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The extracranial segment of the vertebral artery is well protected, and the rate of occurrence of extracranial vertebral aneurysms is very low. We describe the case of a 40-year-old woman who presented with a large aneurysm of the left vertebral artery in the angiographic absence of a right vertebral artery. Her medical history included a motorcycle accident at the age of 20, at which time a neck sprain had been diagnosed. Computed tomography of the chest and neck revealed a 6- x 4-cm aneurysm with mural thrombus in the left thoracic outlet and in the first portion of the left vertebral artery before the entrance of the transverse foramen of the 6th cervical vertebra. Angiography of the arch vessels confirmed both the presence of an aneurysm of the left vertebral artery and the absence of a right vertebral artery. Due to the lack of contralateral vertebral flow, we planned to perform a graft interposition under deep hypothermic circulatory arrest, for cerebral protection. Unfortunately, the patient refused the operation and was lost to follow-up. To our knowledge, there has been no previous report of an extracranial vertebral artery aneurysm in the absence of a contralateral vertebral artery. We believe that deep hypothermic circulatory arrest with graft interposition is the best treatment strategy, although we did not, in this case, have opportunity to treat the patient.

This paper reports on the design and development of a multi-axis (up to 6 axes) mechanical tester for spinal research and testing. The developed spine tester allowed true motion to be simulated on a specimen in pure or combined modes. To demonstrate the capability of the new tester flexural stiffness properties of sheep lumbar motion segments were evaluated together wiith a non-contact speckle displacement measurement system. The flexural stiffness of the specimens was measured and compared under constrained and non-constrained testing conditions; with relieving of shear forces (non-constrained), it was found that the specimen behaved in a 'stiffer' manner.

Prosthetic aortic valve replacement for aortic valve endocarditis remains a primary practice of most cardiac surgeons. Usually it cures endocarditis and restores cardiac function. However, in advanced aortic valve endocarditis with complex annular destruction, complications following prosthetic aortic valve replacement do occur and present a formidable challenge for reoperation. Herein, we describe a case of an adult man who was operated on initially for advanced aortic valve endocarditis with a large periannular abscess cavity and who developed congestive heart failure 3 months later. Furthermore, he was diagnosed with a giant pseudoaneurysm around the aortic root without evidence of recurrent infection or aortic prosthetic incompetence. During his reoperation, a cryopreserved aortic homograft as a root replacement that included reimplantation of bilateral coronary artery buttons was used to exteriorize this pseudoaneurysm and reconstruct a left ventricular outflow tract. The postoperative course was unremarkable, and the patient, during a follow-up of 2 years, remained in New York Heart Association functional class I. Aortic root pseudoaneurysm following prosthetic aortic valve replacement for infective endocarditis is rare in clinical practice and can cause rapid hemodynamic deterioration which requires imminent reoperation. Homograft aortic root replacement has proven to be a versatile treatment option of this complex disease.

Background: Myocardial revascularization with a minimal-access incision is used in many patients who undergo an elective coronary artery bypass grafting (CABG) operation. To evaluate whether this method could be used for patients who undergo an emergent CABG operation, we compared patients in whom emergent minimal-access CABG was used as the method of revascularization with patients who underwent emergent conventional CABG., Methods: From June 1996 to April 1998, 63 patients underwent emergent CABG operation due to unstable angina, percutaneous transluminal coronary angioplasty accident, or critical left main lesion. Ten patients received minimal-access CABG via limited left parasternal incision (MI), and 53 patients received conventional CABG via median sternotomy (CS)., Results: There were 2 deaths in the MI group and 13 deaths in the CS group. We used the Society of Thoracic Surgery computer program to predict the mortality of both groups. The expected hospital mortality of the MI group was significant higher than that of the CS group. The 24-hour drainage amount in the MI group was significant less than that of the CS group. There were no significant differences in cross-clamping time, the duration of extracorporeal circulation, the intensive care unit stay, or the average hospital stay. Total costs of the MI group were similar to those of the CS group, except that the blood transfusion fee was significantly lower (9,406 +/- 1,259 vs. 12,059+ 3,994 New Taiwan dollars, p = 0.003)., Conclusion: This technique combines minimally invasive surgical conditions with the safety and cost standards of emergent CABG surgery. Even emergent and high-risk coronary artery disease can be treated using this approach.

