Biomedical subjects

Carl L Backer

Publications and source records attributed to Carl L Backer.

33 records · Page 2Linked to original sources

PubMed2003

Beyond Fontan conversion: Surgical therapy of arrhythmias including patients with associated complex congenital heart disease.

BACKGROUND: Arrhythmia operations may be extended to patients with failed ablation procedures or associated structural defects requiring surgical intervention. The purpose of this study is to review our experience with arrhythmia operations in 29 patients who did not have Fontan conversions after the introduction of catheter ablation. METHODS: Between July 1992 and January 2002, 29 patients had operations for refractory atrial (n = 24) or ventricular (n = 5) arrhythmias. Mechanisms of arrhythmia included atrial reentry (n = 11), atrial fibrillation (n = 5), automatic atrial (n = 3), accessory connections (n = 6), atrioventricular nodal reentry (n = 2), and ventricular tachycardia (n = 5). Median age at operation was 12.3 years (range, 6 days to 45 years). Two patients had structurally normal hearts; the remaining 27 patients underwent concomitant repair of structural heart disease, including atrioventricular valve replacement or repair (n = 8), anatomy-specific repair of Ebstein's anomaly (n = 4), tetralogy of Fallot repair or revision (n = 4), atrial septal defect closure (n = 3), ventricular septal defect repair (n = 2), Mustard takedown with arterial switch (n = 2), initial Fontan (n = 2), right ventricle-to-pulmonary artery conduit revision (n = 2), Norwood procedure (n = 1), 1 ventricular repair for Uhl's anomaly (n = 1), Mustard baffle revision (n = 1), pulmonary valve replacement with aneurysm resection (n = 1), and aortic valve replacement with complex repair (n = 1). RESULTS: No patient developed heart block, and the surgical mortality rate was 7%. One patient died after Mustard takedown and arterial switch operation, and 1 neonate died after repair of severe Ebstein's anomaly. There was one late death after arterial switch conversion at another institution. Recurrent clinical supraventricular tachycardia was present in 2 patients (2 of 27, 7.4%) and 2 patients had new-onset tachycardias with different underlying mechanisms of arrhythmia at late follow-up (median follow-up 47 months). CONCLUSIONS: Successful surgical therapy of arrhythmias can be performed safely at the time of repair of complex congenital heart disease or in patients with failed catheter ablation procedures. Early consideration for single-stage therapy of arrhythmia and structural heart disease is indicated.

Adolescent↗

PubMed2003

The incidence of dysphagia in pediatric patients after open heart procedures with transesophageal echocardiography.

BACKGROUND: Pediatric patients who undergo open heart operations may be at risk for the development of dysphagia because of interventions such as intubation and transesophageal echocardiography. Although the occurrence of dysphagia after cardiac surgical procedures in adults is reported to be 3% to 4%, the incidence in children and adolescents has not been documented. This study was undertaken to determine the incidence of and risk factors contributing to dysphagia in pediatric patients after open heart procedures. METHODS: Fifty patients were evaluated after open heart operations with transesophageal echocardiography between March 1, 1999, and September 30, 1999. The diagnosis of dysphagia was made by a speech pathologist using a clinical swallowing evaluation. Potential predictors examined included demographic variables, anatomical diagnosis, surgical procedure, size of the transesophageal echocardiographic probe in relation to body size, length of probe insertion time, preoperative patient acuity status, duration of intubation, and time until discharge. RESULTS: Dysphagia was found in 9 (18%) of the 50 patients. Risk factors identified were age of less than 3 years (odds ratio, 20.4; 95% confidence interval, 2.7 to 157; p = 0.002), intubation prior to operation (odds ratio, 17.7; 95% confidence interval, 9.4 to 210; p = 0.004), intubation for more than 7 days (odds ratio, 74.7; 95% confidence interval, 13.8 to 405; p = 0.001), and operation for left-sided obstructive lesions (odds ratio, 1.9; 95% confidence interval, 2.2 to 8.3; p = 0.038). The size of the transesophageal echocardiographic probe in relation to the weight of the patient was found to be predictive (p = 0.0001) of dysphagia. Vocal cord paralysis was noted in 4 (8%) of the 50 patients postoperatively. Adverse events related to aspiration occurred in 2 patients (4%). At discharge, nasogastric tube feedings were required in 6 patients (12%), and thickened feedings were recommended for 3 (6%) of the 50 patients. Resolution of dysphagia ranged from 13 to 150 days. CONCLUSIONS: Eighteen percent of patients had dysphagia after an open heart operation with transesophageal echocardiography. Age of less than 3 years, preoperative patient acuity status, longer intubation times, and operation for left-sided obstructions are risk factors for dysphagia in this cohort of pediatric patients. The size of the transesophageal echocardiography probe in relation to the patient's weight was predictive of dysphagia. Physicians should consider using the new mini-multiplane transesophageal echocardiographic probes in patients weighing less than 5.5 kg. Vigilance in monitoring for the signs of preoperative and postoperative dysphagia with prompt referral to a speech therapist can substantially reduce patient morbidity, length of hospital stay, and requirement of prolonged nasogastric tube use.

