Hemodynamic assessment of mitral mechanical prostheses under high flow conditions: comparison between dynamic...

The study aim was to compare the effects of dobutamine stress and exercise on prosthetic mitral valve hemodynamics.

Twenty-three patients who had recently (3 +/- 1 months) undergone mechanical mitral valve implantation were studied. Hemodynamic variables, two-dimensional echocardiographic and Doppler mitral/aortic flows were recorded at rest, and then repeated during exercise and dobutamine stress. The investigations were randomized place to determine which stress would be performed first.

Heart rates and pressure drops rose significantly from resting values. At maximum stress, exercise produced maximum and mean pressure drops which were statistically greater than with dobutamine (19.4 +/- 6.0 versus 12.8 +/- 4.7 mmHg (p < 0.001) and 10.2 +/- 3.5 versus 6.8 +/- 2.8 (p < 0.01), respectively). Exercise was associated with statistically shorter diastolic filling times and higher transvalvular diastolic flow rates. Dobutamine produced a greater augmentation in mitral effective orifice area (EOA) (p < 0.05). The slopes of pressure drop/cardiac flow were calculated for stress type and shown to be significantly lower during dobutamine administration (p = 0.03).

Normally functioning mitral prostheses can generate significant increases in valvular pressure drops under high flow conditions. Physiological differences exist between dobutamine stress and exercise when assessing diastolic filling. At a given flow rate, dobutamine produces a greater augmentation in the mitral EOA and a smaller drop in transvalvular pressure.