[Calculation of the mitral valve area using Hatle's method. Effect of the preload change induced by nitrates]. / Cálculo del área valvular mitral por el método de Hatle. Efecto de la modificación en la precarga inducida por nitritos.

The aim of the present study was to assess the effect of changes in preload induced by nitrates on calculated mitral valve area by Doppler pressure half-time. Forty patients (mean age 51 +/- 10 years), 23 with mitral stenosis, ten with mechanical prosthesis and seven with bioprosthesis were studied by Doppler echocardiography. Twelve were in sinus rhythm and 28 had atrial fibrillation. Mitral valve area by Doppler pressure half-time, peak and mean mitral gradient and pulmonary artery systolic pressure were measured before and after isosorbide dinitrate (5 mg) or nitroglycerin (0.4 mg). The nitrates produced a significant reduction of pre-load in total group (p less than 0.001) but did not change the mitral valve area (1.9 +/- 0.8 to 1.9 +/- 0.8). The subsets of patients with size valvular area (greater than 2 cm2, less than 2 cm2, less than 1.5 cm2, mechanical prosthesis, bioprosthesis, sinus rhythm and atrial fibrillation) had an insignificant change in mitral valve area after administration of nitrates. We conclude that the mitral valve area by Doppler pressure half-time method do not modify in different conditions of preload. These findings remain in patients with prosthesis, different sizes of mitral valve area and atrial fibrillation.