Abstract
Background:
Hypertrophic cardiomyopathy (HCM) is considered rare in dogs, and there is a lack of clinical data. Cardiac troponin I (cTnI) is a biomarker of cardiomyocyte damage and necrosis and can be used to diagnose cat and human HCM.
Aim:
We investigated whether the presence of cTnI in clinical data can be used in conjunction with echocardiography to diagnose canine HCM.
Methods:
This study comprised client-owned dogs with clinical evidence of concentric hypertrophy on echocardiographic images, serum total thyroxine levels of ≤5 µg/dL, systolic blood pressure of ≤180 mmHg, and absence of aortic stenosis. All cases were necropsied.
Results:
Cardiomyocyte hypertrophy (mean diameter, 18.3 ± 1.8 µm), myocardial fiber disarray (70%), interstitial fibrosis (80%), and small vessel disease (100%) were assessed. In dogs with HCM, the left ventricles were concentric, almost symmetrical, and hypertrophied above the aortic diameter. The end-diastolic interventricular septum normalized to body weight (IVSDN) was 0.788 (interquartile range [IQR], 0.7–0.92), which exceeded the normal range (5%–95%, IQR: 0.33–0.52). In total, 70% of the dogs with HCM had syncope and dispnea, and all dogs had high cardiac troponin I levels (median, 3.94 ng/mL), exceeding the upper limit of normal (0.11 ng/ml) and indicating cardiomyocyte damage. IVSDN and serum cTnI levels were correlated (p = 0.839, P = 0.01).
Conclusion:
Ventricular wall thickening and high serum cTnI levels can provide a presumptive diagnosis of HCM and prompt the initiation of treatment or additional diagnostic investigations.

Key words: Biomarker, Cardiac troponin I, Dog, End-diastolic thickness of the interventricular septum, Hypertrophic cardiomyopathy