[The staged approach--an overview on a strategy to reduce spinal cord injury in thoracoabdominal aortic aneurysm repair]. / Das zweizeitige Vorgehen zur Reduktion der spinalen Ischämie bei der Ausschaltung thorakoabdomineller Aortenaneurysmen - eine Übersicht.

The spinal cord is particularly susceptible to ischaemic injury following repair of extensive descending thoracic and thoracoabdominal aortic aneurysms (TAAA). For the past decade, the Mount Sinai group in New York has intensively studied the anatomy of the extensive vascular network surrounding the spinal cord, as well as its dynamic morphology in response to decreased blood pressure and flow. Along with clinical data, experimental findings gave rise to the Collateral Network Concept, by which spinal cord injury in open TAAA repair can be significantly reduced. With the more recent widespread use of endovascular repair, strategies to prevent ischaemic spinal cord damage after extensive segmental artery sacrifice/occlusion are still evolving. The hypothesis that dividing extensive aneurysm repair into two steps may mitigate the impact of diminished blood flow to the collateral network has led to a recently conducted series of staged repair experiments. By exploiting the resources of the collateral network, spinal cord injury could be minimised in staged open, as well as in staged hybrid repair and seems equally adoptable for endovascular procedures. The contribution presented herein provides an overview of clinical and experimental studies on the staged approach. Furthermore, it briefly assesses the anatomic rationale for the collateral network concept.

Mathematical model for describing cerebral oxygen desaturation in patients undergoing deep hypothermic circulatory arrest.

BACKGROUND: Surgical treatment for aortic arch disease requiring periods of circulatory arrest is associated with a spectrum of neurological sequelae. Cerebral oximetry can non-invasively monitor patients for cerebral ischaemia even during periods of circulatory arrest. We hypothesized that cerebral desaturation during circulatory arrest could be described by a mathematical relationship that is time-dependent. METHODS: Cerebral desaturation curves obtained from 36 patients undergoing aortic surgery with deep hypothermic circulatory arrest (DHCA) were used to create a non-linear mixed model. The model assumes that the rate of oxygen decline is greatest at the beginning before steadily transitioning to a constant. Leave-one-out cross-validation and jackknife methods were used to evaluate the validity of the predictive model. RESULTS: The average rate of cerebral desaturation during DHCA can be described as: Sct(o(2))[t]=81.4-(11.53+0.37 x t) (1-0.88 x exp (-0.17 x t)). Higher starting Sct(o(2)) values and taller patient height were also associated with a greater decline rate of Sct(o(2)). Additionally, a predictive model was derived after the functional form of a x log (b+c x delta), where delta is the degree of Sct(o(2)) decline after 15 min of DHCA. The model enables the estimation of a maximal acceptable arrest time before reaching an ischaemic threshold. Validation tests showed that, for the majority, the prediction error is no more than +/-3 min. CONCLUSIONS: We were able to create two mathematical models, which can accurately describe the rate of cerebral desaturation during circulatory arrest at 12-15 degrees C as a function of time and predict the length of arrest time until a threshold value is reached.

Results of immediate surgical treatment of all acute type A dissections.

BACKGROUND: Surgery for acute type A aortic dissection is associated with a high mortality rate and incidence of postoperative complications. This study was designed to explore perioperative risk factors for death in patients with acute type A aortic dissection. METHODS AND RESULTS: One hundred twenty-four consecutive patients with acute type A aortic dissection between 1984 and 1998 were reviewed. All underwent operation with resection of the intimal tear and open distal anastomosis: 107 patients had surgery within 24 hours and 17 patients had surgery within 72 hours of symptom onset. Median age was 62 years (23 to 89); 89 were men. Forty-three patients had ascending aortic replacement only, 72 had hemiarch repair, in 2 the entire arch was replaced, and in 7 replacement included the proximal descending aorta. The aortic valve was replaced in 54 patients, resuspended in 52, and untouched in 18. Hospital mortality rate was 15.3% (19 of 124): of these, 3 patients died during surgery, 4 had fatal rupture of the distal aorta before discharge, and 2 died of malperfusion-related complications. Multivariate analysis revealed age >60, hemodynamic compromise, and absence of hypertension as preoperative indicators of hospital death (P:<0.05); the presence of new neurological symptoms was a significant preoperative risk factor in univariate analysis. Ominous intraoperative factors included contained hematoma and a comparatively low esophageal temperature but not cerebral ischemic time (mean 32 minutes). The site of the intimal tear did not influence outcome, but mortality rate was higher with more extensive resection: 43% with resection including the descending aorta died versus 14% with only ascending aorta or hemiarch replacement. Overall 5- and 10-year survival was 71% and 54%, respectively; among discharged patients (median follow-up 41 months) survival was 84% and 64% versus expected US survival of 92% and 79%. CONCLUSIONS: Immediate surgical treatment of all acute type A dissections with resection of the intimal tear and use of hypothermic circulatory arrest for distal anastomosis results in acceptable early mortality rates and excellent long-term survival.

