Michel N. Ilbawi

Detrimental Effects of Cardiopulmonary Bypass in Cyanotic Infants: Preventing the Reoxygenation Injury

BACKGROUNDnRecent experimental studies have shown that acute hypoxia followed by abrupt reoxygenation using cardiopulmonary bypass (CPB) results in an unintended injury mediated by oxygen free radicals, which can be modified by initiating CPB at a lower fraction of inspired oxygen (FiO2) or by leukocyte filtration. However, the clinical relevance of these experimental studies has been questioned because chronic hypoxia may allow compensatory changes to occur.nnnMETHODSnSeven acyanotic infants had CPB initiated at an FiO2 of 1.0. Of 21 cyanotic infants, 7 (group 1) had CPB initiated at an FiO2 of 1.0, 6 (group 2) at an FiO2 of 0.21, and 8 (group 3) underwent CPB using leukocyte filtration. Biopsy of right atrial tissue was performed before and 10 to 20 minutes after the initiation of CPB. The tissue was incubated in 4-mmol/L t-butylhydroperoxide (a strong oxidant), and the malondialdehyde (MDA) level was measured to determine the antioxidant reserve capacity. The more MDA produced, the greater was the depletion of tissue antioxidants secondary to oxygen free radical formation during reoxygenation.nnnRESULTSnThere was no difference in the prebypass antioxidant reserve capacity between cyanotic and acyanotic hearts (492 +/- 72 versus 439 +/- 44 nmol MDA/g protein). However, after the initiation of CPB without leukocyte filtration, MDA production rose markedly in the cyanotic (groups 1 and 2) as compared with the acyanotic hearts (322% versus 40%; p < 0.05), indicating a depletion of antioxidants. In cyanotic hearts, initiating CPB at an FiO2 of 1.0 (group 1) resulted in increased MDA production (407% versus 227%) as compared with hearts in which CPB was initiated at an FiO2 of 0.21 (group 2), indicating a greater generation of oxygen free radicals in group 1. Conversely, there was only a minimal increase in MDA production in 8 of the 21 infants (group 3) in whom white blood cells were effectively filtered (19% versus 322%; p < 0.05).nnnCONCLUSIONSnFirst, increased amounts of oxygen free radicals are generated in cyanotic infants with the initiation of CPB. Second, this production is reduced by initiating CPB at an FiO2 of 0.21 or by effectively filtering white blood cells. Third, these changes parallel those seen in the acute experimental model, validating its use for future study.

Intermediate results of the anatomic repair for congenitally corrected transposition

BACKGROUNDnAnatomic repair of congenitally corrected transposition of the great arteries has several advantages over the traditional approach but lacks long-term evaluation.nnnMETHODSnThe data on 12 patients who had the procedure between January 1989 and June 2000 were retrospectively reviewed. Associated lesions included ventricular septal defect in 12 patients, pulmonary stenosis in 10 patients, and moderate to severe tricuspid valve regurgitation in 4 patients. Mean age at operation was 9+/-3.6 months. All patients had venous switch Mustard procedure. Tunneling of the morphologic left ventricle through the ventricular septal defect to the aorta with insertion of right ventricular to pulmonary artery conduit was performed in 10 patients, and arterial switch operation in 2. Concomitant tricuspid valvuloplasty was done in 2 patients and ventricular septal defect enlargement in 1.nnnRESULTSnThere was one hospital death (9%) in the patient who needed ventricular septal defect enlargement. Complications included atrioventricular block requiring pacemaker insertion in 1 patient (9%) and superior vena caval obstruction in 1 patient (9%). Follow-up is available on all patients 0.5 to 10 years (mean, 7.6+/-3.1 years). All patients are asymptomatic. Exercise test results on the three oldest patients were normal. Bradytachyarrhythmias developed in 4 patients (36%). Right ventricular to pulmonary artery conduit replacement was needed in 5 patients 2.2 to 7.1 years (mean 5.2+/-3.6 years) postoperatively. Mild to moderate tricuspid valve regurgitation persisted in 2 patients. Systemic left ventricular fractional shortening was 36% to 47% (mean, 39%+/-4.6%), and ejection fraction was 49% to 70% (mean, 60.8%+/-7.9%).nnnCONCLUSIONSnThe double switch operation can be performed safely with minimal intermediate and long-term complications.

