Evaluation of Autologous Blood Clot Subsegmental Pulmonary Thromboembolism in Minimally Invasive Experimental Canine Model

The incidence and significance of subsegmental pulmonary (SSP) thromboembolism is currently under investigation. We aimed to evaluate the clinical and diagnostic features of SSP thromboembolism in an experimental canine model. Obstruction of pulmonary arterial branches was induced in three beagle dogs by intravenous injection of a barium-coated autologous blood clot (size, approximately 1.7 × 5 mm). The clinical signs, haemodynamic changes (blood pressure, electrocardiogram, echocardiography), coagulation (aPTT, PT, FDPs and D-dimer test) and cytokine variations (TNF-a, IL-4, IL-6, and IL-10) were evaluated over a 24-hour period. Multidetector computed tomography (MDCT) with contrast was conducted to evaluate the pulmonary obstruction, and histopathological confirmation was performed. Pulmonary artery pressure gradient (PAPG) was increased 12 h after the autologous blood clot injection (14.2 ± 2.8 mmHg to 23.6 ± 1.7 mmHg, P = 0.003) and normalized 24 h later (P < 0.01). Infused radiopaque clots were confirmed with MDCT and histopathological examination. Pulmonary parenchymal changes such as arterial dilation and inflammatory reactions were also confirmed in histopathological examinations and were barely observable in MDCT. Usually small emboli are not easily detected through CT imaging, and the clinical relevance of these emboli is controversial. In this experimental study, we made radiopaque small emboli and induced SSP thromboembolism. Thus, we infer that obstruction of the small segmental and subsegmental pulmonary arteries does result in a pulmonary thromboembolism (PTE) and PTE-related pulmonary parenchymal changes which could be clinically significant.