Cardiac changes in horses with atypical myopathy

Area of Science:

• Veterinary Cardiology
• Equine Internal Medicine
• Toxicology

Background:

• Atypical myopathy (AM) is a severe, often fatal condition in horses, primarily affecting skeletal muscles due to rhabdomyolysis.
• Postmortem studies indicate concurrent myocardial damage in AM cases.
• Limited data exists on the cardiac functional impact of AM in affected and recovering horses.

Purpose of the Study:

• To document electrocardiographic (ECG) and echocardiographic alterations in horses during the acute phase of AM.
• To assess cardiac function changes in surviving horses during a follow-up period.

Main Methods:

• Twelve horses diagnosed with AM underwent clinical evaluation, serum biochemistry, ECG, and echocardiography.
• Cardiac assessments were repeated in four surviving horses 2-10 weeks post-diagnosis.

Main Results:

• Elevated cardiac troponin I levels were observed in all but one horse.
• Ten horses exhibited ventricular premature depolarizations (VPDs).
• All horses presented with prolonged corrected QT (QTcf) intervals and abnormal myocardial wall motion on echocardiography; one survivor still showed VPDs and prolonged QTcf at follow-up.

Conclusions:

• AM induces distinct ECG and echocardiographic changes, often accompanied by elevated cardiac troponin I and VPDs.
• Survivors may exhibit persistent cardiac dysfunction up to 10 weeks post-AM.
• Further research with larger cohorts is needed to fully understand the long-term cardiac implications of AM.