Hemodynamic assessment of mitral mechanical prostheses under high flow conditions: comparison between dynamic exercise and dobutamine stress.
OBJECTIVE
The study aim was to compare the effects of dobutamine stress and exercise on prosthetic mitral valve hemodynamics.


METHODS
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.


RESULTS
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).


CONCLUSIONS
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.
Cardiothoracic Centre, Northern General Hospital, Sheffield Teaching Hospitals NHS Trust, Sheffield, UK. hobsoncaunce@aol.com
Neil A
NA
Hobson
Glen A L
GA
Wilkinson
Graham J
GJ
Cooper
Nigel M
NM
Wheeldon
Jane
J
Lynch
D000293:Adolescent; D000328:Adult; D000368:Aged; D001794:Blood Pressure; D015150:Echocardiography, Doppler; D025401:Echocardiography, Stress; D005080:Exercise Test; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate; D006350:Heart Valve Prosthesis; D019918:Heart Valve Prosthesis Implantation; D006801:Humans; D008297:Male; D008875:Middle Aged; D008944:Mitral Valve Insufficiency / Q000000981:diagnostic imaging* / Q000503:physiopathology* / Q000601:surgery; D008946:Mitral Valve Stenosis / Q000000981:diagnostic imaging* / Q000503:physiopathology* / Q000601:surgery; D011446:Prospective Studies; D011474:Prosthesis Design; D012039:Regional Blood Flow; D012107:Research Design; D013318:Stroke Volume; D016896:Treatment Outcome; D006113:United Kingdom; D016277:Ventricular Function, Left