Efficient low-energy near-infrared KTiOPO(4) optical parametric converter

We report a widely tunable near-infrared holosteric KTiOPO(4) optical parametric converter featuring a low pump energy threshold and high conversion efficiency. The converter uses two 10-mm-long crystals in a simple optical parametric oscillator amplif ier configuration and is tunable from 750 to 1040 nm for the signal. The pump energy threshold at 920 nm is 0.44 mJ for the 532-nm 8-ns 50-Hz input. The system produces as much as 0.45 mJ of energy at 920 nm with an external pump-to-signal energy conversion efficiency of 27% for pump inputs from just two times the threshold value. The internal pump-to-signal and idler energy conversion efficiency is estimated to be 58%. The low pump energy requirement of this system makes it compatible with small laser-diode-pumped solid-state lasers.

[Surgical treatment of type A aortic dissection based on the location of the entry]

From 1987 to February of 1994, 42 cases of acute aortic dissection and 31 cases of chronic dissection have been operated in out institution. Our surgical technique for the treatment of aortic dissection is a tubular graft replacement following a resection of the segment of aorta containing the intimal tear. The location of the entry was, therefore, important to determine the extension of graft replacement and to select the circulatory support method during operation. 52%, 33% and 14% of cases in acute aortic dissection had entries in ascending, arch and descending aorta, respectively. Entries of 52%, 32% and 16% of cases in chronic dissection located in ascending, arch and descending aorta, respectively. In cases with the entry in ascending aorta, ascending aorta and partial aortic arch replacement was performed in 12 and 10, respectively, for acute dissection, whereas more extensive graft replacement procedure was selected for chronic dissection including complete arch replacement in three cases and two of them had concomitant Bentall type operation. Likewise, with the entry in aortic arch, partial arch replacement was performed more often in 9 than complete arch replacement in 5 for acute dissection, on the other hand, complete arch replacement procedure tended to be preferable in 6 cases for chronic dissection. For retrograde dissection with the entry in descending aorta, ascending aorta and complete arch replacement were performed in 4 and 6 cases, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

[Staged operation for aneurysm of the entire aorta: report of four cases]

Between September 1989 and May 1994, 3 patients with aortic dissection and one with atherosclerotic total aortic aneurysm associated with annuloaortic ectasia underwent successful staged operation for aneurysm of the entire aorta and aortic regurgitation. A composite graft was used for total aortic root replacement. Carbrol and Piehler techniques, Carrel patch and saphenous vein grafting were employed for coronary artery reconstruction. En bloc arch reconstruction was performed in one patient and three vessels graft replacement in 3 patients under hypothermic separate cerebral perfusion. Combined antegrade with retrograde oxygenated crystalloid cardioplegia and terminal warm blood cardioplegia were used for myocardial protection during prolonged aortic cross clamping in a simultaneous total aortic root and arch replacement. Elephant trunk was used at the distal arch anastomosis in 3 patients and useful for following thoracoabdominal surgery. In 3 patients, separate perfusion of upper and lower body technique with moderate hypothermia was employed and seemed to be useful in the patients who require extensive thoracoabdominal replacement to prevent spinal cord injury. All patients had no major complications and have been well.

High-sensitivity two-dimensional thermal- and mechanical-stress-induced birefringence measurements in a Nd:YAG rod

A novel polarimeter for measuring the two-dimensional (2D) thermal- and mechanical-stress-induced birefringence in solid-state laser materials such as Nd:YAG is proposed. Using this device, we could sensitively measure the direction of the principal birefringence axis as well as the phase shift δ with sign when δ < π/4. The 2D thermal- and mechanical-stress-induced birefringence in a laser-diode-pumped Nd:YAG rod was successfully measured with the proposed polarimeter. We also found an active quarter-wave Nd:YAG phase retarder.

