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Biomedical subjects

Scott M Bradley

Publications and source records attributed to Scott M Bradley.

At least 19 recordsLinked to original sources
PubMed2006

Right ventricular outflow tract stent as a bridge to surgery in a premature infant with tetralogy of Fallot.

Despite dramatic progress in neonatal cardiac surgery, prematurity and low birth weight remain risk factors for poor outcome. Attempts to delay intervention with supportive therapy have been shown to increase morbidity and mortality. We present a case of an 840 gram, 28-week gestation newborn with tetralogy of Fallot, in whom palliation was achieved with a right ventricular outflow tract stent. This management allowed subsequent successful complete repair.

Heart Ventricles↗
PubMed2006

Complete repair of conotruncal defects with an interatrial communication: oxygenation, hemodynamic status, and early outcome.

BACKGROUND: Complete repair of conotruncal defects frequently uses maintenance of an interatrial communication. Postoperative right ventricular dysfunction may be characterized by elevated right atrial pressure and decreased systemic oxygen saturation owing to right-to-left shunting at the atrial level. METHODS: From January 1996 to December 2005, 112 patients younger than 6 months of age underwent complete repair of tetralogy of Fallot or truncus arteriosus. An interatrial communication was used in 80 of 112 patients (71%). Hemodynamic data were determined during the first 48 hours after surgery. RESULTS: In patients with an atrial communication, mean oxygen saturation reached a nadir of 94% +/- 6%, and mean arterial PO2 a nadir of 73 +/- 25 mm Hg at 16 to 24 hours after surgery; both increased during the second 24 hours. At hospital discharge, median oxygen saturation was 98% (range, 86% to 100%). During the first 48 hours, mean oxygen saturation was less than 90% in 13 patients; the only multivariate risk factor was younger patient age. Mean right atrial pressure was greater than 10 mm Hg in 30 patients; multivariate risk factors were older patient age and repair with a transannular patch. CONCLUSIONS: After complete repair of conotruncal defects using an interatrial communication, systemic oxygenation reaches a nadir at 24 hours after surgery, and improves by the time of hospital discharge. Clinically significant desaturation occurs in a small minority of patients. Infants undergoing repair before 2 months of age are at higher risk for systemic desaturation. The effects of an interatrial communication on systemic oxygenation should not be considered a contraindication to complete repair in early infancy.

Cardiac Surgical Procedures↗
PubMed2006

Neoaortic root modification for late thrombosis after Norwood palliation.

A 5-year-old child with hypoplastic left heart syndrome presented with myocardial infarction 2 years after Fontan completion. Evaluation identified a thrombus in his native aortic root. Retrospective review of a prior catheterization revealed stasis in the native aortic root. Surgical thrombectomy was performed after failed medical management. The neoaortic root was revised at the time of thrombectomy in an attempt to reduce stasis in the native aortic root. This case suggests the need to identify anatomic findings that may predispose to coronary artery thrombus formation after Norwood palliation.

Aorta↗
PubMed2006

Prevention of thrombosis and embolism in children and adolescents with mechanical valve prostheses: warfarin versus antiplatelet agents.

BACKGROUND AND AIM OF THE STUDY: Postoperative thromboembolic complications associated with mechanical valve prosthesis implantation can be reduced with either antiplatelet agents or warfarin. Warfarin been shown to be more effective in adults, but the data are less clear in the pediatric population. METHODS: Seventy-two children and adolescents who survived mechanical valve implantation on the left side of the heart at the authors' institution were followed prospectively from August 1979 until December 2003. All patients underwent surgery before the age of 20 years, and follow up was included up to the age of 20 years. Initially, 53 patients received warfarin alone; mean follow up was 5.9 years, and total follow up 312 patient-years (pt-yr). Likewise, 19 patients received antiplatelet agents; mean follow up was 5.2 years, and total follow up 99 pt-yr. Results were examined using intent-to-treat analyses. RESULTS: Age, gender, race, valve size and position, mean time of follow up and crossover rates were not different between groups. No differences were detected in survival or freedom from thromboembolic and hemorrhagic events. Complications associated with warfarin use were substantially more severe than those associated with antiplatelet agents. CONCLUSION: The study results were inconclusive due to the small numbers of patient-years of follow up, but suggest that antiplatelet agents may be associated with less severe complications than warfarin. Moreover, warfarin and antiplatelet agents may be equally effective for clotting prophylaxis in children after valve replacement with St. Jude Medical prostheses.

