Factor XIII levels, clot strength, and impact of fibrinogen concentrate in infants undergoing cardiopulmonary bypass: a mechanistic sub-study of the FIBCON trial.

BACKGROUND: Acquired factor XIII (FXIII) deficiency after major surgery can increase postoperative bleeding. We evaluated FXIII contribution to clot strength and the effect of fibrinogen concentrate administration on FXIII activity in infants undergoing cardiac surgery using cardiopulmonary bypass. METHODS: We conducted a prospectively planned, mechanistic sub-study, nested within the Fibrinogen Concentrate Supplementation in the Management of Bleeding During Paediatric Cardiopulmonary Bypass: A Phase 1B/2A, Open-Label Dose Escalation Study (FIBCON) trial, which investigated fibrinogen concentrate supplementation during cardiopulmonary bypass (ISRCTN: 50553029) in 111 infants (median age 6.4 months). The relationships between platelet number, fibrinogen concentration, and FXIII activity with rotational thromboelastometry clot strength (EXTEM-MCF) in blood taken immediately before cardiopulmonary bypass and after separation from bypass were estimated using multivariable linear regression. Changes in coagulation variables over time were quantified using a generalised linear model comparing three groups: fibrinogen concentrate-supplemented infants, placebo, and a third cohort with lower bleeding risk. RESULTS: Overall, 48% of the variability (multivariable R2) in EXTEM-MCF clot strength was explained by three factors: the largest contribution was from FXIII activity (partial R2=0.21), followed by platelet number (partial R2=0.14), and fibrinogen concentration (partial R2=0.095). During cardiopulmonary bypass, mean platelet count fell by a similar amount in the three groups (-36% to -41%; interaction P=0.98). Conversely, fibrinogen concentration increased in all three groups: 132% in the fibrinogen concentrate-supplemented group, 26% in the placebo group, and 51% in the low-risk group. A similar increase was observed for FXIII activity (61%, 23%, and 25%, respectively; interaction P<0.0001). CONCLUSIONS: FXIII contribution to clot strength is considerable in infants undergoing cardiac surgery. Fibrinogen concentrate supplementation also increased FXIII activity, and hence clot strength. CLINICAL TRIAL REGISTRATION: ISRCTN: 50553029.

Early superior cavopulmonary connection with preoperative computer tomography shows comparable outcomes for infants following Norwood palliation.

OBJECTIVES: There is increasing evidence that performing superior cavopulmonary connection (SCPC) at 3 months reduces mortality: reducing the risky 'interstage' period, volume off-loading the ventricle and reducing coronary steal, hopefully preserving ventricular function. Our objective was to describe our experience of early SCPC with preoperative computer tomography (CT) assessment compared to later connection at 6 months. METHODS: Patients undergoing Norwood procedure from 2005 to 2020 were divided into 2 eras were described and compared. Era 1 from 2005 to 2016 when SCPC was undertaken at 6 months: and era 2 (2017-2020) when an earlier operation was performed. Demographics, mortality (interstage, early and late following SCPC) and data on postoperative course and complications were recorded. RESULTS: In era 1, 191 patients underwent Norwood (120 survivors to SCPC) and 28 patients (23 survivors) in era 2. There were no significant differences in the demographics. Interstage mortality was 17.8% in era 1 and 8.0% in era 2 but not significantly significant (P = 0.22). The median (interquartile range) age at pre-imaging and SCPC was significantly lower: 99 (81-120) vs 77 (47-102) days and 175 (117-208) vs 106 (102-122) days in era 1 vs era 2 (P < 0.005). Weight was lower at SCPC in era 2 [mean (standard deviation) 6.2 kg (1.2) vs 5.1 kg (0.8), P < 0.05]. Intubation time and total length of stay were not statistically different. Median intensive care unit stay was statistically significantly longer, but not clinically significant: 2.5 (2-4) vs 3 (3-5) days, respectively (P < 0.05). There was no significant difference in early or late mortality, rates of diagnostic or interventional catheter, postoperative magnetic resonance imaging/CT or stroke. Logistic regression analysis demonstrates increasing age at SCPC was associated with increased chance of stroke or early death (P = 0.043). CONCLUSIONS: Early SCPC with CT assessment is feasible and although intensive care unit length of stay was slightly longer there was no change in the overall length of stay and no change in postoperative mortality or complications.

Unlocking the Non-invasive Assessment of Conduit and Reservoir Function in the Aorta : The Obstructive Descending Aorta in HLHS.

