Long-Term Surgical Outcomes of Patients With Isomeric Right and Left Atrial Appendages.

Objectives: To compare the long-term outcomes of biventricular, univentricular, and so-called one-and-one-half ventricular repairs in patients with left and right isomerism. Methods: Surgical correction was undertaken, between 2000 and 2021, in 198 patients with right, and 233 with left isomerism. Results: The median age at operation was 24 days (interquartile range [IQR]: 18-45) and 60 days (IQR: 29-360) for those with right and left isomerism, respectively. Multidetector computed-tomographic angiocardiography demonstrated more than half of those with right isomerism had superior caval venous abnormalities, and one-third had a functionally univentricular heart. Almost four-fifths of those with left isomerism had an interrupted inferior caval vein, and one-third had complete atrioventricular septal defect. Biventricular repair was achieved in two-thirds of those with left isomerism, but under one-quarter with right isomerism (P < .001). Hazard regression for mortality revealed odds for prematurity at 5.5, pulmonary atresia at 2.81, atrioventricular septal defect with a common valvar orifice at 2.28, parachute mitral valve at 3.73, interrupted inferior caval vein at 0.53, and functionally univentricular heart with a totally anomalous pulmonary venous connection at 3.77. At a median follow-up of 124 months, the probability of survival was 87% for those with left, and 77% for those with right isomerism (P = .006). Conclusions: Multimodality imaging characterizes and delineates the relevant anatomical details, facilitating surgical management of individuals with isomeric atrial appendages. Continuing higher mortality despite surgical intervention in those with right isomerism points to the need for the reassessment of strategies for management.

Fontan failure: phenotypes, evaluation, management, and future directions.

OBJECTIVES: Management of "failing" and "failed" Fontan circulation, particularly the indications, timing, and type of re-intervention, currently remains nebulous. Factors contributing to pathogenesis and mortality following Fontan procedure differ between children and adults. METHODS: Since organ systems in individual patients are affected differently, we searched the extant literature for a "failing" and "failed" Fontan reviewing the clinical phenotypes, diagnostic modalities, pharmacological, non-pharmacological, and surgical techniques employed, and their outcomes. RESULTS: A total of 410 investigations were synthesised. Although proper candidate selection, thoughtful technical modifications, timely deployment of mechanical support devices, tissue-engineered conduits, and Fontan takedown have decreased the peri-operative mortality from 9 to 15% and 1 to 3% per cent in recent series, pernicious changes in organ function are causing long-term patient attrition. In the setting of a failed Fontan circulation, literature documents three surgical options: Fontan revision, Fontan conversion, or cardiac transplantation. The reported morbidity of 25% and mortality of 8-10% among Fontan conversion continue to improve in select institutions. While operative mortality following cardiac transplantation for Fontan failure is 30% higher than for other CHDs, there is no difference in long-term survival with actuarial 10-year survival of around 54%. Mechanical circulatory assistance, stem cells, and tissue-engineered Fontan conduit for destination therapy or as a bridge to transplantation are in infancy for failing Fontan circulation. CONCLUSIONS: An individualised management strategy according to clinical phenotypes may delay the organ damage in patients with a failing Fontan circulation. At present, cardiac transplantation remains the last stage of palliation with gradually improving outcomes.

Transposition physiology in the setting of concordant ventriculo-arterial connections.

