Heart: congestive heart failure

f felis

Contributor(s):

Yolanda Martinez Pereira

Mark Oyama

Mark Rishniw

Liz Bode

Synonym(s): CHF

Introduction

Cause: underlying heart disease:
- Primary:
  - Poor diastolic function (compliance failure).
  - Poor systolic function (myocardial or pump failure), rare.
  - Congenital heart disease.
- Secondary:
  - Hyperthyroidism.
  - Systemic hypertension.
  - Taurine deficiency.
- Arrhythmias.
Signs: respiratory difficulty, poor appetite, activity intolerance.
Treatment: control fluid retention, counter adverse neuroendocrine activation, correction of arrhythmia, improving systolic or diastolic function.
Prognosis: guarded.

Systolic failure:
- Dilated cardiomyopathy Heart: dilated cardiomyopathy (DCM). Rare.
- Arrhythmogenic right ventricular cardiomyopathy (affecting right-sided chambers). Rare.
Diastolic failure:
- Hypertrophic cardiomyopathy Heart: hypertrophic cardiomyopathy. Common.
- Restrictive cardiomyopathy Heart: restrictive cardiomyopathy. Common.
- Pericardial disease Pericardial disease. Rare.
- Secondary to hyperthyroidism Hyperthyroidism.
Volume overload:
- Severe mitral regurgitation Atrioventricular valve dysplasia.
- Tricuspid regurgitation Atrioventricular valve dysplasia.
- Patent ductus arteriosus Patent ductus arteriosus.
- Ventricular septal defect Ventricular septal defect; large left-to-right shunting.
Pressure overload:
- Aortic stenosis Heart: aortic stenosis.
- Severe systemic hypertension (rare cause of CHF) Hypertension.
- Pulmonic stenosis.
- Pulmonary hypertension Pulmonary arterial hypertension (PHT).
Dysrhythmias:
- Ventricular tachycardia Heart: dysrhythmia.
- Supraventricular tachycardia.
- Atrial fibrillation Atrial fibrillation.
- High grade second degree or third degree atrioventricular block Heart: dysrhythmia.

Cardiac injury → activation of sympathetic nervous system, renin-angiotensin-aldosterone and arginine-vasopressin systems to maintain blood pressure → detrimental in chronic cases → decreased cardiac function → progressive vicious cycle.
Decreased cardiac output → decreased blood pressure activates 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 and pleura (left-sided heart failure) or liver and abdomen (right-sided heart failure).
Pleural effusions are very common in cats with both left and right sided cardiac failure.
See Pathophysiology of CHF for more detail Heart: pathophysiology of CHF.