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Biomedical subjects

Marc R de Leval

Publications and source records attributed to Marc R de Leval.

At least 19 recordsLinked to original sources
PubMed2006

Does the Aristotle Score predict outcome in congenital heart surgery?

OBJECTIVE: The Aristotle Score has been proposed as a measure of 'complexity' in congenital heart surgery, and a tool for comparing performance amongst different centres. To date, however, it remains unvalidated. We examined whether the Basic Aristotle Score was a useful predictor of mortality following open-heart surgery, and compared it to the Risk Adjustment in Congenital Heart Surgery (RACHS-1) system. We also examined the ability of the Aristotle Score to measure performance. METHODS: The Basic Aristotle Score and RACHS-1 risk categories were assigned retrospectively to 1085 operations involving cardiopulmonary bypass in children less than 18 years of age. Multiple logistic regression analysis was used to determine the significance of the Aristotle Score and RACHS-1 category as independent predictors of in-hospital mortality. Operative performance was calculated using the Aristotle equation: performance = complexity x survival. RESULTS: Multiple logistic regression identified RACHS-1 category to be a powerful predictor of mortality (Wald 17.7, p < 0.0001), whereas Aristotle Score was only weakly associated with mortality (Wald 4.8, p = 0.03). Age at operation and bypass time were also highly significant predictors of postoperative death (Wald 13.7 and 33.8, respectively, p < 0.0001 for both). Operative performance was measured at 7.52 units. CONCLUSIONS: The Basic Aristotle Score was only weakly associated with postoperative mortality in this series. Operative performance appeared to be inflated by the fact that the overall complexity of cases was relatively high in this series. An alternative equation (performance = complexity/mortality) is proposed as a fairer and more logical method of risk-adjustment.

Adolescent↗
PubMed2006

Quality assurance in congenital heart surgery.

OBJECTIVE: The aim of this study was to develop a graphical method of risk-stratified outcome analysis in paediatric cardiac surgery to provide a means of continuous, prospective performance monitoring and allow real-time detection of change in outcomes. METHODS: Risk-adjusted survival following open-heart surgery was prospectively measured over a 15-month period (n=460). Outcomes were charted using variable life-adjusted display (VLAD) charts, which indicate the cumulative difference in observed minus expected survival against the cumulative number of cases performed. Risk stratification was based on RACHS-1 (risk adjustment in congenital heart surgery) risk category and age at surgery, using our previously published risk model. The probability of deviation in performance from the expected baseline level was determined using a mathematical model. RESULTS: By the end of the series, observed survival (443/460=96.3%) exceeded that predicted by the risk model (434.5/460=94.5%), equivalent to a one-third reduction in expected mortality. Mathematical modelling indicated a 1-5% likelihood that this difference would have occurred by random variation alone, suggesting the outcomes represented genuine improvement. CONCLUSIONS: VLAD charts provide an effective, easily visualised display of surgical performance and can be applied to paediatric cardiac surgery. Early detection of change, whether improvement or deterioration, is important for ongoing quality assurance within a cardiac surgery programme.

Cardiopulmonary Bypass↗
PubMed2006

Is complete heart block after surgical closure of ventricular septum defects still an issue?

BACKGROUND: A serious complication after surgical closure of ventricular septal defect (VSD) is complete heart block. In this retrospective study, we reviewed the incidence of complete heart block after surgical closure of a VSD at Great Ormond Street Hospital from 1976 to 2001 to identify any particular anatomic features that still predisposed patients to surgically-induced complete heart block and to provide anatomic guidelines to avoid this in future. METHODS: Data were extracted from our local database for patients having (1) isolated VSD or VSD in the setting of (2) tetralogy of Fallot with pulmonary stenosis or (3) tetralogy of Fallot with pulmonary atresia; (4) absent pulmonary valve syndrome; (5 and 6) coarctation or interruption of the aortic arch; and (7) subaortic fibrous shelf. We carefully reviewed the operative notes from all patients with postoperative complete heart block to discover any predisposing anatomical reasons to explain the complication. RESULTS: Two thousand seventy-nine patients had a VSD closure. Permanent complete heart block developed in 7 of 996 patients (0.7%) with an isolated defect and in 1 of 847 patients (0.1%) with tetralogy of Fallot. Four more patients had postoperative complete heart block. CONCLUSIONS: Instances of iatrogenic complete heart block continue to occur after surgical VSD closure, either because of unexpected biological variations or because of unawareness of the disposition of the atrioventricular conduction axis in particular circumstances. This report emphasizes the latter aspect in details and suggests a risk of iatrogenic complete heart block of less than 1%.