BACKGROUND AND AIM: To review the anatomical details, diagnostic challenges, associated cardiovascular anomalies, and techniques and outcomes of management, including re-interventions, for the rare instances of transposition physiology with concordant ventriculo-arterial connections. METHODS: We reviewed clinical and necropsy studies on diagnosis and surgical treatment of individuals with transposition physiology and concordant ventriculo-arterial connections, analyzing also individuals with comparable flow patterns in the setting of isomerism. RESULTS: Among reported cases, just over two-thirds were diagnosed during surgery, after initial palliation, or after necropsy. Of the patients, four-fifths presented in infancy with either cyanosis or congestive cardiac failure, with complex associated cardiac malformations. Nearly half had ventricular septal defects, and one-fifth had abnormalities of the tricuspid valve, including hypoplasia of the morphologically right ventricle. A small minority had common atrioventricular junctions We included cases reported with isomerism when the flow patterns were comparable, although the atrioventricular connections are mixed in this setting. Management mostly involved construction of intraatrial baffles, along with correction of coexisting anomalies, either together or multistaged. Overall mortality was 25%, with one-fifth of patients requiring pacemakers for surgically-induced heart block. The majority of survivors were in good functional state. CONCLUSIONS: The flow patterns produced by discordant atrioventricular and concordant ventriculo-arterial connections remain an important, albeit rare, indication for atrial redirection or hemi-Mustard's procedure with bidirectional Glenn. The procedure recruits the morphologically left ventricle in the systemic circuit, producing good long-term functional results. The approach can also be used for those with isomeric atrial appendages and comparable hemodynamic circuits.

The surgical anatomy of hearts with isomeric atrial appendages-implications for surgical management.

OBJECTIVES: The most severe combinations of cardiac malformations exist in individuals having jumbled-up thoracic and abdominal organs. These patients make up 2 distinct syndromes. As yet, the consensus is lacking on how best to describe the subsets. The subsets are frequently grouped together in terms of 'heterotaxy'. The surgical approaches to the subsets, however, are markedly different. We reviewed our experiences with regard to the anatomy as observed in the autopsy room, by the analysis of computed tomographic studies, and in the operating room, to assess whether the lesions might be segregated on the basis of isomerism of the atrial appendages. METHODS AND RESULTS: A review of our findings from the examination of specimens from several archives, along with investigation of a large cohort of patients being prepared for surgical treatment, showed that individuals can uniformly be segregated into subgroups on the basis of isomeric arrangement of the atrial appendages. In all instances, this was made possible by using the criterion of the extent of the pectinate muscles within the appendages as judged relative to the atrial vestibules. Segregation on this basis, which correlated excellently with the bronchial arrangement, sets the scene for an appropriate description of the remainder of the heart, providing the cardiac surgeon with all the inferences required for appropriate surgical intervention. CONCLUSIONS: When assessing individuals having the features of so-called 'heterotaxy', it is possible to segregate the groups into subsets of individuals having either isomeric right or left atrial appendages. This approach provides the framework for the assessment of appropriate surgical management.

Surgical management of hearts with isomeric atrial appendages.

BACKGROUND AND AIM: On the basis of previously published accounts, coupled with our own experience, we have assessed the surgical approaches to patients with isomeric atrial appendages. METHODS: We reviewed pertinent published studies on surgical treatment of individuals with isomeric atrial appendages, with the pertinent surgical details provided by most of the manuscripts. RESULTS: Half of patients with right isomerism, and two-thirds of those with left isomerism have bilateral superior caval veins. Azygos extension of the inferior caval vein is reported in three-quarters of those with left isomerism. The coronary sinus is universally absent in right isomerism, along with totally anomalous pulmonary venous connection, and is absent in two-fifths of those with left isomerism. Univentricular atrioventricular connections are expected in up to three-quarters of those with right isomerism. Atrioventricular septal defect is reported in up to four-fifths, more frequently in right isomerism, with such patients typically having discordant ventriculoatrial connections or double outlet right ventricle. Reported mortalities extend to 85% for those with right, and 50% for those with left isomerism. In right isomerism, mortality is up to 54% for systemic-to-pulmonary arterial shunting, up to 75% for univentricular repair, and up to 95% for repair of totally anomalous pulmonary venous connection itself. No more than one-quarter had undergone Fontan completion, with reported mortalities of 21%. CONCLUSION: Early surgical results are satisfactory in patients with left isomerism, but disappointing for those with right. Recent advances in cardiac and liver transplantation may offer improved survival.

A reappraisal of the sinus venosus defect.