Adolescent↗
PubMed2005

Laryngopharyngeal dysfunction after the Norwood procedure.

OBJECTIVE: We sought to evaluate the incidence and significance of recurrent laryngeal nerve and swallowing dysfunction after a Norwood procedure compared with that after biventricular aortic arch reconstruction. METHODS: From April 2003 through December 2004, 36 neonates underwent a Norwood procedure; 33 of 36 had postoperative fiberoptic laryngoscopy and modified barium swallow. Study results were used to guide the transition from nasogastric tube to oral feeding and placement of gastrostomy tubes. During the same time period, 18 neonates underwent aortic arch reconstruction as part of a biventricular repair. RESULTS: After a Norwood procedure, laryngoscopy showed left true vocal fold (cord) paralysis in 3 (9%) of 33 patients. The results of a modified barium swallow were abnormal in 16 (48%) of 33 patients, with aspiration in 8 (24%) of 33 patients. Of the 3 patients with vocal fold paralysis, 2 had a normal modified barium swallow result, and 1 had aspiration. Gastrostomy tubes were placed in 6 (18%) of 33 patients, all with an abnormal modified barium swallow result. Hospital stay was longer in patients with an abnormal modified barium swallow result: 34 +/- 13 versus 22 +/- 7 days (P < .01). After biventricular repair with aortic arch reconstruction, left true vocal fold paralysis occurred in 4 (25%) of 16 patients; results of a modified barium swallow were abnormal in 10 (59%) of 17 patients, with aspiration in 6 (35%) of 17 patients (all nonsignificant vs patients undergoing the Norwood procedure). Follow-up laryngoscopy in 4 patients with vocal fold paralysis showed no change in 3 of 4 patients and improvement in 1 patient. Follow-up modified barium swallow showed resolution of aspiration in 11 (85%) of 13 patients. Hospital survival was 32 (89%) of 36 patients for the Norwood procedure and 18 (100%) of 18 patients for biventricular repair. There has been 1 sudden death before second-stage palliation. CONCLUSIONS: After a Norwood procedure, swallowing dysfunction occurs in 48% of patients, with aspiration in 24%, and results in increased length of hospital stay. Left recurrent laryngeal nerve injury, seen in 9% of patients, is an uncommon cause of swallowing dysfunction. Postoperative aspiration generally resolves over time, whereas vocal fold paralysis does not. Systematic evaluation of swallowing function allows appropriate tailoring of feeding regimens and might contribute to decreased hospital and interstage mortality.

Cardiac Surgical Procedures↗
PubMed2005

Postoperative management: the role of mixed venous oxygen saturation monitoring.

The results of the Norwood operation have improved considerably over the last decade, due in part to improvement in postoperative care. Mixed venous oxygen saturation (MvO2) monitoring has been an important addition to postoperative management. Our use of MvO2 monitoring in Norwood patients has included 96 infants operated from 1996 to the present. This strategy has proven to be technically straightforward and adds information not provided by monitoring systemic saturation alone. MvO2 has a nadir at 6-12 hours after surgery and below a value of 30% is associated with anaerobic metabolism. It identifies patients at risk for early mortality. It also allows evaluation of management of treatment strategies that evolve over time and of specific interventions in individual patients. Optimizing MvO2 constitutes an important goal of postoperative management after the Norwood procedure.

Blood Gas Analysis↗
PubMed2005

Preoperative management of hypoplastic left heart syndrome.

