Congestive Heart Failure

CHAPTER 43 Congestive Heart Failure

Congestive heart failure is a complex clinical syndrome that results from any structural or functional cardiac abnormality that impedes the ability of the heart to fill with or eject blood at a rate that meets the metabolic needs of the tissues. This results in activation of the adrenergic nervous system and renin-angiotensin-aldosterone system and enhanced release of vasopressin, leading to renal sodium and water retention. Consequently, venous pressures increase, resulting in congestion and fluid accumulation. This condition is uncommon in horses. Underlying causes for congestive heart failure in the horse include congenital defects, degenerative valvular disease, valvulitis, endocarditis, myocarditis, cardiomyopathy, pericarditis, vascular disease, pulmonary hypertension, persistent tachyarrhythmia, and neoplasia.


Clinical signs of congestive heart failure are often divided into those associated with left-sided heart failure (e.g., heart failure secondary to mitral or aortic valve regurgitation), right-sided heart failure (secondary to tricuspid or pulmonic valve lesions, pericarditis, or pulmonary hypertension), and biventricular heart failure (associated with cardiomyopathy or mitral and tricuspid valve regurgitation). Signs common to all three categories include tachycardia and a loud third heart sound (S3).

Left-Sided Heart Failure

Signs of left-sided congestive heart failure include those associated with pulmonary edema, such as increased bronchovesicular sounds, crackles, cough, tachypnea, and in the most severe cases respiratory distress and a white to pink foamy nasal discharge. Left-sided heart failure results most commonly from mitral valve insufficiency, in which case auscultation will reveal a typical band-shaped holosystolic or pansystolic murmur with the point of maximal intensity at the left apex, radiating dorsally and toward the left heart base and aortic valve area. The murmur may have a honking quality if it is associated with rupture of chordae tendineae. Arrhythmias that may be associated with mitral regurgitation include atrial fibrillation, atrial premature contractions, and ventricular premature contractions.

Left-sided congestive heart failure results infrequently from aortic valve regurgitation alone, but is more likely to develop with concurrent mitral valve insufficiency or atrial fibrillation. The murmur of aortic valve regurgitation is typically a holodiastolic, decrescendo, frequently musical murmur with the point of maximal intensity over the left side of the heart base. A water-hammer pulse can be detected if it is associated with left ventricular volume overload. In addition to atrial fibrillation, arrhythmias that may be associated with aortic regurgitation include atrial premature contractions and ventricular premature contractions.

Bacterial endocarditis usually affects the aortic or mitral valve and is more likely to result in left-sided rather than right-sided heart failure. However, it may also affect the tricuspid and pulmonic valves, resulting in right heart failure, and may affect multiple sites, including the endocardial wall. Arrhythmias may be present. Horses with bacterial endocarditis or pericarditis typically have signs of systemic illness, including depression, poor appetite, weight loss, and fever. In addition, horses with bacterial endocarditis may have signs of disseminated sepsis, including shifting limb lameness, swollen joints or tendon sheaths, pneumonia, hematuria, and pyuria.

May 28, 2016 | Posted by in EQUINE MEDICINE | Comments Off on Congestive Heart Failure

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