Aortic surgeries in congenital conditions, such as hypoplastic left heart syndrome (HLHS), aim to restore and maintain the conduit and reservoir functions of the aorta. We proposed a method to assess these two functions based on 4D flow MRI, and we applied it to study the aorta in pre-Fontan HLHS. Ten pre-Fontan HLHS patients and six age-matched controls were studied to derive the advective pressure difference and viscous dissipation for conduit function, and pulse wave velocity and elastic modulus for reservoir function. The reconstructed neo-aorta in HLHS subjects achieved a good conduit function at a cost of an impaired reservoir function (69.7% increase of elastic modulus). The native descending HLHS aorta displayed enhanced reservoir (elastic modulus being 18.4% smaller) but impaired conduit function (three-fold increase in peak advection). A non-invasive and comprehensive assessment of aortic conduit and reservoir functions is feasible and has potentially clinical relevance in congenital vascular conditions.

Contemporary surgical outcome and symptomatic relief following vascular ring surgery in children: effect of prenatal diagnosis.

OBJECTIVES: Our goal was to describe postoperative complications and outcomes in a large contemporary cohort of children with an isolated double aortic arch (DAA) or a right aortic arch (RAA) with left arterial ligament and to assess the impact of foetal diagnosis on outcomes. METHODS: We performed a retrospective analysis of all patients who underwent surgery for DAA or RAA with left arterial ligament between 2005 and 2019. RESULTS: A total of 132 children were operated on for a DAA (n = 77) or a RAA (n = 55). Prenatal diagnosis was made in 100/132 (75.8%). Median age at surgery for DAA was 5.0 (1.7-13.3) months and for RAA was 13.9 (6.4-20.1) months. There was no difference in the age at surgery between the prenatal and postnatal cases (8.6 [4.0-15.6] vs 5.4 months [1.8-17.7]; P = 0.37). No surgical deaths occurred. Vocal cord palsy was the most common complication, occurring in 12/132 (9%): of these, 11 resolved spontaneously and 1 required a temporary tracheostomy. Logistic regression demonstrated that older age at operation was the only predictor for a postoperative complication (P = 0.02). Overall, 21/67 (31%) of prenatally detected, symptomatic cases reported residual symptoms/signs 1 year after surgery compared to 18/28 (64%) of postnatally detected cases. Postnatal diagnosis was associated with persistent postoperative symptoms/signs [P = 0.006, odds ratio = 3.9 (95% confidence interval 1.5-9.4)]. CONCLUSIONS: Surgery to relieve a vascular ring resolves trache-oesophageal compressive symptoms in most cases, but parents/patients should be aware that symptoms/signs may persist in the first postoperative year despite effective release of the vascular ring. Earlier surgery and prenatal diagnosis may improve outcomes.

Multisite Veno-Venous Cannulation for Neonates and Nonambulatory Children.

OBJECTIVES: Neonates with respiratory failure are ideally supported with veno-venous rather than veno-arterial extracorporeal membrane oxygenation due to the reduced rate of neurologic complications. However, the proportion of neonates supported with veno-venous extracorporeal membrane oxygenation is declining. We report multisite veno-venous extracorporeal membrane oxygenation, accessing the neck, returning to the inferior vena cava via the common femoral vein in neonates and children less than 10 kg. DESIGN: Retrospective case series with 1 year minimum follow-up. PATIENTS: Patients less than 10 kg supported with veno-venous extracorporeal membrane oxygenation accessing the jugular and returning to the femoral vein. SETTING: A 30-bed pediatric intensive care delivering extracorporeal membrane oxygenation to approximately 20 children annually. INTERVENTIONS: Veno-venous extracorporeal membrane oxygenation accessing the jugular and returning to the femoral vein was delivered using two single lumen cannulae. MEASUREMENTS AND MAIN RESULTS: January 2015 to August 2019, 11 patients underwent veno-venous extracorporeal membrane oxygenation accessing the jugular and returning to the femoral vein with median weight of 3.6 kg (interquartile range 2.8-6.1 kg), and median corrected gestational age of 13 days (interquartile range, 2-175 d). The smallest patient weighed 2.1 kg. Seven patients had comorbidities. Extracorporeal membrane oxygenation was technically successful in all patients with median flows of 126 mL/kg/min (interquartile range, 120-138 mL/kg/min) and median arterial oxygenation saturation of 94% (interquartile range, 91-98%) at 24 hours. Nine survived to home discharge, and two were palliated. Common femoral vein occlusion was observed in all patients on ultrasound post decannulation. There was no clinical or functional deficit in the cannulated limb at follow-up, a minimum of 1 year post extracorporeal membrane oxygenation. CONCLUSIONS: Veno-venous extracorporeal membrane oxygenation accessing the jugular and returning to the femoral vein was performed safely in patients under 10 kg with the smallest patient weighing 2.1 kg. Although occlusion of the common femoral vein was observed in patients post decannulation, subsequent follow-up demonstrated no clinical implications. We challenge current practice that veno-venous extracorporeal membrane oxygenation accessing the jugular and returning to the femoral vein cannot be performed in nonambulatory patients and suggest that this strategy is preferred over veno-arterial extracorporeal membrane oxygenation in infants requiring extracorporeal membrane oxygenation for respiratory failure.