Adolescent↗

PubMed2003

A comparison of intravascular ultrasound with coronary angiography for evaluation of transplant coronary disease in pediatric heart transplant recipients.

BACKGROUND: The purpose of this study was to assess the sensitivity of coronary angiography versus intravascular ultrasound for detecting significant transplant coronary artery disease in children. We also examined associations between potential risk factors for transplant coronary artery disease and intravascular ultrasound findings, and evaluated the safety of intravascular ultrasound. METHODS: All pediatric heart transplant patients who had intravascular ultrasound following routine coronary angiography were included. Transplant coronary artery disease was quantified by assigning Stanford classes and calculating intimal indices for intravascular ultrasound images. These findings were compared with qualitative coronary angiography findings. Risk factors for transplant coronary artery disease, cardiac events and complications were recorded. RESULTS: Sixteen patients had 27 intravascular ultrasound procedures during the study period. All patients had evidence of transplant coronary artery disease at their latest intravascular ultrasound study. Of the patients whose most severely afflicted coronary artery underwent both imaging modalities at the latest study, 50% had significant transplant coronary artery disease (Stanford Class >/=II) by intravascular ultrasound and normal coronary angiography. A higher mean first-year biopsy score may be associated with significant transplant coronary artery disease by intravascular ultrasound, but a large number of patients will be required to determine this with statistical certainty. One major complication occurred early in the experience. CONCLUSIONS: In children, intravascular ultrasound is more sensitive for detecting significant transplant coronary artery disease than coronary angiography, but may add cost, time and potential morbidity to screening protocols. Prospective, multicenter studies are needed to best utilize intravascular ultrasound in this patient population.

Adolescent↗

PubMed2003

The effect of pulmonary circulation hemodynamics on right ventricular unloading via the bidirectional Glenn shunt: implications for congenitally corrected transposition repair.

The bidirectional Glenn shunt has been successfully applied as an adjunct to ventricular septal defect closure and pulmonary valvulotomy to treat congenitally corrected transposition of the great arteries (ccTGA). The purpose of this study was to examine the volume and pressure unloading effects of the bidirectional Glenn shunt on the hypertrophied pulmonary ventricle in a canine model of ccTGA. Five beagles underwent survival surgery to band the pulmonary artery. Three months later, a polytetrafluoroethylene graft was anastomosed to the superior vena cava and right pulmonary artery. The graft or superior vena cava was clamped to create the normal or bidirectional Glenn circulation, and hemodynamic data were recorded. The bidirectional Glenn shunt significantly reduced right ventricular volume loading and stroke work. Dogs with normal pre-bidirectional Glenn cardiac outputs had greatly reduced right ventricular volumes and pressures with the bidirectional Glenn shunt. Dogs with pre-bidirectional Glenn right ventricular dysfunction had moderate volume but no pressure decreases with the bidirectional Glenn shunt owing to improved left ventricular output. In these dogs it is likely that the decreased level of pressure and volume unloading is because of a concomitant improvement in left ventricular output post-bidirectional Glenn shunt placement. The bidirectional Glenn shunt is effective at unloading the right ventricle in a canine model of ccTGA.

