Nelson Alphonso

Contrast enhanced micro-computed tomography resolves the 3-dimensional morphology of the cardiac conduction system in mammalian hearts.

The general anatomy of the cardiac conduction system (CCS) has been known for 100 years, but its complex and irregular three-dimensional (3D) geometry is not so well understood. This is largely because the conducting tissue is not distinct from the surrounding tissue by dissection. The best descriptions of its anatomy come from studies based on serial sectioning of samples taken from the appropriate areas of the heart. Low X-ray attenuation has formerly ruled out micro-computed tomography (micro-CT) as a modality to resolve internal structures of soft tissue, but incorporation of iodine, which has a high molecular weight, into those tissues enhances the differential attenuation of X-rays and allows visualisation of fine detail in embryos and skeletal muscle. Here, with the use of a iodine based contrast agent (I2KI), we present contrast enhanced micro-CT images of cardiac tissue from rat and rabbit in which the three major subdivisions of the CCS can be differentiated from the surrounding contractile myocardium and visualised in 3D. Structures identified include the sinoatrial node (SAN) and the atrioventricular conduction axis: the penetrating bundle, His bundle, the bundle branches and the Purkinje network. Although the current findings are consistent with existing anatomical representations, the representations shown here offer superior resolution and are the first 3D representations of the CCS within a single intact mammalian heart.

Gerbode's defect resulting from infective endocarditis

We present a report of a Gerbodes defect (left ventricular-right atrial communication) resulting from bacterial endocarditis in a 63-year-old man. Also presented is a brief overview of the literature and a possible preoperative echocardiographic diagnostic criterion relating to this unusual condition.

Assisted Fontan procedure: animal and in vitro models and computational fluid dynamics study

Fontan connection with intermittent compression by wrapped latissimus dorsi (LD) was tested in vivo, in vitro and by means of computational fluid dynamics (CFD). Experimental study: LD was conditioned in four pigs for three weeks before Fontan connection by valved conduit wrapped with LD. Mock circuit: Inflatable cuff wrapped around valved conduit provided intermittent external compression, with pressure and flow measured at driving pressure of 8 or 16 mmHg. CFD study: A circuit was tested for possible increase above basal flow (4 l/min) with intermittent external compression. Experimental study: Intermittent conduit compression by LD provided mean 7% decrease of baseline PA pressure, with simultaneous flow increase of 2%. Mock circuit: By raising the driving pressure from 8 to 16 mmHg, the flow increased with baseline PVR (56%) and with elevated PVR (80%). Total pulmonary flow was reduced during intermittent external compression with both baseline and elevated PVR. CFD study: Compression with 13.0 mmHg provided 4.9% increase of total pulmonary flow with substantial increase of the peak flow (92%). In vivo and in vitro, the increased flow produced by compressing a conduit was confounded by the inevitable intermittent flow restriction. Mathematical model using lower pressure for intermittent external compression showed potential for increase in pulmonary flow.

Mediastinal haemangiomas in children

A 5-month-old girl presented with upper airway obstruction and was found to have a mediastinal mass compressing the trachea. She successfully underwent resection of this mass, later confirmed to be a juvenile haemangioma. This case highlights mediastinal haemangiomas in the paediatric population as a diagnostic and therapeutic challenge, and the importance of a multidisciplinary approach in the management of such patients.

Multiple Ventricular Septal Defects: A New Strategy

Introduction: A multicenter prospective study was conducted to evaluate a new strategy for multiple Ventricular Septal Defects (VSDs). Materials and Methods: From 2004 to 2012 17 consecutive children (3 premature, 14 infants), mean age 3.2 months (9 days–9 months), mean body weight 4.2 kg (3.1–6.1 kg), with multiple VSDs underwent Pulmonary Artery Banding (PAB) with an adjustable FloWatch-PAB®. Associated cardiac anomalies included patent ductus arteriosus (1), aortic coarctation (2), hypoplastic aortic arch (2), and left isomerism (3). Five patients (5/17 = 29.4%) required pre-operative mechanical ventilation, with a mean duration of 64 days (7–240 days) Results: There were no early or late deaths during a mean follow-up of 48 months (7–98 months), with either FloWatch removal or last observation as end-points. FloWatch-PAB® adjustments were required in all patients: a mean of 4.8 times/patient (2–9) to tighten the PAB, and a mean of 1.1 times/patient (0–3) to release the PAB with the patient’s growth. After a mean interval of 29 months (8–69 months) 10/17 (59%) patients underwent re-operation: 7/10 PAB removal, with closure of a remaining unrestrictive VSD in 6 (peri-membranous in 3 patients, mid-muscular in 2, and inlet in 1) and Damus–Kaye–Stansel, bi-directional Glenn, and atrial septectomy in 1; 3/9 patients required only PAB removal. All muscular multiple VSDs had closed in all 10 patients. PA reconstruction was required in 1/10 patient. In 5/7 of the remaining patients with the PAB still in situ, all muscular VSDs had already closed. The only 2 patients with persistent muscular multiple VSDs are the 2 patients with the shortest follow-up. Conclusion: This reproducible new strategy with an adjustable PAB simplifies the management of infants with multiple VSDs and provides the following advantages: (a) good results (0% mortality), delayed surgery with a high incidence (15/17 = 88%) of spontaneous closure of multiple muscular VSDs, and facilitated closure of residual unrestrictive VSD (peri-membranous, mid-muscular, or inlet) at an older age and higher body weight; PAB with FloWatch-PAB® and its subsequent removal can potentially be the only procedure required for Swiss cheese multiple VSDs without an associated peri-membranous unrestrictive VSD.