Aortic Coarctation↗
PubMed2005

Multiscale modelling in biofluidynamics: application to reconstructive paediatric cardiac surgery.

Multiscale computing is a challenging area even in biomechanics. Application of such a methodology to quantitatively compare postoperative hemodynamics in congenital heart diseases is very promising. In the treatment of hypoplastic left heart syndrome, which is a congenital heart disease where the left ventricle is missing or very small, the necessity to feed the pulmonary and systemic circulations is obtained with an interposition shunt. Two main options are available and differ from the sites of anastomoses: (i) the systemic-to-pulmonary conduit (Blalock-Taussig shunt known as the Norwood Operation (NO)) connecting the innominate artery (NO-BT) or the aorta (NO-CS) to the right pulmonary artery and (ii) the right ventricle to pulmonary artery shunt (known as Sano operation (SO)). The proposition that the SO is superior to the NO remains controversial. 3-D computer models of the NO (NO-BT and NO-CS) and SO were developed and investigated using the finite volume method. Conduits of 3, 3.5 and 4 mm were used in the NO models, whereas conduits of 4, 5 and 6 mm were used in the SO model. The hydraulic nets (lumped resistances, compliances, inertances and elastances) which represent the systemic, coronary and pulmonary circulations and the heart were identical in the two models. A multiscale approach was adopted to couple the 3-D models with the circulation net. Computer simulation results were compared with post-operative catheterization data. Results showed that (i) there is a good correlation between predicted and observed data: higher aortic diastolic pressure, decreased pulmonary arterial pressure, lower pulmonary-to-systemic flow ratio and higher coronary perfusion pressure in SO; (ii) there is a minimal regurgitant flow in the SO conduit. The close correlation between predicted and observed clinical data supports the use of mathematical modelling, with a mandatory multiscale approach, in the design and assessment of surgical procedures.

Algorithms↗
PubMed2005

Anomalous origin of the right pulmonary artery from the ascending aorta with fibrous continuity to the pulmonary trunk.

A 1-month-old patient was brought to our institution with clinical signs of pulmonary hypertension. Cross-sectional echocardiography suggested a diagnosis of aortopulmonary window. At the time of surgery, we found that the right pulmonary artery was arising anomalously from the left side of the ascending aorta, but was also connected to the pulmonary trunk by a fibrous cord. We reimplanted the right pulmonary artery into the pulmonary trunk, closing the resultant opening in the ascending aorta by direct suture. The postoperative course was uneventful. On follow-up, the patient is asymptomatic without medication.

Electrocardiography↗
PubMed2005

The potential impact of percutaneous pulmonary valve stent implantation on right ventricular outflow tract re-intervention.

OBJECTIVE: To assess the impact of a percutaneous technique for pulmonary valve implantation on the conventional surgical valve/conduit approach to right ventricular outflow tract re-intervention. METHODS: We have retrospectively reviewed our results following surgical or percutaneous re-intervention to the right ventricular outflow tract in both paediatric and adult groups. Between November 1998 and March 2004, 94 patients underwent surgical re-intervention to the right ventricular outflow tract. Percutaneous pulmonary valve implantation was introduced in October 2002 and 35 procedures were performed to March 2004. The median age was 26 years (6-65 years) in the surgical group and 16 years (9-39 years) in the percutaneous group. Tetralogy of Fallot was the commonest original diagnosis (64.9 and 62.9%, respectively). The predominant indication for re-intervention in the surgical group was pulmonary regurgitation (64.9%) compared to the percutaneous group in which it was homograft/conduit stenosis or a mixed lesion (68.6%). RESULTS: There has been one (1.1%) early death reported in the surgical series and none in the percutaneous group. In the surgical group 9 (9.6%) experienced a procedural complication whilst 3 (8.5%) of those undergoing a percutaneous valve experienced a significant procedural event necessitating urgent surgery. Important early morbidity was 8 (8.5%) in the surgical group and 2 (5.7%) in the percutaneous group. Freedom from re-operation at 1 year was 100% in the surgical group and 86.1% in the percutaneous group due to late restenosis. Median hospital stay in the surgical group was 7 (4-114) days and 2 (2-22) days in the percutaneous group. CONCLUSIONS: Preliminary data suggests that percutaneous pulmonary valve implantation provides a promising additional and complementary approach to a successful surgical programme. Both approaches are safe with acceptable levels of morbidity and low mortality. With current technology the aneurysmal outflow tract remains a problem for the percutaneous approach. Follow-up remains too short, at present, to prove longevity of the percutaneous conduit.

Adolescent↗
PubMed2005

Multiscale modeling of the cardiovascular system: application to the study of pulmonary and coronary perfusions in the univentricular circulation.