Fistular communication between an internal iliac artery aneurysm and rectum presenting as massive lower gastrointestinal tract bleeding is a rare entity in clinical practice. Prompt diagnosis and experienced therapeutic application determine the outcome. Herein we report the successful management of such a complication. A 68-year-old male had multiple aneurysms over the abdominal aorta and bilateral iliac arteries. It was the largest aneurysm arising from the right internal iliac artery which ruptured into the rectum and resulted in massive hematochezia. After extraanatomical bypass with right axillo-femoral and femoro-femoral crossover grafts to restore the circulation to the bilateral lower limbs, the infrarenal abdominal aorta just immediately above the proximal aneurysm was transected and closed as a blind stump. All the aneurysms were included in this resection and as much of the infected aneurysm tissue was debrided as possible. The rectum was exteriorized using Hartmann's procedure. The patient survived the operation and was discharged in good condition.

A 76-year-old woman suffered from sudden loss of consciousness while sitting in a chair. She was sent to a local hospital and found to be in shock. After a brief period of external cardiac massage, she was transferred to our hospital. In our emergency department she was lethargic with cool, clammy extremities. Her blood pressure dropped from 113/53 mmHg on arrival to 72/42 mmHg 2 hours later. Echocardiography showed massive pericardial effusion, fair left ventricular contractility and no abnormal segmental motion. The echocardiographic appearance suggested fibrin-like substance in the pericardial space, which was felt to indicate the presence of blood. Enhanced chest computerized tomography showed extravasation of contrast medium from the right ventricular outflow tract. At surgery, a small perforation was found at the infundibular area of the right ventricle, and a total of 500 mL of blood had accumulated in the pericardial space. She was discharged 7 days postoperatively, having made an uneventful recovery. External cardiac massage may cause cardiac disruption, and this should be considered in patients who have secondary hemodynamic instability following successful cardiopulmonary resuscitation.

Background: Experiments were designed to evaluate the effect of warm blood cardioplegia on endothelium-dependent contraction of the coronary endothelium after cardiac global ischemia and reperfusion., Method: Dogs (n = 12 in each group) were exposed to extracorporeal circulation with the body temperature at 37 degrees C (group 1) or 28 degrees C (groups 2 and 3). The ascending aorta was crossclamped for 120 minutes while continuous infusion of warm blood cardioplegec solution (group 1) or intermittent infusion of cold (4 degrees C) crystalloid cardioplegic solution (group 2) was performed via the coronary arteries through the aortic root. Cardioplegic solution was not used in group 3 animals. The heart was then allowed to function for 60 minutes of reperfusion. Reperfused (groups 1, 2, and 3) and control (group 4) coronary arteries were then harvested for study., Results: Perfusate hypoxia caused endothelium-dependent contraction in the arteries of all four groups that could be attenuated by NG-monomethyl-L-arginine (L-NMMA) or L-NMMA plus D-arginine, but not by L-NMMA plus L-arginine or endothelin receptor A and B antagonist PD 145065. The endothelium-dependent contraction results in groups 2 and 3 (75% +/- 4% and 80% +/- 5%, respectively) were significantly greater than those in groups 1 and 4 (15% +/- 3% and 18% +/- 5%, respectively). Scanning electron microscope studies showed that platelet adhesion and aggregation, areas of microthrombi, disruption of endothelial cells, and separation of the intercellular junction could be found in coronary segments from groups 2 and 3, but not in vessels from groups 1 and 4., Conclusion: These experiments suggest that global ischemia and reperfusion enhances hypoxia-mediated endothelium-dependent contraction of the coronary endothelium and damages the ultrastructure. These kinds of changes can be prevented by continuous antegrade infusion of warm blood cardioplegic solution during global ischemia.

A 39-year-old woman having a pure gonadal choriocarcinoma with lung metastasis was referred to our hospital after hysterectomy and bilateral salpingo-oophorectomy. She was found to have a 45XO/46XY karyotype and gonadal dysgenesis. The patient's serum beta-hCG was normalized after six courses of chemotherapy with cisplatin and etoposide of conventional dose (100 mg/m2, 100 mg/m2 x 3 days), but began to fluctuate. Thoracoscopic resection of a remaining pleural lesion was negative for malignancy. However, the disease relapsed as multiple metastatic nodules in bilateral lung fields and the mediastinum. After one course of priming chemotherapy with conventional dose (1 g/m2 cyclophosphamide, 400 mg/m2 carboplatin, and 500 mg/m2 etoposide), high-dose chemotherapy with a total dose of 1500 mg/m2 carboplatin, 1200 mg/m2 etoposide, and 5 g/m2 ifosfamide followed by autologous bone marrow transplantation and peripheral stem cell support was given. Thoracoscopic surgery was performed to resect two residual solitary metastatic lung lesions. With these salvage treatments, the patient obtained complete remission and remained disease free at last follow-up (17 months). Our result suggests that high-dose chemotherapy may be effective in chemosensitive nongestational choriocarcinoma when first chemotherapy has failed.