Effects of cyclosporine and 15-deoxyspergualin on coronary arteriosclerosis after heart transplantation in the rat

The development of graft coronary arteriosclerosis remains a serious consequence after heart transplantation and may limit long-term survival. The purpose of this study was to evaluate the effects of 15-Deoxyspergualin on graft coronary arteriosclerosis after heterotopic heart transplantation in a rat model and compare the effects to those of cyclosporine treatment. Two groups of Lewis rats (n = 7 each group) underwent heterotopic heart transplantation from Fischer 344 donors and were treated with either cyclosporine (10 mg/kg/day) or 15-Deoxyspergualin (3 mg/kg/day). Histologic evaluations of rejection (scale: 0 = none, 3 = severe) and graft coronary arteriosclerosis (scale: 0 = normal, 4 = occluded) were made 60 days after transplantation. No significant difference was found between the two groups with respect to the degree of rejection (2.0 +/- 0.7 in the cyclosporine-treated group versus 2.0 +/- 0.5 in the 15-Deoxyspergualin-treated group). However, the extent of graft coronary arteriosclerosis in the 15-Deoxyspergualin-treated group was significantly less than that seen in the cyclosporine-treated group (1.11 +/- 0.34 versus 1.71 +/- 0.24, p < 0.01). Furthermore, the incidence of diseased vessels among all observed vessels was significantly lower in the 15-Deoxyspergualin-treated group compared with the cyclosporine-treated group (63% +/- 12% versus 76% +/- 7%, p < 0.05). Although the protective mechanism of 15-Deoxyspergualin is unknown, it most likely possesses a different immunosuppressive mechanism of action from cyclosporine. We concluded that 15-Deoxyspergualin is superior to cyclosporine in preventing graft coronary arteriosclerosis after heart transplantation.

Thoracic aortic aneurysmectomy with a sutureless intraluminal ringed graft

Forty-two patients underwent replacement of the thoracic aorta with a sutureless intraluminal graft. Early and long-term results were evaluated. The operative mortality rate was 7.1%. There were two postoperative complications related to a ringed graft. One complication, the formation of a pseudoaneurysm, was caused by insufficient fixation of the graft; the other, a cerebral infarction, was related to the location of the proximal anastomosis with respect to the origin of the left subclavian artery. The 3- and 5-year actuarial survival rates were 86 and 69.5%, respectively. These were similar to survival rates of age-matched controls in the general Japanese population. Replacement of the thoracic aorta using a sutureless intraluminal graft can be performed with acceptable operative mortality, with good long-term results.

[Comparison of the late hemodynamics following corrective surgery of congenital heart diseases: ventricular septal defect, tetralogy of Fallot, Mustard operation and Fontan operation]

Late hemodynamics following corrective surgery for congenital heart diseases were evaluated in 65 patients. The patients were divided into 4 groups due to the operative procedures including closure of ventricular septal defect (VSD group = 15 patients), repair of tetralogy of Fallot (TOF group = 20), Mustard operation (Mustard group = 19) and Fontan operation (Fontan group = 11). The postoperative period was 3.8 +/- 3.8, 1.0 +/- 0.1, 5.7 +/- 4.3 and 3.2 +/- 4.9 years in VSD, TOF, Mustard and Fontan groups, respectively. Postoperative pulmonary to systemic arterial pressure ratio in VSD group significantly decreased to 0.38 +/- 0.13 from the preoperative value of 0.97 +/- 0.04. Pulmonary vascular resistance (Rp) in VSD group significantly decreased from 4.88 +/- 2.40 to 2.56 +/- 0.75 U.m2 and Rp in Fontan group significantly increased from 1.63 +/- 0.70 to 3.66 +/- 0.47 U.m2 postoperatively. Postoperative cardiac indices in VSD, TOF, Mustard and Fontan groups were 4.30 +/- 1.34, 4.28 +/- 0.72, 3.83 +/- 1.38 and 3.48 +/- 1.38 l/min/m2, respectively, without significant differences. Ejection fraction (EF) of the systemic ventricle (left ventricle) in VSD, TOF and Fontan groups were 0.66 +/- 0.06, 0.65 +/- 0.07 and 0.63 +/- 0.08, respectively. In Mustard group, EF of the systemic ventricle (right ventricle) was 0.56 +/- 0.12 and significantly less than left ventricular EF in the other 3 groups. The hemodynamic characteristics after these operative procedures should be considered for patient management.

