Exercise capacity following heart-valve replacement is dependent on how close to normal the artificial device can restore valve function, to what degree a preoperative impaired myocardial function and/or an increased pulmonary vascular resistance is normalized. The postoperative functional result can be determined by the subjective improvement of the patient, his functional capacity, exercise capacity, the central hemodynamics at rest and during exercise, and the systolic and diastolic function of the left and right ventricular myocardium. The subjective improvement of individual symptoms is obviously dependent on the degree of postoperative normalization of hemodynamics, especially of pressures in the pulmonary circulation. Subjective improvement can be objectified by comparing the functional capacities before and after surgery. Post-operative normalization of central hemodynamics and myocardial function does not happen immediately but within 3 to more than 12 months. A 12-month period can generally be expected in patients with mitral stenosis and increased pulmonary vascular resistance (> 400 dyn.sec.cm(-5)) prior to surgery. In patients with mitral and aortic regurgitation as well as with aortic stenosis and preoperative decrease of their left ventricular ejection fraction during exercise, continuous improvement of left ventricular pump function also may need up to 12 months. Physiological hemodynamic conditions generally are not restored by valve replacement. All prostheses are stenotic to forward blood flow because of the obstruction created by the narrowing of the valve area by sewing cuff and valve poppet. This may result in a hemodynamically important stenosis, especially after atrio-ventricular valve implantation, and may limit subjective and functional improvement. Exercise capacity after aortic valve replacement depends mainly on whether or not myocardial damage persists postoperatively. A workload of 1.5 w/kg body weight (BW) has been performed by 100% of patients aged 45 to 55 years with prostheses implanted for aortic stenosis. The significant lower exercise capacity all patients with valve replacement for aortic regurgitation have experienced (0.4 w/kg BW) indicates that a substantial number of these patients has irreversible myocardial damage prior to surgery. The workload experienced by patients with mitral valve prostheses varies between 0.4 and 2.0 w/kg BW (mitral stenosis) and 0.3-2.3 w/kg BW (mitral regurgitation), respectively. To objectify the functional result of heart-valve replacement, hemodynamic-metabolic measurements of functional improvement, determination of left, eventually also of right-ventricular function by echocardiography and additional invasive measurements of the central hemodynamics and myocardial pump function parameters at rest and during exercise might be necessary.
