Heaves And Heart Failure: Is There A Connection?

A new study out of Canada shows that uncontrolled respiratory disease in horses may put them at risk for pulmonary artery changes that lead to heart failure.

People with severe asthma can have thickening of the pulmonary arteries, which leads to pulmonary hypertension. Severe equine asthma, like asthma in humans, presents as airway inflammation, coughing and labored breathing; therefore it's feasible that equine asthma can also lead to pulmonary artery thickening, reports EQUUS magazine.

Often called “heaves,” this condition is triggered by mold or dust in hay or the environment. The affected horse must be managed so exposure to these environmental triggers is minimized. Best management practices for horses with heaves include as much turnout as possible, removing horses from stalls when they are cleaned and rebedded, and soaking hay.

Dr. Serena Ceriotti and other researchers at the University of Montreal looked at multiple post-mortem lung samples from 18 horses — six that were in heaves episodes when they died; six with heaves that was in remission because of management practices; and six with no history of heaves.

The scientists measured arterial thickness and found that the horses experiencing active heaves episodes had thicker arteries than the other horses.

Though it's unclear why the arteries thicken, experiments in rodents suggest the low oxygen content and inflammation may increase smooth muscle in the arterial wall. This increase in the muscle decreases the area for blood to flow and may increase muscle contractions, which leads to pulmonary hypertension, minimizing blood flow and limiting cardiac function. This condition can eventually lead to the enlargement and failure of the right ventricle of the heart.

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A second portion of the study tested two potential pulmonary hypertension treatments on live horses. One involved reducing the horse's exposure to dust for an entire year and on using hay alternatives. The second used the medication fluticasone for six months then added in dust-control strategies for an additional six months.

The researchers found that both treatments lead to a reversal in artery wall thickness, but this could only be seen once the dust control measurements were enacted. The team notes that hay is the main trigger for heaves; often just changing the horse's diet to include a forage alternative is enough to control the disease.

They conclude that arterial wall remodeling is reversible, but only with strict dust control measures. Inhaled corticosteroids can rapidly improve a horse in experiencing a heaves flareup, but an improved environment is the only way to manage the condition long term.

Read more at EQUUS magazine.

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Study: Heaves Can Wreak Havoc On More Than Just Lungs

Horses with uncontrolled respiratory disease have more organs at risk than simply their lungs, new Canadian research shows. Drs. Serena Ceriotti, Michela Bullone, Mathilde Leclere, Francesco Ferrucci and Jean-Pierre Lavoie have discovered that horses with uncontrolled respiratory disease are at risk of having pulmonary arterial changes that could lead to heart failure.

Horses that suffer from severe equine asthma have inflamed airways; they also cough and have difficulty breathing. The researchers hypothesized that this condition, which is triggered by dust and mold in a horse's hay and environment, can put horses at risk of pulmonary hypertension. Pulmonary hypertension occurs when the walls of the pulmonary arteries thicken and increase the horse's blood pressure.

For the study, the research team obtained multiple post-mortem lung samples from 18 horses: six that were in heaves episodes when they died; six that were in remission from heaves from being kept in a dust-free environment; and six that had no heaves and served as controls.

The researchers measured the thickness of the arteries and found that horses with uncontrolled asthma had thicker arterial walls than other horses in the study.

Why the artery walls thicken when a horse has breathing trouble is unknown, but it is hypothesized that the low oxygen content and inflammation may increase the amount of smooth muscle in the artery walls, which makes it more difficult for blood to move out of the lungs. Eventually, this condition could lead to an enlargement and failure of the right ventricle of the heart.

The final part of the team's study focused on potential treatments for pulmonary hypertension in horses: they used 11 asthmatic horses divided into two groups that were treated for a full year with two different treatment protocols. One group had reduced dust exposure, primarily through the feeding of hay alternatives. The second group went on a corticosteroid for the first six months, the had dust control measures added in. Both treatments led to a reversal in arterial wall thickness, but changes in the second group were not seen until the dust control measures were taken.

They scientists determined that the thickening of arterial walls in horses with heaves can be reversed, but environmental changes must be made; the administration of corticosteroids, while helpful, must be made in conjunction with changes in management.

Read the full study here.

Read more at EQUUS magazine.

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