A case of right bronchial rupture demonstrated by computed tomography (CT) is reported. Chest radiographs of a 55-year-old man who sustained blunt chest trauma showed bilateral pneumomediastinum, hydropneumothorax, and subcutaneous emphysema with fracture of the left 3rd and 4th ribs. CT showed wall defect over the right main bronchus with the air in airway contiguous to that in the mediastinum. Bronchoscopy and thoracostomy confirmed the CT findings and the patient was treated by bronchorrhaphy with end-to-end anastomosis. The airway should be meticulously evaluated in cases of mediastinal and subcutaneous emphysema, especially after trauma.

Objective: To evaluate the effect of University of Wisconsin solution on endothelium-dependent relaxation and contraction of human hepatic arteries in vitro., Design: Human hepatic arteries were harvested from 24 patients with hepatocellular carcinoma who had undergone hepatectomy., Setting: A tertiary care center., Interventions: Human hepatic arteries (n = 6 in each group) were harvested during resection for hepatocellular carcinoma. The arteries in group 1 (i.e., the control group) were immediately studied without preservation. The arteries in group 2 were preserved in cold (4 degrees C) physiological solution for 1 hour, while the arteries in groups 3 and 4 were preserved in University of Wisconsin solution for 1 and 16 hours, respectively. Segments of control and preserved hepatic arteries with or without endothelium were then suspended in organ chambers to measure the isometric force., Results: The relaxation of segments of the hepatic arteries with endothelium in response to acetylcholine and adenosine diphosphate was significantly (P < .05) greater than that of segments without endothelium. The maximal relaxation of hepatic arterial segments with endothelium in groups 3 and 4 in response to acetylcholine was notably different from that of segments in groups 1 and 2. The maximal relaxation of hepatic arterial segments with endothelium in groups 3 and 4 in response to adenosine diphosphate was notably different from that of segments in groups 1 and 2. Perfusate hypoxia (mean +/- SD PO2, 30 +/- 5 mm Hg) caused the endothelium-dependent contraction of the arteries (the median initial tension in groups 1, 2, 3, and 4 was 251%, 233%, 276%, and 260%, respectively; P > .05)., Conclusions: The endothelium-dependent relaxation of human hepatic arteries in response to acetylcholine and adenosine diphosphate was notably attenuated by University of Wisconsin solution. The impaired endothelium-dependent relaxation by University of Wisconsin solution and the prominent endothelium-dependent contraction of human hepatic arteries would favor vasospasm and thrombosis after hepatic transplantation.

The simultaneous operation of near-field scanning optical microscopy (NSOM) in reflection and transmission modes is demonstrated. In the transmission mode, a low-noise, large-area silicon photodetector was mounted between the piezoelectric transducer scanning stage and the sample. In the reflection mode, either a photomultiplier tube or two large-area silicon detectors was used for signal collection. The reflection-mode setup consisting of two silicon detectors provides a large numerical aperture of 0.9 as well as symmetrical detection of emitting photons. The dielectric thin films and the light-emitting polymers were used to demonstrate the capability of these two modes of NSOM. A comparison between these two different setups is also presented.

Background: Circulatory arrest (CA), which provides a bloodless field and good visualization without the need of aortic cross-clamp, is commonly used to facilitate repair of aortic lesions. However, extended periods of CA may impair cerebral metabolism and cause ischemic injury. Studies were performed to evaluate the efficacy of retrograde cerebral perfusion (RCP) in protecting the brain from ischemic injury during a prolonged period of CA in moderate hypothermia., Methods and Results: Twenty-three patients (18 men and 5 women) were operated on for aortic lesions (17 acute type A aortic dissection and 6 chronic type A aortic dissection with Marfan's syndrome). The aortic operations were performed with CA (58 to 104 minutes; mean +/- SD, 75 +/- 12 minutes) at a rectal temperature of 23.3 +/- 0.5 degrees C (21 degrees C to 25 degrees C). For RCP, cold (14 degrees C to 18 degrees C) oxygenated blood (300 mL/min) was pumped to the superior vena cava with internal jugular venous pressure of 15 +/- 5 mm Hg. The cardiopulmonary bypass time was 157 +/- 18 minutes. Cortical blood flow during RCP detected by subdural laser Doppler probe was 10 +/- 5% of baseline. Percent oxygen extraction and pyruvate and lactate levels (26 +/- 2% and 0.43 +/- 0.17 and 45 +/- 16 mg/dI) were insignificantly different from those before CA (28 +/- 3% and 0.71 +/- 0.08 and 62 +/- 20 mg/dL, P > .05). Creatine kinase-BB isoenzyme was undetectable. All but 1 patient survived the operation (95.5%) and woke up without neurological deficit. Follow-up (mean, 13 months) was complete in all survivors. There were no late deaths. Cerebral functional studies performed 3 months after discharge showed results insignificantly different from those of the normal control subjects., Conclusions: There is no evidence of ischemia of the brain during prolonged moderate hypothermic CA with the aid of RCP. Retrograde cerebral perfusion effectively extends the safe time of CA. Deep hypothermia during CA seems unnecessary.

