canis - Articles
Heart: congestive heart failure
Synonym(s): CHF
Introduction
- 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.
Classifications
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.
Presenting signs
Left-sided CHF
- Shortness of breath.
- Cough.
- Increased respiratory rate (tachypnea).
- Dyspnea (may be just exertional).
- Exercise intolerance.
- Tussive syncope.
- Orthopnea.
- Tachycardia.
Right-sided CHF
- Progressive abdominal distension.
- Exercise intolerance.
- Dyspnea.
- Syncope.
- Tachycardia.
- Weight loss.
Acute presentation
Left-sided CHF
- Extreme dyspnea.
- Cyanosis.
- Productive cough: pink/clear frothy fluid: (edema + surfactant → stable foam).
- Circulatory collapse.
Age predisposition
- If severe underlying congenital disease often present in first 2 years of life.
- Adult animals for degenerative or acquired conditions.
Breed/Species predisposition
- Depends on underlying heart disease and specific treatment required.
Cost considerations
- Depends on underlying heart disease and specific treatment required.
Special risks
Stress
- Treat ISACHC Class IV heart failure symptomatically (eg oxygen, intravenous diuretics, cage rest, sedation if required with opioid), before undertaking diagnostic procedures.
Must drain pericardial effusions immediately if cardiac tamponade Pericardiocentesis. Do not use diuretics prior to pericardiocentesis. - Suspicion of pericardial effusion Pericardial disease , usually based on signalment, ascultation and ECG/radiography.
Radiography
- If dyspneic: sedate safely to limit anxiety and use dorsoventral view (rather than ventrodorsal), to avoid impairing respiration.
- Often a single lateral view suffices.
Sedation
- See guidance under anesthesia Anesthesia: for cardiovascular insufficiency.
General anesthesia
- See guidance under anesthesia Anesthesia: for cardiovascular insufficiency.
- Avoid if CHF is uncontrolled unless absolutely unavoidable.
Warn owner of increased risk of anesthesia.
Electrocardiography
- Essential diagnostic procedure ECG: overview , if suspected life-threatening dysrhythmia Heart: dysrhythmia.
Can obtain Lead II rhythm strip with animal in any position for rhythm assessment - not essential to place in right lateral recumbency if this causing stress or compromising respiration.
Intravenous fluid therapy
- Fluids cannot be given if CHF is present except for cardiac tamponade prior to pericardiocentesis.
- See details under fluid therapy Fluid therapy: acute circulatory collapse.
Diet
- Increased sodium intake may increase water retention and congestive signs.
- Avoid sudden increase in sodium intake, eg salty treats.However, use of sodium restricted diets is controversial especially with ACE inhibitor therapy ACE inhibitor: overview.
Pathogenesis
Etiology
Causes of left-sided CHF
- Degenerative mitral valve disease Heart: mitral valve degenerative disease.
- Dilated cardiomyopathy Heart: dilated cardiomyopathy (DCM).
- Patent ductus arteriosus Patent ductus arteriosus.
- Ventricular septal defect Ventricular septal defect.
- Mitral dysplasia Atrioventricular valve dysplasia.
- Mitral stenosis (rare).
Causes of right-sided CHF
- Pericardial disease Pericardial disease.
- Degenerative tricuspid valve disease Endocardiosis: tricuspid valve.
- Tricuspid dysplasia Atrioventricular valve dysplasia , or stenosis.
- Pulmonic stenosis Pulmonic stenosis.
- Severe heartworm disease Canine cardiopulmonary dirofilariasis.
- Cor pulmonale (less common) Cor pulmonale.
- Cor triatriatum dexter (rare).
Specific
- Underlying heart disease.
Pathophysiology
Categories of underlying heart disease
- Systolic failure, eg due to dilated cardiomyopathy Heart: dilated cardiomyopathy (DCM).
- Diastolic failure, eg due to hypertrophic cardiomyopathy or pericardial disease Pericardial disease.
- Volume overload, eg due to mitral regurgitation Heart: mitral valve degenerative disease , tricuspid regurgitation Endocardiosis: tricuspid valve , patent ductus arteriosus Patent ductus arteriosus , ventricular septal defect Ventricular septal defect.
- Pressure overload, eg due to aortic stenosis Heart: aortic stenosis , severe systemic hypertension, pulmonic stenosis Pulmonic stenosis , pulmonary hypertension Pulmonary Arterial Hypertension (PHT). - rarely produces CHF unless severe and chronic.
- Dysrhythmias Heart: dysrhythmia : ventricular tachycardia Ventricular tachycardia , supraventricular tachycardia, atrial fibrillation Heart: atrial fibrillation , high grade second degree or third degree atrioventricular block (rare) Heart: second degree atrioventricular block Heart: 3rd degree atrioventricular block.
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.
Timecourse
- Depends on underlying heart disease; most heart conditions (except cardiac tamponade), are progressive and eventually cannot be controlled.
Diagnosis
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Treatment
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Further Reading
Publications
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 Medicine 6th 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 Medicine 6th 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 Cardiology 2nd edn. Eds M S Miller & L P Tilley. Philadelphia: W B Saunders. pp 473. (Modern method of classifying CHF in dogs.)