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Although adenosine markedly increases fetal pulmonary blood flow, the specific changes in pulmonary trunk (PT), ductus arteriosus (DA), and conduit pulmonary artery (PA) flow interactions that support this increased flow are unknown. To address this issue, seven anesthetized late-gestation fetal sheep were instrumented with PT, DA, and left PA micromanometer catheters and transit-time flow probes. Blood flow profile and wave intensity analyses were performed at baseline and after adenosine infusion to increase PA flow approximately fivefold. With adenosine infusion, DA mean and phasic flows were unchanged, but increases in mean PT (500 ± 256 ml/min, P = 0.002) and the combined left and right PA flow (479 ± 181 ml/min, P < 0.001) were similar (P > 0.7) and related to a larger flow-increasing forward-running compression wave arising from right ventricular (RV) impulsive contraction. Moreover, while the increased PT flow was confined to systole, the rise in PA flow spanned systole (316 ml/min) and diastole (163 ml/min). This elevated PA diastolic flow was accompanied by a 170% greater discharge from a PT and main PA reservoir filled in systole (P < 0.001), but loss of retrograde blood discharge from a conduit PA reservoir that was evident at baseline. These data suggest that 1) an increase in fetal pulmonary blood flow produced by adenosine infusion is primarily supported by a higher PT blood flow (i.e., RV output); 2) about two-thirds of this increased RV output passes into the pulmonary circulation during systole; and 3) the remainder is transiently stored in a central PT and main PA systolic reservoir, from where it discharges into the lungs in diastole.

Lumped parameter and one-dimensional models of the cardiovascular system generally employ ideal cardiac and/or venous valves that open and close instantaneously. However, under normal or pathological conditions, valves can exhibit complex motions that are mainly determined by the instantaneous difference between upstream and downstream pressures. We present a simple valve model that predicts valve motion on the basis of this pressure difference, and can be used to investigate not only valve pathology, but a wide range of cardiac and vascular factors that are likely to influence valve motion., (Copyright © 2011 John Wiley & Sons, Ltd.)

Separating pressure, flow/velocity and wave intensity signals into forward and backward components provide insights about arterial wave propagation and reflection. A linear wave separation is normally used, but ignores the pressure-dependence of wave speed. While a non-linear separation could incorporate this pressure-dependence, no such method exists for wave intensity decomposition. Moreover, although linear separation errors for pressure (5-10 %) have been quantified previously, errors for velocity and wave intensity have not. Accordingly, we describe a non-linear wave separation technique based on the method of characteristics. Data from a computer model suggest that the percentage linear separation errors for velocity and wave intensity are approximately one-half and twice that for pressure, respectively. Although comparable to measurement uncertainty in many instances, linear separation errors may become more significant: (1) if wave speed varies substantially over the cardiac cycle, e.g. if pulse pressure or vessel compliance is high, (2) if the degree of wave reflection in the arterial system is large, or (3) if the constant wave speed used for the linear separation is closer to the minimum or maximum pressure-dependent value rather than the mean. Consideration of linear separation errors may therefore be important in some physiological settings.

Background: Perioperative brain injury is common in infants undergoing cardiac surgery. Amplitude-integrated electroencephalography (aEEG) provides real-time neurologic monitoring and can identify seizures and abnormalities of background cerebral activity. We aimed to determine the incidence of perioperative electrical seizures, and to establish the background pattern of aEEG, in neonates undergoing Norwood-type palliations for complex congenital heart disease in relation to outcome at 2 years., Methods: Thirty-nine full-term neonates undergoing Norwood-type operations underwent aEEG monitoring before and during surgery and for 72 hours postoperatively. The perfusion strategy included full-flow moderately hypothermic cardiopulmonary bypass with antegrade cerebral perfusion. Amplitude-integrated electroencephalography tracings were reviewed for seizure activity and background pattern. Survivors underwent neurodevelopmental outcome assessment using the Bayley Scales of Infant Development (3rd edition) at 2 years of age., Results: Thirteen (33%) infants had electrical seizures, including 9 with intraoperative seizures and 7 with postoperative seizures. Seizures were associated with significantly increased mortality, but not with neurodevelopmental impairment in survivors. Delay in recovery of the aEEG background beyond 48 hours was also associated with increased mortality and worse motor development., Conclusions: Perioperative seizures were common in this cohort. Intraoperative seizures predominantly affected the left hemisphere during antegrade cerebral perfusion. Delayed recovery in aEEG background was associated with increased risk of early mortality and worse motor development. Ongoing monitoring is essential to determine the longer-term significance of these findings., (Copyright © 2012 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.)

