Ascending aortic false aneurysm following cannulation for perfusion

A case of false aneurysm originating from the ascending aortic cannulation site in the absence of mediastinal infection is described. Surgical treatment was carried out by means of limited cardiopulmonary bypass and hypothermic circulatory arrest, but the patient died early in the postoperative period. The technical failures responsible for the unsuccessful outcome are emphasized.     

Consequences of electroencephalographic-suppressive doses of propofol in conjunction with deep hypothermic circulatory arrest

BACKGROUND: Some patients who undergo cerebral aneurysm surgery require cardiopulmonary bypass and deep hypothermic circulatory arrest. During bypass, these patients often are given large doses of a supplemental anesthetic agent in the hope that additional cerebral protection will be provided. Pharmacologic brain protection, however, has been associated with undesirable side effects. These side effects were evaluated in patients who received large doses of propofol. METHODS: Thirteen neurosurgical patients underwent cardiopulmonary bypass and deep hypothermic circulatory arrest to facilitate clip application to a giant or otherwise high-risk cerebral aneurysm. Electroencephalographic burst suppression was established before bypass with an infusion of propofol, and the infusion was continued until the end of surgery. Hemodynamic and echocardiographic measurements were made before and during the prebypass propofol infusion and again after bypass. Emergence time also was determined. RESULTS: Prebypass propofol at 243 +/- 57 micrograms.kg-1.min-1 decreased vascular resistance from 34 +/- 8 to 27 +/- 8 units without changing heart rate, arterial or filling pressures, cardiac index, stroke volume, or ejection fraction. Propofol blood concentration was 8 +/- 2 micrograms/ml. Myocardial wall motion appeared hyperdynamic at the end of cardiopulmonary bypass, and all patients were weaned therefrom without inotropic support. After bypass, vascular resistance decreased further, and cardiovascular performance was improved compared to baseline values. Nine of the 13 patients emerged from anesthesia and were able to follow commands at 3.1 +/- 1.4 h. Three others had strokes and a fourth had cerebral swelling. CONCLUSIONS: Propofol infused at a rate sufficient to suppress the electroencephalogram does not depress the heart or excessively prolong emergence from anesthesia after cardiopulmonary bypass and deep hypothermic circulatory arrest.     

Improved exposure of the pulmonary arteries for thromboendarterectomy

Pulmonary thromboendarterectomy is a surgical technique for treating pulmonary hypertension caused by unresolved pulmonary embolism. It has been recommended to perform this procedure under deep hypothermic circulatory arrest. Here we describe two technical modifications: (1) improved exposure to the right pulmonary artery by division of the superior caval vein and (2) thromboendarterectomy in normothermic cardiopulmonary bypass, with beating heart or electrically induced ventricular fibrillation. These modifications allow complete endarterectomy of both pulmonary arteries under normothermic conditions, thus avoiding hypothermic circulatory arrest, which results in short cardiopulmonary bypass times and reduces the morbidity and mortality of this procedure.     

Cerebral physiology in paediatric cardiopulmonary bypass

PURPOSE: To analyze studies of neurological injury after open-heart surgery in infants and children and to discuss the effects of cardiopulmonary bypass, hypothermia and deep hypothermic circulatory arrest on cerebral blood flow, cerebral metabolism and brain temperature. SOURCE: Articles were obtained from the databases, Current Science and Medline, from 1966 to present. Search terms include cardiopulmonary bypass (CPB), hypothermia, cerebral blood flow (CBF), cerebral metabolism and brain temperature. Information and abstracts obtained from meetings on the topic of brain and cardiac surgery helped complete the collection of information. PRINCIPAL FINDINGS: In adults the incidence of neurological morbidity is between 7 to 87% with stroke in about 2-5%, whereas the incidence of neurological morbidity increases to 30% in infants and children undergoing cardiopulmonary bypass. Besides the medical condition of the patient, postoperative cerebral dysfunction and neuronal ischaemia associated with cardiac surgery in infants and small children are a combination of intraoperative factors. Deep hypothermic circulatory arrest impairs CBF and cerebral metabolism even after termination of CPB. Inadequate and/or non-homogenous cooling of the brain before circulatory arrest, as well as excessive rewarming of the brain during reperfusion are also major contributory factors. CONCLUSION: Newer strategies, including the use of low-flow CPB, pulsatile CPB, pH-stat acid-base management and a cold reperfusion, are being explored to ensure better cerebral protection. Advances in monitoring technology and better understanding of the relationship of cerebral blood flow and metabolism during the different modalities of cardiopulmonary bypass management will help in the medical and anaesthetic development of strategies to improve neurological and developmental outcomes.     