Animals↗

PubMed2003

Physiologic versus anatomic repair of congenitally corrected transposition of the great arteries.

When biventricular repair of congenitally corrected transposition of the great arteries (ccTGA) is possible, complete anatomic (left ventricle to the aorta, right ventricle to the pulmonary artery, and associated atrial baffle operation) or physiologic (left ventricle to pulmonary artery, right ventricle to aorta) connections are complex and associated with significant long-term problems such as arrhythmias, subaortic obstruction, valvar dysfunction, ventricular-to-pulmonary artery conduit changes, and deteriorating ventricular function. Recent advances have supported physiologic, anatomic, and single-ventricle repairs. The purpose of this article is to review the natural history of ccTGA, compare and contrast the physiologic and anatomic repairs, and reintroduce a new concept of physiologic repair for patients with ccTGA, ventricular septal defect, and pulmonary stenosis using left ventricular unloading techniques via a bidirectional shunt.

Adaptation, Physiological↗

PubMed2003

Arrhythmia surgery in association with complex congenital heart repairs excluding patients with fontan conversion.

Surgical arrhythmia therapy may be performed for patients failing the catheter ablation approach or incorporated into repair of complex congenital heart disease. Variations in atrial and ventricular anatomy that may limit the catheter approach can be directly addressed surgically assuring lesion depth and continuity of anatomic lines of block. Between July 1992 and August 2002, we performed arrhythmia surgery on 34 patients for refractory atrial (n = 29) or ventricular (n = 5) arrhythmias. Not included in this series are patients who had arrhythmia surgery during Fontan conversion. The majority of patients had various forms of complex congenital heart disease; two had structurally normal hearts. Median age at surgery was 13.0 years (range, 7 days to 45 years). Five patients were infants (mean age, 25 days). Twenty-two patients (65%) had an average of 2.8 previous cardiac procedures; all required resternotomy. Operative mortality was 5.9% (2 of 34 patients) because of low cardiac output in one patient following Mustard takedown and arterial switch operation and in one neonate with Ebstein's anomaly and pulmonary atresia. Ablative surgery for supraventricular tachycardia (atrial re-entry, automatic atrial, atrioventricular nodal re-entry, and atrial fibrillation) had a 93% success rate (25 of 27 patients). Clinical tachycardia recurred in two of 27 surviving patients (7%) with atrial arrhythmia, one after an arrhythmia-free interval of several years. Ventricular tachycardia was inducible postoperatively in two of three patients with ventricular arrhythmias and congenital heart disease. Patient size or anatomic complexity should not be limiting factors in the combined surgical arrhythmia approach. Because older patients undergoing surgical revision of prior surgical repairs of congenital heart disease are at increased risk for the later development of atrial arrhythmias, incorporation of arrhythmia therapy into any planned surgical revision should be routinely considered.

Arrhythmias, Cardiac↗

PubMed2003

Dexamethasone reduces postoperative troponin levels in children undergoing cardiopulmonary bypass.

OBJECTIVE: We previously demonstrated that dexamethasone treatment before cardiopulmonary bypass in children reduces the postoperative systemic inflammatory response. The purpose of this study was to test the hypothesis that dexamethasone administration before cardiopulmonary bypass in children correlates with a lesser degree of myocardial injury as measured by a decrease in cardiac troponin I release. DESIGN: A prospective, randomized, double-blind study. SETTING: The cardiac surgery operating room and intensive care unit of a pediatric referral hospital. SUBJECTS: Twenty-eight patients who underwent open-heart surgery for congenital heart defects. INTERVENTIONS: Patients received either placebo (group I, n = 13) or dexamethasone, 1 mg/kg iv (group II, n = 15), 1 hr before initiation of cardiopulmonary bypass. Plasma cardiac troponin I samples were obtained at three time points: immediately before study agent (sample 1), 10 mins after protamine sulfate administration after cardiopulmonary bypass (sample 2), and 24 hrs postoperatively (sample 3). MEASUREMENTS AND MAIN RESULTS: Mean cardiac troponin I levels (+/-sd) were significantly lower at sample time 3 in group II (dexamethasone; 33.4 +/- 20.0 ng/mL) vs. group I (control; 86.9 +/- 81.1) (p =.04). CONCLUSION: Dexamethasone administration before cardiopulmonary bypass in children resulted in a significant decrease in cardiac troponin I levels at 24 hrs postoperatively. We postulate that this may represent a decrease in myocardial injury, and, thus, a possible cardioprotective effect produced by dexamethasone.