Aortic arch aneurysm repair using selective cerebral perfusion

Seventy-seven patients underwent aortic arch aneurysm repair using selective cerebral perfusion from January 1987 to August 1992. Early and long-term results and preoperative and postoperative cerebral function were evaluated. Cerebral function was assessed by the mini mental state-Himeji test and the Wechsler adult intelligence scale. Thirty-six patients had true aneurysms, and 41 had dissection. Hospital mortality for true and dissecting aneurysms was 19.4% and 7.3%, respectively. The 5-year actuarial survival rates for true and dissecting aneurysms were 59.0% and 65.3%, respectively (not significant). There were no significant differences in test scores before or after operation. Repair or replacement of the aortic arch using selective cerebral perfusion is a safe procedure with acceptable hospital mortality.

Protection of the brain during hypothermic perfusion

The adequacy of the circuits for brain perfusion has been explored by hemodynamic assessment using the ability of the brain to autoregulate blood flow as an indicator, and by morphologic observation using carbon black or Evans blue infusion into the brain perfused antegradely or retrogradely. It is concluded that the safe pressure of cerebral perfusion needed to maintain cerebral integrity is between 40 and 50 mm Hg in both normothermic and hypothermic perfusions, a pressure that can be generated by nonpulsatile pump flows through the pump greater than 40 mL.kg-1 x min-1. Morphologic studies revealed development of focal infarctions in the brain and destruction of the blood-brain barrier by retrograde cerebral perfusion. The retrograde approach, therefore, is definitely inferior to the antegrade method. Antegrade perfusion for 90 minutes, however, produced minimal cerebral edema, suggesting the need for further improvement even in techniques of antegrade perfusion.

Risk analysis of low cardiac output syndrome after valve replacement

In order to obtain a better understanding of the pathogenesis of the postoperative low cardiac output syndrome (LOS), a multivariate regression analysis was performed, evaluating predictive risk factors quantitatively as a function of plural preoperative variables. A total of 145 cases including 76 MVR (MS 36 MR 40), 42 AVR and 27 DVR were analyzed in this study. Ten historical, 10 hemodynamic and 4 operative risk factors were collected to compose the data file with corresponding status of postoperative cardiac function which was classified as follows. Patients who were not associated with postoperative LOS (Score 1), associated with the LOS which required and responded to ordinal dosage of a catecholamine (Score 2) associated with the LOS which required and responded to maximal dosage of the catecholamine and/or mechanical circulatory support (Score 3), and died of LOS (Score 4). Variables with significant relationships to postoperative LOS, regression equation to LOS score and their multiple correlation coefficients (R) of each group were as follows. MVR group: technical trouble (TT), extracorporeal circulation time (ECCT), change of myocardial preservation methods, delta LVSWI/delta LVEDP, diseased duration, aortic cross clamping time, CTR, Y = -1.16 + 1.01 (TT) + 0.05(ECCT) + 0.16(delta LVSWI/delta LVEDP) + 0.02(CTR), R = 0.76. AVR group: LVMMI, ECCT, cardiac failure, NYHA, Y = -0.71 + 0.03(LVMMI) + 0.004 (ECCT) + 0.22(NYHA), R = 0.78. DVR group: delta LVWI/delta LVEDP, LVMMI, NYHA, LV diastolic eccentricity ratio, ECCT, Y = -0.50 + 0.60 (delta LVWI/delta LVEDP) + 0.003(LVMMI) + 1.18(NYHA) + 0.38(delta LVSWI/delta LVEDP) + 0.003(ECCT), R = 0.87. It was demonstrated that preoperative ergometer exercise study during cardiac catheterization was useful in prediction of postoperative outcomes, especially in the MVR (MS) group.

[Surgical treatment in the patients with ocular type myasthenia gravis associated with thymoma]

During past 16 years, 192 patients underwent surgery for myasthenia gravis including 40 patients with pure ocular symptoms in our institute. In these 40 patients, 8 were associated with thymoma. The clinical stages of the thymomas were registered into Stage I (n = 5), Stage II (n = 1), Stage III (n = 1), Stage IV (n = 1) according to the classification of Masaoka and colleagues. All patients underwent extended thymothymectomy. The patient in stage III had been well until generalized myasthenic symptoms appeared 4 years after the surgery. Since the chest X-ray film revealed the tumor shadow on the right diaphragm, removal of the tumor was performed. Although he developed myasthenic crisis postoperatively, he is well controlled medically. Other 7 patients have been doing well. We concluded that a close postoperative follow up should be performed for the patients with ocular type myasthenia gravis associated with thymoma.

