Objective-To assess autonomic function in dogs with mild mitral regurgitation (MR) that did not have clinical signs of the condition. Animals-6 healthy adult Beagles. Procedure-Mild MR was experimentally induced. A 24-hour ambulatory ECG was recorded before and after induction of MR. Heart rate variability was analyzed in frequency domains by use of the ambulatory ECG. Low-frequency (LF) and high-frequency (HF) power were calculated by integrating over their frequency intervals, and the ratio of LF to HF was also calculated. Measurements of frequency domains were analyzed for 4 time periods (midnight to 6 AM, 6 AM to noon, noon to 6 PM, and 6 PM to midnight). Results-Dogs with experimentally induced MR were classified as International Small Animal Cardiac Health Council class Ia. The HF power of dogs with MR was significantly decreased between 6 AM and noon. The ratio of LF to HF in dogs with MR was significantly increased for the periods between midnight and 6 AM, 6 AM and noon, and noon and 6 PM. Conclusions and Clinical Relevance-Compensatory response through autonomic modulation was observed in dogs with mild MR that did not have abnormalities, except for cardiac murmur, during clinical examination. This result suggests that treatment during the early stages of mild MR may be beneficial. Additional studies are necessary to determine whether such treatment will delay the onset of congestive heart failure and prolong survival in dogs affected with mild MR.

The purpose of this study was to collect initial data to determine the potential clinical usefulness of a 13C-aminopyrine demethylation blood test, and whether additional clinical investigation is warranted. Six dogs, initially suspected of having hepatic disease based on their history, physical examination, imaging studies, general laboratory parameters, or any combination of the above, were enrolled in the study. A baseline blood sample was collected, 2 mg/kg 13C-aminopyrine was administered intravenously, and another blood sample was collected 45 min afterwards. Carbon dioxide was extracted from the blood samples and analyzed using fractional mass spectrometry. Results from the 13C-aminopyrine demethylation blood test were compared to clinical data and histologic findings. Intravenous administration of 13C-aminopyrine leads to a decrease in the percent dose of 13C recovered from dogs with histologically confirmed liver disease. Based on our results, a full-scale investigation of the potential clinical usefulness of a 13C-aminopyrine demethylation blood test for assessment of hepatic function in dogs is warranted.