Use of rabbit antithymocyte globulin in cardiac transplantation. Relationship of serum clearance rates to clinical outcome.

Serum rabbit globulin (RG) clearance rates were determined in 30 consecutive cardiac transplant recipients by radioimmune assay of serum RG levels after completion of an initial postoperative course of rabbit anti-human antithymocyte globulin (RATG). Twenty patients, who exhibited rapid RG elimination rates (average half-life, 1.6 days), had a rejection onset time of 16.2 days rejection frequency of 3.9 episodes/100 patient days, and a 1-year survival rate of 59%, respectively, as compared with 28.3 days, 1.9 episodes/100 patient days, and 80%, respectively, for the 10 patients with more prolonged initial RG elimination rates (average half-life, 11.4 days); Nineteen patients received one or more repeat courses of RATG. In 16 of these a progressive increase in RG half-life during subsequent RATG administration could be demonstrated. A close correlation was observed between total RATG doses given in the initial course and peak serum levels of RG obtained (r = 0.82) and between onset of rejection and initial t1/2 RG (r = 0.69). This latter correlation was improved by the elimination of one of the 30 patients (r = 0.81) or by considering only those patients treated from a single RATG batch (r = 0.85; n = 15). No significant relationship was detected between any of the parameters assayed and (1) total RATG dose, or (2) rosette inhibition titers of RATG administered. Survival and rejection parameters of the first 30 patients receiving RATG were compared with the previous 20 receiving equine antithymocyte globulin; these 50 comprising the entire population in which rejection was confirmed by cardiac biopsy. Rejection onset was 20 versus 12 days, rejection frequency was 3.1 versus 5.0 episodes/100 patient days, and graft survival at 1 year was 66 versus 41% for the RATG-equine antithymocyte globulin-treated patients, respectively. From these data it was concluded that (1) RATG administration favorably affects transplantation outcome; (2) RATG half-life, as reflected by RG clearance rates, was the most important variable governing RATG effectiveness, (3) variation in rosette inhibition titers within RATG batches made in the same fashion from large rabbit pools were of minimal clinical importance; and (4) monitoring of serum RG levels provided a necessary and rational basis for effective modulation of immunosuppressive therapy.

Radioimmune assay of heterologous serum gamma-globulin in patients receiving rabbit antihuman thymocyte globulin.

A radioimmune assay (RIA) method for detecting heterologous serum rabbit gamma-globulin (RG) and antibody to this protein is described. The methodology is used for monitoring serum levels of rabbit globulin in patients receiving rabbit ATG (RATG). In 7 cardiac recipients receiving RATG, maximum serum levels of RG were achieved 1-3 days after administration of final dose. RG half-life subsequent to peak serum levels was rapid (X = 36 hr) in 4 patients and prolonged (X = 18 days) in 3 patients. Patient antibody to rabbit gamma-globulin was detectable only in those patients with short RG half-life. Antirabbit antibody titers in these patients were extremely low and barely detectable by RIA.

Coronary arterial narrowing in Takayasu's aortitis.