[Continuous irrigation followed by combined omental transposition and pectral muscle rotation for treatment of postoperative mediastinitis with DIC in a child]

A 8-year-old boy was complicated with mediastinitis with DIC 20 days after replacement of the stenotic right ventricular outflow conduit. Open drainage and débridement were performed and semi-closed continuous irrigation with 1% povidone iodine was continued for 10 days to control DIC. Thereafter, the pedicled omentum was mobilized to the upper anterior mediastinum, however, it was too thin to obliterate there. To obliterate the upper anterior mediastinum and cover the infected graft, the major pectoral muscle flap was introduced to the anterior mediastinum through the window created by removing a part of left second rib. The sternum was closed primarily. The postoperative course has been well and no recurrence has been proved for 1 year.

Replacement of the transverse aortic arch for type A acute aortic dissection

Surgical treatment of acute aortic dissection involving the segment of transverse aortic arch is difficult and often associated with a high mortality and morbidity. The high mortality and morbidity are primarily related to anatomic features and techniques of cerebral protection employed during the period of aortic branch occlusion needed for reconstruction. This study reports our experience of 20 consecutive cases of acute type A aortic dissection treated by repair or replacement of the transverse aortic arch during emergency operation. Ages of the patients ranged from 56 to 76 years. All patients were referred to us within 2 weeks of onset (mean time, 58 hours). Selective cerebral perfusion or deep hypothermia with complete circulatory arrest was employed during the period of aortic branch occlusion. Duration of cerebral perfusion, circulatory arrest, myocardial ischemia, and cardiopulmonary bypass averaged 106 minutes, 32 minutes, 127 minutes, and 248 minutes, respectively. There were three operative deaths. All three dissections were ruptured ones, and the patients died of hemorrhage, deep coma, or multiple organ failure. One patient died of infection 3 months after operation. The remaining patients are alive and well without any detectable neurological deficit 1 month to 4 years postoperatively. This experience emphasizes that repair or replacement of acute type A aortic dissection involving the aortic arch can be performed safely by adequate selection of patients, supportive measures, and operative methods.

Sound spectral analysis of prosthetic valvular clicks for diagnosis of thrombosed Björk-Shiley tilting standard disc valve prostheses

To evaluate clinical usefulness of sound spectral analysis in the early detection of prosthetic thrombosis, we analyzed specific patterns of thrombus formation in Björk-Shiley tilting standard disc prostheses in relation to the sound spectral analysis of their click sounds. Among a total of 365 Björk-Shiley tilting standard disc prostheses, nine became thrombotic. These consisted of seven prostheses in the mitral position and two in the aortic position, and the affected valves were replaced in all cases. The sound spectral analysis system includes a wide-frequency microphone and a sound spectral analyzer. To quantify the amplitude of the metallic clicks that are specific to the prosthetic valve sounds, we used a normalized maximal frequency as a diagnostic parameter for valve thrombosis. Thrombus formation was localized at the minor strut in two cases, and these demonstrated abnormally low normalized maximal frequency values only on opening clicks. In four cases thrombus formations were noted at both minor and major struts, and these showed abnormally low normalized maximal frequency values on both opening and closing clicks. In two cases with pannus formation, no abnormalities were found by sound spectral analysis. In one case, which had demonstrated abnormally decreased normalized maximal frequency values of both opening and closing clicks, the normalized maximal frequency values were normalized after thrombolytic therapy, suggesting resolved thrombosis. Reoperation, which was performed for concomitant complication of perivalvular leak, revealed no noticeable thrombus formation. The thrombi were seen on the minor strut during surgical procedures in all cases in which valve thrombosis was indicated by the sound spectral analysis. Therefore, the minor strut is considered to be the prevalent area of thrombus formation, and diagnosis could be made after observation of abnormally low normalized maximal frequency on opening clicks. We found the sound spectral analysis to be an extremely useful diagnostic tool for early detection of thrombosis in the Björk-Shiley tilting standard disc prostheses, especially because the opening clicks of the tilting disc valve were too low in amplitude for auscultation to detect the existence of mild abnormality.

