BackgroundPercutaneous mitral valvuloplasty is currently the treatment of choice in patients with rheumatic mitral stenosis with suitable valvular anatomy. After the procedure, the development of severe mitral regurgitation is still a challenge. Objective To determine the causes of severe mitral regurgitation after percutaneous mitral valvuloplasty. Material and Methods A total of 110 percutaneous mitral valvuloplasties were consecutively performed in 107 patients (3 procedures were repeated due to restenosis) at the Instituto de Cardiología y Cirugía Cardiovascular in Cuba between June 17, 1998 and June 30, 2004 (106 using the Inoue technique and 4 with the Multi-Track system). The average follow-up was 24.6 months (maximum 72 and minimum 1.93 months). The severity of mitral regurgitation was evaluated according to the regurgitant jet area measured by Doppler echocar-diography: mild regurgitation when the area was <4 cm2, moderate when the area ranged from 4-8 cm2, and severe when it was >8 cm2. Left ventriculography was also used to quantify the severity of mitral regurgitation using Seller’s criteria. The calibration of Doppler echocardiographic measures of the degree of mitral regurgitation (3 degrees of severity) by angiographic grading (4 degrees) provided the following grading ranges: 1+, mild regurgitation; 2+ and 3+, moderate regurgitation; and 4+, severe regurgitation. ResultsA total of five severe mitral regurgitations developed after the procedure (4.54%). A mitral valve replacement was necessary in three of them due to rupture of the anterior valve. The remaining two cases are still under medical treatment. Conclusion Multifactorial mechanisms are responsible for the development of mitral regurgitation after percutaneous mitral valvuloplasty, which may occur even in expert hands.