Analysis of Variance↗

PubMed2002

Comparison of anatomic isthmus block with the modified right atrial maze procedure for late atrial tachycardia in Fontan patients.

BACKGROUND: Late atrial reentry tachycardia (AT) after Fontan repair is common, with limited efficacy of medical therapy in preventing AT recurrence. In this study, two approaches to surgical arrhythmia ablation in patients with refractory AT undergoing Fontan revision are compared: cryoablation of the inferomedial right atrium (RA), and a more extensive modified RA maze procedure designed to eliminate all potential RA reentrant circuits. METHODS AND RESULTS: Fontan revision was performed in 23 patients with AT, using inferomedial RA cryoablation (Group 1, n=8) and modified RA maze procedure (Group 2, n=15). There was no difference in age at initial Fontan, age at Fontan revision, age at onset of AT, or number of failed antiarrhythmic medications. Patients underwent preoperative, intraoperative, and postoperative electrophysiological studies. Thirty-eight different tachycardia circuits were induced in preoperative studies with 3 major areas of RA involvement: the lower lateral RA, the atrial septum, and the inferomedial RA. At postoperative electrophysiological study, AT was inducible in 62% of Group 1 patients but only 7% of Group 2 patients (P<0.02). With mean follow-up of 43 months, 5 of 8 patients in Group 1 experienced AT recurrence compared with none in Group 2 (P<0.001). There was no significant difference in length of hospital stay or complication rate comparing the two groups. CONCLUSION: Modified RA maze procedure is superior to anatomic isthmus block in treating reentrant AT in postoperative Fontan patients. The modified RA maze has eliminated AT recurrence at mid-term follow-up with low morbidity and mortality.

Adolescent↗

PubMed2002

Serum vascular endothelial growth factor as a surveillance marker for cellular rejection in pediatric cardiac transplantation.

BACKGROUND: Early detection and treatment of acute rejection in cardiac transplant recipients significantly improves long-term survival. Endomyocardial biopsy is used routinely for diagnosing allograft rejection; however, in young children, this procedure carries some risk. We evaluated serum vascular endothelial growth factor (VEGF) as a potential surveillance marker of acute cellular rejection. METHODS: Blood samples (n=62) were analyzed from 23 patients and compared with controls (n=18) using an ELISA for VEGF. Results were correlated with endomyocardial biopsy rejection grades. RESULTS: Mean baseline VEGF levels of the transplant population were consistently higher than controls. Serum VEGF levels were significantly higher during acute cellular rejection when compared with the non-rejecting transplant group (700.7+/-154 pg/ml vs. 190.5+/-29 pg/ml). VEGF decreased two- to eightfold after immunosuppressive therapy in 9 of 11 rejection episodes. CONCLUSIONS: These data suggest that VEGF may play a role in the pathogenesis of acute allograft rejection and it may serve as a reliable serologic surveillance marker.

Acute Disease↗

PubMed2002

Anomalous origin of the left coronary artery from the pulmonary artery: collective review of surgical therapy.

Anomalous origin of the left coronary artery from the pulmonary artery is an extremely rare but potentially fatal congenital coronary anomaly. Prompt surgical reestablishment of a two-coronary system on diagnosis yields excellent results and allows progressive and nearly total myocardial recovery. Follow-up of all patients is required to assess the adequacy of repair and to exclude ongoing or recurrent myocardial insult.

Coronary Vessel Anomalies↗

PubMed2002

Repair of congenital tracheal stenosis.

