Oxygen utilization and hemodynamic response during exercise in children after Fontan procedure.

Eight patients, 9.1 to 16.5 years of age, were studied 2.8 to 8.5 years after Fontan operation. Oxygen utilization was determined during upright bicycle exercise. The cardiac index and stroke index were measured by echocardiography and the anaerobic threshold was determined. The results were compared with 10 patients after surgical closure of the atrial septal defect. Anaerobic threshold (AT) in Fontan patients was lower than in the control subjects. Oxygen consumption at each stage of exercise was significantly lower in the Fontan group compared with the control subjects. From the beginning of exercise until AT, the increase in stroke index was lower in the Fontan patients than in the control subjects. After that point, the stroke index decreased significantly in the Fontan patients while it remained almost at the same level in the control subjects. Significant correlations were observed between the oxygen pulses and the stroke index at AT both in the control and Fontan groups. These results suggest that impaired exercise capacity in Fontan patients is mainly due to a subnormal response of the stroke index at AT and to the decreased response of the stroke index and the heart rate at the maximal workload.

[Target heart rate for exercise echocardiography].

The exercise stress test with a semi-supine position bicycle ergometer was evaluated in 10 normal subjects and five cardiac patients to define the appropriate target heart rate for exercise echocardiography. The normal healthy subjects were aged between 24 and 30 years, while the five patients with artificial aortic valves were aged between 13 and 54 years. The workload was continuously increased from 0 W to the maximum achieved workload at 20 W/min for normal subjects and 10 W/min for patients. Echocardiography was recorded every minute during the test procedure. End-diastolic and end-systolic dimensions were measured and ejection fraction was calculated. The ejection fraction at heart rates 50, 60, 70 and 80% of predicted maximum heart rate and at maximum workload were compared. Heart rates at the maximum workload for normal subjects were 76 to 94% (86.3 +/- 6.3%) of the maximum heart rate predicted from the age of the subjects and 70 to 102% (84.0 +/- 12.6%) for the patients. The largest election fraction values during exercise stress were obtained at 70% of the maximum predicted heart rate in normal subjects, and at 60% in the patients. The target heart rate for exercise echocardiography is 70% of the maximum calculated heart rate.

[A role of valvuloplasty in surgical treatment of isolated tricuspid regurgitation].

Seven surgical cases of isolated tricuspid regurgitation were reviewed. From pathological point of view, the patients were classified into three groups. Two were due to abnormalities of subvalvular system, four to annular dilatation and one to anomalous leaflet. Among four cases of annular dilatation, two were diagnosed as dilated cardiomyopathy. In one, it was very rare myopathy confined to right ventricle. Three cases, two subvalvular and one leaflet abnormalities, underwent valvuloplasty which included chordal reconstruction using Gore-Tex suture. Among annular dilatation group, three underwent valve replacement (two with mechanical valve and one with bioprosthetic valve), while fourth underwent annuloplasty. When We look at 89 surgical patients with secondary tricuspid regurgitation, thrombosed mechanical valve was seen in two cases, one of them necessitating re-valve replacement. On the other hand, late results of tricuspid annuloplasty with Carpentier-Edwards ring was excellent without re-operation. Although isolated tricuspid regurgitation has very complicated pathological features, we now think it very important to manage to repair regurgitant tricuspid valve utilizing all available techniques including redundant valve tissue resection, chordal reconstruction, and annuloplasty, thus avoiding valve replacement especially with mechanical valve.

[Surgical treatment of acute aortic dissection in the aged: a case report].

A 77-year-old woman with Stanford type A acute aortic dissecting aneurysm was successfully treated by the sutureless technique using arringed intraluminal graft. A month after the operation, re-dissection to the distal abdominal aorta occurred. Because of the poor condition of the patient and her great age, we chose an antihypertensive therapy instead of a reoperation. Two years after the operation this patient leads a sound life without any symptoms. In a case of acute aortic dissection of the aged, special consideration may be allowed to a surgical method and a decision-making for a reoperation.

Diagnosis of cardiac allograft rejection by the detection of circulating plasma cardiac myosin light chains.

