When pulmonary embolism is acute and there is a large pulmonary embolism that is lethal, there will be a significant drop in blood pressure for two main reasons: the first one is that when there is a large pulmonary embolism, the heart function will be very severely and fatally hit in a short time, but this time there will be shock. Because the function of the heart has been caused by pulmonary embolism will be a very big blow, so its ejection function these will be affected, there will be a circulation very unstable or even shock of this kind of performance, so it is a per se effect on the heart. Secondly, after massive pulmonary embolism, some kinins and hormones will be released under the condition of pulmonary hypertension, which in turn will lead to a further drop in blood pressure, and this persistent drop in blood pressure is often a sign of poor prognosis of massive pulmonary embolism. In general, the heart is hit hard by the massive pulmonary embolism, and the lung itself releases some blood pressure lowering factors, both of which lead to a significant drop in blood pressure.