Blood pressure is not constant over the course of a 24-h period, but exhibits a predictable and characteristic rise and decline during the day. Although the general shape of this pattern is similar from patient to patient, the knowledge of an individual's blood pressure at one or two points on this curve is of no predictive value in estimating the remainder of the curve. Since critical events are associated with both the maximum and minimum blood pressures that an individual experiences, a characterization of this curve can be very important. The development of antihypertensive agents historically presumed that the reduction in blood pressure associated with therapy would be, if not constant, at least adequate throughout the entire period. However, with the advent of less frequent dosing, the importance of assuring that blood pressure was adequately controlled over the 24-h period became important. This created interest in two basic types of comparisons. One is the comparison of dosing regimens, e.g., comparing a once-a-day regimen with a twice-a-day regimen. The second is a comparison of two therapies with the same regimen; for example, two doses designed to be administered twice a day. The shape of the curves in the first case is inherently different, whereas they have a similar configuration in the second. Many techniques have been attempted, but few recommended for these types of comparisons. Examples include time series, the use of composite indices, univariate statistical procedures, multivariate procedures, and mathematical characterization of the curves with subsequent comparison of model parameters. This presentation will provide a background and overview of several of these methodologies and their relative utility.

From January 1986 to December 1991, 100 modified Blalock-Taussig Shunts (MBTS) using PTFE (polytetrafluoroethylene) grafts were performed on 86 patients with complex cyanotic congenital cardiac malformations at this hospital. The ages of patients ranged from 15 days to 22 years. Thirty-seven were operated upon in infancy and one in the neonatal period. Varying sizes of grafts were used: 3 mm in 3 cases, 4 mm in 18, 5 mm in 44, 6 mm in 34 and 8 mm in one. The mean follow-up period was 13.5 months (ranged from one to 50 months). There were one hospital mortality and one morbidity. One year shunt patency rate was 90%. Univariate analysis showed the age of the patient operated upon and graft size were risk factors for shunt patency. With an encouraging 90% early shunt patency rate, we can now adopt MBTS as an alternative without hesitancy. Yet, the surgical technique and perioperative care of those cyanotic neonates receiving this palliation still remain a challenge.

In clinical trials and behavioral sciences, there exist situations where paired responses are obtained from each subject on an ordinal scale. Existing methods for analyzing such data in a factorial design are reviewed and new methods are developed with a special emphasis on pre- and post-treatment responses. The distribution of a square table is decomposed into successively independent pairs of discordant vectors, and assuming a logistic model, a statistics is computed to measure the shift in the marginal distributions. The approach is similar to McCullagh's approach (1). Two other criteria are proposed, one based on a Lehmann alternative used for comparing two distribution functions and the other based on a proportional odds model. These criteria are applied to the marginal distributions of a square table. For each case, a statistic measuring lack of marginal homogeneity and its variance are computed for each independent square table of a factorial design. Given such statistics, one can estimate a set of linear contrasts and compute its dispersion matrix for making inference. A numerical example is given.

Patel analysed a two-period cross-over design with baseline measurements assuming bivariate normality for the joint distribution of the period responses. In this paper, we propose non-parametric methods for analysing this design, including the use of the Wilcoxon rank sum test to derive the preliminary tests from the baseline measurements. We fit a robust regression line of the treatment response on baseline for each period and compute residuals. We also fit a robust locally weighted regression as an alternative method for computing residuals. Then, following Koch's procedure, we analyse the residuals for testing the significance of the treatment x period interaction and the treatment difference. We provide a numerical example to illustrate the methods.

