Pulmonary hypertension (PH) is a disease condition leading to right-sided cardiac hypertrophy and, eventually, right-sided heart failure. Cardiac troponin I (cTnI) is a circulating biomarker of cardiac damage. Hypothesis: Myocardial damage can occur in dogs with precapillary and postcapillary PH. Animals: One hundred and thirty-three dogs were examined: 26 healthy controls, 42 dogs with mitral valve disease (MVD) without PH, 48 dogs with pulmonary hypertension associated with mitral valve

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... e (PH-MVD), and 17 dogs with precapillary PH. Methods: Prospective, observational study. Serum cTnI concentration was measured with a commercially available immunoassay and results were compared between groups. Results: Median cTnI was 0.10 ng/mL (range 0.10-0.17 ng/mL) in healthy dogs. Compared with the healthy population, median serum cTnI concentration was increased in dogs with precapillary PH (0.25 ng/mL; range 0.10-1.9 ng/mL; P o .001) and in dogs with PH-MVD (0.21 ng/mL; range 0.10-2.10 ng/mL; P o .001). Median serum cTnI concentration of dogs with MVD (0.12 ng/mL; range 0.10-1.00 ng/mL) was not significantly different compared with control group and dogs with PH-MVD. In dogs with MVD and PH-MVD, only the subgroup with decompensated PH-MVD had significantly higher cTnI concentration compared with dogs with compensated MVD and PH-MVD. Serum cTnI concentration showed significant modest positive correlations with the calculated pulmonary artery systolic pressure in dogs with PH and some echocardiographic indices in dogs with MVD and PH-MVD. Conclusions and Clinical Importance: Serum cTnI is high in dogs with either precapillary and postcapillary PH. Myocardial damage in dogs with postcapillary PH is likely the consequence of increased severity of MVD.