Heart rate variability (HRV) reflects autonomic nervous system (ANS) activity through nonlinear mechanisms, including complex beat-to-beat fluctuations and chaos-like dynamics of healthy cardiac rhythms. However, conventional HRV indices often show inconsistent interpretations of sympathetic activity across studies, making its evaluation difficult. Recently, nonlinear indices such as Acceleration Capacity (AC), Deceleration Capacity (DC), and the non-Gaussianity index have been introduced to separately evaluate sympathetic and parasympathetic nervous activity. We hypothesized that these indices are applicable in dogs and could reflect age-related changes in ANS function. This study provides the first longitudinal evaluation of nonlinear HRV indices, including AC, DC, and the non-Gaussianity index, during puppy growth, highlighting new insights into autonomic maturation in young dogs. HRV was longitudinally measured in eight healthy puppies (4 to 12 months old) of various breeds every two months. HRV analysis was conducted during sleep using 48-h Holter ECG recordings. We applied frequency-domain (nHF, LF/HF), time-domain (SDNN, RMSSD), geometric (SD1, SD2, SD1/SD2), and nonlinear analyses (AC, DC, non-Gaussianity index). Parasympathetic indicators (RMSSD, SD1) and overall HRV indices (SDNN, SD2) significantly increased with age, while the sympathetic indicator AC significantly decreased. No significant changes were observed in nHF, LF/HF, SD1/SD2, DC, or the non-Gaussianity index. HRV analysis suggests that puppies are initially sympathetic-dominant, shifting toward parasympathetic dominance as they grow. AC may serve as a useful marker of sympathetic activity in young dogs, whereas DC and the non-Gaussianity index may provide stable ANS assessments regardless of age.

A 2-month-old Shiba Inu was presented to an emergency veterinary clinic with decreased activity and was diagnosed with pulmonary hypertension secondary to a ventricular septal defect. The dog was referred to the TUAT Veterinary Medical Center for further evaluation. During treatment, a diverticulum was incidentally identified at the apex of the left ventricle. While the diverticulum caused no clinical symptoms, a cardiac synchronous computed tomography (CT) scan was performed to accurately assess its anatomical location and size. This case highlights the value of advanced imaging techniques in diagnosing complex congenital cardiac anomalies.

Undifferentiated sarcoma is a malignant tumor characterized by the absence of a distinct cellular origin, as determined by morphological and immunohistochemical analyses, and is known for its highly invasive and proliferative behavior

Chylopericardium is an extremely rare disorder in dogs, and its underlying mechanisms and optimal management strategies remain poorly defined. This report describes a dog with chylopericardium complicated by concurrent chylothorax, bilateral brachiocephalic vein thrombosis, and mesothelioma. A 6-year-old neutered male Shiba Inu presented with respiratory distress and was diagnosed with chylothorax and chylopericardium based on fluid analysis. Computed tomography revealed multiple thoracic ducts and bilateral brachiocephalic vein thrombosis but no definitive site of lymphatic leakage. Surgical management included thoracic duct ligation, subtotal pericardiectomy, and cisterna chyli ablation. Histopathological examination of resected pericardial and mediastinal tissues confirmed mesothelioma. Postoperatively, pleural effusion initially decreased but subsequently recurred, and intrathoracic chemotherapy with carboplatin was administered, resulting in long-term control of chylous effusion. Antithrombotic therapy was also initiated for venous thrombosis. The dog remained free of chylous fluid accumulation until death from an unrelated disease. This case highlights the complex interactions among lymphatic, vascular, and neoplastic disorders and suggests that a comprehensive, multimodal diagnostic and therapeutic approach may be effective for managing complicated cases of chylopericardium in dogs.