The objective of this study is to compare the coronary and pulmonary blood flow dynamics resulting from two configurations of systemic-to-pulmonary artery shunts currently utilized during the Norwood procedure: the central (CS) and modified Blalock Taussig (MBTS) shunts. A lumped parameter model of the neonatal cardiovascular circulation and detailed 3-D models of the shunt based on the finite volume method were constructed. Shunt sizes of 3, 3.5 and 4 mm were considered. A multiscale approach was adopted to prescribe appropriate and realistic boundary conditions for the 3-D models of the Norwood circulation. Results showed that the average shunt flow rate is higher for the CS option than for the MBTS and that pulmonary flow increases with shunt size for both options. Cardiac output is higher for the CS option for all shunt sizes. Flow distribution between the left and the right pulmonary arteries is not completely balanced, although for the CS option the discrepancy is low (50-51% of the pulmonary flow to the right lung) while for the MBTS it is more pronounced with larger shunt sizes (51-54% to the left lung). The CS option favors perfusion to the right lung while the MBTS favors the left. In the CS option, a smaller percentage of aortic flow is distributed to the coronary circulation, while that percentage rises for the MBTS. These findings may have important implications for coronary blood flow and ventricular function.

Blood Flow Velocity↗
PubMed2005

Subneoaortic stenosis complicating the arterial switch operation.

We report obstruction of the reconstructed left ventricular outflow tract diagnosed 18 months after an arterial switch operation that included closure of a ventricular septal defect. We speculate that either turbulences created by the patch used to close the ventricular septal defect, or postoperative modifications of ventricular geometry, were responsible for producing this unusual complication.

Aortic Stenosis, Subvalvular↗
PubMed2005

The Fontan circulation: a challenge to William Harvey?

The Fontan operation, which places the systemic and pulmonary circulations in series and is driven by a single ventricular chamber, is the treatment of choice for patients born with one ventricle. Its introduction 35 years ago was the result of a flurry of experimental and clinical research that had started in the 1940s. A large number of children have benefited and continue to benefit from the Fontan operation, but there is a genuine concern that, despite the refinement of the surgical procedures in the past 20 years, continuing attrition might be inevitable. This adverse effect can lead to a decline in functional capacity, and premature late death.

Collateral Circulation↗
PubMed2005

On the use of computational models for the quantitative assessment of surgery in congenital heart disease.

The surgical repair of congenital heart disease often involves significant modifications to the circulatory tree. Resections, reconstructions, graft insertions and the deployment of implants and biomedical devices have an impact on local and systemic haemodynamics, which may be difficult to foresee or to assess quantitatively by clinical investigation alone. Mathematical models can be employed to visualise, estimate or predict events and physical quantities that are difficult to observe or measure, and can be successfully applied to the study of the pre- and post-operative physiology of cardiovascular malformations. This paper analyses the potentialities of computation fluid dynamics in this respect, outlining the method, its requirements and its limitations. Examples are given of lumped parameter models, axi-symmetric models, three-dimensional models, fluid-structure interaction simulations and multiscale computing applied to total cavo-pulmonary connection, aortic coarctation and aortic arch reconstruction.

Cardiovascular Surgical Procedures↗
PubMed2004

Extending the boundaries of the primary arterial switch operation in patients with transposition of the great arteries and intact ventricular septum.

BACKGROUND: We have previously suggested that the primary arterial switch operation is a feasible strategy for patients with transposition of the great arteries and intact ventricular septum (TGA-IVS) up to age 2 months. This study reports our current results with this approach and examines whether this policy could be extended beyond age 2 months. METHODS AND RESULTS: 380 patients who underwent arterial switch for TGA-IVS were reviewed. 275 patients were younger than 3 weeks at the time of surgery (early switch group); 105 patients were 3 weeks or older (range, 21 to 185 days) (late switch group). There was no difference in outcome in terms of in-hospital mortality (5.5% versus 3.8%) or need for mechanical circulatory support (3.6% versus 5.7%) between early and late switch groups. However, duration of postoperative ventilation (4.9 versus 7.1 days, P=0.012) and length of postoperative stay (12.5 versus 18.9 days, P<0.001) were significantly prolonged in the late switch group. Primary left ventricular failure resulting in death occurred in 2 patients in the late switch group, with no deaths in 9 patients aged 2 to 6 months. CONCLUSIONS: This experience confirms that in TGA-IVS, the left ventricle maintains the potential for systemic work well beyond the first month of life. Consequently, neonates at high risk or late referrals can benefit from delayed arterial switch, even beyond age 2 months. However, the need for mechanical support in some of the older patients may limit the widespread adoption of such a strategy.

Age Factors↗