OBJECTIVES: The phenotypic features and morphogenesis of the 'sinus venosus defect' remain controversial. The phenotypic features are anomalous systemic connections of 1 or more pulmonary veins that retain their left atrial connection, usually associated with a biatrial connection of the superior caval vein. Cases with these features, however, have not always been described as sinus venosus defects. METHODS: We reviewed the findings documented in the literature from 11 patients with a biatrial connection of the superior caval vein, most reported following an autopsy examination. We compared these findings with the anatomical details of 50 patients undergoing surgical correction in our centre, paying particular attention to the override of the superior caval vein. RESULTS: In only two-thirds of those undergoing surgery did the superior caval vein override the rims of the oval fossa, with the degree of override >50% in only 2 individuals. It is only these latter 2 cases that are directly comparable to the reported cases of biatrial connection of the superior caval vein. CONCLUSIONS: Our comparisons provide new insights into the developmental background and phenotypic features of the superior sinus venosus defect. The defects exist because of the anomalous systemic connection of the pulmonary veins that retain their left atrial connections but not always in association with a biatrial connection of the superior caval vein. In extreme cases, nonetheless, they can underscore the connection of the caval vein to the morphologically left atrium, frequently described previously as a 'biatrial connection'. The sinus venosus defect is better considered a venovenous malformation than a septal defect.

Concomitant Transthyretin Amyloidosis and Severe Aortic Stenosis in Elderly Indian Population: A Pilot Study.

BACKGROUND: Prevalence of both degenerative severe aortic stenosis (AS) and transthyretin cardiac amyloidosis (ATTR-CA) increases with age. Dual disease (AS+myocardial ATTR-CA) occurs in significant proportion of patients undergoing surgical aortic valve replacement (SAVR). OBJECTIVES: This study aimed to determine the prevalence of ATTR-CA in severe AS in the Indian population, identify noninvasive predictors of its diagnosis, and understand its impact on prognosis. METHODS: Symptomatic severe AS patients aged ≥65 years undergoing SAVR were enrolled. ATTR-CA diagnosis was based on preoperative 99m-technetium pyrophosphate (PYP) scan and intraoperatively obtained basal interventricular septum biopsy for myocardial ATTR-CA, and excised native aortic valve for isolated valvular ATTR-CA. Primary amyloidosis was excluded by serum/urine protein electrophoresis with serum immunofixation. RESULTS: SAVR was performed in 46 AS patients (age 70 ± 5 years, 70% men). PYP scan was performed for 32 patients, with significant PYP uptake in 3 (n = 3 of 32, 9.4%), suggestive of myocardial ATTR-CA. On histopathological examination, none of the interventricular septum biopsy specimens had amyloid deposits, whereas 33 (71.7%) native aortic valves showed amyloid deposits, of which 19 (57.6%) had transthyretin deposition suggestive of isolated valvular amyloidosis. Noninvasive markers of dual disease included low myocardial contraction fraction (median [interquartile range], 28.8% [23.8% to 39.1%] vs 15.3% [9.3% to 16.1%]; P = 0.006), deceleration time (215 [144 to 236] ms vs 88 [60 to 106] ms; P = 0.009) and global longitudinal strain (-18.7% [-21.1% to -16.9%] vs -14.2% [-17.0% to -9.7%]; P = 0.030). At 1-year follow-up, 2 patients died (4.3%); 1 each in myocardial ATTR-CA negative and positive groups (3.4% vs 33.3%; P = 0.477). CONCLUSIONS: Dual disease is not uncommon in India. Isolated valvular amyloidosis in severe AS is much more common.

A Review of the Surgical Management of Aorto-ventricular Tunnels.