Coronary aneurysms, myocardial dysfunction, and shock in a COVID-19 child, role of ECMO, immunomodulation, and cardiac CT.

Coronary artery aneurysms in children were observed as a rare complication associated with coronavirus disease 2019 (COVID-19). This case report describes the severe end of the spectrum of the new multisystem inflammatory syndrome in a 12-year-old child with coronary aneurysms, myocardial dysfunction, and shock, managed successfully with extracorporeal membrane oxygenation support and immunomodulation therapy. This report also highlights the additional benefits of cardiac CT in the diagnosis and follow-up of coronary aneurysms.

Application of the Boston Technical Performance Score to intraoperative echocardiography.

BACKGROUND: The Technical Performance Score (TPS) developed by Boston Children's Hospital showed surgical outcomes correlate with adequacy of technical repair when implemented on pre-discharge echocardiograms. We applied this scoring system to intraoperative imaging in a tertiary UK congenital heart surgical centre. METHODS: After a period of training, intraoperative TPS (epicardial and/or transesophageal echocardiography) was instituted. TPS was used to inform intraoperative discussions and recorded on a custom-made database using the previously published scoring system. After a year, we reviewed the feasibility, results and relationship between the TPS and mortality, extubation time and length of stay. RESULTS: From 01 September 2015 to 04 July 2016, there were 272 TPS procedures in 251 operations with 208 TPS recorded. Seven patients had surgery with no documented TPS, three had operations with no current TPS score template available. Patients left the operating theatre with TPS optimal in 156 (75%), adequate 34 (16%) and inadequate 18 (9%). Of those with an optimal score on leaving theatre, ten had more than one period of cardiopulmonary bypass. All four deaths <30 days after surgery (1.9%) had optimal TPS. There was a statistically significant difference in extubation times in the RACHS category 4 patients (3 days vs 5 days, P < 0.05) and in PICU and total length of stay in the RACHS category three patients (2 and 8 days vs 12.5 and 21.5 days respectively) if leaving theatre with an inadequate result. CONCLUSIONS: Application of intraoperative TPS is feasible and provides a way of objectively recording intraoperative imaging assessment of surgery. An 'inadequate' TPS did not predict mortality but correlated with a longer ventilation time and longer length of stay compared to those with optimal or adequate scores.

Ventricular function and vascular dimensions after Norwood and hybrid palliation of hypoplastic left heart syndrome.

OBJECTIVE: Norwood and hybrid procedure are two options available for initial palliation of patients with hypoplastic left heart syndrome (HLHS). Our study aimed to assess potential differences in right ventricular (RV) function and pulmonary artery dimensions using cardiac magnetic resonance (CMR) in survivors with HLHS. METHODS: 42 Norwood (mean age 2.4±0.8) and 44 hybrid (mean age 2.0±1.0 years) patients were evaluated by CMR after stage II palliation prior to planned Fontan completion. Initial stage I Norwood procedure was performed using a modified Blalock-Taussig shunt, while the hybrid procedure consisted of bilateral pulmonary artery banding and arterial duct stenting. Need for reinterventions and subsequent outcomes were also assessed. RESULTS: Norwood patients had larger RV end-diastolic dimensions (91±23 vs 80±31 mL/m2, p=0.004) and lower heart rate (90±15 vs 102±13, p<0.001) than hybrid patients. Both Norwood and hybrid patients showed preserved global RV pump function (59±9 vs 59%±10%, p=0.91), while RV strain, strain rate and intraventricular synchrony were superior in the Norwood group. Pulmonary artery size was reduced (lower lobe index 135±74 vs 161±62 mm2/m2, p=0.02), and reintervention rate was significantly higher in the hybrid group whereas subsequent outcome did not differ significantly (p=0.24). CONCLUSIONS: Norwood and hybrid strategy were associated with equivalent and preserved global RV pump function while development of the pulmonary arteries and reintervention rate were superior using the Norwood approach. Impaired RV myocardial deformation as a potential marker of early RV dysfunction in the hybrid group may have a negative long-term impact in this population.

