Conal Austin

Less invasive techniques for mitral valve surgery

OBJECTIVE Minimally invasive surgical techniques aim at reducing the consequences of currently used large incisions, such as bleeding, pain, and risk of infection. Although this new approach developed rapidly in coronary surgery, it remains questionable in mitral valve surgery. This article reports the longest experience with minimally invasive mitral valve surgery, with particular attention to approach and techniques. METHODS From February 1996, the date of the first case of minimally invasive mitral valve reconstruction, to April 1997, 22 patients with a mean age of 54 +/- 2.7 years were subjected to mitral valve surgery performed with less invasive techniques. Exposure of the mitral valve was achieved through a minithoracotomy (n = 12) or a ministernotomy (n = 10). Video assistance was used in all cases. Peripheral arterial cannulation (n = 21) and venous drainage (n = 22) were used in most cases. RESULTS In this series, valve surgery consisted in 19 repairs, two replacements, and one closure of a periprosthetic leak. In two cases it was necessary to convert to a larger incision. The average duration of cardiopulmonary bypass was 157 +/- 8.2 minutes, ventilatory assistance 16 +/- 4.6 hours, and intensive care unit stay 2.1 +/- 0.4 days. Two patients required reoperation for bleeding and another for early recurrence of mitral valve regurgitation. There were no deaths and all patients were discharged with normal valve function. At most recent follow-up, all patients were in functional class I, with resumption of normal activity. CONCLUSION Mitral valve surgery can be performed safely by means of less invasive techniques, but with increased technical difficulty. A low asymmetric median sternotomy seems preferable to an anterior thoracotomy.

The Relationship Among Thromboelastography, Hemostatic Variables, and Bleeding After Cardiopulmonary Bypass Surgery in Children

BACKGROUND:Mediastinal bleeding is common after pediatric cardiopulmonary bypass (CPB) surgery. Thromboelastography (TEG®) may predict bleeding and provide insight into likely mechanisms. We aimed to (a) compare perioperative temporal profiles of TEG® and laboratory hemostatic variables between patients with significant hemorrhage (BLEED) and those without (CONTROL), (b) investigate the relationship between TEG® variables and routine hemostatic variables, and (c) develop a model for prediction of bleeding. METHODS:TEG® and laboratory hemostatic variables were measured prospectively at 8 predefined times for 50 children weighing <20 kg undergoing CPB. RESULTS:Patients who bled demonstrated different TEG® profiles than those who did not. This was most apparent after protamine administration and was partly attributable to inadequate heparin reversal, but was also associated with a significantly lower nadir in mean (SD) fibrinogen for the BLEED group compared with CONTROL group: 0.44 (0.18) and 0.71 (0.40) g/L, respectively (P = 0.01). Significant nonlinear relationships were found between the majority of TEG® and laboratory hemostatic variables. The strongest relationship was between the maximal amplitude and the platelet-fibrinogen product (logarithmic r2 = 0.71). Clot strength decreased rapidly when (a) fibrinogen concentration was <1 g/L, (b) platelets were <120 × 109/L, and (c) platelet-fibrinogen product was <100. A 2-variable model including the activated partial thromboplastin time at induction of anesthesia and TEG® mean amplitude postprotamine discriminated well for subsequent bleeding (C statistic 0.859). CONCLUSIONS:Hypofibrinogenemia and inadequate heparin reversal are 2 important factors contributing to clot strength and perioperative hemorrhage after pediatric CPB. TEG® may be a useful tool for predicting and guiding early treatment of mediastinal bleeding in this group.

Hybrid procedure as an alternative to surgical palliation of high-risk infants with hypoplastic left heart syndrome and its variants

OBJECTIVES Despite improvements in the surgical management of neonates with the hypoplastic left heart syndrome and its variants, there is a subset of children who have a high predicted mortality. We have analyzed and report our results with the hybrid approach in the management of these high-risk patients. METHODS Children identified by our selection criteria underwent the initial hybrid procedure performed in the catheterization laboratory. This consists of surgical banding of the branch pulmonary arteries and stenting of the arterial duct. This was followed 3 to 6 months later by the combined stage I and II Norwood operation or biventricular repair. RESULTS Between December 2005 and May 2008, 21 neonates were selected for the hybrid procedure, of whom 16 had typical hypoplastic left heart syndrome. The remaining 5 neonates had severe aortic stenosis with borderline left ventricular dimensions or poor left ventricular function at presentation. Four neonates had a virtually intact interatrial septum and required urgent intervention immediately after birth. There were 6 deaths as inpatients or up to 30 days after the procedure and 1 interstage death before the combined stage I and II operation. Thus far, of 12 babies who have undergone the next operation, 9 have had the combined stage I and II operation and 3 have had a biventricular repair. Two of these 12 babies have died after the combined stage I and II operation. CONCLUSION A hybrid approach may be a valuable alternative to the management of high-risk neonates with hypoplastic left heart syndrome and its variants.

