To evaluate the extension of the indications for operation and up-to-date problems in the surgical therapy of the acquired valvular disease, 581 consecutive patients of prosthetic valve replacement from January 1974 through December 1987 were analysed. The age at operation was 39.1 years (range 22 to 68) at 1974, but increased to 51.9 years (range 9 to 75) at 1987 (p<0.05). Early mortality was 3 deaths in 9 patients (33.3%) who were older than 70 years old, but its range was 0% through 7.7% in the younger patient group (p<0.05). Hospital mortality of the combined valve procedure for aortic, miral and tricuspid valvular disease was analysed. It was higher in the group of tricuspid valve replacement (30.0%) than the group of tricuspid annuloplasty (8.3%) (p<0.01). The former group was in poor preoperative state (cachexia, total bilirubin>2mg/dl, mean right atrial pressure>10mmHg and systolic pulmonary artery pressure >75mmHg), compared to the latter group. The cases of re-replacement of the prosthetic valve increased since 1985. The incidence of poor prognosis after operation, that included early death, late death and retire from society, was 47.1% in NYHA Class TV, and from 0 to 15.8% in NYHA Class I to Class III (p<0.01). 60 cases underwent valve replacement for infective endo-carditis, and 16 urgent operations were required in 23 active stage operations. Total early and late mortality was higher in active stage operation (30.0%) than in healed stage operation (2.7%) (p<0.01). In these way, the extension of the indications for operation was carried on the patients of advanced age, combined valve procedure for multiple valve disease, valve re-replacement and infective endocarditis. The operative risk was high in the patients older than 70 years old, the patients who had the risk factors of multiple organ failure after operation, valve re-replacement in NYHA Class IV, and the urgent operation at active stage of infective endocarditis.

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Spinal cord injury is a dreaded and serious complication of operative procedures on the descending aorta. To avoid this serious complication, 53 patients underwent somatosensory evoked potential (SEP) monitoring during operations on the aorta which required cross-clamping of the descending aorta. 38 patients whose SEPs were kept normal during and after operations did not develop spinal cord injury. Among the 14 patients who developed both abnormal decrease in amplitude and elongation of peak latency, 13 lost their SEPs during aortic cross-clamping. Peripheral nerve ischemia seemed to be the cause of those abnormalities in 8 to whom cross-clamping was given to the abdominal aorta. Inadequate perfusion of the distal aorta was suspected in 6 to whom cross-clamping was given to the descending thoracic aorta. In these cases, however, SEP monitoring was not specific in differentiating spinal cord ischemia from peripheral nerve ischemia. Spinal cord injury was noted in only one of the 6 patients. The remaining one patient developed complete loss of SEP and spinal cord injury on the first postoperative day despite the well preserved SEP during the operation. Since this patient underwent flow reversal and thromboexclusion method for the dissecting aneurysm, gradual thrombotic occlusion of the important radicular arteries draining to spinal cord might have resulted delayed appearance of the spinal cord injury. In conclusion, SEP monitoring is the reliable method to detect the spinal cord ischemia which might be developed during cross-clamping of the descending aorta. However, this method bears limitation in its clinical application due to the following reasons. First, intraoperative SEP monitoring cannot predict delayed occurence of spinal cord injury. Secondly, this method cannot detect the qualitative extent of ischemia of spinal cord and the safe range of the cross-clamp time.

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