In most cases, pulmonary embolism is caused by a blood clot in the leg that breaks loose and travels to the lungs. A blood clot in a vein close to the skin is not likely to cause problems. But having blood clots in deep veins (deep vein thrombosis) can lead to pulmonary embolism.
St. Petersburg. 1  St. Petersburg is a city with a long and eventful history. 2  Altai is perhaps the most beautiful region of Russia. 3  Moscow is the capital of Russia, as well as the nationâs epicentre of arts, music, science, academics, and politics.  For a step back in time, Olkhon Island is a wonderful place to visit.
1 The drainage basin of the Volga includes most of Western Russia, an area that is home to 11 of the 20 largest cities in Russia.  One of the most fascinating destinations along the river is the city of Yaroslavl, founded in the 11th century. The city is famous for its several cathedrals and beautiful frescoes.