Congenital Heart Disease Requires a Lifetime Continuum of Care: A Call for a Regional Registry

5 David Celermajer Q1 , MBBS, DSc, FRACP, FAA , Geoff Strange, PhD, 6 Rachael Cordina, MBBS, FRACP , Lisa Selbie, PhD, GAICD, 7 Gary Sholler, MBBS, FRACP, FCSANZ, FACC , 8 DavidWinlaw,MBBS,MD, FRACS , Nelson Alphonso, MBBS, FRCS, FRCSI , 9 Robert Justo, MBBS, FRACP , Mugur Nicholae, MD, FRACP , 10 Nadine Kasparian, PhD, MAPS , Robert G. Weintraub, MBBS, FRACP, 11 Michael Cheung, MBChB, MD, MRCP, (UK), FRACP, FCSANZ , 12 Leeanne E. Grigg, MBBS, FRACP, Christian P. Brizard, MD, 13 Gavin Wheaton, MBBS, FRACP , Patrick Disney, MBBS, FRACP, FCSANZ, 14 Simon Stewart, PhD, NFESC, FAHA, FCSANZ, 15 Andrew Bullock, MBBS, FRACP, FCSANZ , 16 James Ramsay, MBBS, MRCP, FRACP, FCSANZ , 17 Thomas Gentles, MD, FRACP , Yves D’Udekem, MD, PhD, FRACS n*

Cardiac catheter procedures during extracorporeal life support: a risk-benefit analysis.

Background: Extracorporeal life support (ECLS) is a valuable tool for situations in which cardiac disease acutely threatens the life of a child. Residual anatomic lesions have a strong negative influence on survival when ECLS is used after cardiac operations. Accurate diagnostic information is essential, and although noninvasive studies are preferred (eg, echocardiography and thoracic computed tomographic angiography), they are not always logistically practical nor adequate in complex situations under the loading and nonpulsatile flow conditions of ECLS. Methods: We analyzed our experience (February 2009 to August 2012) with cardiac ECLS for 59 children. Of the 59 children, 22 (median age and weight 19.5 days and 4 kg) with advanced cardiac dysfunction had catheter studies performed during support. Results: The 22 patients had 28 studies, without major adverse events relating to the procedure or transport. Problems leading to further therapeutic procedures (catheter based seven, hybrid two, or surgical eight) were discovered in 17 of the 22 patients. For 22 catheterized patients, total time on ECLS, weaning probability, and survival to discharge were 151.6 ± 122.6 hours, 81%, and 68%, respectively, similar to that for the 37 cardiac support patients not requiring catheter studies during support (P = 0.94, 0.37, and 0.59, respectively). Conclusion: Assuming that undiscovered anatomic and/or hemodynamic issues would have had a strong negative influence on survival, we may conclude that the risk–benefit ratio was positive and favorable. Catheter studies during ECLS are safe and should be performed expeditiously when diagnostic questions cannot be resolved by noninvasive means.

Complete atrioventricular septal defect: outcome of pulmonary artery banding improved by adjustable device.

OBJECTIVE We sought to evaluate pulmonary artery banding in infants with complete atrioventricular septal defects. METHODS From 2000 to 2009, 20 infants with complete atrioventricular septal defects underwent pulmonary artery banding because of unsuitable anatomy (unbalanced ventricles, associated lesions, or both) or clinical condition (infection, chronic lung disease, or noncardiac malformation). Patients were divided into 2 groups: the conventional PAB group (n = 13 [65%]; mean age, 74 ± 56 days [range, 6-187 days]; mean weight, 3.3 ± 1.1 kg [range, 2.1-5.8 kg]) and the FloWatch-PAB group (n = 7 [35%]; mean age, 111 ± 40 days [range, 81-187 days]; mean weight, 4.3 ± 1.2 kg [range, 3.2-6.1 kg]). There was no statistical difference in age or weight. Preoperative mechanical ventilation was required in 3 (23%) of 13 infants in the conventional PAB group and 5 (71%) of 7 infants in the FloWatch-PAB group (P < .05). RESULTS Ten (77%) of 13 infants in the conventional PAB group died versus 0 (0%) of 7 infants in the FloWatch-PAB group (P < .001). Sternal closure was delayed in 6 (46%) of 13 infants in the conventional PAB group and 0 (0%) of 7 infants in the FloWatch-PAB group (P < .05). The mean duration of mechanical ventilation, intensive care unit stay, and hospital stay was significantly longer (P < .05) in the conventional PAB group than in the FloWatch-PAB group (21 ± 17 days [range, 4-61 days] vs 3 ± 2 days [range, 1-8 days], 22 ± 18 days [range, 5-61 days] vs 7 ± 6 days [range, 2-21 days], and 54 ± 12 days [range, 40-71 days] vs 29 ± 25 days [range, 9-81 days], respectively). Left atrioventricular valve regurgitation increased (mild to moderate) in 2 infants in the conventional PAB group and decreased (severe to moderate) in 2 infants in the FloWatch-PAB group. Six of 10 survivors (1 in the conventional PAB group and 5 in the FloWatch-PAB group) underwent pulmonary artery debanding and repair after a median interval of 125 days (range, 34-871 days); 4 of 10 are awaiting repair. CONCLUSIONS In selected patients with complete atrioventricular septal defects, pulmonary artery banding followed by late repair is a viable alternative strategy. In our study the FloWatch-PAB device resulted in improved survival and made later repair possible in a better clinical state.