A patient with Takayasu's aortitis and angina pectoris due to severe narrowing of the right and left coronary arterial ostia is described. Takayasu's arteritis produces a panaortitis, with thickening of the adventitia predominating, and an inflammatory cell infiltrate involving the adventitia, outer media and vasa vasorum. Narrowing of the coronary arteries in this disease is due to extension into these arteries of the processes of proliferation of the intima and contraction of the fibrotic media and adventitia that occur in the aorta. The distal coronary arteries usually do not manifest arteritis and are normal in caliber. Angina pectoris may be the first symptom of the disease if the coronary arteries are the initial site of severe arterial narrowing. The coronary arterial bypass graft operation is effective therapy for treating coronary arterial narrowing due to Takayasu's arteritis.

Survival in neonatal biventricular repair of left-sided cardiac obstructive lesions associated with hypoplastic left ventricle.

Patients with left ventricular hypoplasia and left-sided heart obstructive lesions other than critical aortic stenosis may be inappropriately subjected to single ventricular repair because their assessment is based on faulty qualitative evaluations or on quantitative methods developed for critical aortic stenosis. Patients with left ventricular hypoplasia and left-sided heart obstructions other than critical aortic stenosis successfully underwent biventricular repair despite "failing" to pass established criteria for critical aortic stenosis.

Tissue valve replacement of prosthetic heart valves for thromboembolism.

Twenty-five patients who had repeated thromboemboli from a prosthetic mitral valve were treated with reoperation using a tissue valve prosthesis. Reoperation was performed an average of 4.0 years after the original valve replacement in 14 men and 11 women, with an average age of 50 (range 35 to 65) years. A stented allograft was used in the first 7 patients and a porcine xenograft in the last 18 patients. There were one hospital death and two late deaths. With the first prosthetic valve there were 66 documented embolic episodes in 101.5 patient years (0.65 embolus/year). Only four embolic episodes in 67.4 patient years (0.059 embolus/year) occurred after tissue valve replacement (P less than 0.001). These results indicate that in patients with recurrent or severe embolization after prosthetic heart valve replacement, rereplacement with a tissue prosthesis can be safely performed and significantly reduces the likelihood that additional embolic episodes will occur.

Surgical treatment of degenerative mitral regurgitation.

Between October 1965 and April 1975, mitral valve replacement was preformed in 66 patients with myxomatous degeneration of the mitral valve ("floppy valve syndrome"). Operative mortality was 6 percent (four patients). Current evaluation was obtained for all patients; the average postoperative follow-up interval for surviving patients was 3.5 years (range 1 month to 9.9 years); the total duration of postoperative follow-up for all patients was 180 patient-years. Overall survival rates, calculated by the actuarial method, were 81, 68 and 50 percent, respectively, 1, 2 and 5 years after mitral valve replacement. Preoperative variables with a significantly adverse effect on patient survival included patient age greater than 50 years, New York Heart Association functional class IV, left ventricular end-diastolic pressure greater than 12 mm Hg and mean pulmonary arterial wedge pressure greater than 16 mm Hg. Support is advanced for the concept that mitral valve dysfunction associated with myxomatous degeneration constitutes a broad spectrum of clinicopathologic involvement. Acute clinical and hemodynamic deterioration may often occur in the setting of chronic mitral valve dysfunction. Postoperative mortality is directly related to preoperative functional disability and hemodynamic evidence of impaired left ventricular function. Consideration should be given to earlier operative intervention in patients with myoxmatous mitral degeneration and mitral insufficiency before severe and probably irreversible impairment of ventricular function occurs.

Usefulness of intermittent monitoring of mixed venous oxygen saturation after stage I palliation for hypoplastic left heart syndrome.