Glutamate excitotoxicity: a mechanism of neurologic injury associated with hypothermic circulatory arrest

Glutamate, the major central nervous system neurotransmitter, may have potent neurotoxic activity under conditions of metabolic stress. By receptor autoradiography, we have demonstrated that brain regions most vulnerable to injury during prolonged hypothermic circulatory arrest have the highest density of glutamate receptors. To test the hypothesis that such injury could be mediated by glutamate excitotoxicity, we used dizocilpine (MK-801), a selective N-methyl-D-aspartate-glutamate receptor antagonist in a canine survival model of hypothermic circulatory arrest. Eighteen male dogs (20 to 25 kg) were supported by closed-chest cardiopulmonary bypass, subjected to 2 hours of hypothermic circulatory arrest at 18 degrees C, and rewarmed on cardiopulmonary bypass. All were mechanically ventilated and monitored for 20 hours before extubation and survived for 3 days. Group A dogs (n = 9) received a prearrest intravenous bolus of dizocilpine (0.75 mg/kg) followed by continuous infusion (75 micrograms/kg per hour), resulting in electroencephalographic silence. Dizocilpine was weaned before extubation. Group B dogs received vehicle only. According to a species-specific behavior scale that yielded a neurologic deficit score ranging from 0 (normal) to 500 (brain dead), all animals were neurologically assessed every 12 hours. After the dogs were killed at 72 hours, brains were examined by receptor autoradiography and histologically for patterns of selective neuronal necrosis; they were scored blindly from 0 (normal) to 100 (severe injury). Group A dogs had better neurologic function than group B (neurologic deficit score 21 +/- 15 versus 192 +/- 40, p < 0.001) and had less neuronal injury (7.3 +/- 3 versus 48.3 +/- 9, p < 0.0001). Densitometric receptor autoradiography revealed preservation of neuronal N-methyl-D-aspartate-glutamate receptor expression in group A only. These results represent the first direct evidence of a role for glutamate excitotoxicity in the development of hypothermic circulatory arrest-induced brain injury and suggest that selective glutamate receptor antagonists may have a neuroprotective capacity in prolonged periods of hypothermic circulatory arrest.     

Technical advances in the surgical management of thoracoabdominal aortic aneurysms]

Thoracoabdominal aortic aneurysmectomy ranks among the major cardiovascular surgical procedures. During the last two decades perioperative results have improved to the point that surgery should be discussed in the vast majority of patients seen with a thoracoabdominal aortic aneurysm. This progress is largely attributable to a variety of technical improvements including: aortic reconstruction using the graft inclusion technique, usually with direct reattachment of aortic branches to the prosthetic graft; distal aortic perfusion; selective use of deep hypothermic circulatory arrest in anatomically complex situations; preoperative visualization of arterial blood supply to the spinal cord using selective arteriography of intercostal and lumbar arteries. Current perioperative mortality is around 10% whereas the spinal cord complication rate is between 5% and 20% according to clinical and anatomical conditions. Future efforts should concentrate on the prevention of spinal cord complications.     

Effects of cardiopulmonary bypass and circulatory arrest on endothelium-dependent vasodilation in the lung

