 CT pulmonary angiography, effect of the thrombus load, and right ventricular function in acute pulmonary thromboembolism. I am Dr. Swastika Lamthure from CGS Medical College in KM Hospital, Mumbai. Aim of our study was to evaluate the role of CT pulmonary angiography in diagnosis and prognosis of patient in cases with pulmonary thromboembolism. The other aim was also to correlate the thrombus load which was done using modified miller score with right ventricular dilatation which was measured as right ventricle to the left ventricular diameter ratio. So, pulmonary thromboembolism is a significant cause of cardiovascular morbidity and it ranks only third after myocardial infarction and stroke. Studies have shown the incidence of pulmonary thromboembolism to be 53 to 162 per 1 lakh population. And the most common clinical presentation is acute onset dyspnea and the other symptoms are cow chest pain. The most common cause of death in this patient is right ventricular dysfunction and hypertension. Thus, right ventricular pressure changes is a significant prognostic factor. So, as you can see, this is a brief chart showing the pathophysiology of the pulmonary thromboembolism. So, after a thrombus is dislodged in the pulmonary artery, there is an increase in pulmonary arterial pressure. Thus, increase in the right ventricular afterload. Now, this has two effects. One is it will increase the right ventricular stress which increases the oxygen demand. And because of this oxygen demand, there is an increase in right ventricular isstemia. This isstemia causes right ventricular dysfunction and because of the increased afterload, that directly itself causes right ventricular dysfunction as well as dilatation. So, now this again, it causes decreased right ventricular output then displacement of the interventricular septum and thus there is decrease in the left ventricular preload. This causes decreased cardiac output, thus decreased systemic and coronary perfusion which causes further isstemia and this whole cycle becomes a very vicious cycle leading to further ventricular dysfunction. So, the gold standard for diagnosis of pulmonary thromboembolism is catheter angiography. However, CTPA, that is CT pulmonary angiography has become the investigation of choice due to its falling advantages. One, there is direct marginalization of the thrombus. Second, it causes, it can determine the thrombus load and third, it can assess the right ventricular strain. Now, this thrombus load can be assessed by one either a mod-finalis code or a canary index or valve score. Now, there are few direct signs and few indirect signs of pulmonary thromboembolism on CTPA. So, as you can see in this chart, there are few direct signs wherein one, there is complete occlusion of the artery and thus there is non-opacification of that vessel on angiography. Secondly, there can be a centrally, centrally this large thrombus which causes a filling to fit centrally. However, there is a peripheral contrast opacification which is known as polament size or a polament sign or a tram track sign as you can see in the image below. And the third way is a peripheral thrombus which forms an acute angle with the wall of the vessel. The indirect signs of pulmonary thromboembolism are mosaic attenuation, pulmonary infarcts, linear or band-like cataleptases, pleural effusion and dilatation of the main pulmonary artery. Apart from the diagnosis of the pulmonary thromboembolism, we can also assess the right ventricular function. The signs are right ventricular dilatation. So, as you can see in this first image, the ratio of the right ventricular diameter to the left ventricular diameter is more than one. Normally, this ratio is less than 0.9. Secondly, there is flattening or bulging of the interventricular septum on the left side. As you can see in this image, there is bulging of the septum on the left side. Thirdly, there is reflex of the contrast into the IVC that is inferior vena cava and into the hepatic waves. So, in our study, which was a non-interventional cross-section observational study, which was done over a period of 18 months, it was done in the Department of Rated Diagnosis. And the sample size was 130, which was calculated by approximately a number of patients that is 6 to 7 patients per month. So, since the study was done over a period of 18 months, the total comes to 126, which we have rounded off to 130. The inclusion criteria was any patient undergoing CTPA with pulmonary thromboembolism, who was willing to participate in the study, give a written informed consent, and the age was 18 or more than 18. The patient excluded from the study was who were not willing to participate, then whose serum creatinine was elevated, who have had a history of contrast allergy in the past, who have undergone contrast studies, urinated contrast studies intravenously or intra-RT in the past 24 hours and pregnant females. So, the procedure was done using a Toshiba 160-slice CT unit. The field of view was from the thoracic inlet up to the inferior extent of the diaphragm. The parameters were set such that the FOV was 500 mm, the thickness was 2 mm, the increment was 1 mm, the lung filter was used and the window was 40 to 400. Now, after a plane scan, 80 ml of intravenous-idonated contrast was pushed at an infusion rate of 4 ml per second, followed by 20 ml of normal saline at an infusion rate of 4 ml per second. Now, post-image acquisition, after the acquisition of the image, the modified meliscol was used in our study for assessment of thrombus load. Now, as you can see, it was calculated by giving a score of 0 or 1. So, 0 is given when there is no thrombus and 1 is given when there is either a partial human occluding thrombus or a complete human occluding thrombus. Now, this score was calculated using occlusion of the segmental arteries. So, the maximum score was 0, maximum score is 16 because 9 on the right and 7 on the left and the minimum score is 0 wherein there is no thrombus. And then later on, the right ventricle and the left ventricular ratio was calculated using the minor axis of the right ventricle and the left ventricle chamber in the axial plane. And the widest points were measured from the interventricular septum to the inner surface of the ventricle. Now, as you can see, out of the 130 patients that were enrolled in the study, the mean age was 53 and 55 percent of the patients were mean. According to this chart, as you can see, the most commonly involved vessel is the right mean pulmonary artery. And in 6 percent of the patients, all segmental branches were used, that is, there was saddle thrombus involving all 16 segmental arteries. This shows between the total thrombus load and the right ventricular function. Now, the total thrombus load was calculated using modified molar score and the right ventricular function was assessed using the right ventricle to the left ventricular ratio, diameter ratio. And as you can see, the p-value is less than 0.001, which is significant. So, there is a strong correlation between the thrombus load and the right ventricular function. So, Stein et al. in his studies had concluded that although the clinical suspicion might be low, CTPA is a useful modality to rule out pulmonary thromboembolism when the diagnosis is uncertain. Using CTPA, we diagnose acute pulmonary thromboembolism as well as the right ventricular function can be assessed using the dimensions of the right ventricle. Wong et al. in his study had also used modified molar score and had correlated it with the right ventricular dysfunction. And there also he found a strong correlation between the two, which was consistent with our studies. In another study conducted by Atesia et al, he used a different parameter, that is, the thrombus load was calculated using the Canadi index. And there again, there was this strong correlation between the thrombus load and the right ventricular dysfunction. Thus, he concluded that the right ventricular strain is an independent parameter for the prognosis of the pulmonary thromboembolism. In our study, the limitations were that this measurements were done by a single radiologist. So, the inter-observer variability was not taken into the concentration. And the protocols that we used was right ventricular and left ventricular diameters. However, the better parameters are the ventricular volumes, which was used in Cong et al. However, due to commonly practiced modalities and daily use, we have used right ventricular and left ventricular diameters. So, in conclusion, I would like to say that CTPA not only is a diagnostic modality in case of pulmonary thromboembolism, but it can be used for prognosis of this patient as the thrombus load in itself is an independent prognostic factor. Thank you.