Hypoplastic left heart syndrome (HLHS) is the most common functional single ventricle congenital cardiac defect. This syndrome is characterised by a functional single right ventricle and systemic outflow obstruction. The systemic and pulmonary circulations compete for cardiac output with a resultant precarious balance among systemic, pulmonary and coronary blood flows. A once fatal diagnosis, advances in operative and perioperative care have resulted in a dramatic improvement in survival. The preoperative management of neonates with HLHS is based predominately on clinical experience and extrapolated data from the postoperative literature. Management focuses on maintaining patency of the systemic outflow, balancing the pulmonary and systemic blood flows, and preserving the function of a single right ventricle to maximise oxygen delivery to the tissues. This paper reviews the available therapies for the preoperative management of HLHS.

Cardiovascular Agents↗
PubMed2004

Effectiveness of cardiac surgery in trisomies 13 and 18 (from the Pediatric Cardiac Care Consortium).

Because of severely reduced lifespan in children with trisomies 13 and 18, surgical repair of congenital heart lesions has rarely been offered. With data from a multicenter registry, we report 35 cases of cardiac surgery in infants and children with trisomy 13 or 18 with a 91% hospital survival rate. Those patients without an extended preoperative ventilatory requirement did not require prolonged mechanical ventilation after surgery.

Canada↗
PubMed2004

Fresh frozen plasma in the pediatric pump prime: a prospective, randomized trial.

BACKGROUND: The aim of this study was to determine whether the use of fresh frozen plasma (FFP) in the infant pump prime can avoid dilution of fibrinogen, decrease the need for blood product transfusion after bypass, and decrease exposure to donor blood products. METHODS: Twenty infants weighing less than 8 kg were prospectively randomized to receive either 1 U of FFP (10 patients) or no FFP (10 patients) in the pump prime. Mean age (4.2 +/- 2.8 months), weight (4.3 +/- 1.1 kg), total prime volume (641 +/- 96 ml), cardiopulmonary bypass time, cross-clamp time, lowest temperature on bypass, and preoperative coagulation parameters did not differ between the two groups. RESULTS: At the end of bypass, the mean fibrinogen level was significantly higher in the FFP than the no FFP group (123 +/- 20 versus 58 +/- 17 mg/dL; p < 0.0001), whereas the mean platelet count did not differ (60 +/- 25 versus 52 +/- 26 K/mm(3); p = 0.5). Patients in the FFP group received significantly fewer units of cryoprecipitate (0.4 +/- 0.8 versus 2.0 +/- 0.9 U/patient; p < 0.001), and had a mean total donor exposure of 4.1 +/- 1.5 U/patient versus 5.4 +/- 1.4 U/patient in the no FFP group (p = 0.06). The mean chest tube output over the first 24 hours did not differ between groups. CONCLUSIONS: The use of FFP in the pump prime significantly limited dilutional hypofibrinogenemia, decreased the transfusion of cryoprecipitate after bypass, and tended to decrease the overall mean patient exposure to blood products.

Cardiopulmonary Bypass↗
PubMed2004

Hemodynamic status after the Norwood procedure: a comparison of right ventricle-to-pulmonary artery connection versus modified Blalock-Taussig shunt.

BACKGROUND: The aim of this study is to compare hemodynamic status, in particular systemic oxygen delivery, in patients undergoing a Norwood procedure with a right ventricle-to-pulmonary artery (RV-PA) versus a modified Blalock-Taussig (mBT) shunt. METHODS: From June 2000 to November 2003, 44 consecutive neonates with hypoplastic left heart syndrome underwent a Norwood procedure. The first 25 patients received an mBT shunt; the subsequent 19 an RV-PA shunt. Hemodynamic data, including mixed venous oxygen saturation, was determined during the first 48 hours after surgery. RESULTS: The mBT and RV-PA shunt patients had no significant differences in systemic oxygen saturation, mixed venous oxygen saturation, arteriovenous oxygen saturation difference, or oxygen excess factor during the first 48 hours. Mixed venous saturation declined to a nadir in both groups at 6 to 12 hours. The RV-PA patients had significantly higher diastolic and mean blood pressures, and lower systolic blood pressure. Mean heart rate, common atrial pressure, and inotrope score did not differ between the two groups. The RV-PA patients received higher fraction of inspired oxygen and minute ventilation to achieve partial pressures of arterial oxygen and carbon dioxide, and pH, similar to mBT patients. Durations of mechanical ventilation, intensive care unit stay, and hospital stay did not differ between mBT and RV-PA patients. Operative survival in the mBT versus RV-PA group was 20 of 25 (80%) versus 17 of 19 (89%; p = 0.7). CONCLUSIONS: Indicators of postoperative systemic oxygen delivery are equivalent in neonates who have undergone a Norwood procedure with an mBT or RV-PA shunt. Both mBT and RV-PA patients undergo similar declines in hemodynamic status 6 to 12 hours after surgery. Any advantages of one approach over the other lie in areas other than systemic oxygen delivery, such as resistance to physiologic insults, or preservation of ventricular function.