[Management of myasthenia gravis (MG) associated with thymoma]

From June 1975 to June 1992, we experienced 203 patients with MG. Sixty patients had associated thymoma, registering stages I (n = 31), II (n = 18), III (n = 9), and IV a (n = 2), according to the classification of Masaoka and colleagues. Fifty patients had generalized MG and 10 had ocular MG. Histopathological findings indicated round-oval, polygonal cell type in 46 patients and mixture of round-oval and spindle cell type in 11 patients and invasive thymomas had a tendency to have a predominantly epithelial type with and increased epithelial element as compared with non-invasive thymomas. An extended thymectomy including thymoma was performed in all patients. Three patients in stage II, 7 patients in stage III, and 2 patients in IV a received postoperative radiation therapy. Twenty-one patients needed prolonged respiratory care for respiratory crisis. Fifty-three patients have been doing well with the alternate-day corticosteroid therapy, however, 4 patients had an excavation of myasthenic symptoms associated with recurrence of thymoma on the pleura. In conclusion, early extended thymectomy including thymoma is markedly effective therapy for MG with thymoma and a careful attention should be paid for recurrence in the patients with invasive thymoma.

Cyclovergence: a comparison of objective and psychophysical measurements

Several psychophysical procedures have been used to measure cyclovergence but none has been adequately validated with respect to an objective measure. Scleral search coils were used to measure cyclovergence induced by dichoptic textured patterns which cyclorotated in antiphase through 6 degrees at frequencies between 0.05 and 2 Hz. In one psychophysical procedure subjects nulled the apparent oscillatory motion of radial nonius lines superimposed on a small black disc at the center of a large cyclorotating display. In the second, subjects nulled the apparent inclination in depth of a vertical line displayed in the same way. The amplitude of cyclovergence measured objectively and the magnitude of oscillation of the nonius lines were similar at low stimulus frequencies. At higher frequencies of cyclorotation, both amplitudes declined but the nonius amplitude exceeded that of cyclovergence. The apparent inclination of the vertical test line, as indicated by the nulling procedure, also declined with increasing frequency of cyclorotation, but not at the same rate. At low frequencies, the apparent inclination of the test line was greater than that corresponding to the cyclodisparity induced into the line and almost as great as that corresponding to the relative disparity between the oscillating pattern and the line. The implications of these results for measuring cyclovergence and for an understanding of stimuli driving cyclovergence and perceived inclination in depth are discussed.

[The study of neuropsychological alterations following coronary artery bypass operation as predicted by computed tomography scan of the brain]

The objective of this clinical study is to provide information regarding the association between coexistent cerebrovascular disease and neuropsychological abnormalities after coronary artery bypass operations. Computed tomography scan of the brain was performed in 104 patients pre-operatively, and their post-operative neuropsychological functions were evaluated. The patients were categorized as follows according to the CT findings: Seventy-three patients showed normal or slight cerebral cortical atrophy which usually seen in patients over fifty of age (group A). Sixteen showed moderate or severe cortical atrophy (group B). Fifteen patients demonstrated the characteristic findings of Binswanger type; severe white matter hypodensity especially in frontal horns and dilated ventricles (group C). Overt neuropsychological dysfunction was not observed in patient in groups A and B. Six patients in group C showed a combination of dementia, bizarre behavior, disorientation and gait dyspraxia following bypass operations. The pseudobulbar signs were also found in 3 patients. These clinical abnormalities persisted for six days to three weeks, and were most often reversible. Although the underlying mechanism of these deleterious alterations is not elucidated, the ischemic nature of the characteristic white matter lesions was highly suspected. The arteriosclerotic changes of the arteriole of the cerebral cortex and hypoperfusion during cardio-pulmonary bypass were supposed to be responsible. Therefore it was concluded that special attention should be focused on neurological evaluation for bypass surgery in group C patients.

Permanent pacemaker implantation in premature infants less than 2,000 grams of body weight

Pacemaker implantation in premature infants presents technical problems because of the relatively larger size of the pulse generator compared with their bodies. A new technique with which successful generator implantation was performed in 2 premature infants less than 2,000 g of body weight is described. The generator is wrapped in a Gore-Tex surgical membrane. A piece of membrane overlying the electrical contact surface of the generator is removed, and the generator is fixed to the abdominal wall in the peritoneal cavity. The technique is simple to perform and would give relative ease in generator exchange.

