QT interval instability and variability in dogs with naturally-occurring hypercortisolism

Area of Science:

• Veterinary Cardiology
• Endocrinology

Background:

• Hypercortisolism is a common endocrine disease in dogs.
• Human studies link hypercortisolism to cardiovascular events, but canine data is limited.

Purpose of the Study:

• To investigate the arrhythmogenic risk in dogs with naturally-occurring hypercortisolism (NOHC).
• To assess QT interval variability and instability in NOHC dogs compared to healthy controls.

Main Methods:

• Retrospective analysis of 38 NOHC dogs and prospective study of 12 healthy dogs.
• Electrocardiographic parameters including QT interval variance (QTv), total instability (TI), short-term (STI), long-term (LTI), and mean (QTm) were analyzed.
• NOHC subgroups were defined by cortisol suppression patterns in the low-dose dexamethasone suppression test.

Main Results:

• All QT interval instability parameters, except QTm, were significantly higher in NOHC dogs versus controls.
• STI and QTv correlated positively with left ventricle wall thickness.
• NOHC dogs with partial or absent cortisol suppression showed elevated electrocardiographic indices compared to healthy dogs.

Conclusions:

• Naturally-occurring hypercortisolism in dogs is associated with increased ventricular repolarization heterogeneity and potential arrhythmogenic risk.
• Cortisol's influence on the hypothalamus-pituitary-adrenal axis may impact electrical instability, warranting further investigation.