Is the medical treatment for arterial hypertension after primary aortic coarctation repair related to age at surgery? A retrospective cohort study.

BACKGROUND: Hypertension following primary coarctation repair affects up to a third of subjects. A number of studies suggest that future hypertension risk is reduced if primary repair is performed at a younger age. OBJECTIVES: The objective of this study was to evaluate the risk of future medical treatment for hypertension depending on age of primary coarctation repair. METHODS: This study was carried out at a tertiary paediatric cardiology referral centre. Retrospective database evaluation of children aged 28 days and ⩽12 months), and children (>12 months). Main outcome measure is the need for long-term anti-hypertensive medication. The risk for re-coarctation was also evaluated. RESULTS: A total of 87 patients were analysed: 60 neonates, 17 infants, 10 children. Among them, 6.7% neonates, 29.4% infants, and 40% children required long-term anti-hypertensive medications. Group differences were statistically significant (p=0.004). After adjustment for type of repair, the risk of long-term anti-hypertensive therapy was 4.5 (95% confidence interval 1.2-16.9, p=0.025) and 10.5 times (95% confidence interval 2.6-42.3, p=0.001) higher if primary repair was carried out in infancy and childhood, respectively, compared with neonates. Among all, 13 patients developed re-coarctation: 21.7% in the neonatal group, 5.9% in the infant group, and 20% in the child group. We could not demonstrate a significant difference between these proportions or calculate a reliable risk for developing re-coarctation. CONCLUSIONS: Risk of medical treatment for hypertension was lowest when primary repair was carried out during the neonatal period, rising 10-fold if first operated on as a child. Knowing the likelihood of hypertension development depending on age of primary repair is useful for long-term surveillance and counselling.

Hybrid Procedure for Neonates With Hypoplastic Left Heart Syndrome at High-Risk for Norwood: Midterm Outcomes.

BACKGROUND: Hybrid procedure offers patients with severe congenital heart disease an alternative initial procedure to conventional surgical reconstruction. We report the midterm outcomes of a cohort of neonates who had a hybrid procedure for variants of hypoplastic left heart syndrome because they were at high risk for the Norwood procedure. METHODS: Between December 2005 and January 2013, 41 neonates underwent bilateral pulmonary artery banding followed by ductal stenting by means of a sternotomy at a median age of 6 days (range, 2 to 18 days) and weight of 2.6 kg (range, 1.5 to 3.7 kg). Thirty-five patients had hypoplastic left heart syndrome, and 6 patients had critical aortic stenosis with hypoplastic left ventricle. Primary indications for the hybrid procedure were low birth weight in 17 patients, hypoplastic left ventricle with the possibility of later biventricular repair in 6 patients, intact or near-intact atrial septum in 5 patients, and poor patient condition in 13 patients. Echocardiographic, angiographic, operative, and clinical data were reviewed. Outcomes were summarized with descriptive statistics and risk factors for mortality identified. RESULTS: All but 6 patients had an antenatal diagnosis, and 24 patients were from other congenital cardiac centers. Nine patients had perioperative balloon aortic valvuloplasty, 1 patient had fetal balloon aortic valvuloplasty, and 17 patients had intervention to their atrial septum (41.4%). There were 9 inpatient deaths (21.9%) and 4 interstage deaths (9.8%) after the hybrid procedure. Twenty-eight patients subsequently underwent either the Norwood procedure (11 patients), combined stage I and II (14 patients), or biventricular repair (3 patients). No patient had heart transplantation. Among the patients who had combined stage I and II as a second procedure after the hybrid procedure, there were 2 early deaths, 1 late death before the Fontan, and 1 late death after the Fontan completion after combined stage I and II. All patients who had subsequent Norwood procedure were midterm survivors. Three of the 4 patients who had biventricular repair were midterm survivors. Overall survival was 56.1% at a median follow-up of 32.0 months. By univariate analysis, patient factors, intact or near-intact atrial septum, and aortic atresia were associated with nonsurvival. CONCLUSIONS: Hybrid procedure as an alternative to the Norwood procedure offers good midterm survival in patients deemed at high risk for neonatal reconstruction.

Second stage after initial hybrid palliation for hypoplastic left heart syndrome: Arterial or venous shunt?