We have used six different techniques in 61 operations performed at Children's Memorial Hospital (Chicago, IL) between 1982 and 2001 on 54 infants with complete tracheal rings and primary or recurrent tracheal stenosis. Short-term and long-term outcomes are reviewed for all techniques including pericardial tracheoplasty, tracheal autograft, tracheal resection, cartilage tracheoplasty, slide tracheoplasty, and aortic homograft patch tracheoplasty. Patients' ages ranged from 7 days to 72 months; mean age at operation was 6 months. There were 33 boys and 21 girls. Associated pulmonary artery sling was present in 19 of 54 patients (35%). Significant associated intracardiac anomaly was present in 13 of 54 patients (24%). The number of complete tracheal rings involved ranged from two to 18 rings (mean, 14+/-5). All procedures were performed with the use of cardiopulmonary bypass. Simultaneous repair of pulmonary artery sling and cardiac abnormalities was undertaken. There were three early deaths, two after pericardial tracheoplasty and one after tracheal autograft. There were eight late deaths, five after pericardial tracheoplasty, one after tracheal autograft, one after slide tracheoplasty, and one after tracheal resection. Median length of hospital stay was 60 days for pericardial tracheoplasty, 28 days for tracheal autograft, 14 days for tracheal resection, and 18 days for the slide tracheoplasty. Follow-up is complete in all patients. Tracheal autograft is currently our procedure of choice for patients with long-segment tracheal stenosis because of its use of all-autologous material, technical ease of performance, already-present epithelial lining of the autograft, intrinsic maintenance of the cartilage contour, potential for growth, and ready availability. We limit the use of tracheal resections to patients with eight or less rings of tracheal stenosis.

Cardiopulmonary Bypass↗

PubMed2002

The beneficial effects of total cavopulmonary conversion and arrhythmia surgery for the failed Fontan.

Postoperative Fontan patients can develop hemodynamic abnormalities and refractory atrial arrhythmias resulting in significant morbidity and mortality. We present our experience with total cavopulmonary artery conversion and arrhythmia surgery. Between 1994 and 2001, 41 patients underwent total cavopulmonary artery conversion and arrhythmia surgery. Significant hemodynamic lesions were repaired concomitantly: aortic aneurysm (n=1), atrioventricular valve insufficiency (n=8), and pulmonary artery stenosis (n=9). Thirty-five patients were in New York Heart Association class III or IV. Mean age at original Fontan was 7.5+/-6.5 years, at Fontan conversion, 18.7+/-9.0 years. Arrhythmia surgery for atrial re-entry tachycardia evolved from isthmus cryoablation (n=10) to right-sided maze (n=17). Maze-Cox III was used for 14 patients with atrial fibrillation. Atrial (n=34) and dual chamber (n=5) pacemakers were placed. Mortality and reoperation for bleeding rates are 0%. Chest tubes were removed on postoperative day 9.0+/-6.0. Mean hospital stay was 11.8+/-6.6 days. Three patients required cardiac transplantation at 8 days, 9 months, and 33 months postoperatively. There was one long-term death from acute myocardial infarction 2 years postoperatively. For the entire series, arrhythmia recurrence is 12.2% (5/41). Only 9.8% of patients (4/41) receive chronic antiarrhythmic medications; these patients were among the first eight in the series. Most patients are in New York Heart Association I or II. Bruce protocol in 12 patients showed increased tolerance (P<.05) Total cavopulmonary artery conversion with concomitant arrhythmia surgery is excellent therapy for patients with failed Fontan. It is safe, improves New York Heart Association class, improves exercise tolerance, and the incidence of recurrent arrhythmias is low.

Adolescent↗

PubMedDate not supplied

Platelet and leukocyte activation and design consequences for thoracic artificial lungs.