Endothelial injury with failure of pulmonary endothelium-dependent vasodilatation has been proposed as a possible cause for the increased pulmonary vascular resistance observed after cardiopulmonary bypass, but the mechanisms underlying this response are not understood. An in vivo piglet model was used to investigate the role of endothelium-dependent vasodilatation in postbypass pulmonary hypertension. The pulmonary vascular responses to acetylcholine, a receptor-mediated endothelium-dependent vasodilator, and nitric oxide, an endothelium-independent vasodilator, were studied in one group of animals after preconstriction with the thromboxane A2 analog U46619 (n = 6); a second group was studied after bypass with 30 minutes of deep hypothermic circulatory arrest (n = 6). After preconstriction with U46619, both acetylcholine and nitric oxide caused significant decreases in pulmonary vascular resistance (34% +/- 6% decrease, p = 0.007, and 39% +/- 4% decrease, p = 0.001). After cardiopulmonary bypass with circulatory arrest, acetylcholine did not significantly change pulmonary vascular resistance (0% +/- 8% decrease, p = 1.0), whereas nitric oxide produced a 32% +/- 4% decrease in pulmonary vascular resistance (p = 0.007). These results demonstrate a loss of receptor-mediated endothelium-dependent vasodilatation with normal vascular smooth muscle function after circulatory arrest. Administration of the nitric oxide synthase blocker Ngamma-nitro-L-arginine-methyl-ester after circulatory arrest significantly increased pulmonary vascular resistance; thus, although endothelial cell production of nitric oxide may be diminished, it continues to be a major contributor to pulmonary vasomotor tone after cardiopulmonary bypass with deep hypothermic circulatory arrest. In summary, cardiopulmonary bypass with deep hypothermic circulatory arrest results in selective pulmonary endothelial cell dysfunction with loss of receptor-mediated endothelium-dependent vasodilatation despite preserved ability of the endothelium to produce nitric oxide and intact vascular smooth muscle function.     

Reconstruction of the aortic arch in invasive thymoma under retrograde cerebral perfusion

Extensive en-bloc resection of the aortic arch and anterior wall of the main pulmonary artery was performed in a 46-year-old man with invasive thymoma. The aortic arch was replaced with a Hemashield vascular graft under hypothermic circulatory arrest with retrograde cerebral perfusion. Patch plasty with Xenomedica was performed for the anterior wall of the main pulmonary artery under cardiopulmonary bypass. The patient was treated with postoperative radiotherapy and has remained asymptomatic for 15 months after the operation. An extensive operation is considered necessary to improve the prognosis of invasive thymoma.     

Hypothermic circulatory arrest does not increase the risk of ascending thoracic aortic aneurysm resection

OBJECTIVE: The purpose of this study was to investigate the safety and efficacy of a period of deep hypothermic circulatory arrest (DHCA) during elective replacement of the ascending thoracic aorta. SUMMARY BACKGROUND DATA: DHCA has been implemented in ascending thoracic aortic aneurysm resection whenever the anatomy or pathology of the aorta or arch vessels prevents safe or adequate cross-clamping. Profound hypothermia and retrograde cerebral perfusion have been shown to be neurologically protective during ascending aortic replacement under circulatory arrest. METHODS: The authors conducted a retrospective analysis of 91 consecutive patients who underwent repair of chronic ascending thoracic aortic aneurysms from 1986 to present. The authors hypothesized that patients undergoing DHCA with or without retrograde cerebral perfusion during aneurysm repair were at no greater operative risk than patients who received aneurysm resection while on standard cardiopulmonary bypass. RESULTS: There were no significant differences in hospital mortality, stroke rate, or operative morbidity between patients repaired on DHCA when compared to those repaired on cardiopulmonary bypass. CONCLUSIONS: DHCA with or without retrograde cerebral perfusion does not result in increased morbidity or mortality during the resection of ascending thoracic aortic aneurysms. In fact, this technique may prevent damage to the arch vessels in select cases and avoid the possible complications associated with cross-clamping a friable or atherosclerotic aorta.     

A mechanistic study of beta-adrenoceptor antagonists on ethanol-induced gastric damage

BACKGROUND: In the first weeks of life there are important maturational changes in the central nervous system in many species in energy metabolism, synapse number, and concentration of neuronal excitatory receptors. METHODS: Four groups of 10 piglets (aged 1, 2, 4, and 10 weeks) underwent 1 hour of deep hypothermic circulatory arrest at 15 degrees C, with cooling and rewarming on cardiopulmonary bypass. Cerebral blood flow and metabolic rate measurements and electroencephalographic recordings were obtained from 5 animals per group. The remaining animals underwent cerebral magnetic resonance spectroscopy. RESULTS: Preoperative cerebral blood flow and glucose consumption were higher at 4 and 10 weeks than at 1 and 2 weeks. Cerebral adenosine triphosphate content decreased more rapidly during deep hypothermic circulatory arrest at 4 and 10 weeks. Phosphocreatine recovery was greater at 30 minutes of reperfusion at 10 weeks compared with 1 week. Recovery of cerebral phosphocreatine/ adenosine triphosphate ratio and intracellular pH was remarkably uniform at all ages. Latency to recovery of electroencephalographic activity decreased with increasing age (p = 0.04). CONCLUSIONS: Differences in acute recovery of brain energy metabolism and electroencephalogram after cardiopulmonary bypass and 1 hour of deep hypothermic circulatory arrest in piglets between 1 and 10 weeks of age are small. Further studies are required to correlate these acute findings with subsequent neurologic outcome.     