OBJECTIVE: Hybrid palliation for hypoplastic left heart syndrome has been developed as an alternative to neonatal Norwood surgery. At the second stage, a source of pulmonary blood flow has to be established. Options include an arterial modified Blalock-Taussig or a venous superior cavopulmonary shunt. METHODS: We retrospectively reviewed patients who received second-stage palliation after the initial hybrid. Patients were stratified according to the source of pulmonary blood supply into the arterial shunt (n = 17 patients) or venous shunt (n = 26 patients). RESULTS: Age and weight at second stage were lower in the arterial group (85 [45-268] days vs 152.5 [61-496] days, P = .001 and 3.6 [2.7-9.4] kg vs 5.1 [2.97-9.4] kg, P = .001, respectively). All recorded surgical times were shorter in the arterial group. Mechanical ventilation and intensive care stay were shorter in the venous group (5.82 [2.01-14.9] days vs 2.42 [0.56-13.67] days, P = .005 and 8.5 [3.6-23.7] vs 5.75 [0.8-17.6] days, P = .036, respectively) There was no difference in mortality (2/17 vs 5/26; P = .685) or incidence of complications between the 2 groups. There was a tendency toward a higher need for intervention in the immediate postoperative period in the venous group, but this did not reach significance (6/17 vs 13/26, P = .342). The arterial group has shown better development of the branch pulmonary arteries with a higher lower lobe index (158.38 ± 39.43 mm(2)/m(2) vs 113.33 ± 43.96 mm(2)/m(2), respectively, P = .037). CONCLUSIONS: Both arterial and venous shunts are viable options with mortality and morbidity results comparable to those in the literature. The arterial shunt pathway (2-stage Norwood I) may offer better pulmonary arterial growth than the venous shunt (comprehensive/combined Norwood I and II).

Technical and anatomical factors affecting the size of the branch pulmonary arteries following first-stage Norwood palliation for hypoplastic left heart syndrome.

OBJECTIVES: Branch pulmonary artery (BPA) size is one of the factors that influence the efficacy of the Fontan circulation. Central pulmonary artery stenosis and small left pulmonary artery (LPA) are well-known problems following Norwood palliation for hypoplastic left heart syndrome (HLHS). We investigated anatomical and technical factors that may stand behind these problems. METHODS: A total of 47 consecutive patients were included in the study. All had complete magnetic resonance imaging (MRI) study pre-second-stage palliation. Measurements were taken using a first-pass 3D angiography technique after intravenous injection of an extravascular contrast agent. Factors investigated included the following: size and site of the pulmonary artery bifurcation stump in relation to the Damus-Kaye-Stansel (DKS) anastomosis, interaortic distance/ratio (neoaorta to descending aorta distance/antero-posterior dimension of the chest) (IAD/IAR), distance from the under surface of the arch and the size of native aorta and pulmonary artery. IAD/IAR were compared between two different arch reconstruction techniques. RESULTS: Stenosis occurred either centrally, at the origin of the BPA, or more distally, in the mid-LPA (posterior to DKS). There was a significant lower incidence of central BPA stenosis when the pulmonary artery stump was placed in the mid-position compared with right/left position (26 vs 67%; P = 0.011). A more bulky pulmonary artery stump was also found in those patients with central BPA stenosis (186 vs 137 mm(2)/m(2); P = 0.047). The mid-LPA consistently showed antero-posterior compression (mean cranio-caudal diameter 3.82 mm vs mean antero-posterior diameter 3.07 mm, P < 0.001). Indexed mid-LPA area was only correlated with IAD/IAR (r = 0.49 and 0.51, P < 0.001). No correlation was shown with the distance to the under surface of the arch (r = 0.14, P = 0.37), again confirming antero-posterior compression of the LPA rather than cranio-caudal. In multivariable analysis, the only predictor of indexed mid-LPA area was the IAR (P < 0.001). There was no significant difference in the IAD or IAR between the two arch reconstruction techniques [mean IAD 15.5 vs 13.5 mm (P = 0.14)]; [mean IAR 0.17 vs 0.19 (P = 0.21)]. CONCLUSIONS: Of all studied factors, IAR and the size and position of the pulmonary artery bifurcation plays the main role in LPA growth and central BPA stenosis.

Self-expanding stent implantation in arterial duct during hybrid palliation of hypoplastic left heart syndrome: midterm experience with a specially designed stent.