We present a synthesis of 95 published investigations of the exceedingly rare tunnels that can exist between the aortic root and the left or right ventricles. From the 220 suitable cases included in these investigations, we reviewed the clinical presentations, modalities used for diagnosis, surgical approaches, and outcomes. Diagnostic information was provided by clinical presentation, radiographic findings, saline contrast echocardiography, computed tomographic angiocardiography, magnetic resonance imaging, cardiac catheterization, and angiocardiography. These techniques elucidated the coronary arterial origins and associated defects and defined the disease before surgery. Patients occasionally present with an asymptomatic cardiac murmur and cardiomegaly, but most suffer cardiac failure in the first year of life when the tunnel enters the left ventricle. Antenatal diagnosis by fetal echocardiography is reliable after 18 weeks of gestation. Associated defects, involving the proximal coronary arteries or the aortic or pulmonary valves, are present in nearly half the cases. Prompt diagnosis and surgical repair are important for a favorable outcome. Overall, operative mortality has been cited to be between 3% and 8.3%. Associated congenital coronary arterial anomalies, residual severe aortic stenosis, poor left ventricular function, and rupture of an infected suture line have been the reported causes of death. Despite early surgical intervention, an incidence of 16% to 60% postoperative residual aortic regurgitation of varying severity has been reported. The requirement of further repair or replacement of the aortic valve ranges from 0% to 50%. We submit that an increased appreciation of these details relative to the tunnels will contribute to improved surgical management.

Total Pericardiectomy Using a Modified Left Anterolateral Thoracotomy Without Cardiopulmonary Bypass.

BACKGROUND: We sought to ascertain the short- and long-term results of total pericardiectomy for chronic constrictive pericarditis using a modified left anterolateral thoracotomy without cardiopulmonary bypass on postoperative low cardiac output, normalization of intracardiac pressures, survival, and reoperations. METHODS: Between January 2005 and December 2019 a series of 127 consecutive patients (91 male patients) between ages 4 and 72 years (median, 25 years; interquartile range, 18-38) underwent radical total pericardiectomy using a modified left anterolateral thoracotomy without cardiopulmonary bypass. RESULTS: Operative and late mortalities were 3.1% and 1.6%, respectively. Thirty-one patients (24.4%) had postoperative low cardiac output, and none required reoperations. At a median follow-up of 99 months (interquartile range, 56-141) the actuarial survival was 97.6% ± 0.01% months (95% confidence interval, 92.8-99.2). At their last follow-up 113 (93.4%) and 8 (6.6%) survivors were in New York Heart Association class I and II, respectively. CONCLUSIONS: Total pericardiectomy is associated with lower perioperative and late mortality and decreased low cardiac output syndrome and confers significant long-term advantage of superior hemodynamics.

Long-Term Outcomes of the Double-Barrel Technique for Superior Sinus Venosus Defect With Partially Anomalous Pulmonary Venous Connection.

BACKGROUND: Repair of superior sinus venosus defect with high partially anomalous pulmonary venous connection (PAPVC) using an intracardiac baffle may be complicated by systemic or pulmonary venous pathway obstruction and sinus nodal dysfunction (SND). Our surgical strategy for repair of all types of superior sinus venosus defect has evolved chiefly to avoid the abovementioned complications and preserving the growth potential of the superior cavoatrial junction. METHODS: Between 2007 and 2019, fifty consecutive patients aged 2 to 60 (mean, 17.6±16.7) years underwent repair of superior sinus venosus defect using the double-barrel technique as described. The anomalous pulmonary veins drained into the superior cavoatrial junction in 17 patients and more than 2 cm above the cavoatrial junction in 33 patients. RESULTS: There were no early or late deaths and no reoperations. At a mean follow-up of 103.9 (±50.2) months, all survived the operation, and actuarial freedom from SND was 97.9% (±standard error, 0.02%; 95% CI: 0.86-0.99). No patient had systemic or pulmonary venous pathway obstruction. A permanent pacemaker was required in one (2%) patient for sick sinus syndrome. CONCLUSIONS: The double-barrel method is an expedient, safe, and effective technique in superior sinus venosus defect. It provides dual drainage of superior vena cava preserving the superior cavoatrial junction without causing systemic or pulmonary venous pathway obstruction and can be utilized in all cases including those with high PAPVC. Preservation of the cavoatrial junction and use of autogenous atrial tissue for systemic venous pathway avoids SND and preserves growth potential.