Aortic valve operations under deep hypothermic circulatory arrest for the porcelain aorta: "no-touch" technique

BACKGROUND: Aortic valve replacement or repair becomes a high-risk procedure in patients in whom the ascending aorta cannot be clamped either because of extensive calcification and risk of cerebral embolus or because of extensive adhesions precluding safe dissection and clamping. METHODS: We report the results of aortic valve replacement or repair with deep hypothermic circulatory arrest in 3 patients. Techniques to improve results include routine use of epiaortic and transesophageal echocardiography, avoidance of manipulation of the ascending aorta until the circulation is arrested, avoidance of antegrade cardioplegia, routine use of retrograde cardioplegia and retrograde cerebral perfusion, when feasible, and minimal aortotomy (just enough to excise and replace or repair the valve). RESULTS: Operations were accomplished in approximately 1 hour each with minimal manipulation of the aorta, thus minimizing aortic trauma and subsequent risk of cerebral embolus. Each patient had an unremarkable recovery without neurologic complications. CONCLUSIONS: Aortic valve replacement or repair using the "no-touch" technique and deep hypothermic circulatory arrest is the preferred method when dealing with the porcelain or unclampable aorta.     

Surgical treatment of acute type A aortic dissection with an intraluminal sutureless graft

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.     

Operation for chronic traumatic aortic aneurysm: when and how?

BACKGROUND: There are few guidelines for surgical intervention late after unoperated traumatic aortic rupture. We reviewed our experience and the literature to determine when and how to operate. METHODS: Between 1987 and 1997, we treated 9 patients aged 22 to 82 years with chronic traumatic aneurysm. Seven patients underwent aneurysm resection. Two patients have not been operated on. The injury-to-operation interval ranged from 8 weeks to 18 years (mean, 4.1 years). One patient underwent median sternotomy and patch repair during hypothermic circulatory arrest. Six patients underwent left thoracotomy: 2 were operated on with left atrio-femoral bypass, and 4 with hypothermic circulatory arrest and ascending aortic cannulation. RESULTS: There was no surgical mortality or morbidity. The 2 patients who were not operated on remained asymptomatic without radiologic change in the aneurysm after follow-up of 2 and 9 years. CONCLUSIONS: From this limited experience and literature review, we make the following subjective observations: (1) all patients with new symptoms should be operated on promptly, and (2) asymptomatic densely calcified aneurysms detected more than 2 years after the accident can be observed by repeated tomography unless new symptoms arise.     

Traumatic aortic rupture: diagnosis and management

BACKGROUND: Traumatic aortic rupture is a relatively uncommon lesion that presents the cardiothoracic surgeon with unique challenges in diagnosis and management. To address controversial aspects of this disease, we reviewed our experience. METHODS: The study was performed by retrospective chart review. RESULTS: Forty-two patients with traumatic thoracic aortic ruptures were managed between January 1988 and June 1997. Nine arrived without vital signs and died in the emergency department. Admission chest radiographs were normal in 3 patients (12%) and caused significant delays in diagnosis. Four of 30 patients admitted with vital signs had rupture before thoracotomy and died. Twenty-six underwent aortic repair. In 1 patient repair was performed with simple aortic cross-clamping, whereas a second was managed with a Gott shunt. The remaining 24 patients had repair with partial left heart bypass. In 1 patient hypothermic circulatory arrest was required. Two patients (7.7%) died. There were no cases of new postoperative paraplegia in the bypass group. There was no morbidity directly attributable to the administration of heparin for cardiopulmonary bypass. CONCLUSIONS: In a discrete group of patients with traumatic rupture of the aorta, the rupture will become complete during the first few hours of hospital admission; aggressive medical treatment with beta-blockade and vasodilators in the interval before the operation is an essential aspect of management. Active distal circulatory support with partial left-heart bypass provides the optimal means of preventing spinal cord ischemia during repair of acute traumatic aortic rupture.     

