Damage to sections of the myocardium reduces the ability of the heart to contract and therefore reduce the hearts ability to pump blood to the vital organs. The term acute heart failure usually is used to indicate a large area of damage in the myocardium and severe reduction in the heart’s ability to deliver blood to the tissues. Horses with internal parasite infestations are more prone to developing acute heart failure than those with a good history of de-worming practices. Acute heart failure is seen to have a ____________________ , with severe shortness of breath, exercise intolerance, foamy and pink nasal discharge, pain, anxiety, systemic edema and death. Diagnosis of acute heart failure is made through the clinical signs and symptoms as well as EKG revealing an area of necrosis in the myocardium. Treatment of acute heart failure is difficult in the horse. If it is suspected that a horse is suffering from acute heart failure it should be treated as a medical emergency. Exercise should be halted immediately, and the horse should be kept calm and warm. The veterinarian may administer vasodilators and ____________________ , as well as ACE inhibitor and beta-blocker medications to promote blood delivery to the tissues of the heart and the rest of the body. Digitalis may also be administered to improve and regulate cardiac function.
Prognosis for horses affected by acute heart failure is poor to grave.
Congestive Heart Failure
Congestive heart failure is caused by any situation that impairs heart function or requires the prolonged _______________ of the heart muscle. Congenital heart defects, infection of the thorax, valvular disease or parasitic infection all may cause congestive heart failure. Horses with internal parasite infestations or those with a poor history of de-worming may be at higher risk of developing congestive heart failure. The pathogenesis of congestive heart failure is similar to that of acute heart failure, although the area and severity of damage to the myocardium is considerably less. Infarction of the myocardium results in an impaired ability of the heart to deliver blood to the vital organs. In an attempt to compensate for the reduced contractility of the myocardium, the heart contracts ____________ . The increased heart rate is able to maintain the oxygenation of the body tissues, though it taxes the heart muscle causing _______________ and enlargement of the ventricles. Hypertrophy of the ventricular myocardium reduces the volume of the ventricle and reduces the stroke volume. This, in turn, reduces the amount of oxygenated blood being pumped to the tissues, which triggers a compensatory increase in _________________ , and so on. This positive
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