A Review of the Surgical Management of Anomalous Connection of the Right Superior Caval Vein to the Morphologically Left Atrium and Biatrial Drainage of Right Superior Caval Vein.

The present perspective is a synthesis of published investigations in the setting of anomalous connection of the right superior caval vein to the morphologically left atrium or biatrial drainage of the right caval vein. We identified 57 suitable cases from 97 investigations, reviewing the clinical presentation, diagnostic modalities utilized, surgical techniques used, and their outcomes. Clinical presentation, radiographic findings, saline contrast echocardiography, computed tomographic angiocardiography, radionuclide perfusion scan, magnetic resonance imaging, and angiocardiography provided the diagnostic information and were used to define the disease entities before surgery. We have also addressed several issues concerning the influence of the so-called heterotaxy: the establishment of the diagnosis, the variation in clinical presentation, and subsequent management. For the overall group of patients undergoing either surgical intervention or transcatheter treatment with an Amplatzer vascular plug, the operative mortality remains high at 9.5%. We submit that an increased appreciation of these disease entities will contribute to improved future surgical management.

Histologic Abnormalities of the Ascending Aorta: Effects on Aortic Remodeling after Intracardiac Repair of Tetralogy of Fallot.

We evaluated aortic tissue specimens from patients undergoing tetralogy of Fallot repair, to determine whether histologic abnormalities affect postsurgical aortic remodeling and other patient-related variables. Using light microscopy, we studied full-thickness aortic wall tissue operatively excised from 118 consecutive patients undergoing intracardiac repair of tetralogy of Fallot. We performed multiple linear regression analysis to identify independent predictors of change in aortic root dimensions, which we measured with echocardiography after repair and every 3 months thereafter. Thirty histologically normal specimens were used as controls. Elastic fiber fragmentation was found in 74.6% of the abnormal specimens, mucoid extracellular matrix accumulation in 49.2%, smooth muscle cell nuclei loss in 39%, smooth muscle cell disorganization in 28.8%, and medial fibrosis in 52.5%. At a mean follow-up time of 83.55 ± 42.08 months, mean aortic sinotubular diameter decreased from 28.79 ± 9.15 to 27.16 ± 8.52 mm/m2 (r =-0.43; P <0.001). Aortic sinotubular diameter decreased by 0.6 mm/m2 among females (ß =0.6, SE=0.31; P =0.05) and by 0.88 mm/m2 in patients who had elastic fiber fragmentation or loss (ß =0.88, SE=0.38; P =0.02). In bivariate and multiple linear regression analysis, duration of follow-up emerged as an independent predictor of aortic remodeling. The aortic histopathologic changes in our patients had an independent negative impact on the degree of aortic remodeling after surgery. We observed the most improved aortic sinotubular diameter in patients who had either histologically normal aortas or aortas with elastic fragmentation.

A Review on the Surgical Management of Subvalvular Aneurysm.

The present perspective is a synthesis of published investigations in the setting of subvalvular aortic aneurysms. We identified 75 investigations and reviewed the clinical presentation, diagnostic modalities used, surgical techniques employed, and their outcomes. Clinical presentation, radiographic findings, transthoracic and transesophageal echocardiography, electrocardiogram-gated computerized tomography, and magnetic resonance imaging provided the diagnostic information and were used to define the disease entity before surgery. In this article, we have attempted to address several issues concerning establishment of diagnosis, varied clinical presentation, and their management. We submit that an increased appreciation of this disease entity will contribute to improved surgical management.

Aortic Root Enlargement and Aortic Valve Replacement for Calcified Supravalvular and Valvular Aortic Stenosis in Homozygous Familial Hypercholesterolemia: A Case Report.