Mortality among workers in the pulp-paper industry. A successive follow up of the cohort

Neuropathologic findings are described, for the first time, in a neonatal dog model of circulatory arrest in normothermic conditions, and the findings are compared to those reported in neonatal dogs with hypothermic circulatory arrest. Total circulatory arrest was produced in 3- to 6-day-old anesthetized, paralyzed and ventilated, normothermic dogs either by asphyxiation or cardioplegia. Duration of circulatory arrest was 8-20 min and 10-40 min in asphyxiated and cardioplegic animals, respectively. The animals were resuscitated and maintained under controlled systemic physiologic conditions until neuropathologic examination after 8 or 24 h of recovery. The results suggest that the minimal durations of circulatory arrest for brain damage to occur following asphyxia or cardioplegia are 10 and 15 min, respectively. Ischemic lesions in both groups consisted of neuronal necrosis and involved mainly the brain stem structures, particularly the reticular nuclei and the spinal cord gray matter. The medulla was more severely involved than midbrain and pons. There was a direct correlation between the length of circulatory arrest and the severity of damage in the medulla (P = 0.001) and overall brain stem damage (P = 0.004) in animals with cardioplegia, but not in animals with asphyxia. These findings are compared to the neuropathologic changes previously described in newborn dogs subjected to hypothermic circulatory arrest, in which ischemic lesions are focused on the cerebral cortex and basal ganglia. It is concluded that hypothermia in this model not only prolongs the period of circulatory arrest that is required to produce brain damage, but also shifts the pattern of regional ischemic vulnerability from caudal to more rostral structures.     

Open-heart correction of tetralogy of Fallot in an acyanotic dog

Tetralogy of Fallot was diagnosed in an acyanotic 11-month-old dog. Predicted pressure gradient across the pulmonic valve, as assessed by use of continuous wave Doppler echocardiography, was 94.5 mm Hg. Bidirectional shunting was identified by means of selective angiography. Open-heart correction was performed, using a transatrial approach with limited ventriculotomy and cardiopulmonary bypass. The hypertrophied infundibulum was resected, the ventricular septal defect was closed primarily, and a transannular pericardial patch graft was applied. Pressure gradients across the pulmonic valve were 52.9 and 22.8 mm Hg 2 weeks and 4 months after surgery, respectively. Advances in cardiopulmonary bypass, anesthetic management, and use of the transatrial approach may improve the success of open-heart correction of tetralogy of Fallot in dogs.     

Hypothermic cardiac standstill for cerebral aneurysm surgery

Surgical management of giant cerebral aneurysms remains a major technical challenge for modern neurosurgeons. Endovascular approaches for giant aneurysms does not provide an acceptable alternative to direct surgical approaches. The use of deep hypothermic circulatory arrest as an adjunct during clipping of complex giant aneurysms shows promise as a treatment for otherwise incurable lesions. Patient selection and techniques of circulatory arrest surgery are discussed.     

Presynaptic inhibitory effect of baclofen on hippocampal inhibitory synaptic transmission involves a pertussis toxin-sensitive G-protein

We used the collagen-impregnated woven double-velour Dacron graft in 120 patients undergoing 122 aortic reconstructions. Seventy-nine aortic root, ascending, or arch replacements were performed during cardiopulmonary bypass with or without circulatory arrest; 53 of the 79 were for acute aortic dissection. In addition, three infants and one child underwent repair of truncus arteriosus. There were no deaths caused by hemorrhage or bleeding-related complications. For aortic root replacement, the impervious nature of the collagen-impregnated woven double velour Dacron graft allowed elimination of wrap-around techniques. Eight deaths occurred as a result of multisystem organ failure, which followed late diagnosis of type A dissection. Two patients underwent reoperation for late complications of type A dissection. Thirty-nine patients underwent treatment for disease of the descending aorta; eight of these patients underwent a central cannulation technique with profound hypothermic cardiopulmonary bypass. The other 31 underwent repair with aortic crossclamping without bypass. Four of these patients died: two as a result of multisystem organ failure, one as a result of uncontrolled bleeding from the native dissected aorta, and one as a result of intestinal necrosis. Follow-up studies for 2 months to 5 years revealed three late deaths caused by the rupture of a persistent aneurysmal false lumen after type A dissection. The intraoperative advantages of the collagen-impregnated woven double velour Dacron graft represent an important advance in vascular graft technology. Its handling and suturing characteristics are excellent, and the graft is completely impervious in its originally manufactured state. Needle holes self-seal rapidly. Medium-term follow-up by clinical, angiographic, computed tomographic, and magnetic resonance imaging techniques showed no late graft complications--specifically, no dilatation or thrombus formation.     