Latent Hypoparathyroidism in Children With Conotruncal Cardiac Defects

BACKGROUNDnDiGeorge anomaly is characterized by hypoplasia or atresia of the thymus and parathyroid glands resulting in T cell-mediated deficiency, hypocalcemic hypoparathyroidism, and conotruncal cardiac defects. It usually is associated with deletions of chromosomal region 22q11. We hypothesized that the stimulated (secretory reserve) but not the constitutive secretion of parathyroid hormone would be reduced in normocalcemic children with conotruncal cardiac defects but no overt immune deficiency and would be related to the presence of a deletion in the DiGeorge chromosomal region of 22q11.nnnMETHODS AND RESULTSnBlood-ionized calcium and serum-intact parathyroid hormone were measured at baseline and seven more times during hypocalcemia induced during cardiopulmonary bypass in 22 patients and 10 control subjects with an atrial septal defect. Chromosomal deletions were detected by fluorescent in situ hybridization and DNA dosage analysis. There were no differences in basal calcium and parathyroid hormone levels between patients and control subjects. All had increased parathyroid hormone in response to hypocalcemia; despite lower calcium levels, parathyroid hormone levels were lower in patients. The parathyroid hormone secretory reserve in 14 of 22 patients was reduced compared with control subjects; 4 of the 14 had deletions.nnnCONCLUSIONSnA significant number of children with conotruncal cardiac defects have normocalcemia and a normal constitutive level of parathyroid hormone but deficient parathyroid hormone secretory reserve; about 30% also have 22q11 deletions. Such children may be at risk for the later development of hypocalcemic hypoparathyroidism.

Reducing postischemic reperfusion damage in neonates using a terminal warm substrate-enriched blood cardioplegic reperfusate

BACKGROUNDnIn adult cardiac operations, a warm cardioplegic reperfusate (hot shot) before removing the aortic cross-clamp improves postbypass myocardial function and metabolic recovery. This modality, however, is rarely used in infants, despite the fact that postbypass cardiac dysfunction remains problematic, especially in cyanotic (stressed) patients.nnnMETHODSnTo produce stress, 15 neonatal piglets underwent 60 minutes of ventilator hypoxia (fraction of inspired oxygen, 8% to 10%). All piglets then received similar protection with multidose cold blood cardioplegic solution during 70 minutes of arrest and were separated into three groups to examine the role of a warm reperfusate as well as possible augmentation by aspartate and glutamate enrichment. In 5 piglets (group 1), the cross-clamp was simply removed; in 5 (group 2), an unsupplemented warm blood cardioplegic reperfusate was given; and in 5 (group 3), the warm reperfusate was enriched with aspartate and glutamate. Myocardial function was assessed using pressure-volume loops and expressed as a percentage of control.nnnRESULTSnCompared with hearts receiving reperfusion with unmodified blood (group 1), a warm unsupplemented cardioplegic reperfusate (group 2) slightly improved systolic contractility (end-systolic elastance, 41% versus 50%; p < 0.05 versus group 1) and preload recruitable stroke work (41% versus 52%; p < 0.05 versus group 1), reduced diastolic stiffness (263% versus 245%; p < 0.05 versus group 1), and increased adenosine triphosphate (10.7 versus 11.9 microg/g tissue, p < 0.05 versus group 1). However, if aspartate and glutamate was included in the warm reperfusate (group 3), there was complete recovery of systolic function (end-systolic elastance, 105%+/-3%; p < 0.001 versus all groups) and preload recruitable stroke work (103%+/-2%; p < 0.001 versus all groups), a minimal rise in diastolic stiffness (154%+/-7%; p < 0.001 versus all groups), and preservation of adenosine triphosphate (15.5+/-0.5 microg/g; p < 0.001 versus all groups).nnnCONCLUSIONSnA warm cardioplegic reperfusate helps reduce the reperfusion injury, resulting in improved myocardial function and metabolic recovery in hypoxic (stressed) neonatal hearts, and this effect is maximized if the reperfusate is enriched with aspartate and glutamate, which completely preserves myocardial function.

Modification of the subclavian patch aortoplasty for repair of aortic coarctation in neonates and infants

BACKGROUNDnCoarctation repair in neonates or small infants, using a subclavian patch, has a relatively high risk of restenosis, especially if complicated by the presence of a short subclavian artery or long coarctation segment. We introduce a technical modification that facilitates the use of a subclavian flap, and decreases the restenosis rate in this subgroup of patients. It consists of a side-to-side transverse aortic anastomosis at the level of the coarctation, which widens the coarctation segment, shortens the isthmus, and pulls the distal end of the aortotomy proximally, allowing a tension-free subclavian flap aortoplasty.nnnMETHODSnFifty-three consecutive neonates or infants less than 18 weeks old, with complex coarctation, underwent repair using this technique. Mean age was 26+/-3 days and 36 patients (68%) were less than 28 days old. Weights ranged from 1.4 to 6.4 kg (mean 3.4+/-0.2 kg), and 26 patients had other cardiac anomalies. Preoperative gradient by Doppler measurement ranged from 25 to 90 mm Hg (mean 49+/-2 mm Hg).nnnRESULTSnMean aortic cross-clamp time was 27+/-1 minutes (range 19 to 34 minutes). There were no deaths or surgical complications. Follow-up echocardiogram 4 to 52 months postoperatively (mean 25+/-2 months) demonstrated no significant pressure gradient (less than 20 mm Hg) in 51 of 53 patients (96%), and a significant gradient in 2 patients (4%), which was subsequently corrected with balloon angioplasty.nnnCONCLUSIONSnThe technical modification described shortens the isthmus, and thus allows for a longer aortotomy distal to the area of coarctation resulting in a tension-free repair especially in patients with a short subclavian artery. It also widens the area of coarctation, and as a result leads to a lower early recoarctation rate in this high-risk group. With increasing emphasis on the need for a longer aortotomy to prevent restenosis, this modification will have increasing application, especially in the neonatal population.

