26th ed., p. 514

Thoracic Radiography

• Cardiomegaly (increased vertebral heart score, VHS)
• Pulmonary venous congestion, interstitial/alveolar pattern (pulmonary edema)
• Pleural effusion possible
• Increased cardiothoracic ratio (>0.5)

Cardiac Biomarkers

• NT-proBNP — elevated; predicts progression, CHF risk, and survival; useful for screening in breeds at risk
• Cardiac Troponin I (cTnI) — elevated indicates myocardial damage; correlates with severity; useful screening biomarker in Dobermans
• Both biomarkers recommended in occult phase screening

Laboratory Tests

• CBC, serum chemistry (BUN, creatinine, electrolytes)
• Liver function tests
• Thyroid-stimulating hormone (TSH) — rule out hypothyroid cardiomyopathy
• Serum taurine and carnitine concentrations (especially in Golden Retrievers, Cockers, any dog on grain-free diet)
• Urinalysis

8. Treatment

A. Heart Failure Management

"Supportive therapy includes sodium and fluid restriction, avoidance of alcohol and other toxins, and use of established heart failure medications." — Goldman-Cecil Medicine, 26th ed., p. 441

B. Antiarrhythmic Therapy

• Atrial fibrillation: diltiazem, digoxin, atenolol (rate control)
• Ventricular arrhythmias (VPCs/VT): sotalol (drug of choice in Dobermans/Boxers), mexiletine (especially in Dobermans), amiodarone
• Implantable cardioverter-defibrillators (ICD) — used in human DCM; under investigation in large dogs

C. Nutritional Supplementation

• Taurine: 500–1000 mg PO q8–12h (dogs with documented taurine deficiency or on grain-free diets)
• L-Carnitine: 50–100 mg/kg PO q8h (Boxers, Cocker Spaniels with suspected deficiency)
• Dietary change away from grain-free, high-legume formulations strongly recommended when nutritional DCM is suspected

D. Occult DCM — Pimobendan (PROTECT Trial)

• The landmark PROTECT study (Doberman Pinschers with occult DCM) showed pimobendan significantly delayed onset of CHF by ~9 months and extended survival
• Pimobendan is now recommended for dogs with echocardiographic evidence of occult DCM (Stage B2)

E. Emerging Therapies

• Gene therapy approaches targeting PDK4 and TTN mutations in dogs are under active investigation
• Canine iPSC (induced pluripotent stem cell) models being developed for drug testing and disease modeling
• Dogs are recognized as a valuable bidirectional translational model for human DCM due to shared genetic pathways and similar disease progression

Shen L et al. J Vet Cardiol. 2022; PMID: 34147413 Gaar-Humphreys KR et al. Animals (Basel). 2022; PMID: 35804579

9. Prognosis

10. Screening Recommendations

• Start at 3 years of age for predisposed breeds
• Holter monitoring annually for Dobermans and Boxers (most sensitive for arrhythmic form)
• Echocardiography annually for breeds with predominantly myocardial form (Great Dane, Irish Wolfhound)
• Biomarkers (NT-proBNP, cTnI) as adjunct screening tools
• A single negative screen does not rule out future disease — lifelong annual screening recommended

Wess G. J Vet Cardiol. 2022; PMID: 34732313

References

1. Robbins & Kumar Basic Pathology, 10th ed. — Dilated Cardiomyopathy, pp. 371–372
2. Goldman-Cecil Medicine, 26th ed. — Dilated Cardiomyopathy, pp. 513–514 (Chapter 47)
3. Braunwald's Heart Disease, 11th ed. — Gap Junction Channels and Arrhythmogenesis in DCM models
4. Wess G. Screening for dilated cardiomyopathy in dogs. J Vet Cardiol. 2022 Apr. PMID: 34732313
5. Shen L, Estrada AH, Meurs KM et al. A review of the underlying genetics and emerging therapies for canine cardiomyopathies. J Vet Cardiol. 2022 Apr. PMID: 34147413
6. Gaar-Humphreys KR et al. Genetic Basis of Dilated Cardiomyopathy in Dogs and Its Potential as a Bidirectional Model. Animals (Basel). 2022 Jun. PMID: 35804579
7. Mornard L, Brasileiro ACM, Marcondes-Santos M. Role of Diet as a Predisposing Factor for Dilated Cardiomyopathy in Dogs. Vet Sci. 2025. PMID: 41295744

Important note: The library available here contains human medical textbooks. The pathological, genetic, and clinical information on human DCM from Robbins Pathology and Goldman-Cecil Medicine is directly applied to canine DCM given the well-established parallel disease biology. Canine-specific epidemiology, staging, screening, and management data are sourced from peer-reviewed veterinary cardiology literature (PubMed, 2022–2025).