Most deaths after stage I palliation for hypoplastic left heart syndrome have occurred within the first 24 hours after surgery. Efforts to improve 1-day survival should therefore have significant impact on improving overall survival. Early death has most often been attributed to low cardiac output and abnormalities of pulmonary to systemic flow ratio (Qp/Qs). Thirteen infants underwent stage I palliation and had a catheter inserted in the high superior vena cava (SVC) for intermittent measurement of SVC oxygen saturation. Calculation of Qp/Qs was achieved using SVC saturation as a mixed venous oxygen saturation, and estimating pulmonary venous oxygen saturation. Eleven patients survived, and 2 patients died within the first 24 hours. Abnormalities in Qp/Qs were noted in 12 of 13 patients after operation. In 10 of these 12 patients, there was a high Qp/Qs, which has been associated with poor outcome. High Qp/Qs was noted even in patients with acceptable arterial oxygen saturations (< 85%). SVC saturation increased in all survivors during the first 24 hours, and was associated with a decrease in Qp/Qs. Measurement of SVC oxygen saturation appears to be a valuable adjuvant in the postoperative management of infants after stage I palliation of hypoplastic left heart syndrome. Major abnormalities in Qp/Qs can be detected even with acceptable arterial saturations. With this information, early ventilator/pharmaceutical adjustments can be made which may improve stage I survival.

Total correction of tetralogy of Fallot. How to deal with the complicated ascending aorta-right pulmonary artery anastomosis.

Ascending aorta-right pulmonary artery anastomosis may be complicated by deformity at the anastomotic site leading to discontinuity between pulmonary artery branches. Simple closure of such shunts through the ascending aorta is associated with residual stenosis and pressure gradients. An alternative approach which allows reconstruction of the entire intrapericardial pulmonary arterial system at the initial corrective operation is described. The transection of the ascending aorta facilitates the exposure necessary for this extensive repair. Two illustrative cases are presented.

Surgical correction of types II and III truncus arteriosus.

In truncus arteriosus types II and III, one or both pulmonary arteries arise independently from either side of the truncus. In the surgical correction of this anomaly, we have utilized on operative technique in which the essential features are as follows: ventricular septal defect (VSD) closure, which directs left ventricular outflow into the truncus: (2) anastomosis of a Dacron tube containing a glutaraldehyde-preserved procine aortic heterograft to the right ventriculotomy: (3) removal of a circumferential band of the truncus containing both pulmonary artery orifices; (4) tailoring of the band of truncus tissue into a generous cuff which is anastomosed to the distal end of the valved Dacron conduit; and (5) restoration of aortic continuity with a tubular Dacron graft. Since 1971, 4 children ages 2 to 9 years have undergone successful correction of truncus arteriosus types II or III by this technique. In one patient with marked pulmonary hypertension and congestive heart failure preoperatively, the pulmonary vascular resistance had reverted to normal by 3 years after the operation. In one patient in whom bronchial collaterals to the right pulmonary artery were present, postoperative left ventricular failure required reoperation for ligation of the collaterals. All 4 patients are asymptomatic and fully active 5 to 60 months postoperatively. None has evidence of stenosis or insufficiency of the heterograft valve.

Experience with profound hypothermia and circulatory arrest in the treatment of aneurysms of the aortic arch. Aortic arch replacement for acute arch dissections.

In a series of 21 consecutive patients, the aortic arch, varying portions of the ascending and descending aorta, and in some the aortic valve were replaced with the aid of a standard method of profound total body hypothermia and circulatory arrest. Fourteen patients underwent elective and seven patients emergency arch replacement. A combination of surface cooling and cardiopulmonary bypass was used to produce total body hypothermia. Replacement of the aortic arch was performed during a single period of circulatory arrest. Cardiopulmonary bypass was utilized for core rewarming. The average cerebral ischemic time was 37 +/- 14 minutes at an average core temperature of 13.7 degrees +/- 1.8 degrees C. The average myocardial ischemic time was 79 +/- 28 minutes with an average duration of cardiopulmonary bypass of 130 +/- 32 minutes. Of the 14 patients undergoing elective operation, three died; of the seven patients undergoing emergency operations, three died (two with ruptured aneurysms and one with acute arch dissection). Fifteen patients are alive and well 2 months to 7 years following the operation. All are free of neurologic sequelae. One has an asymptomatic residual dissection in the descending aorta. This experience indicates that profound total body hypothermia with circulatory arrest is a safe and effective method for elective surgical treatment of enlarging aneurysms of the aortic arch and for emergency treatment of acute dissections if the intimal tear is located in the aortic arch. The technique is simple and produces results superior to those reported for methods which involve selective cerebral perfusion during arch replacement.

