Canis ISSN: 2398-2942

Heart: congestive heart failure

Synonym(s): CHF

Contributor(s): Mark Rishniw, Simon Swift, Yolanda Martinez Pereira


  • Cause : underlying heart disease → either poor systolic function, poor diastolic function, volume overload, pressure overload, compliance failure or dysrhythmias → if severe enough → congestive heart failure syndrome (CHF).
  • Signs : syndrome characterized by fluid retention. Left congestive heart failure leads to pulmonary edema, whereas right congestive heart failure leads to ascites, pleural effusion.
  • Affected animal uses normal homeostatic mechanisms of cardiovascular system (activation of sympathetic nervous system and other neuroendocrine systems), to maintain blood pressure → detrimental in chronic cases → decreased cardiac function → progressive vicious cycle.
  • Diagnosis : signs, radiography, echocardiography.
  • Treatment : specific measures for underlying heart disease, control fluid retention, countering adverse neuroendocrine activation, correction of dysrhythmia (if present), improving systolic or diastolic function.
  • Prognosis : guarded - only palliative treatment available, which may stabilize condition but reversal of disease process is unlikely.


International Small Animal Cardiac Health Council System

  • Class I: asymptomatic.
  • Class IA: no evidence of compensation for underlying heart disease. (No volume overload or pressure overload detected radiographically or echocardiographically.)
  • Class IB: clinical signs of compensation for underlying heart disease. (Volume overload or pressure overload detected radiographically or echocardiographically.)
  • Class II: mild to moderate heart failure with clinical signs at rest or with mild exercise. Treatment required.
  • Class III: advanced heart failure; clinical signs of severe congestive heart failure.
    • Class IIIA: home treatment possible.
    • Class IIIB: requires hospitalization.

American College of Internal Medicine (ACVIM) classification for heart disease and heart failure - adapted from human AHA/ACC

  • Stage A: patient at risk of developing heart disease in the future, eg patient from breed with high predisposition for cardiac disease.
  • Stage B: asymptomatic patients with evidence of structural heart disease, eg presence of murmur:
    • B1: with no evidence of cardiac remodeling (radiographically or echocardiographically).
    • B2: with evidence of cardiac remodeling.
  • Stage C: patients with clinical signs of congestive heart failure (either past or present).
  • Stage D: refractory heart failure. Patients showing clinical signs in spite of standard treatment for congestive heart failure.
    Follow the diagnostic tree for CHF Complications.



Causes of left-sided CHF Causes of right-sided CHF


  • Underlying heart disease.


Categories of underlying heart disease Their effect
  • Decreased cardiac output → decreased blood pressure → activate baroreceptors → reflex increased sympathetic activity/decreased vagal activity → increased heart rate, increased contractility and vasoconstriction → maintain blood pressure.
  • Sympathetic activation and poor renal perfusion → activates renin-angiotensin-aldosterone system (RAAS) → further vasoconstriction, sodium and water retention → increased sympathetic outflow and release of vasopressin (antidiuretic hormone) → further vasoconstriction and water retention → increased venous pressures and eventually capillary pressures → extravasation of fluid into lungs (left-sided congestive heart failure), or abdomen (right-sided congestive heart failure).
  • Increased venous pressure and volume = increased preload → structural changes in myocardial sarcomeres.