Blood Gas Analysis↗
PubMed2004

Redefining the impact of oxygen and hyperventilation after the Norwood procedure.

OBJECTIVE: Postoperative management after the Norwood procedure is aimed at optimizing systemic oxygen delivery and mixed venous oxygen saturation. High levels of fraction of inspired oxygen and hyperventilation may increase pulmonary blood flow at the expense of systemic flow. This study determines the effects of these interventions on mixed venous saturation and systemic oxygen delivery in postoperative neonates. METHODS: We prospectively studied the effects of 100% fraction of inspired oxygen and hyperventilation in 14 neonates (median age 8 days) 1 to 3 days after the Norwood procedure, while they were sedated, paralyzed, and mechanically ventilated. After establishment of baseline conditions (fraction of inspired oxygen = 29% +/- 2%, normal ventilation), patients were exposed to each of the 2 interventions in random order. Mixed venous saturation was measured through a transthoracic line in the superior vena cava. Oxygen excess factor (Omega = systemic oxygen delivery/oxygen consumption) was used as an indicator of systemic oxygen delivery. RESULTS: High levels of fraction of inspired oxygen produced significant increases from baseline in systemic saturation (90% +/- 1% vs 80% +/- 1%, P <.01), mixed venous saturation (54% +/- 3% vs 44% +/- 2%, P <.01), and oxygen excess factor (2.6% +/- 0.2% vs 2.3 +/- 0.2%, P <.01), but there was no change in arteriovenous saturation difference or blood pressure. Hyperventilation resulted in no changes in systemic or mixed venous saturation, arteriovenous saturation difference, oxygen excess factor, or blood pressure. CONCLUSIONS: High levels of fraction of inspired oxygen can improve mixed venous oxygen saturation and systemic oxygen delivery after the Norwood procedure. Hyperventilation does not change either mixed venous saturation or oxygen delivery. Management protocols aimed at minimizing the fraction of inspired oxygen and carefully controlling ventilation may not be warranted.

Blood Pressure↗
PubMed2004

Outcome following, and impact of, prenatal identification of the candidates for the Norwood procedure.

OBJECTIVES: Our study evaluates hospital survival following prenatal identification of candidates for the Norwood procedure, and the impact of prenatal diagnosis on survival, preoperative stability, and postoperative morbidity. METHODS: We reviewed records of all patients who were identified prenatally as candidates for the Norwood procedure, and compared them to all postnatally diagnosed patients who underwent the Norwood procedure between August 1995 and May 2002. RESULTS: Of the 98 patients studied, 45 (46%) were diagnosed prenatally. Of these, 35 underwent the Norwood procedure, 29 (83%) of who survived. Thus, 29 of 45 (64%) patients survived from prenatal diagnosis to discharge following the Norwood procedure. Of the 53 postnatally diagnosed patients who underwent the Norwood procedure, 42 (79%) survived. Prenatal diagnosis was not associated with improvement in survival, preoperative stability, or postoperative morbidity. By multivariate analysis, ascending aortic diameter equal to or greater than 2 mm (p = 0.01), and gestational age 36 weeks or greater (p = 0.01) independently predicted survival. Based on this, patients were stratified into groups at low risk, consisting of 69 patients, and at high risk, consisting of 19 patients. Prenatal diagnosis was unassociated with improved survival in either group. Results were unchanged when the analysis was restricted to patients with hypoplasia of the left heart. CONCLUSION: From the time of prenatal diagnosis, 64% of patients survived to discharge following the Norwood procedure. Prenatal diagnosis did not affect preoperative stability, survival or postoperative morbidity. This remained the case after stratifying patients by risk, or restricting analysis to patients with hypoplasia of the left heart. Ascending aortic diameter and gestational age independently predicted survival.