Experiments were designed to determine whether hyperkalemic crystalloid cardioplegic solution enhances endothelium-dependent contraction of coronary arteries. Segments of canine coronary arteries (n = 8 in each group) were preserved in cold (4 degrees C) crystalloid cardioplegic solution (group 1) and physiologic solution (group 2) for 60 minutes. Segments of preserved and control (group 3) coronary arteries with or without endothelium were suspended in organ chambers to measure isometric force. Perfusate hypoxia (oxygen tension 35 +/- 5 mm Hg) caused endothelium-dependent contraction in the arteries of all three groups. However, vascular segments with endothelium of group 1 exhibited hypoxic contraction (68.5% +/- 15.3% of the initial tension contracted by prostaglandin F2 alpha 2 x 10(-6) mol/L, p < 0.05) that was significantly greater than contraction of the group 2 and group 3 segments with endothelium (26.6% +/- 5.6% and 20.6 +/- 4.4%). The hypoxic contraction in arteries of group 1 could be attenuated by NG-monomethyl-L-arginine, the blocker of endothelial cell synthesis of the nitric oxide from L-arginine. The action of NG-monomethyl-L-arginine could be reversed by L-arginine but not D-arginine. Thus after preservation with cardioplegic solution, augmented endothelium-dependent contraction, occurs by L-arginine-dependent pathway, would favor coronary vasospasm after cardiac operation.

Ginseng, a panacea in the Orient, has been widely investigated in the last two decades and found to possess a wide range of pharmacological activities including anti-fatigue properties, a transient regulatory action on metabolism and blood pressure, and an increase in the hypothalamo-pituitary-adrenocortical activities. However, a panoramic clinical chemistry study including adrenal and thyroid functions has never been done before. Two experiments with the same design but different concentrations of dexamethasone were performed in this study. The results obtained from the two experiments indicated that ginseng administration at this regime did not influence the blood chemistry profiles in normal rats, but significantly decreased AST and ALT levels from those in dexamethasone-treated ones. It implies that ginseng has a liver-protective effect. Meanwhile, ginseng therapy restores the adrenal and thyroid functions of rats inhibited by dexamethasone treatment.

University of Wisconsin (UW) solution has been used almost routinely in the preservation of the hepatic, pancreatic, renal, and cardiac allografts. However, its effect on vascular endothelium is unknown. Experiments were designed to evaluate its effect on canine coronary endothelium. Canine coronary arteries (n = 8 in each group) were preserved in cold (4 degrees C) UW solution (group 1) and physiological solution (group 2) for 6 hr immediately after harvesting. Segments of preserved and control (group 3) coronary arteries with or without endothelium were then suspended in organ chambers to measure isometric force. Perfusate hypoxia (pO2 30 +/- 5 mmHg) caused endothelium-dependent contraction in the arteries of all 3 groups. However, vascular segments with endothelium of group 1 exhibited hypoxic contractions (107 +/- 26% of the initial tension contracted by prostaglandin F2 alpha 2 x 10(-6) mol/L, P < 0.05) that were significantly greater than those of the group 2 and group 3 segments with endothelium (25 +/- 5% and 20 +/- 4%). The hypoxic contraction in arteries of group 1 could be attenuated by NG-monomethyl-L-arginine (L-NMMA), the blocker of endothelial cell synthesis of the nitric oxide from L-arginine. The action of L-NMMA could be reversed by L-arginine but not D-arginine. Endothelium-dependent relaxation of coronary endothelium to acetylcholine and adenosine diphosphate and endothelium-independent relaxation and contraction of coronary smooth muscle were not altered by the UW solution. After preservation with the UW solution, endothelium-dependent contraction of the canine coronary arteries, occurs by L-arginine-dependent pathway, is enhanced. This augmentation by the UW solution would favor vasospasm after transplantation.

Healy (1) and Dempster et al. (8) proposed statistical methods to evaluate the treatment effects in animal reproductive toxicology research. Both methods assume homogeneous variance for the dams and the pups, respectively, in all the treatment groups. In this paper, via mixed effect modeling, we propose a method to estimate the treatment effects allowing heterogeneous variances for the dams and the pups, respectively, in different treatment groups. Covariates will also be included in the model. A procedure to test the fixed effects is also discussed. An example from an animal reproductive toxicological study is used to illustrate the procedures.

