DEAR DR. ROACH: A colleague of mine recently had a pulmonary embolus at age 45. She is otherwise healthy. What must she be concerned about? -- N.R.
ANSWER: A pulmonary embolus is a blood clot that travels to the lung. Although they can originate in any large vein, they most commonly come from the deep veins of the pelvis and thighs. The clots can break off with or without physical activity, and they usually travel through the right side of the heart into the lungs.