Cardiac Surgical Procedures↗
PubMed2004

Valve-sparing aortic root replacement: experience at MUSC.

Approximately 30 to 40 percent of patients requiring aortic root replacement have a normal or repairable aortic valve. At the Medical University of South Carolina Medical Center, 12 patients have recently undergone aortic root replacement using a valve sparing technique to preserve the native valve and avoid the potential complications of mechanical or bioprosthetic tissue valves. The early results are excellent and support the use of this procedure for aortic root replacement in the presence of an anatomically normal aortic valve.

Adolescent↗
PubMed2003

Twenty-year experience with the St Jude Medical mechanical valve prosthesis.

BACKGROUND: We have prospectively followed all adult St Jude Medical mechanical valve recipients at the Medical University of South Carolina since the initial implant in January 1979 and now present our 20-year experience. METHODS: We prospectively followed 837 valve recipients (aortic valve replacement; n = 478; mitral valve replacement; n = 359) from January 1979 to December 2000 at 12-month intervals. RESULTS: Ages ranged from 19 to 84 years. Follow-up averaged (mean +/- standard deviation) 7 +/- 5 years (98% complete). Patients were in New York Heart Association class III or IV in 77% (aortic valve replacement) and 89% (mitral valve replacement) preoperatively. A 19-mm valve was implanted in 15.5% of aortic valve replacement patients. Coronary bypass was required in 31% of aortic valve replacements and 20% of mitral valve replacements. Operative mortality was 17/478 (3.6%) in aortic valve replacement and 19/359 (5.3%) in mitral valve replacement, and multivariable predictors were 19-mm valve size, 3 or more coronary bypass grafts, and New York Heart Association class IV for aortic valve replacement and New York Heart Association class IV and age for mitral valve replacement. Actuarial survivorship at 10 and 20 years was 57% +/- 3% and 26% +/- 5% for aortic valve replacement and 61% +/- 3% and 39% +/- 4% for mitral valve replacement. Multivariable predictors of late death were African-American ethnicity, New York Heart Association class III or IV, coronary bypass, and age for aortic valve replacement and New York Heart Association class III or IV, coronary bypass, and age for mitral valve replacement. For aortic valve replacement, effective orifice area was univariately (P =.002) but not multivariately (P =.378) predictive of late death. Structural valve deterioration was not observed. For aortic valve replacement, actuarial freedom (at 10 and 20 years) from reoperation was 93% +/- 1% and 90% +/- 2%; thromboembolism, 82% +/- 3% and 68% +/- 8%; bleeding events, 77% +/- 3% and 66% +/- 6%; prosthetic valve endocarditis, 94% +/- 1% and 94% +/- 1%; valve-related mortality, 94% +/- 2% and 86% +/- 4%; and valve-related mortality or morbidity, 58% +/- 3% and 32% +/- 8%. For mitral valve replacement, actuarial freedom (at 10 and 20 years) from reoperation was 96% +/- 1% and 90% +/- 3%; thromboembolism, 77% +/- 3% and 59% +/- 7%; bleeding events, 86% +/- 2% and 65% +/- 8%; prosthetic valve endocarditis, 98% +/- 1% and 96% +/- 2%; valve-related mortality, 89% +/- 0.2% and 74% +/- 8%; and valve-related mortality or morbidity, 63% +/- 3% and 29% +/- 7%. CONCLUSIONS: After 2 decades of observation with close follow-up, the St Jude Medical mechanical valve continues to be a reliable prosthesis.

Actuarial Analysis↗