Recent Advances in Neonatal Cardiac Surgery

Several major advances in the field of neonatal cardiac surgery have improved the outcome of these severely ill patients. Among the preoperative advances are improvement in the management of patients with single ventricle equivalents, prenatal diagnosis, and interventional procedures. Intraoperative advances include better understanding of the inflammatory process caused by cardiopulmonary bypass and ways to manage it, newer techniques for treating hypoplastic left heart syndrome and aortic valve disease, and primary repair of complex lesions. Postoperative refinements in managing pulmonary hypertension, low cardiac output state, and ventricular assist devices have decreased surgical mortality and morbidity. Although his primary interest has been adult cardiac surgery, Dr. Geha has contributed directly and indirectly to these advances.

Surgical Repair of Anomalous Coronary Arteries Arising from the Opposite Sinus of Valsalva in Infants and Children

Abstractu2002 Background: Unroofing of anomalous coronary artery originating from the opposite sinus of Valsalva has become the procedure of choice for this congenital lesion, with surgery performed in children as young as two years old. An increasing number of this anomaly is diagnosed in infancy with no clear indication whether surgical repair should be done in this age group. This paper reviews our experience with this anomaly, and focuses on its surgical management in infants. Methods: Between April 2002 and February 2007, eight patients underwent surgical repair of anomalous coronary artery arising from the opposite sinus of Valsalva and coursing between the aorta and pulmonary artery. Patients’ age varied from two months to 28 years with a mean of 11.7 ± 11.1 years. Surgical Technique: Surgical repair involved unroofing the intramural segment of the anomalous coronary artery using cardiopulmonary bypass. Results: Two patients were younger than one year (Group A), and six patients were older than one year (group B). The mean intensive care unit stay was 2.5 ± 0.7 days for Group A and 2.8 ± 1.9 for Group B. The mean hospital stay was 4 ± 1.4 days for Group A and 4.3 ± 2.4 days for Group B. There was no mortality and no complications. The mean follow‐up period is 14 ± 15.7 months with a range of one to 39 months. At the time of the last follow‐up, all patients were asymptomatic in New York Heart Association class I and follow‐up echocardiography on six of eight patients showed wide open coronary ostium. Conclusion: Unroofing the anomalous coronary artery arising from the opposite sinus of valsalva can be done in infants with minimal morbidity and mortality. Longer follow‐up is needed to assess long‐term results.

Pericardial Leaflet Extension for Aortic Valve Repair: Techniques and Late Results

A modified technique to repair aortic valve is described. The technique consists of tailored extension of the old valve leaflets with gluteraldehyde treated autologous pericardium. The technique has excellent intermediate results and is an alternative to valve replacement in pediatric patients. Copyright 1999 by W.B. Saunders Company

Evolution of the Surgical Approach to Congenitally Corrected Transposition of the Great Arteries

The traditional surgical approach (physiologic repair) of congenitally corrected transposition of the great arteries (ccTGA) attempts at restoring normal physiology by repairing the associated lesions. It fails to address the most serious anatomic abnormality, mainly ventriculoarterial discordance, and results in less than optimal long-term outcomes. Anatomic repair was introduced to incorporate the left ventricle into the systemic circulation. The excellent short-term and intermediate results of the double switch operation and its modifications make it the procedure of choice for the treatment of ccTGA.

Improved Results of Aortic Arch Reconstruction in the Norwood Procedure.

BACKGROUNDnDespite several surgical modifications, the reported incidence of neoaortic coarctation after stage 1 palliation (S1P) of hypoplastic left heart syndrome remains high. A modification of aortic arch reconstruction that may decrease the incidence of neoaortic coarctation after S1P is described.nnnMETHODSnBetween January 2008 and May 2013, 114 patients with hypoplastic left heart syndrome underwent S1P. The hospital records of the 101 surviving patients (89%) were reviewed. Demographic data and perioperative variables for S1P were collected. A modified technique for aortic arch reconstruction that contains a bovine pericardial patch tailored and sutured in a specific way was used in 51 patients (group MT), whereas the traditional technique was used in 50 patients (group TT). Clinical echocardiographic and cardiac catheterization data were analyzed to determine the incidence and location of neoaortic coarctation.nnnRESULTSnThere were no significant differences in the baseline characteristics, the intraoperative course, or hospital mortality between the two groups of subjects. Duration of ventilation, intensive care unit stay, and hospitalization were significantly shorter in group MT. The mean follow-up was 2.02 ± 0.63 years and 3.98 ± 0.66 years in each group, respectively. Coarctation developed in 4 of 51 patients (7.8%) in group MT compared with 10/50 patients (20%) in group TT. Multivariable logistic regression analysis showed that the estimated odds of coarctation for group MT were 0.41 (95% confidence interval: 0.04, 4.32) times the estimated odds of coarctation for group TT.nnnCONCLUSIONSnThe described technique may decrease the incidence of recoarctation after S1P by minimizing aortic arch and descending aorta distortion and providing ample enlargement of the aorta at its narrowest diameter.