Echocardiographic assessment of the right ventricular function plays an important role in diagnosis of pulmonary hypertension (PH). However, it has not been fully understood about utility of echocardiography in assessment of progressive PH. The purpose of the present study was to evaluate utility of the echocardiographic assessment of PH. One hundred and eight 12-week-old, male Sprague-Dawley rats were injected with monocrotaline (MCT) or saline solution (MCT-injected rats: n=54; saline: n=54). Serial echocardiography and right ventricular systolic pressure (RVSP) measurements via a cardiac catheter were performed. Histologic examination of the small intrapulmonary arteries at week 2 revealed pathologic vascular remodeling leading to narrowing of the vascular lumen. Tissue Doppler imaging in the MCT-injected rats showed a significant difference compared with that in the saline group at week 2. RVSP in the MCT group showed a significant increase compared with the saline group at week 4 (saline group 28.0±4.7 mmHg, MCT group 60.2±14.9 mmHg). Two-dimensional echocardiography in the MCT group showed a significant difference compared with that in the saline group at week 4. The right ventricular (RV) remodeling characterized by interstitial myocardial fibrosis was observed in the MCT group at week 6. The ratio of peak trans-tricuspid early diastolic wave velocity to active filling with atrial systolic velocity showed diastolic dysfunction in the MCT group at week 7. It is considered that echocardiographic analysis permits accurate determination of the stage of disease development in MCT-induced RV failure.

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We investigated the assay reliability and clinical utility of plasma cardiac troponin-I (cTnI) measurements in dogs with heart disease. This retrospective clinical study enrolled dogs referred to two university veterinary teaching hospitals between 2005 and 2013. The study population consisted of 60 left-sided heart diseases, 9 pulmonic stenosis, and 16 non-heart diseases. Clinically healthy dogs were recruited from healthy beagles in the laboratory. All dogs underwent physical examination, echocardiography, thoracic radiography, and blood sampling before treatment. Plasma cTnI concentrations were determined by chemiluminescence enzyme immunoassay. Intra-assay coefficient of variation (CV) was under 10%. Plasma cTnI concentrations showed an increase concomitant with the severity of volume overload. Plasma cTnI concentrations were significantly increased in the heart failure group as compared with the non-heart disease group. Using a plasma cTnI concentration>0.075 ng/ml to identify dogs with left-sided heart failure, resulted in a sensitivity of 75.0% and specificity of 80.6%. The area under the curve for plasma cTnI concentration measurements was 0.87. Plasma cTnI concentration in dogs with pulmonic stenosis was significantly higher than those of non-heart disease dogs. Using a plasma cTnI concentration>0.074 ng/ml to identify dogs with pulmonic stenosis, resulted in a sensitivity of 77.8% and specificity of 90.9%. The area under the curve for plasma cTnI concentration measurements was 0.93. Measurements of plasma cTnI concentrations have a clinical utility as an additional screening method to diagnose the severity of left-sided heart diseases and pulmonic stenosis.

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Measurements of autonomic nervous activities are thought to be useful to assess health conditions and physical ages. However, their measurement methods have not been established in dogs. A new apparatus (Kiritsu Meijin^®) was developed that can measure autonomic nervous activities automatically, simply, easily and quickly in humans. In this study, we investigated whether autonomic nervous activities in dogs could be measured by using this apparatus. The results obtained were as follows. 1) Although heart rate increased in each dog in active standing tests, the change of autonomic nervous activities was not constant. 2) In the heart rate variability analysis, antagonistic reflexes were not observed between sympathetic nerve activity (LF/HF ratio) and parasympathetic one (HF) in some cases. These findings may reflect restlessness and/or unique breathing maneuver in dogs, which would have significantly affected the heart rate variability. These results suggest that although the new apparatus for human autonomic nervous activities will not necessarily useful for dogs, it can be used for tame dogs.

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Pulmonary hypertension (PH) may affect left ventricular function in dogs with myxomatous mitral valve disease (MMVD). We evaluated the echocardiographic left ventricular function in 30 dogs with PH secondary to MMVD classified into 3 classes based on the International Small Animal Cardiac Health Council classification and healthy controls. Higher left atrial pressure in class Ib dogs may induce PH. Dogs with PH and MMVD had lower forward and total stroke volume, regardless of larger volume overload in class III dogs. These left ventricular functional abnormalities may contribute to severe clinical signs observed in PH dogs (such as syncope and collapse).

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[in Japanese]

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