Changes in myocardial beta-adrenergic receptors during acute rejection of heterotopically transplanted rat hearts

To evaluate changes of the myocardial beta-adrenergic receptors in acute cardiac graft rejection, the density and binding affinity value of the myocardial beta-adrenergic receptors in heterotopically transplanted rat isografts and allografts were analyzed. Hearts from Fisher rat donors were transplanted either to the Fisher rats (isografts) or to Lewis rats (allografts). Histologic examination of the allografts showed mild to moderate rejection on the seventh and fourteenth days and showed severe rejection on the twenty-first day after transplantation. The density values in the allografts and isografts similarly increased significantly (p < 0.05) above the normal level on the seventh and fourteenth days after transplantation. The density in allografts on the twenty-first day decreased significantly (p < 0.05) below the normal level, while that in isografts remained at the normal level. In contrast, the binding affinity value of myocardial beta-adrenergic receptors in both isografts and allografts did not change after transplantation. These results demonstrated that myocardial beta-adrenergic receptors presented upregulation in mild to moderate rejection, whereas these receptors presented downregulation in severe rejection. The data suggested that downregulation of myocardial beta-adrenergic receptors plays a major role in decreased cardiac contractility during severe rejection, but not during mild and moderate rejection.

Hemodynamic performance in a heterotopically transplanted dog heart: proposal of techniques for working left heart model of heterotopic (abdominal) heart transplantation

To study hemodynamics together with various aspects of rejection after experimental heart transplantation, we developed a technique to produce a working left heart model of heterotopic (abdominal) heart transplantation. The interatrial septum and tricuspid valve of the donor heart are removed. The pulmonary arterial trunk, pulmonary veins, and inferior vena cava are ligated, and the stumps of the donor aorta and superior vena cava are anastomosed in an end-to-side fashion to the recipient abdominal aorta and inferior vena cava, respectively. Arterial blood from the recipient abdominal aorta thus perfuses the donor myocardium through the coronary artery, and the donor left ventricle receives venous blood from the recipient inferior vena cava as preload. In this model, the donor left ventricle does not pump out enough venous blood to desaturate the recipient femoral arterial blood but does generate approximately the same pressure as the recipient's heart. This model is reproducible, easy to manage, and can be applied to heterotopic heart transplantation in various experimental animals including rats.

[Malfunction of prosthetic valves: pathogenesis and diagnostic measure]

Modality of the malfunction of prosthetic valve often reflects the specific features of its design and materials of the prosthesis. During past 17 years, a total of 499 cases of valve replacements were performed in our institute and among them, 50 cases received redo surgery, in which 52 prosthetic valves were replaced due to their malfunctions. Those replaced prosthetic valves were analyzed in terms of their pathogenesis, onset durations and diagnostic methods of each type of malfunction. The malfunctions included hemolytic anemia, thrombosis or tissue overgrowth and tissue failure of bioprostheses. Hemolytic anemia was experienced in 8 cases with Starr-Edwards (S-E) 2320 (n = 7) and Omni-Science (n = 1) both in the aortic position and those prostheses were replaced at 1-9.6 (mean 4.5) postoperative years (POY). The linearized rate of the complication with the S-E 2320 was 3.0%/patient-years (p-y) and its actuarial event free rate was 62% at 11 POY. Operative findings disclosed cloth wear in 5 and perivalvular leakage in 5 cases. Fourteen Hancock (H) and 3 Angell-Shiley (A-S) bioprostheses experienced tissue failure of valves and they were subjected to reoperation at 3.2-10.0 (mean 6.5) POY. The linearized rates were 4.1%/p-y for H and 4.5%/p-y for A-S with actuarial event free rates at 12 POY of 59 and 56%, respectively. Prosthetic valve thrombosis and/or tissue overgrowth were seen in 17 valves at 1.6-15.1 (mean 9.1) POY.(ABSTRACT TRUNCATED AT 250 WORDS)

