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Congestive heart failure/cor pulmonale

obovis

Synonym(s): CHF


Introduction

  • Congestive heart failure can be unilateral or bilateral, acute or chronic.
  • The term 'Cor Pulmonale' relates to pulmonary cardiovascular disease and relates to right sided heart failure secondary to (usually chronic) pulmonary artery hypertension.
  • 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 pleural effusion and occasionally ascites.
  • 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: clinical signs, echocardiography.
  • Treatment:
    • Treatment involves specific measures to treat the underlying heart disease, control fluid retention, counter adverse neuroendocrine activation, correct dysrhythmias (if present) and improve systolic or diastolic function.
    • Treatment is rarely economically viable in cattle, but may be attempted in very valuable animals.
    • Drugs are not ususally licensed for use in cattle. 
  • Prognosis: Poor - only palliative treatment is available and normally not a viable option.

Pathogenesis

Etiology

Causes of left-sided CHF

Causes of right-sided CHF

  • Pericardial disease, e.g. secondary to traumatic reticulitis Traumatic reticulitis.
  • Tricuspid valve disease, e.g. vegetative valvular endocarditis Endocarditis.
  • Pulmonary hypertension.
  • Brisket disease/ Bovine high altitude disease is seen worldwide and causes pulmonary arterial hypertension leading to right sided heart failure.
    • Cor pulmonale arises as a result of increased pulmonary artery pressure due to changes in pulmonary vascular bed: vasoconstriction (e.g. Alveolar hypoxemia) or obstruction (e.g. embolus).

Pathophysiology

Categories of underlying heart disease

  • Systolic failure, e.g. due to dilated cardiomyopathy.
  • Diastolic failure, e.g. due to pericardial disease or hypertrophic cardiomyopathy
  • Volume overload, e.g. due to mitral or tricuspid valve endocarditis, patent ductus arteriosus PDA, ventricular septal defect VSD.
  • Pressure overload, e.g. due to severe systemic hypertension, (very rare in cattle pulmonary hypertension).
  • Dysrhythmias: ventricular tachycardia, supraventricular tachycardia, atrial fibrillation, third degree atrioventricular block (rare). Dysrhythmias

Effects

  • Decreased cardiac output → decreased blood pressure → activation of 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 leading to pulmonary edema), or chest and abdomen (right-sided congestive heart failure; pleural effusion and occasionally ascites).
  • Increased venous pressure and volume = increased preload → structural changes in myocardial sarcomeres.

Cor pulmonale

  • Right ventricular enlargement secondary to respiratory disease or high altitude disease.
  • In some cases may be the first indicator that severe pulmonary disease exists.
  • Increased pulmonary vascular resistance → pulmonary hypertension.
  • This increases the work that the right heart has to do → compensatory hypertrophy of the right ventricle.
  • If hypertension persists then right-sided failure ultimately develops.

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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Outcomes

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed And VetMedResource.
  • Christopher R, Malherbe, Marquard J, David E et al (2012) Right ventricular hypertrophy with heart failure in Holstein heifers at elevation of 1,600 meters. J Vet Diag Invest 24 (5), 867-77.
  • Buczinski S, Francoz D, Fecteau G & DiFruscia R (2010) Heart disease in cattle with clinical signs of heart failure: 59 cases. CN Vet J 51 (10), 1123–1129 PubMed.

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