Familial homozygous hypercholesterolemia is a rare disease with diverse clinical presentations ranging from premature ischemic heart disease to aortic root stenosis but rarely presents with anginal symptoms due to supravalvular and valvular aortic stenosis. We report a 19-year-old male patient with familial homozygous hypercholesterolemia with progressive supravalvular and valvular aortic stenosis that ultimately required aortic root enlargement and aortic valve replacement using a mechanical prosthesis, despite aggressive medical therapy. Surgical importance of this rare condition is highlighted.

Successful Use of Intra-aortic Balloon Counterpulsation for Systemic Ventricular Failure Following Total Pericardiectomy for Calcific Chronic Constrictive Pericarditis.

We report two male patients aged 18 and 19 years, respectively, undergoing total pericardiectomy for chronic calcific constrictive pericarditis who developed systemic ventricular failure unresponsive to medical management following surgery. The failing circulation was successfully reestablished using intra-aortic balloon counterpulsation. Aortic counterpulsation facilitates recovery of ventricular function and appears to be a reasonable alternative in select instances of refractory cardiac failure following pericardiectomy.

Bentall's Procedure for Annuloaortic Ectasia and Severe Aortic Regurgitation in a Patient With Repaired Tetralogy of Fallot and Aortic Valvular Reconstruction.

A 21-year-old female patient with repaired tetralogy of Fallot and aortic valvular reconstruction with aneurysmal aortic root and severe aortic regurgitation underwent aortic root replacement. Intrinsic aortopathy in tetralogy of Fallot and its surgical importance are highlighted.

Histopathology of the right ventricular outflow tract and the relation to hemodynamics in patients with repaired tetralogy of Fallot.

OBJECTIVE: To evaluate the relationship between myocardial histopathology and tissue Doppler imaging (TDI) variables of the right ventricle and postoperative peak systolic right-to-left ventricular pressure ratio (Prv/Plv) in patients undergoing intracardiac repair for tetralogy of Fallot (TOF). METHODS: Operatively resected crista supraventricularis muscle specimens from 93 patients undergoing intracardiac repair for TOF, aged 18 months to 26 years (mean, 7.02 ± 5.35 years) were subjected to light microscopy. TDI-derived parameters between the normal and abnormal categories of myocardium, the evolution of Prv/Plv, and its relationship to TDI-derived variables were tested using generalized linear random effects model using xtreg command. RESULTS: The incidence of myocyte hypertrophy, myocytolysis, and perivascular fibrosis was 89.2%, 83.8%, and 77.4%, respectively. Although tricuspid annular peak systolic excursion, peak myocardial velocity during systole (s'), and early diastolic basal lengthening of right ventricle (e') continued to improve among patients with myocardial hypertrophy, myocytolysis, and perivascular fibrosis, there was an absence of improvement of the late diastolic relaxation of right ventricular free wall (a') in patients with perivascular fibrosis. Although there was improvement of postoperative Prv/Plv in patients with myocardial fibrosis as compared with normal histology, the values were not statistically significant (ß [standard error] -0.07 [0.08], P = .3). CONCLUSIONS: The great majority of myocardial tissues in cyanotic TOF indicate pre-existing hypertrophic, degenerative, and fibrotic changes. Perivascular fibrosis affects the diastolic compliance of the right ventricle and may account for the absence of improvement of late diastolic relaxation (a') and greater postoperative Prv/Plv in the absence of a residual surgical lesion.

Effect of goal-directed therapy on post-operative neutrophil gelatinase-associated lipocalin profile in patients undergoing on-pump coronary artery surgery.

