Congestive Heart Failure

CHAPTER 43 Congestive Heart Failure



Sarah Y. Gardner


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


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.



Right-Sided Heart Failure


Signs of right-sided congestive heart failure include gen-eralized venous distension, jugular pulsation, ventral edema, hepatic congestion, ascites, pleural effusion, and small-volume pericardial effusion. In most instances, a murmur of tricuspid valve regurgitation will be present, indicated by a band-shaped holosystolic or pansystolic murmur with the point of maximal intensity over the right apex. With severe regurgitation, the murmur can be heard on the left hemithorax at the second intercostal space. In the presence of underlying pulmonary hypertension, the murmur may be very loud, and there may be a tympanic quality to the pulmonic component of the second heart sound (S2). Arrhythmias associated with tricuspid regurgitation include atrial fibrillation and atrial premature contractions. With pericarditis, auscultation may reveal muffled heart sounds and pericardial friction rubs.



Biventricular Heart Failure


Signs of biventricular congestive heart failure include some combination of signs of right- and left-sided heart failure. Biventricular congestive heart failure results most commonly from severe mitral valve regurgitation that has resulted in pulmonary hypertension, leading to right ventricular dilation and tricuspid valve regurgitation.


Congestive heart failure resulting from myocardial disease most commonly leads to signs of left-sided or biventricular failure. Auscultation may reveal sinus tachycardia, arrhythmias, or systolic murmurs of atrioventricular insufficiency, and the horse may be febrile. Additional clinical signs that may be seen in horses with myocardial disease resulting from monensin toxicosis include profuse sweating, muscle fasciculations, colic, diarrhea, ataxia, and recumbency. Regardless of the type of congestive signs (i.e., right-sided, left-sided, or biventricular), signs of low cardiac output, such as exercise intolerance, collapse, syncope, azotemia, weak pulses, and poor tissue perfusion, are commonly seen.



DIAGNOSIS

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

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