Constriction of the fetal ductus arteriosus (DA) has disparate effects on mean and phasic hemodynamics, as mean DA blood flow is preserved until constriction is severe, but DA systolic and diastolic blood velocities change with only mild constriction. To determine the basis of this disparity and its physiological significance, seven anesthetized late-gestation fetal sheep were instrumented with pulmonary trunk (PT), DA, and left pulmonary artery (PA) micromanometer catheters and transit-time flow probes. Blood flow profile and wave intensity analyses were performed at baseline and during mild, moderate, and severe DA constriction (defined as pulmonary-aortic mean pressure differences of 4, 8, and 14 mmHg, respectively), produced with an adjustable snare. With DA constriction, mean DA flow was initially maintained but decreased with severe constriction (P < 0.05) in conjunction with a reduction (P < 0.05) in PT flow (i.e., right ventricular output). By contrast, DA systolic flow fell progressively during DA constriction (P < 0.001), due to decreased transmission of both early and midsystolic proximal flow-enhancing forward-running compression waves into the DA. However, DA constriction was also accompanied by greater systolic storage of blood in the PT and main PA (P < 0.025), and increased retrograde diastolic flow from compliant major branch PA (P < 0.001). Transductal discharge of these central and conduit PA blood reservoirs in diastole offset systolic DA flow reductions. These data suggest that, during DA constriction in the fetus, enhanced central and conduit PA reservoir function constitutes an important compensatory mechanism that contributes to preservation of mean DA flow via a systolic-to-diastolic redistribution of phasic DA flow.

Although the distribution of average fetal pulmonary trunk (PT) blood flow favors the ductus arteriosus (DA) over the lungs, the phasic aspects of this distribution during systole and diastole are not well understood. Accordingly, flow profile and wave intensity (WI) analyses were performed at baseline and during brief flow increases accompanying an extrasystole (ES) in 10 anesthetized late-gestation fetal sheep instrumented with PT, DA, and left pulmonary artery (PA) micromanometer catheters and transit-time flow probes. At baseline, 83% of mean PT flow crossed the DA and 17% entered the lungs. However, early systolic flow associated with a forward-running compression wave (FCW(is)) was higher in the PA and predominant DA flow only emerged in midsystole when a large PA backward-running compression wave (BCW(ms)), which reduced PA flow, was transmitted into the DA as a forward-running compression wave (FCW(ms)) that increased flow. Subsequent protodiastolic forward DA flow occurring during pulmonary valve closure was associated with substantial retrograde PA flow, but insignificant PT flow. Conversely, forward DA flow in the remainder of diastole occurred with forward PT but near-zero PA flow. These flow and WI patterns, in conjunction with the results of mathematical modeling, suggest that 1) fetal PT flow preferentially passes into the PA during early systole due to a lower PA-than-DA characteristic impedance, while DA flow predominates in mid- and late systole due to flow effects arising from the PA BCW(ms), and 2) forward DA flow is mainly sustained by reversal of PA flow in protodiastole but discharge of a more central reservoir in diastole.

Ventricular septal defects account for up to 40% of all congenital cardiac malformations. The diagnosis encompasses a broad range of anomalies, including isolated defects and those associated with other congenital cardiac malformations. Presentation, symptoms, natural history, and management of ventricular septal defects depend on size and anatomical associations of the anomaly, patient's age, and local diagnostic and interventional expertise. In this Seminar, we describe the anatomical range of ventricular septal defects and discuss present management of these malformations. Genetic determinants, diagnostic techniques, physiological considerations, and management challenges are examined in detail. Unfortunately, in many circumstances, evidence on which to guide optimum management is scarce. We present some longer term considerations of ventricular septal defects in adolescents and adults, with particular emphasis on patients with raised pulmonary vascular resistance and Eisenmenger's syndrome., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Objective: To describe the clinical course of a group of patients who received a rotating inotrope regimen, including levosimendan, for decompensated congestive heart failure., Design: Case series., Setting: Pediatric intensive care unit in a tertiary care children's hospital., Patients: Nine pediatric patients with severe, decompensated heart failure., Intervention: The study patients received a rotating inotrope regimen, including levosimendan, dobutamine, and, in some cases, milrinone., Measurements and Main Results: Six patients were weaned from positive-pressure ventilation. Eight patients were discharged from the intensive care unit, and seven survived to hospital discharge. Two patients were successfully bridged to orthotopic cardiac transplantation. The therapies were generally well tolerated., Conclusions: Rotating inotropes were safe and seemed to be effective in this heterogeneous population of infants and children with decompensated heart failure. This therapeutic regimen warrants prospective comparative analysis.

