Serum cardiac troponin I in canine syncope and seizures

To determine if serum cardiac troponin I (cTnI) concentration distinguishes between cardiogenic syncope and collapsing dogs presenting with either generalized epileptic seizures (both with and without cardiac disease) or vasovagal syncope.

Seventy-nine prospectively recruited dogs, grouped according to aetiology of collapse: generalized epileptic seizures (group E), cardiogenic syncope (group C), dogs with both epileptic seizures and cardiac disease (group B), vasovagal syncope (group V) or unclassified (group U).

Most patients had ECG (n = 78), echocardiography (n = 78) and BP measurement (n = 74) performed. Dogs with a history of intoxications, trauma, evidence of metabolic disorders or renal insufficiency (based on serum creatinine concentrations >150 μmol/L and urine specific gravity <1.030) were excluded. Serum cTnI concentrations were measured and compared between groups using non-parametric statistical methods. Multivariable regression analysis investigated factors associated with cTnI. Receiver operator characteristic curve analysis examined whether cTnI could identify cardiogenic syncope.

Median cTnI concentrations were higher in group C than E (cTnI: 0.165 [0.02-27.41] vs. 0.03 [0.01-1.92] ng/mL; p<0.05). Regression analysis found that serum cTnI concentrations decreased with increasing time from collapse (p=0.015) and increased with increasing creatinine concentration (p=0.028). Serum cTnI diagnosed cardiogenic syncope with a sensitivity of 75% and specificity of 80%.

Serum cTnI concentrations were significantly different between groups C and E. However, due to the overlap in cTnI concentrations between groups cTnI, measurement in an individual is not optimally discriminatory to differentiate cardiogenic syncope from collapse with generalized epileptic seizures (both with and without cardiac disease) or vasovagal syncope.