Acute Heart Failure:

• Acute cardiac failure results from a sudden stoppage of effective cardiac contraction, and may cause death even within minutes.
• It can occur when there is severe defect in filling, failure of heart as pump either due to tachycardia, bradycardia or arrhythmia and when there is sudden increase in workload.
• Catecholamines are responsible for severe tachyarrhythmias along with severe excitement enough to cause acute heart failure.

Etiology:

• Disorder of filling: pericardial tamponade due to rupture of atria and ventricle, aortic and pulmonary artery rupture
• Tachyarrhythmias: myocarditis, Nutritional deficiency myopathies, ingestion of poisonous plant, electrocution, lightning strikes
• Bradycardia: Iatrogenic, e.g. intravenous calcium gluconate or borogluconate administration, xylazine, tolazoline, concentrated solutions of potassium chloride
• Plant poisoning
• Increased workload: Rupture of aortic valve, acute anaphylaxis

Clinical Signs:

• Brain is first affected and signs are neurological in acute cases.
• Pallor is prominent sign due to reduced blood flow
• Respiratory distress due to pulmonary edema
• Dyspnoea, staggering and falling
• Death occurs within seconds or minutes of appearance of signs
• Incoordinate movement of limbs
• Deep asphyxia gaps follow death.
• Absence of palpable pulse, bradycardia
• Absence of heart sounds
• Horses during racing or training dies suddenly due to acute heart failure.
• In typical acute cases, engorgement of visceral veins may be observed grossly during necropsy examination if attack has lasted for minutes.
• There are no gross lesion characteristics of acute heart failure.

Treatment:

• Treatment is usually not possible or practical in large animals due to short course of disease.
• Deaths under anesthesia can be controlled through external or internal cardiac compression to some exent.
• Intracardiac injections of very small doses of epinephrine in conjunction with external cardiac compression by jumping up and down on the thorax with the knees can be tried, with occasional success.