Picture the valve as a sail. Normally it should be caught by the wind and snapped into place, but in mitral valve prolapse the sail is a little too big, or its ropes too long, and instead it rattles in the wind, closing kind of sloppily and letting some of the wind (that is, the blood) get past. That faulty process irritates the nerves in the atrium, which in turn can cause palpitations, sweating, and panic attacks.
Fifteen percent of women are diagnosed with mitral valve prolapse. Although men also have abnormal valves, the syndrome of anxiety attacks, sweating, and fast heart rates associated with these floppy valves is usually found in young women. It can be treated with drugs called beta blockers, but most folks end up outgrowing the condition.