Bovine Congestive Heart Failure Study Guide

Overview and Clinical Importance

Congestive heart failure (CHF) in cattle represents the terminal manifestation of various cardiac diseases. Unlike small animals where left-sided failure predominates, right-sided heart failure is more common in cattle due to anatomy and common disease processes. The major causes include traumatic pericarditis (most common, greater than 80% of cases), bacterial endocarditis, bovine high mountain disease (brisket disease), cor pulmonale, and monensin toxicosis.

Heart disease in cattle is challenging to diagnose and treat due to low incidence and typically guarded to poor prognosis. Understanding these conditions is essential for NAVLE success.

Pathophysiology of Bovine CHF

Heart failure occurs when compensatory mechanisms become overwhelmed. The progression: initial cardiac insult leads to compensatory responses (neurohormonal activation, chamber dilation, hypertrophy), followed by decompensation.

Right-Sided Heart Failure (More Common)

Clinical Signs: Brisket and submandibular edema (pitting), jugular vein distension and pulsation, ascites, hepatomegaly with chronic passive congestion (nutmeg liver), pleural effusion.

Left-Sided Heart Failure (Less Common)

Clinical Signs: Pulmonary congestion with tachypnea, dyspnea, coughing, pulmonary edema, exercise intolerance. Often progresses to biventricular failure.

1. Traumatic Reticulopericarditis (Hardware Disease)

Traumatic reticulopericarditis (TRP) is the most common cause of pericarditis and CHF in cattle (approximately 82% of cases). It results from ingestion of metallic foreign bodies (nails, wire from degrading tires) that perforate the reticular wall, penetrate the diaphragm, and enter the pericardial sac.

Etiology and Risk Factors

• Cattle are indiscriminate feeders with mixed/prepared feeds
• Wire from degrading tires on silage clamps is common source
• Honeycomb structure of reticulum traps foreign bodies
• Reticular contractions, gravid uterus, parturition promote penetration
• Higher incidence in dairy cattle versus grazing beef cattle

Clinical Signs

Diagnosis

Physical Examination: Foreign body tests (back grip, pole test, withers pinch) to elicit grunt. Muffled heart sounds with pericardial effusion. Splashing/washing machine sounds with gas-producing bacteria.

Ultrasonography (Gold Standard): Pericardial effusion (anechoic to hypoechoic fluid). Fibrin strands (hyperechoic). Cardiac compression. Thickened irregular pericardium.

Laboratory: Leukocytosis with neutrophilia. Hyperfibrinogenemia (greater than 700 mg/dL). Elevated cardiac troponin I, AST, CK-MB, LDH.

Treatment

Prevention

Replace tires on silage clamps with sandbags. Magnets in mixer wagons. Prophylactic rumen magnet administration (cost-effective). Regular tire inspection. Avoid feeding near construction sites.

2. Bacterial Endocarditis

Bacterial endocarditis (BE) is the most common acquired valvular disease in cattle. The tricuspid valve is most frequently affected (58%), followed by mitral (31%). Results from bacteremia with colonization of damaged endocardium.

Etiology

Most Common Organism: Trueperella pyogenes (formerly Actinomyces pyogenes). Also Streptococcus spp., Staphylococcus aureus, E. coli, Helcococcus ovis.

Sources: Metritis, mastitis, foot abscess, traumatic reticuloperitonitis, liver abscess, chronic pneumonia, indwelling catheters. VSD predisposes due to turbulent flow.

Clinical Signs

• Recurrent/intermittent fever unresponsive to antibiotics
• Progressive weight loss, decreased milk production
• Lameness or polyarthritis (embolic spread) - approximately 50% of cases
• Tachycardia (greater than 80 bpm) - approximately 80% of cases
• Heart MURMUR over affected valve (key differentiator from pericarditis)
• CHF signs in advanced cases; embolic pneumonia from tricuspid lesions

Diagnosis and Treatment

Echocardiography (Gold Standard): Vegetative lesions (hyperechoic irregular masses on valves), valvular regurgitation on Doppler.

Treatment: Long-term bactericidal antibiotics (4-6 weeks). Penicillin G 22,000 IU/kg IM BID. Furosemide for CHF. Prognosis guarded to poor; culling usually recommended.

3. Bovine High Mountain Disease (Brisket Disease)

Bovine high mountain disease (BHMD), also called brisket disease, is right-sided CHF (cor pulmonale) caused by hypoxia-induced pulmonary hypertension at high altitudes (greater than 1,500 m or 5,000 ft). Significant economic concern in Rocky Mountain region (Colorado, Wyoming, New Mexico, Utah).

Pathophysiology

• Low environmental oxygen causes alveolar hypoxia
• Hypoxic pulmonary vasoconstriction (HPV)
• Chronic HPV leads to pulmonary arterial remodeling
• Increased pulmonary vascular resistance causes pulmonary hypertension
• Right ventricular hypertrophy, then dilation and failure

Bovine predispositions: Small lung-to-body weight ratio, lobulated lungs with limited collateral ventilation, robust pulmonary arterial muscularization.

Risk Factors

Clinical Signs

Cardinal sign is pitting brisket edema extending to intermandibular space and ventral abdomen. Also: jugular distension/pulsation, exercise intolerance, dyspnea, open-mouth breathing with exertion, diarrhea, collapse/death with forced exertion.

Diagnosis: PAP Testing

Pulmonary Arterial Pressure (PAP) Testing: Gold standard. Catheterize jugular vein, advance to pulmonary artery. Mean PAP greater than 49 mmHg = high risk. Mean PAP less than 41 mmHg = likely tolerant.

Treatment and Prevention

Treatment: Relocation to lower elevation is most effective. Diuretics for symptomatic relief. Cardiac damage usually irreversible once CHF develops.

Prevention: Genetic selection using PAP testing. American Angus Association publishes PAP EPD. Avoid bringing susceptible cattle to high altitude.

4. Monensin (Ionophore) Toxicosis

Monensin (Rumensin) is a polyether ionophore used in cattle for improved feed efficiency and coccidiosis prevention. While cattle have wide safety margin, overdose causes fatal cardiomyopathy and CHF. Mechanism: disrupts cellular ion transport, causes calcium influx, activates proteases leading to myocyte death.

Species Sensitivity (LD50)

Clinical Signs

Acute: Sudden anorexia, diarrhea, tachycardia, arrhythmias, ruminal atony, myoglobinuria (brown urine), recumbency, sudden death.

Chronic/Delayed: Weight loss, exercise intolerance, CHF signs, sudden death with stress weeks after exposure.

Diagnosis and Treatment

Diagnosis: History of feed change, multiple animals affected. Elevated CK, AST, LDH, cardiac troponin I. Feed analysis for ionophore concentration.

Treatment: NO SPECIFIC ANTIDOTE. Remove suspected feed immediately. Supportive care only. Minimize stress. Cardiac damage often permanent. Survivors marked for salvage after withdrawal.