Electrocardiographic changes in induced hyperkalemia in ponies.

Area of Science:

• Veterinary Cardiology
• Electrophysiology
• Equine Medicine

Background:

• Hyperkalemia is a critical condition that can lead to severe cardiac arrhythmias.
• Understanding the electrocardiographic manifestations of hyperkalemia is crucial for timely diagnosis and intervention in equine patients.

Purpose of the Study:

• To investigate the sequential electrocardiographic (ECG) changes associated with experimentally induced hyperkalemia in ponies.
• To correlate specific plasma potassium concentrations with distinct ECG alterations and cardiac events.

Main Methods:

• Hyperkalemia was induced in 11 crossbred ponies via intracardiac infusion of potassium chloride.
• Electrocardiograms were continuously monitored to document changes in P waves, T waves, QRS intervals, and heart rate.
• Plasma potassium levels were measured and correlated with observed ECG findings.

Main Results:

• ECG changes progressed through four distinct stages, including P wave disappearance, T wave amplitude increase, QRS widening, and eventual cardiac arrest or ventricular fibrillation.
• Significant increases in T-wave amplitude and QRS duration were observed at plasma potassium levels exceeding 7.5 mM/L and 9-10 mM/L, respectively.
• P waves were absent at potassium levels of 9.4-12.6 mM/L, with cardiac standstill or fibrillation occurring between 11.3-17.3 mM/L.

Conclusions:

• Acute hyperkalemia induces predictable and progressive ECG changes in ponies.
• Specific plasma potassium thresholds are associated with distinct and potentially life-threatening electrocardiographic abnormalities.
• These findings enhance the understanding of hyperkalemia's cardiac effects in horses, aiding clinical management.