The strong ion gap predicts mortality in children following cardiopulmonary bypass surgery.

Objective: Stewart’s strong ion theory quantifies unmeasured tissue acids produced following hypoxia or hypoperfusion, by calculation of the strong ion gap. Our study objectives were as follows: a) to determine the 24-hr profile of the strong ion gap following cardiopulmonary bypass surgery; and b) to compare the prognostic value in terms of intensive care unit mortality of this variable with blood lactate. Design: Prospective, observational study. Setting: Tertiary pediatric intensive care unit. Patients: Eighty-five children following surgery for congenital heart disease. Interventions: None. Measurements and Main Results: Arterial blood samples for lactate and strong ion gap calculation were obtained at intensive care unit admission and at 24 hrs. A raised strong ion gap (>3 mEq/L) was present in 41.1% and 51.7% of admission and 24-hr samples, respectively, being elevated at both time points in 30.5%. Both the strong ion gap and lactate increased with surgical complexity, but neither was correlated with length of bypass (r = .13 and −.02) or aortic cross-clamp (r = .13 and .10). The crude mortality was 5.8% (5/85). Four of the five deaths were associated with a persistently elevated strong ion gap, in contrast to two with ongoing hyperlactatemia (>2 mmol/L). The admission strong ion gap (cutoff, >3.2 mEq/L) was superior to lactate (cutoff, >3.0 mmol/L) as a mortality predictor (area under receiver operating characteristic curve of 0.85 [95% confidence interval, 0.74–0.95] vs. 0.71 [95% confidence interval, 0.44–0.98], respectively). Conclusions: An elevated strong ion gap occurs commonly following bypass surgery and appears to be superior to lactate as a mortality predictor.

Management strategy and long term outcome for truncus arteriosus

OBJECTIVE Evaluation of a consistent policy of elective repair of truncus arteriosus at 2-3 months of age for the patients who are independent of hospital ward care, and long-term outcome. METHODS Retrospective study of 82 patients with truncus arteriosus who underwent total repair at the Victorian Paediatric Cardiac Surgical Unit between 1979 and December 1995. The timing was based on a consistent policy of elective repair at 2-3 months of age for patients who were independent of hospital ward care. Earlier repair was performed when the patients were in uncontrolled congestive heart failure. RESULTS Follow-up was complete for all patients with a mean of 76 months (1-183). There were 11 hospital deaths (13.4% CL 9-18.5), and five late deaths, actuarial survival at 80 months was 81% (CL 70-88%) with 39 patients uncensored at that point. For the purpose of this presentation, patients have been grouped according to their age at repair; 1, neonates n = 17 (hospital mortality = 5); 2, infants 1-6 months of age n = 48 (hospital mortality = 4); 3, patients beyond 6 months n = 17 (hospital mortality = 2). This series includes 10 patients with interrupted aortic arch with no mortality, and 10 patients with discontinuous pulmonary artery (hospital mortality = 2). Thirty-seven patients have had 54 conduits replaced to date. Using multiple regression, body weight < 3 kg was the only significant independent risk factor for hospital mortality. CONCLUSIONS Our management policy tended to gather patients with risk factors described elsewhere into presentation group 1 and low risk truncus patients into presentation group 2. Deferral of surgery to 2-3 months of age is possible and lowers the surgical risk.

Serial Magnetic Resonance Imaging in Hypoplastic Left Heart Syndrome Gives Valuable Insight Into Ventricular and Vascular Adaptation