Hypothermic circulatory arrest is commonly used to facilitate repair of complex congenital heart defects and aortic lesions and for complex neurosurgical procedures. However, extended periods of circulatory arrest may impair cerebral metabolism and cause ischemic injury. Retrograde cerebral perfusion has been applied recently in aortic surgery to protect the brain. From January 1991 to December 1993, 29 patients underwent emergency operations to repair acute type A aortic dissection with the aid of hypothermic circulatory arrest. Six patients received hypothermic circulatory arrest without retrograde cerebral perfusion with a rectal temperature of 16.4 degrees +/- 0.9 degrees C (mean +/- standard error of the mean, group 1). Retrograde cerebral perfusion during hypothermic circulatory arrest was performed in 15 patients with a rectal temperature of 15.9 degrees +/- 0.5 degrees C (group 2) and in eight patients with a rectal temperature of 21.7 degrees +/- 0.8 degrees C (group 3). The hypothermic circulatory arrest times were 25 +/- 4, 42 +/- 4, and 63 +/- 6 minutes, respectively (p < 0.05). The cardiopulmonary bypass times were 173 +/- 5, 184 +/- 7, and 143 +/- 6 minutes, respectively (p < 0.05). All patients survived the operation and regained consciousness with no neurologic defects. Follow-up (mean 23.2, 14.5, and 5.1 months, respectively) was complete in all patients except one. This patient, from group 2, was killed in a road traffic accident 12 months after the operation. Our experience suggests that retrograde cerebral perfusion can effectively protect the brain from ischemic injury and extend the safe period of hypothermic circulatory arrest. With the aid of retrograde cerebral perfusion, prolonged circulatory arrest can probably be performed safely with moderate hypothermia.

The surgical treatment of acute type A aortic dissection remains a great challenge to all cardiac surgeons. From January 1991 to June 1993, 21 consecutive patients (13 men and eight women, aged 34 to 74 years) underwent emergency operations to repair acute type A aortic dissection, with the aid of hypothermic circulatory arrest. The intima tear was located in the ascending aorta in 13 patients, in the aortic arch in five patients, and in the descending aorta in three patients. The dissected ascending aorta was replaced with sutureless, intraluminal vascular grafts in all 21 patients. The intima tears in the aortic arch of five patients were primarily repaired. Modified Cabrol's shunts were created in seven patients for hemostasis, and Dacron grafts were used to wrap the ascending aorta in 18 patients. Retrograde cerebral perfusion during circulatory arrest was performed on 15 patients. The circulatory arrest time was 37 +/- 10 minutes (mean +/- SD). All patients survived the operation and regained consciousness in the early postoperative period without neurologic deficit. Post-treatment follow-ups (mean, 18.2 months) were completed in all patients except one, who died 12 months after the operation as a result of a traffic accident. All of the surviving patients are doing well without any further aortic operations. Our experience suggests that surgical repair of the acute type A aortic dissection can be a simple and safe procedure if sutureless intraluminal grafts are used and hypothermic circulatory arrest and retrograde cerebral perfusion are utilized.

Thrombotic obstruction, a rare but often fatal complication of cardiac valve prostheses, appears to occur more frequently in tilting-disc valves than in other valve designs. Its diagnosis and surgical treatment remain a challenge. Ten consecutive patients who had thrombosis of a tilting-disc valve prosthesis were treated in Chang Gung Memorial Hospital from November 1982 to August 1990. Preoperative clinical features, including exertional dyspnea, new murmur, and absence of a metallic click from the prosthetic valve, occurred in all of the patients. Symptoms were present for 1 week or more before reoperation in 70% of the patients; nevertheless, many patients were referred only after acute exacerbation of heart failure and development of pulmonary edema. Echocardiography confirmed prosthetic valve malfunction in 90% of the patients. One unconfirmed case was later documented by cardiac catheterization. Anticoagulant therapy was in the therapeutic range for only half of the patients at the time of admission. Prompt reoperation was performed for thrombectomy (8 patients, all survived) or valve replacement (2 patients, one death). Long-term outcome was satisfactory in all survivors with a mean follow-up of 31.6 months. These findings emphasize the importance of considering the diagnosis of thrombosis in patients with mechanical heart valve prostheses who are first seen with nonspecific symptoms and minor changes of their physical findings. The diagnosis could be easily made by echocardiography. Thrombectomy is an easy, fast, and safe procedure, especially for these critically ill patients.

A FORTRAN computer program written to perform a multivariate analysis of growth and response curves is described. The underlying statistical methodology is particularly applicable with incomplete observations, and may offer improved power performance to the distribution-free methods described previously.