PURPOSE: Neutrophil gelatinase-associated lipocalin (NGAL) is an early biomarker of acute kidney injury (AKI). Goal-directed therapy (GDT) in on-pump coronary artery bypass grafting (CABG) has been associated with lower post-operative NGAL levels in recent studies. The present study aimed at comparing plasma (P) and urinary (U)-NGAL levels following the use of GDT versus conventional haemodynamic therapy (CT) in patients undergoing on-pump CABG. METHODS: A prospective randomised controlled study conducted in a single university hospital. A total of 54 patients in the GDT group and 56 patients in CT group after exclusions. RESULTS: U-NGAL was significantly lower immediately post-surgery (T 1) in GDT group (25.11 ± 1.5 versus 27.80 ± 1.7 µg/L; p < 0.001) and at 4 h (T 2) (38.19 ± 23.6 versus 52.30 ± 28.3 µg/L; p = 0.006) and at 24 h post-operatively (T 3) (34.85 ± 14 versus 39.7 ± 11.1 µg/L; p = 0.047). P-NGAL was comparable between groups at T 1 but lower in the GDT group at T 2 (92.81 ± 4.8 versus 94.77 ± 4.5 µg/L; p = 0.03) and T 3 (67.44 ± 3.7 versus 75.96 ± 5.3 µg/L; p < 0.001). U-NGAL levels correlated well with the peak post-operative creatinine as compared to P-NGAL. On-pump patients manifest neutrophil activation, accounting for comparable levels of P-NGAL in the two groups at T 1. GDT-based haemodynamic management resulted in lower U-NGAL levels at T 1, T 2 and T 3 and lower P-NGAL levels at T 2 and T 3. CONCLUSIONS: Haemodynamic optimisation with GDT prevents further renal insult initiated with the inflammatory activation with cardiopulmonary bypass (CPB), as evidenced by lower post-operative U-NGAL levels.

Randomized Controlled Trial of Heparin Versus Bivalirudin Anticoagulation in Acyanotic Children Undergoing Open Heart Surgery.

OBJECTIVE: To determine the safety and efficacy of bivalirudin as an anticoagulant for pediatric open heart surgery (OHS) and to determine its appropriate dosage for this purpose. DESIGN: Prospective, randomized controlled trial. SETTING: Tertiary care hospital. PARTICIPANTS: Fifty acyanotic children aged 1-12 years undergoing OHS. INTERVENTIONS: The children were randomized to receive either 4 mg/kg of heparin (n = 25, group H) or 1 mg/kg of bivalirudin bolus followed by 2.5 mg/kg/h infusion (n = 25, group B) as the anticoagulant. The doses were adjusted to maintain activated clotting time (ACT) above 480 seconds. At the conclusion of surgery, protamine (1.3 mg/100 U of heparin) was administered to children in group H. MEASUREMENTS AND MAIN RESULTS: The children were comparable in both groups with regard to demographic characteristics. The mean age and weight were 51.5 months and 13.4 kg in group H, and 59.3 months and 13.4 kg in group B. The dose of anticoagulant required was 4.0 ± 0.2 mg/kg in group H and 1.7 ± 0.2 mg/kg followed by 3.0 ± 0.7 mg/kg/h infusion in group B (p < 0.001). One child in group H required an additional dose compared to 13 (54.2%) children in group B. Intraoperatively, the ACT achieved was higher in group H compared to group B (p < 0.05). The ACT returned to baseline value after protamine administration in group H, but it remained elevated for 2 hours after termination of cardiopulmonary bypass (CPB) in group B (p < 0.01). The ACT was higher in group B compared to group H for 6 hours after termination of CPB (p < 0.05). Heparin prolonged the onset of clotting, decreased the rate and strength of thrombus formation, and inhibited platelet function to a greater extent than bivalirudin on viscoelastic coagulation testing. The total duration of surgery was prolonged in group B. The postoperative chest tube drainage was similar in group B (4.9 mL/kg) as in group H (5.9 mL/kg) in spite of higher ACT. The transfusion requirements were similar. No adverse event occurred in any patient. CONCLUSION: Bivalirudin is a safe and effective anticoagulant for pediatric OHS. Though it is not suitable as a routine anticoagulant for this purpose, it may be used as a heparin alternative in instances when heparin cannot be used. The dose required to maintain ACT for more than 480 seconds was 1.7 ± 0.2 mg/kg followed by 3.0 ± 0.7 mg/kg/h infusion. The ACT remained elevated for 2 hours after stopping the infusion. Bivalirudin did not increase postoperative bleeding and transfusion requirement.