Blood contact with the prosthetic surfaces of artificial lungs causes extensive activation of molecular and cellular mediators of coagulation and inflammation that can lead to patient morbidity and mortality. To determine the effects of artificial lung fiber bundle shear stress and surface area on blood activation, porcine blood was recirculated for 4 hours through circuits containing mock artificial lungs with bundle shear stresses of 11.6, 7.3, and 3.9 dynes/cm2 and surface areas of 5.2, 3.5, and 1.7 cm2/ml of circuit volume. Blood from these circuits was assayed for platelet and leukocyte counts, soluble P-selectin concentrations, and lactoferrin concentrations to determine the level of platelet and leukocyte adherence to the circuit, platelet activation, and leukocyte activation, respectively. Neither platelet nor leukocyte counts were significantly affected by shear stress or surface area. P-selectin and lactoferrin concentrations were significantly greater at a fiber bundle shear stress of 11.6 dynes/ cm2. P-selectin and lactoferrin concentrations were significantly greater at a fiber bundle surface area of 5.2 cm2/ml of circuit volume. Artificial lungs, therefore, should be designed with average bundle shear stresses < 11.6 dynes/cm2 and with surface areas < 5.2 cm2/ml of circuit volume. Current thoracic artificial lungs meet both these requirements.

Animals↗

PubMedDate not supplied

Hemodynamic and gas transfer properties of a compliant thoracic artificial lung.

A compliant thoracic artificial lung (TAL) has been developed for acute respiratory failure or as a bridge to transplantation. The development goal was to increase TAL compliance, lower TAL impedance, and improve right ventricular function during use. Prototypes were tested in vitro and in vivo in eight pigs between 67 and 79 kg to determine hemodynamic and gas transfer properties. The in vitro compliance was 16.2 +/- 4.4 ml/mm Hg at pressures < 7.8 mm Hg and 4.3 +/- 1.1 ml/mm Hg above 7.8 mm Hg. In vivo, this compliance significantly reduced blood flow pulsatility from 1.7 at the inlet to 0.36 at the outlet. Device resistance was 1.9 and 1.8 mm Hg/(L/min) at a flow rate of 4 L/min in vitro and in vivo, respectively. Approximately 75% of the resistance was at the inlet and outlet. In vivo TAL O2 and CO2 transfer rates were 188 and 186 ml/min, respectively, at 4 L/min of blood and gas flow, and average outlet O2 saturations exceeded 98% for average flow rates up to and including the maximum tested, 5.3 L/min. The new design has a markedly improved compliance and excellent gas transfer but also possesses inlet and outlet resistances that must be reduced in future designs.

Animals↗

PubMedDate not supplied

Inhaled prostacyclin following surgical repair of congenital heart disease--a pilot study.

BACKGROUND: The development of additional therapies for the treatment of pulmonary hypertension would be a significant advancement in the treatment of congenital heart disease. Recently, studies have found inhaled prostacyclin (PGI2) is an effective pulmonary vasodilator, comparable with nitric oxide. In this prospective interventional pilot study, we examined the physiologic effects of inhaled PGI2 in children with congenital heart disease and pulmonary hypertension. METHODS: Six children (median age 6 months, range 5 to 21 months) with congenital heart disease and preoperative pulmonary hypertension (mean pulmonary artery pressure [MPAP] greater than 50% systemic) received a 15-minute course of inhaled PGI2 intraoperatively postrepair. The inhaled PGI2 was delivered by aerosolizing the IV formulation (Flolan, Glaxo-Wellcome) to achieve a dose of 50 ng/kg/min. Physiologic parameters measured during the medication period were compared with measurements taken during two 15-minute baseline periods before and after the medication period. RESULTS: Inhaled PGI2 significantly reduced the mean pulmonary artery pressure from 25 +/- 3 to 21 +/- 3 (p < 0.01) and improved the PaO2/FiO2 ratio from 275 +/- 181 to 433 +/- 285 (p = 0.01). There were no significant changes in systemic blood pressure, heart rate, or cardiac index. CONCLUSIONS: Children with congenital heart disease and pulmonary hypertension may benefit from inhaled PGI2. Inhaled PGI2 reduced pulmonary blood pressures and improved oxygenation in this small study. PGI2 acts through cyclic adenosine monophosphate mediated pulmonary vasodilation, a mechanism different from nitric oxide. In children with inadequate response to nitric oxide, inhaled PGI2 may be a useful alternative pulmonary vasodilator.

Administration, Inhalation↗