AIMS: The lack of a specifically designed stent for the arterial duct has led to the off-label use of stents during hybrid palliation of hypoplastic left heart syndrome (HLHS). We evaluated the implantation and performance of a specially designed self-expanding stent in hybrid palliation of HLHS. METHODS AND RESULTS: We implanted 39 sinus-SuperFlex (SSF) stents in 24 patients at a median age of seven days (range 2-27 days) and median weight of 2.85 kg (range 1.3-3.8 kg). A single stent was implanted in nine patients and two overlapping stents in 15 patients. There was one intraoperative death, not related to ductal stenting and one additional in-hospital death. During median follow-up of 137 days (range 38-522 days), nine patients required 11 interstage interventions. Four patients have undergone a biventricular repair, 11 have undergone the next stage of univentricular palliation and seven are awaiting a second-stage palliation. CONCLUSIONS: The SSF stent provides effective maintenance of ductal patency in patients undergoing hybrid palliation of HLHS and its variants. It conforms to the ductal anatomy but the lack of stents longer than 20 mm has required overlapping stents in longer ducts. This has not been of haemodynamic consequence.

Intra-abdominal pectus bar migration--a rare clinical entity: case report.

We present the case of a 20-year-old male who underwent successful surgical correction of pectus excavatum with the Highly Modified Ravitch Repair (HMRR). At 29 months the attempted operative removal of the Ravitch bar was unsuccessful despite the impression of adequate bar location on chest x-ray. Subsequent imaging with computed tomography was unclear in determining whether the bar was supra or infra-diaphragmatic due to the tissue distortion subsequent to initial surgery. Video assisted thoracoscopic surgery (VATS) successfully retrieved the bar and revealed that it was not in the thorax, but had migrated to the intra-abdominal bare area of the liver, with no evidence of associated diaphragmatic defect or hernia. Intra-abdominal pectus bar migration is a rare clinical entity, and safe removal can be facilitated by the use of the VATS technique.

Coronary embolization in bullet wounds: role of perioperative coronary angiography.

The management of patients presenting with signs of myocardial ischemia after a gunshot injury to the chest remains unclear. We report the case of 1 patient shot by a hunting weapon, presenting with clinical signs of tamponade and marked ST segment elevation. At the time of emergency exploration, no coronary lesions were seen. However, an emergency angiogram revealed acute occlusion of the right coronary artery by a pellet. Extraction was done on bypass. We believe that coronary angiography is necessary in case of pellet wounds to the chest presenting with signs of ischemia.

Morphometry of coronary capillaries in hypoplastic left heart syndrome.

BACKGROUND: Hypoplastic left heart syndrome is a condition characterized by a constellation of morphological malformations affecting the left side of the heart. We studied the capillary network, and quantified the capillarization of the ventricular myocardium, which, if different from normal, may have implications for the success of surgical reconstruction. METHODS: The capillaries were detected by immunohistochemistry using a monoclonal antibody (von Willebrand's factor) against the endothelium. Hearts with hypoplastic left heart syndrome have higher mean and maximal diffusion distances from any arbitrary point to the nearest capillary than normal hearts. RESULTS: There was no significant difference in the heterogeneity of capillary distribution between the hearts with hypoplastic left heart syndrome and the control heart. Increase in distance was found in both the right and left ventricles. CONCLUSIONS: Hearts with hypoplastic left heart syndrome show a reduction in the capillarization of both the right and left ventricles compared with age-matched controls. We believe this may be an inherent abnormality of hypoplastic left heart syndrome that may have implications for ventricular development.

The fibrous matrix of ventricular myocardium in hypoplastic left heart syndrome: a quantitative and qualitative analysis.

BACKGROUND: Controversy exists as to whether the right ventricle will be able to cope as the sole pumping chamber following a univentricular repair of hypoplastic left heart syndrome. The significance of the collagenous matrix on ventricular function has been studied extensively yet there is little information available on its quantity and quality in hypoplastic left heart syndrome. METHODS: We selected 23 specimens with hypoplastic left heart syndrome for anatomical study. Using a combination of morphometric analysis and scanning electron microscopy we analyzed the quantity and quality of the collagenous matrix. We compared the results with 16 age-matched controls. RESULTS: Hearts with hypoplastic left heart syndrome have significantly less collagen matrix than normal. The right ventricle has more collagen than the left and there is significant transmural variation. There was no difference in the ratio of the two main collagen subtypes or in the quality of the matrix. CONCLUSIONS: We believe this difference in fibrous matrix to be an inherent abnormality intrinsic to the malformation affecting not only the hypoplastic left but also the "normal" right ventricle. This in turn may have significant implications for the expected long-term outcome of reconstructive surgery.