Twenty adult male Japanese monkeys of the species Macaca fuscata were randomly paired and subjected to heterotopic cardiac transplantation performed by the Ono-Lyndsey method. Without immunosuppression, graft survival ranged between 8 and 27 days, with a mean survival of 14 days. Plasma cardiac myosin light chains were measured by radioimmunoassay, which showed transient increases in myosin levels just following transplantation. Three hearts showed high values at this period and stopped beating when the myosin levels decreased (type 1). The other 7 hearts showed low myosin values after transient increases and 5 of them were rejected with a preceding reincrease in the myosin levels (type 2). Pathological study revealed myocardial necrosis, perivascular cuffing of mononuclear cells and/or neutrophils and/or plasma cells in the type 1 hearts. Measurement of the plasma myosin light chain level was therefore revealed to be of great value in the monitoring of cardiac allograft rejection.

[Oxygen uptake during exercise before and after cardiac valve surgery: anaerobic threshold and maximal oxygen uptake].

Exercise stress tests with bicycle ergometer were performed before and after surgery in 14 patients with valvular heart diseases. Aortic valve replacements were performed in two patients, open mitral commissurotomy in two, mitral valve replacement in eight and combined valvular procedure in two. All patients except one showed improved NYHA function class after the surgery. Oxygen uptake was assessed at anaerobic threshold and peak achieved workload. One patients who failed to increase his heart rates during exercise both before and after surgery revealed unchanged NYHA function class and decreased oxygen uptake postoperatively. The other patients showed statistically significant increases of oxygen uptake not only at anaerobic threshold but also at peak achieved workload. At anaerobic threshold, oxygen uptake was 0.92 + 0.14 l/min before surgery and 1.09 + 0.22 l/min after surgery. Maximal oxygen uptake increased from 1.11 + 0.27 l/min to 1.47 + 0.36 l/min postoperatively. Heart rates at anaerobic threshold and at peak workload showed no significant differences. Postoperative increases of oxygen uptake was achieved by the increases of oxygen pulses, which was considered to be from the increases of stroke volumes.

[Anaerobic threshold and oxygen uptake in patients with mitral stenosis].

The exercise stress test with a bicycle ergometer was performed for 31 patients with mitral stenosis and for 10 normal subjects. The patients were categorized in two groups. Group 1 consisted of 16 patients having indication for surgical intervention and Group 2 consisted of 15 patients without such surgical indications. Oxygen uptakes at the anaerobic threshold and at peak exercise (MAX) were assessed by percent attainment of the predicted normal value from Posner's equation. Heart rates during exercise did not differ between the two groups. However, Group 1 had significantly smaller values of percent attainment of oxygen uptake both at the anerobic threshold and peak exercise than the controls and Group 2. Oxygen pulses in Group 1 were also significantly less than in the controls or Group 2. Seven cases were reassessed six months or more after surgery including open mitral commissurotomy in two and mitral valve replacements in five. The improvement of oxygen pulse showed a statistical significance. Percent oxygen uptake attainment was also significantly improved both at the anaerobic threshold and at peak exercise. Percent attainment of oxygen uptake in mitral stenosis differed significantly according to the NYHA class both at the anaerobic threshold and peak exercise. These values are considered useful for making decisions for surgical treatment in borderline cases.

[Respiratory failure after thymectomy in myasthenia gravis: evaluation of preoperative influencing factors and preventive managements against postoperative respiratory dysfunction].

Postoperative respiratory function was evaluated in 94 patients with myasthenia gravis after thymectomy. Preoperative clinical and pulmonary function data were submitted to statistical analyses. The duration of respiratory support and intratracheal intubation time were significantly correlated to % vital capacity, the clinical stage of myasthenia gravis, and the clinical stage of thymoma. Statistical analyses proved that anticholinesterase drugs taken in immediate postoperative period contributed to the improvement of postoperative respiratory function, and non-depolarizing muscle relaxants, i.e. d-tubocurarine which had been considered to be contraindicated in myasthenia gravis was found to be beneficial immediately after the operation in patients with severely deteriorated respiratory function preoperatively.