Objectives This study sought to investigate changes in magnetic resonance imaging (MRI) ventricular volumes and vascular dimensions before hemi-Fontan (HF) and before total cavopulmonary connection (TCPC) in children with hypoplastic left heart syndrome (HLHS). Background The systemic right ventricle (RV) in HLHS is subject to significant changes in volume loading throughout the surgical stages of palliation, particularly after the HF. Methods Fifty-eight patients had paired pre-HF and pre-TCPC MRI for assessment of changes of RV volumes, neoaortic flow, and vascular dimensions. Results Comparison of pre-HF and pre-TCPC MRI results showed a decrease of indexed RV end-diastolic volume and end-systolic volume (98 ml/m2 to 87 ml/m2 and 50 ml/m2 to 36 ml/m2, respectively) with stroke volume remaining constant (49 ml/m2 vs. 51 ml/m2), leading to an increased RV ejection fraction (51% vs. 59%). These findings persisted after excluding the 3 patients who underwent tricuspid valve repair as part of their HF procedure. Indexed RV end-diastolic volume plotted against neoaortic stroke volume demonstrated a Frank-Starling–like curve that shifted upward after HF. The indexed distal left and right cross-sectional pulmonary artery areas were reduced after HF. Conclusions In HLHS, serial MRI shows the adaptation of the systemic RV after HF with volume reduction in the context of a preserved stroke volume and an increased ejection fraction. The staged palliation in HLHS may be a risk factor particularly for reduced left pulmonary artery growth in itself as no factors investigated in this study were found to significantly impact on this.

Analysis of preoperative condition and interstage mortality in Norwood and hybrid procedures for hypoplastic left heart syndrome using the Aristotle scoring system

Objective The ‘hybrid procedure’, consisting of surgical banding of the pulmonary arteries with intraoperative stenting of the arterial duct, was developed as primary palliation in hypoplastic left heart syndrome (HLHS), avoiding the risks of cardiopulmonary bypass. In many centres, it is reserved for low birth weight, premature or unstable neonates; however, its role in such high risk cases of HLHS has yet to be defined. Methods The preoperative condition of all patients with HLHS who underwent either the hybrid or the Norwood procedure for HLHS between 2005–2011 was analysed retrospectively, using a modified comprehensive Aristotle score. We then compared operative, interstage and 1 year mortalities between the groups after Aristotle adjustment via Cox proportional hazards analyses. Results Of 138 patients with HLHS, 27 had hybrid and 111 Norwood procedures. The hybrid group had significantly higher Aristotle scores (mean 4.1 vs 1.8; p<0.001); however, there was no significant difference in mortality at any stage. At 1 year, the overall unadjusted survival among Norwood and hybrid patients was 58.6% and 51.9%, respectively, yielding an Aristotle adjusted hazard ratio for mortality among hybrid patients of 1.09 (95% CI 0.56 to 2.11, p=0.80). Conclusions Applying a hybrid approach to high risk patients with HLHS produces a comparable early and interstage mortality risk to lower risk patients undergoing the Norwood procedure. Prospective studies are needed to establish whether the hybrid procedure is a viable alternative to the Norwood procedure in all HLHS patients in terms of both mortality and long term morbidity.

Live three-dimensional paediatric intraoperative epicardial echocardiography as a guide to surgical repair of atrioventricular valves.

Real-time three dimensional echocardiography is increasingly used for imaging patients with congenital cardiac malformations. One of the limitations of a transthoracic approach is that intervening structures can impact on the quality of the images obtained. We hypothesised that, during surgery, epicardial three-dimensional echocardiography would provide images of high quality. We report our findings in eight children or young adults, with weights ranging from 2.8 to 70 kilograms, in whom we used this approach. In all cases, we obtained images of good quality, which could be analysed rapidly in the operating room. Of the eight cases, seven had echocardiographic findings which matched exactly the surgical findings. The remaining child had been diagnosed echocardiographically with a cleft in the aortic leaflet of the mitral valve, but was found at surgery to have a double orifice in the valve.

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.

Outcome of children with acetylcholine receptor (AChR) antibody positive juvenile myasthenia gravis following thymectomy.

Most evidence supporting the benefit of thymectomy in juvenile myasthenia gravis (JMG) is extrapolated from adult studies, with only little data concerning paediatric populations. Here we evaluate the outcome of children with generalized JMG who underwent thymectomy between 1996 and 2010 at 2 tertiary paediatric neurology referral centres in the United Kingdom. Twenty patients (15 female, 5 male), aged 13months to 15.5years (median 10.4years) at disease onset, were identified. Prior to thymectomy, disease severity was graded as IIb in 3, III in 11, and IV in 6 patients according to the Osserman classification. All demonstrated positive anti-acetylcholine receptor (AChR) antibody titres. All patients received pyridostigmine and 14 received additional steroid therapy. Transternal thymectomy was performed at the age of 2.7-16.6years (median 11.1years). At the last follow-up (10months to 10.9years, median 2.7years, after thymectomy), the majority of children demonstrated substantial improvement, although some had required additional immune-modulatory therapies. About one third achieved complete remission. The postoperative morbidity was low. No benefit was observed in one patient with thymoma. We conclude that thymectomy should be considered as a treatment option early in the course of generalised AChR antibody-positive JMG.