Survival and function after left ventricular aneurysmectomy.

Operative and late postoperative results in 55 patients undergoing resection of a discrete, saccular type left ventricular aneurysm are described. All patients had occlusive lesions of either the left anterior descending or left main coronary artery, and 72 per cent had significant multivessel disease. Preoperative factors that correlated significantly with decreased long-term survival were age greater than 60 years, severe congestive heart failure, and subnormal cardiac output at rest. The primary determinant of long-term postoperative survival appears to be the functional state of residual myocardium after aneurysmectomy. The survival rate for patients with multivessel disease was not less than that of patients with isolated lesions of the left anterior descending coronary artery. The impact of simultaneous aorto-coronary bypass grafting on postoperative results in patients with multivessel coronary disease is discussed. An advantage to concomitant revascularization with aneurysmectomy cannot be statistically corroborated in this series. However, improvement in results since the routine application of bypass grafting in appropriate cases, the uniform operative survival of bypassed patients with triple vessel disease, and the relatively high frequency of myocardial infarction as a cause of late postoperative death suggest that bypass grafting in patients with multivessel disease should be combined with aneurysmectomy to maximally improve long-term prognosis.

Prosthetic replacement of the aortic arch.

Four patients are reported in whom the aortic arch and variable portions of the ascending and descending aorta were replaced with a prosthesis. In three patients the preoperative diagnosis was dissecting aneurysm of the aortic arch and in one an arteriosclerotic aneurysm of the aortic arch was present. A combination of surface cooling and cardiopulmonary bypass was utilized to produce total body hypothermia. Arch replacement was carried out during a period of total circulatory arrest. Cardiopulmonary bypass was then utilized to warm the patient and resuscitate the heart. The average duration of cerebral ischemia was 43 minutes and the average duration of myocardial ischemia was 74 minutes. The average lowest esophageal temperature was 14 degrees C., and the average lowest rectal temperature was 18 degrees C. Three patients are alive and well 4 to 13 months following surgery. One patient died 4 days postoperatively of pulmonary insufficiency. This experience indicates that by utilizing total body hypothermia and circulatory arrest aortic arch replacement can be carried out with an acceptable mortality rate. Corrective surgery could be offered to patients with life-threatening enlarging aneurysms of the aortic arch.

Urgent operation for acute transverse aortic arch dissection.

Surgical intervention is generally accepted for acute type A dissection, but little is published regarding therapy for acute dissection of the transverse portion of the aortic arch, though involved in approximately 15% of cases. Often, surgical treatment is withheld if aortography suggests a primary tear in the aortic arch. Similarly, resection is limited to the ascending aorta despite intimal tears within the transverse portion of the arch. This work reports a 9-year experience with a policy of emergency resection for all acute aortic dissections involving the aortic arch. Intensive "antiimpulse" therapy is instituted and aortic angiograms are obtained. Type A dissections are resected under moderate hypothermia and, if the primary tear extends into the arch or is not found in the ascending aorta, the arch is explored during a brief period of deep hypothermia and circulatory arrest. If necessary, the arch is replaced during circulatory arrest, the patient's head is packed in ice, steroids are administered, and a barbiturate coma is induced. If arch replacement is anticipated preoperatively, surface cooling is also employed. Sixteen acute (up to 14 days) and three subacute (15 to 28 days) transverse arch dissections were treated in this manner between May 1979 and May 1988, with four (21%) hospital deaths (25%, acute; 0%, subacute). Mortality was related to left main coronary dissection with extensive myocardial infarction in two of our four cases, a third death was related to persistent seizures in a renal transplant patient requiring hemodialysis who had lupus cerebritis, and the fourth resulted from rupture of the descending aorta 15 days after arch replacement.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypothermic circulatory arrest in operations on the thoracic aorta. Determinants of operative mortality and neurologic outcome.

