Visualization of Peripheral Pulmonary Artery Red Thrombi Utilizing Optical Coherence Tomography
A 42-year-old man was transferred to our institution for emergency treatment. He had experienced acute occlusion of the left and right pulmonary arteries caused by a rupture of a massive right atrial thrombus as confirmed by MDCTA (). He received thrombolytic therapy with intravenous administration of 100 mg recombinant tissue plasminogen activator, followed by anticoagulation with subcutaneous lower-molecular-weight heparin. Anticoagulation treatment with oral warfarin was consistently administered. After being discharged one month later, he had shortness of breath under moderate-intensity exertion and was readmitted. MDCTA was performed and the result revealed a complete resolution of the thrombi in both main pulmonary arteries as well as an inconclusive filling defect sign in the peripheral pulmonary artery of the right lower lobe (). To explore pulmonary arteries, pulmonary angiography and selective pulmonary angiography were performed via the right femoral approach, using a 6 Fr sheath, pig tail and multipurpose catheters, respectively. The results revealed several filling defects in the subsegmental pulmonary arteries of both the lower and right upper lobes (). Then, OCT was performed to evaluate these intravascular lesions. An OCT system (Model M2 Cardiology Imaging System, LightLab Imaging, Inc., Westford, MA, USA) with a motorized pull-back system was used. A 0.016-inch OCT image wire (ImageWire, LightLab Imaging, Inc.) was advanced to the distal end of the lesions through a 3 Fr occlusion balloon catheter. In order to remove the blood as well as to obtain clear images, the occlusion balloon was inflated with an inflated device, with the inflating pressure ranging from 0.4 to 1.0 atm (1 atm = 101.3 kPa) at the proximal site of the vessel. Lactate Ringer's solution was infused into the artery from the distal tip of the occlusion balloon catheter at 1.0 to 2.0 mL·s-1. Motorized pullback OCT imaging was performed at a rate of 1.0 mm·s-1 for a length of 30 mm. Images were acquired at 15 frames·s-1 and were digitally archived. The OCT images revealed mostly total occlusive mural protrusions (). After OCT imaging, a multipurpose catheter was advanced to the opening of the pulmonary artery and the proximal connected syringe and was slowly retracted. These retrieved materials were dark red strip-like tissue (), which were fixed in formalin and processed for staining with hematoxylin and eosin. The result of the histological examination was red thrombi (). An immediate check-up angiography showed the disappearance of the filling defects (). OCT was performed again and demonstrated no mural protrusion (). After a half-year of anticoagulation treatment with warfarin, his symptoms were resolved.