Mitral Stenosis

A Clogged Doorway Backs Up the Hallway

Imagine a hotel where guests (blood) flow from the lobby (left atrium) through a grand ballroom door (mitral valve) into the main hall (left ventricle). Normally, the door swings wide open—about the size of a dinner plate—so guests pour through smoothly. But rheumatic fever is like rust and corrosion that welds the door hinges halfway shut, shrinking the opening to the size of a coin. Now guests pile up in the lobby waiting to squeeze through; pressure builds behind them, forcing some to back up into the hallway leading outside (the pulmonary veins and lungs). When the lobby gets so crowded and pressurized that guests start climbing out the windows (pulmonary swelling (edema)), everyone can't breathe. Meanwhile, the crowded, jostling lobby develops electrical short circuits (atrial fibrillation), and standing water in the lobby corners begins to puddle and thicken (clot formation). Finally, the ballroom (left ventricle) gets so little traffic that the rest of the hotel's systems start failing: the back exit (lungs) gets overloaded with backup pressure, and the delivery system (right heart) exhausts itself trying to push against all that congestion upstream.