  • Depends on underlying heart disease; most heart conditions (except cardiac tamponade), are progressive and eventually cannot be controlled.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Bernay F, Bland J M, Haggstrom J, Baduel L, Combes B, Lopez A, Kaltsatos V (2010) Efficacy of Spironolactone on Survival in Dogs with Naturally Occurring Mitral Regurgitation Caused by Myxomatous Mitral Valve Disease. J Vet Intern Med 24, 331-341 PubMed.
  • Atkins C, Bonagura J, Ettinger S, Fox P, Gordon S, Haggstrom J, Hamlin R, Keene B, Luis-Furentes V, Stepien V (2009) Guidelines for the Diagnosis and Treatment of Canine Chronic Valvular Heart Disease. J Vet Intern Med 23, 1142-1150 PubMed.
  • OGrady M R, OSullivan M L, Minors S L, Horne R (2009) Efficacy of Benazepril Hydrochloride to Delay the Progression of Occult Dilated Cardiomyopathy in Doberman Pinschers. J Vet Intern Med 23, 977-983 PubMed.
  • Haggstrom J, Boswood A, OGrady M et al (2008) Effect of pimobendan or benazepril hydrochloride on survival times in dogs with congestive heart failure caused by naturally occurring myxomatous mitral valve disease. The QUEST study. J Vet Intern Med 22, 1124-1135 PubMed.
  • Oyama M, Rush J E, OSullivan M L, Williams R M, Rozanoski E A, Petrie J P, Sleeper M M, Cimino Brown D (2008) Perceptions and priorities of owners of dogs with heart disease regarding quality versus quantity of life in their pets (2008). J Am Vet Med Assoc 233, 104-108 PubMed.
  • Boswood A (1999) Rationale for the use of drugs in treatment of cardiovascular disease - positive ionotropes. In Practice 21 (5), 253-259 InPractice.
  • Packer M (1998) Neurohormonal interactions and adaptations in congestive heart failure. Circulation 77 (4), 721-730 PubMed.
  • The COVE Study Group (1995) Controlled clinical evaluation of enalapril in dogs with heart failure - results of the Cooperative Veterinary Enalapril Study Group. JVIM 9 (4), 243-252 PubMed.
  • The IMPROVE Study Group (1995) Acute and short-term hemodynamic, echocardiographic and clinical effects of enalapril maleate in dogs with naturally acquired heart failure - results of the Invasive, Multicenter, PROspective Veterinary evaluation of Enalapril study. JVIM 9 (4), 234-242 PubMed.
  • Dahlström U & Karlsson E (1995) Captopril and spironolactone therapy for refractory congestive heart failure. Am Journ Cardiol 71 (3), 29A-33A PubMed.
  • Pederson H D, Koch J, Poulson K, Jemsen A L & Flagstad A (1995) Activation of the renin-angiotensin system in dogs with mildly asymptomatic mitral valvular insufficiency. JVIM 9 (5), 328-331 PubMed.
  • Francis G S & Chu C (1994) Compensatory and maladaptive responses to cardiac dysfunction. Current Opinion in Cardiology 9 (3), 280-288 PubMed.
  • Roudebush P, Allen T A, Kuehn N F, Magerkurth J H & Bowers T L (1994) The effect of combined therapy with captopril, furosemide and a sodium-restricted diet on serum electrolyte concentrations and renal function in normal dogs and dogs with congestive heart failure. J Vet Intern Med 8 (5), 337-342 PubMed.
  • Schlesinger D P & Rubin S I (1994) Potential adverse effects of angiotensin converting enzyme inhibitors in the treatment of congestive heart failure. Comp Cont Educ Pract Vet 16 (3), 275-283 VetMedResource.
  • Riegger G A J (1993) ACE inhibitors in early stages of heart failure. Circulation 87 (suppl IV), 117-119 PubMed.
  • Zannad F (1993) Angiotensin-converting anzyme inhibitor and spironolactone combination therapy. New objectives in congestive heart failure management. Am Journ Cardiol 71 (3), 34A-39A PubMed

Other sources of information

  • Summerfield N, Gordon S G (2012)Pimobendan improves survival in Doberman Pinschers with preclinical DCM: The results of PROTECT a double-blind, placebo-controlled randomized clinical trial.In:Proceedings of International Cardiology Veterinary Symposium,Dubai, May 4th-6th, 2012.
  • Bulmer B B & Sisson D D (2005)Therapy of heart failure.Chapter 199. In:Textbook of Veterinary Internal Medicine6th edn. Eds S J Ettinger & E C Feldman. Philadelphia: W B Saunders. pp 948-971. (Well referenced.)
  • Morais H A & Schwartz D S (2005)Pathophysiology of heart failure.In:Textbook of Veterinary Internal Medicine6th edn. Eds S J Ettinger & E C Feldman. Philadelphia: W B Saunders. pp 914-939. (Good logical approach to the syndrome of CHF.)
  • Miller M S & Tilley L P (1995)International Small Animal Cardiac Health Council System of Heart Failure Classification. (Appendix 1 - Recommendations for the diagnosis of heart disease and treatment of heart failure in small animals.)In:Manual of Canine and Feline Cardiology2nd edn. Eds M S Miller & L P Tilley. Philadelphia: W B Saunders. pp 473. (Modern method of classifying CHF in dogs.)