This study was undertaken to determine the factors that influence the final outcome after hypothermic circulatory arrest. Between 1985 and 1992 a uniform method of hypothermic circulatory arrest was used in 200 patients as the primary method of cerebral protection during operations on aneurysms of the thoracic aorta. There were 30 hospital deaths (15%). Age greater than 60 years (relative risk 3.7, p < 0.02), emergency operation and hemodynamic compromise (relative risk 22.2, p < 0.000), concomitant procedures (relative risk 2.7, p < 0.04), presentation with new neurologic symptoms (relative risk 5.2, p < 0.04), and postoperative permanent neurologic deficits (relative risk 9.4, p < 0.000) were found to be significant predictors of operative mortality. A total of 183 patients were available for evaluation of neurologic function and outcome. Multivariate analysis of this cohort of patients by multiple logistic regression showed that temporary neurologic dysfunction occurred in 36 cases (19%). Temporary neurologic dysfunction correlated with the duration of hypothermic circulatory arrest (47 +/- 16 minutes; odds ratio 1.06/minute; p < 0.001) and age (66 +/- 14 years; odds ratio 1.07/year; p < 0.001). Embolic strokes occurred in 22 patients (11%) and were associated with permanent deficits in 13 (7%). Strokes correlated significantly with age (older than 60, 21% versus younger than 60, 1%; p < 0.001) and operations on the arch and descending aortic aneurysms containing clot or atheroma (p < 0.001). This experience shows that the operative mortality is not affected by any parameters related to the use of hypothermic circulatory arrest. The incidence of temporary neurologic dysfunction rises linearly in relation to the age of the patient and the duration of hypothermic circulatory arrest. However, permanent neurologic injury is a result of thromboembolic events and is not related to the method of cerebral protection used. Additional methods to prevent perioperative embolic strokes are needed. Hypothermic circulatory arrest affords adequate cerebral protection if the arrest period is kept less than 60 minutes. We will continue to use this modality until the safety and utility of the alternate methods of cerebral protection are shown to be superior.

Surgical treatment of chronic constrictive pericarditis using cardiopulmonary bypass.

The results of operative treatment of 11 patients with chronic constrictive pericarditis with the aid of cardiopulmonary bypass are described. Ten of the 11 patients had Functional Class III or IV disability preoperatively, and all had evidence of severe constrictive disease on physical examination and cardiac catheterization. Pericardiectomy, performed on cardiopulmonary bypass through a median sternotomy incision, required an average total perfusion time of 80 minutes. There were no intraoperative or hospital deaths, and none of the patients required prolonged postoperative hospitalization, All patients except 1, who died 4 weeks postoperatively of pulmonary embolism, have enjoyed marked functional improvement. The technical advantages of pericardiectomy performed on cardiopulmonary bypass are presented.

The superiority of aortic cross-clamping with profound local hypothermia for myocardial protection during aorta-coronary bypass grafting.

Two different operative techniques for aorta-coronary bypass grafting were utilized in two comparable groups of patients. In one group (155 patients) distal anastomoses were carried out with the aorta cross-clamped and myocardial protection provided by profound local hypothermia (clamped group). In a second group (149 patients) distal anastomoses were carried out with the aorta unclamped and the left ventricle fibrillating and vented (unclamped group). Mortality rates were similar in the two groups (0.6 per cent in clamped group versus 1.3 per cent in unclamped group). The incidence of perioperative infarction was 15 per cent in the unclamped group and 8 per cent in the clamped group (p less than 0.05). Postoperative serum glutamic oxaloacetic transaminase (SGOT) and lactic dehydrogenase (LDH) levels were significantly higher for the first 4 postoperative days in the unclamped group than in the clamped group. Hemodynamic studies in a subset of each group revealed no important differences in left ventricular function in the immediate postoperative period. The data demonstrate that in patients undergoing aorta coronary bypass grafting, performance of distal anastomoses with aortic cross-clamping and profound local hypothermia results in less intraoperative myocardial injury than performance of distal anastomoses in the perfused, fibrillating, and vented left ventricle.

Repair of complex subvalvular aortic aneurysm with a valved conduit.

A subaortic annular aneurysm involving three fourths of the annular circumference was repaired with a valved conduit to which a Teflon felt flange was attached. This unique prosthetic repair assured a strong stable repair and uncompromised coronary flow otherwise unobtainable with previously described repairs.