[Postoperative respiratory dysfunction in patients with Stanford type A aortic dissection]

Between 1986 and 1990, 24 patients with Stanford type A dissection (acute; 14, chronic; 10) underwent surgery through median sternotomy. The patients were divided into two groups by a duration of postoperative ICU stay for respiratory care. Six patients in the long-period group stayed in ICU for more than 15 days and 18 patients in the short-period group stayed for less than 15 days after surgery. Acuity of disease, age, sex, operation time, pump time, aortic clamp time, lowest esophageal temperature, amount of blood transfusion, arch manipulation for cerebral perfusion with or without arch reconstruction, occurrence of phrenic nerve palsy and other postoperative complications, postoperative cardiac, hepatic and renal functions were compared between two groups. Conclusions are as follows: 1) Arch manipulation for cerebral perfusion with or without arch reconstruction, phrenic nerve palsy, other complications (pericardial and pleural fluid accumulation, recurrent nerve palsy, postoperative bleeding and coronary spasm) and high serum creatinine level were main factors for prolonged postoperative ICU stay for respiratory care and 2) arch manipulation in the patients with chronic type A aortic dissection induced high incidence of phrenic nerve palsy.

Thoracic aortic operations in patients aged 70 years or older

Thirty-one patients over the age of 70 years (group A) and 72 patients less than 69 years (group B) underwent a variety of thoracic aortic surgical procedures. Early and long-term results and cerebral function were compared between the two groups. Preoperative and postoperative cerebral function was evaluated using mini mental state-Himeji and Wechsler adult intelligence scale tests. The operative mortality of groups A and B was 12.9% and 11.1%, respectively (not significant). There were no significant differences in postoperative complications between the two groups. The late mortality rates of groups A and B were 11.1% and 9.3%, respectively (not significant). There were no significant differences between the two groups in the mini mental state-Himeji test, digit symbol, vocabulary, and total Wechsler adult intelligence scale scores before and after operation. We conclude that thoracic aortic surgical procedures in patients over 70 years of age can be performed with acceptable mortality and morbidity risks. Most patients showed symptomatic improvement.

[Result of surgical treatment of true or dissected thoracic aneurysm: determinants analysis in operative mortality and morbidity]

Between 1986 and 1990, 69 patients underwent surgery either for thoracic aneurysm (27 patients) or aortic dissection (42 patients). Sixty one patients (88%) survived and 8 patients (12%) died after surgery. Main determinants of deaths in 4 patients with true arch aneurysm were bleeding from the sites of aortic clamping or anastomosis and intraoperative severe LOS. Three patients with acute type A dissection died from bleeding due to clamp injury or myocardial ischemia. The cause of death in the patient with chronic type B dissection was associated with brain damage due to hypoxia developed during left heart bypass. Postoperative cardiac, pulmonary, hepatic and renal functions were analyzed in the operative survivors. Cardiac functions were maintained well in all patients except two patients with chronic type A dissection. Four patients, one with true arch aneurysm, 2 with chronic type A and one with chronic type B dissection, required tracheostomy. The mean of maximum total serum bilirubin exceeded 4 mg/dl in the patients with true arch aneurysm, acute and chronic type A dissection. The level of serum creatinine showed slight increase in all patients but prophylactic peritoneal dialysis was performed in one patient with chronic type A dissection. In conclusion, the cause of deaths in most patients with thoracic aneurysm was due to inappropriate operative techniques and circulatory supports during surgery. Without the complication described above, the patients could tolerate surgery well.

[Surgical treatment of myasthenia gravis associated with Graves's disease]

During past 30 years, we experienced 253 patients who underwent surgery for myasthenia gravis. Among these patients, 9 were associated with Graves' disease. No patients had thymoma. Five patients underwent thymectomy after they had become euthyroid by medical treatment, though four patients required subtotal thyroidectomy before thymectomy. One patient developed myasthenic crisis following thyroidectomy and was treated with respirator for 5 days. But thymectomy was performed without myasthenic crisis in these four patients between 25 days and 60 days after thyroidectomy. They have been doing well and no see-saw phenomenon was presented. Thymectomy is safe and effective even in the patients with Graves's disease, and we recommend to perform it after they become euthyroid by medical or surgical treatment.