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Current diagnosis of pulmonary arterial hypertension (PAH) is by measuring the pulmonary pressure non-invasively with echo Doppler and confirming it with invasive measurement of the pulmonary artery pressure. However, once the PAH is confirmed, the prognosis is poor. In the study of PAH, the pathogenesis of PAH is still being debated. In this study, we suggest a new mechanism explaining the cause of the PAH.
Patients with connective tissue disease (systemic lupus erythematosus, sleroderma, Raynaud's phenomenonetc) are high risk for developing pulmonary HTN. These patients were referred by pulmonologists or rheumatologists and enrolled in the study. These patients were arranged to the new Expansibility of the Femoral Vein test (EFV) first then followed by the right heart catheterization. During the RHC, the baseline femoral vein pressure and during cough were measured. The study group underwent the new Expansibility of the Femoral Vein (EFV) and had treatment based on its results. The EFV is the ultrasound study of the femoral vein examining its size and expansibility during strong cough. In general, the location of the femoral artery and vein to be checked is the sagittal plane immediately proximal to the bifurcation of the superficial and deep femoral artery. The size of the femoral vein is a little larger than the size of the femoral artery. If the size of the femoral vein during cough is 3 times larger than the one at baseline, the test is considered normal. If the size of the femoral vein is >3 times larger than then baseline, it is considered abnormal suggesting excessive venous pooling. If the femoral vein expands only <2 times of the baseline during cough, it is considered abnormal suggesting present or future pulmonary hypertension. If this test was done in conjunction with a right heart catheterization, then the femoral vein pressure at baseline and during cough is recorded.
20 patients were enrolled from January 2015 to April 2016. All came with high suspicion of pulmonary HTN. The results showed that 15/20 patients had abnormal EFV test and ten (50%) had confirmed PAH. Five patients had abnormal EFV test and normal pulmonary HTN (25%). Five patients had normal EFV test and normal pulmonary pressures (25%). The data of femoral vein pressure at baseline and during cough will be presented. These results explained that the venous system is an integral part of the pathogenesis of PAH. When there is any obstruction of the distal flow of the pulmonary artery, the PA does not increase until the distal vein is unable to accommodate the amount of blood and the capacitance of the venous system is overwhelmed, at that time, the PA begins to rise. This is the new mechanism of PAH.
The patients with risk for PAH had normal PA pressure if the peripheral venous system can accommodate the extra amount of blood. Once the capacitance of the venous sytem is overwhelmed, the PA pressure begins to rise. Larger scale of clinical trial or registries of this new technique are needed.