Combined surgery for coronary artery disease and thoracic aortic disease

Combined surgery in 6 cases who had coronary artery disease and thoracic aortic disease simultaneously was analyzed. Case # 1 had ascending aortic replacement under deep hypothermic circulatory arrest because of iatrogenic aortic dissection caused by aortic clamp during the routine coronary artery bypass grafting (CABG). Case # 2 had DeBakey type II chronic dissection. Case # 3 had type I aortic dissection 4 years after the initial CABG. Both case # 2 and # 3 had ascending aortic replacement under retrograde cerebral perfusion along with CABG. Transverse aortic replacement was performed in case # 4, # 5 and # 6 under selective cerebral perfusion along with CABG. Case # 4 was associated with ascending-transverse aortic aneurysm. Case # 5 had aortitis syndrome complicated with severe coronary ostial stenosis and cervical branch stenosis. Case # 6 also had aortitis syndrome, severe coronary ostial stenosis, heavily calcified ascending-transverse aorta, and mitral and aortic regurgitation. This case had mitral and aortic valve replacement additionally. Case # 2 died of low cardiac output syndrome and multi-organ failure postoperatively. Case # 4 did not recover from profound shock that followed the preoperative acute myocardial infarction. The problems of low cardiac output syndrome caused by long interval of ischemic cardiac arrest, and also the problems of proximal anastomotic site of saphenous vein grafts were discussed.     

A comparison of the perioperative neurologic effects of hypothermic circulatory arrest versus low-flow cardiopulmonary bypass in infant heart surgery

BACKGROUND: Hypothermic circulatory arrest is a widely used support technique during heart surgery in infants, but its effects on neurologic outcome have been controversial. An alternative method, low-flow cardiopulmonary bypass, maintains continuous cerebral circulation but may increase exposure to known pump-related sources of brain injury, such as embolism or inadequate cerebral perfusion. METHODS: We compared the incidence of perioperative brain injury after deep hypothermia and support consisting predominantly of total circulatory arrest with the incidence after deep hypothermia and support consisting predominantly of low-flow cardiopulmonary bypass in a randomized, single-center trial. The criteria for eligibility included a diagnosis of transposition of the great arteries with an intact ventricular septum or a ventricular septal defect and a planned arterial-switch operation before the age of three months. RESULTS: Of 171 patients with D-transposition of the great arteries, 129 (66 of whom were assigned to circulatory arrest and 63 to low-flow bypass) had an intact ventricular septum, and 42 (21 assigned to circulatory arrest and 21 to low-flow bypass) had a ventricular septal defect. After adjustment for diagnosis, assignment to circulatory arrest as compared with low-flow bypass was associated with a higher risk of clinical seizures (odds ratio, 11.4; 95 percent confidence interval, 1.4 to 93.0), a tendency to a higher risk of ictal activity on continuous electroencephalographic (EEG) monitoring during the first 48 hours after surgery (odds ratio, 2.5; 95 percent confidence interval, 1.0 to 6.4), a longer recovery time to the first reappearance of EEG activity (only in the group with an intact ventricular septum, P < 0.001), and greater release of the brain isoenzyme of creatine kinase in the first 6 hours after surgery (P = 0.046). Analyses comparing durations of circulatory arrest produced results similar to those of analyses comparing treatments. CONCLUSIONS: In heart surgery in infants, a strategy consisting predominantly of circulatory arrest is associated with greater central nervous system perturbation in the early postoperative period than a strategy consisting predominantly of low-flow cardiopulmonary bypass. Assessment of the effect of these findings on later outcomes awaits follow-up of this cohort.