Histologic Evaluation of Explanted Tissue-Engineered Bovine Pericardium (CardioCel)

CardioCel is a bovine pericardium that is subjected to a novel anticalcification tissue-engineering process. We present the histopathologic findings of human explants of CardioCel that were used in operations for congenital heart disease in children. Six explants were identified from 140 patients undergoing CardioCel implants from October 2012 to March 2015. CardioCel explants were evaluated histologically using hematoxylin and eosin, Masson trichrome, and immunohistochemical staining. A variable inflammatory response was seen in the surrounding native tissue, but not within the CardioCel graft in any of the explants. A neointimal layer of varying thickness developed on the visceral surface of 5 CardioCel explants with endothelialization of the longest duration explant. A granulation tissue layer developed on the parietal surface of the graft (consistently thicker than the neointima). Maintained collagen fiber architecture (laminated) and variable fibroblastic invasion (which increased with the age of the implant) were identified in all 6 cases. Scattered capillary vessels were noted in the majority of the explants with new collagen fibers in one, suggesting early remodeling. Calcium was seen in 1 explant at the interface of the graft and inflammatory response on its parietal surface. Evidence of graft remodeling was noted in the majority of the explants without inflammatory cells or calcification within the explanted graft material. A noticeable feature was the differential thickness of the host reaction to the parietal compared with the visceral surface of the graft. We will continue to evaluate CardioCel as a cardiovascular substitute for extracardiac and intracardiac reconstructions.

Impact of viral respiratory pathogens on outcomes after pediatric cardiac surgery

Objectives: Viral respiratory infection is commonly considered a relative contraindication to elective cardiac surgery. We aimed to determine the frequency and outcomes of symptomatic viral respiratory infection in pediatric cardiac surgical patients. Design: Retrospective cohort study of children undergoing cardiac surgery. Symptomatic children were tested using a multiplex Polymerase Chain Reaction (respiratory virus polymerase chain reaction) panel capturing nine respiratory viruses. Tests performed between 72 prior to and 48 hours after PICU admission were included. Mortality, length of stay in PICU, and intubation duration were investigated as outcomes. Setting: Tertiary PICU providing state-wide pediatric cardiac services. Patients: Children less than 18 years admitted January 1, 2008 to November 29, 2014 for cardiac surgery. Measurements and Main Results: Respiratory virus polymerase chain reaction was positive in 73 (4.2%) of 1,737 pediatric cardiac surgical admissions, including 13 children with multiple viruses detected. Commonly detected viruses included rhino/enterovirus (48%), adenovirus (32%), parainfluenza virus 3 (10%), and respiratory syncytial virus (3%). Pediatric Index of Mortality 2, Aristotle scores, and cardiopulmonary bypass times were similar between virus positive and negative/untested cohorts. Respiratory virus polymerase chain reaction positive patients had a median 2.0 days greater PICU length of stay (p < 0.001) and longer intubation duration (p < 0.001). Multivariate analysis adjusting for age, Aristotle score, cardiopulmonary bypass duration, and need for preoperative PICU admission confirmed that virus positive patients had significantly greater intubation duration and PICU length of stay (p < 0.001). Virus positive patients were more likely to require PICU admission greater than 4 days (odds ratio, 3.5; 95% CI, 1.9–6.2) and more likely to require intubation greater than 48 hours (odds ratio, 2.5; 95% CI, 1.4–4.7). There was no difference in mortality. No association was found between coinfection and outcomes. Conclusions: Pediatric cardiac surgical patients with a respiratory virus detected at PICU admission had prolonged postoperative recovery with increased length of stay and duration of intubation. Our results suggest that postponing cardiac surgery in children with symptomatic viral respiratory infection is appropriate, unless the benefits of early surgery outweigh the risk of prolonged ventilation and PICU stay.