EXERCISE CAPACITY FOLLOWING HEART-VALVE R EPLACEMENT

Exercise capacity following heart-valve replacement is dependent on ho w close to normal the artificial device can restore valve function, to what degree a preoperative impaired myocardial function and/or an inc reased pulmonary vascular resistance is normalized. The postoperative functional result can be determined by the subjective improvement of t he patient, his functional capacity, exercise capacity, the central he modynamics 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 degr ee of postoperative normalization of hemodynamics, especially of press ures in the pulmonary circulation. Subjective improvement can be objec tified 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 mont hs. A 12-month period can generally be expected in patients with mitra l stenosis and increased pulmonary vascular resistance (> 400 dyn.sec. cm(-5)) prior to surgery. In patients with mitral and aortic regurgita tion as well as with aortic stenosis and preoperative decrease of thei r left ventricular ejection fraction during exercise, continuous impro vement of left ventricular pump function also may need up to 12 months . Physiological hemodynamic conditions generally are not restored by v alve replacement. All prostheses are stenotic to forward blood flow be cause of the obstruction created by the narrowing of the valve area by sewing cuff and valve poppet. This may result in a hemodynamically im portant stenosis, especially after atrio-ventricular valve implantatio n, and may limit subjective and functional improvement. Exercise capac ity after aortic valve replacement depends mainly on whether or not my ocardial 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 regur gitation have experienced (0.4 w/kg BW) indicates that a substantial n umber of these patients has irreversible myocardial damage prior to su rgery. The workload experienced by patients with mitral valve prosthes es 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 functiona l result of heart-valve replacement, hemodynamic-metabolic measurement s of functional improvement, determination of left, eventually also of right-ventricular function by echocardiography and additional invasiv e measurements of the central hemodynamics and myocardial pump functio n parameters at rest and during exercise might be necessary.