Arterial wave speed estimated invasively from pressure (P) and velocity (U) measurements using the P-U loop method, or non-invasively from diameter (D) and U measurements using the lnD-U loop method, assume that during early systole 1) backward-running waves are absent and 2) wave speed is constant. These assumptions also form the basis of a method for correcting time lags between P (or lnD) and U in which the R(2) of the early-systolic linear regression is maximized. However, neither of the two assumptions are strictly valid in vivo, where the diastolic pressure decay from the previous beat may give rise to some non-zero backward-running P, U and wave intensity (WI) components, and the pressure-dependency of wave speed may lead to curvilinearity in the early-systolic P-U and lnD-U relations. Accordingly, this study assessed the robustness of three phase correction algorithms, (including two that are not dependent on the two assumptions stated above, i.e., aligning the times of the peak 2nd derivative or peak signal curvature) and of the P-U and lnD-U loop wave speed estimation methods under a range of diastolic decay rates and degrees of vessel wall non-linearity. Results from a simple computer model of the arterial circulation suggested that although an apparent phase lag may be introduced by assuming linearity, the magnitude of this phase lag is likely to be small considering the sample intervals normally used in experimental studies; however, under highly non-linear flow conditions, the apparent lag may be comparable to hardware-related lags. Predicted errors in estimated wave speed using the P-U loop method were generally less than 10%, while somewhat higher errors were found in the lnD-U loop method (up to 15-20%). In both, higher diastolic pressure decay rates were associated with higher wave speed errors, although this effect was eliminated by subtracting the extrapolated diastolic pressure curve from the measured pressure. Overall, each of the time lag correction algorithms and wave speed estimation methods were generally satisfactory, although further experimental work is required to assess the curvature-based phase correction method and pressure adjustment in vivo.

The long-term outcome of patients with congenitally malformed hearts involving abnormal right ventricular morphology and haemodynamics is variable. In most instances, the patients are at risk for right ventricular failure, in part due to morphological differences between the right and left ventricles and their response to chronic volume and pressure overload. In patients after repair of tetralogy of Fallot, and after balloon valvotomy for valvar pulmonary stenosis, pulmonary regurgitation is the most significant risk factor for right ventricular dysfunction. In patients with a dominant right ventricle after Fontan palliation, and in those with systemic right ventricles in association with surgically or congenitally corrected transposition, the right ventricle is not morphologically capable of dealing with chronic exposure to the high afterload of the systemic circulation. In patients with Ebstein's malformation of the tricuspid valve, the degree of atrialisation of the right ventricle determines how well the right ventricle will function as the pump for the pulmonary vascular bed.

Heart failure is an important cause of morbidity and mortality in individuals of all ages. The many-faceted nature of the clinical heart failure syndrome has historically frustrated attempts to develop an overarching explanative theory. However, much useful information has been gained by basic and clinical investigation, even though a comprehensive understanding of heart failure has been elusive. Heart failure is a growing problem, in both adult and pediatric populations, for which standard medical therapy, as of 2010, can have positive effects, but these are usually limited and progressively diminish with time in most patients. If we want curative or near-curative therapy that will return patients to a normal state of health at a feasible cost, much better diagnostic and therapeutic technologies need to be developed. This review addresses the vexing group of heart failure etiologies that include cardiomyopathies and other ventricular dysfunctions of various types, for which current therapy is only modestly effective. Although there are many unique aspects to heart failure in patients with pediatric and congenital heart disease, many of the innovative approaches that are being developed for the care of adults with heart failure will be applicable to heart failure in childhood., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Although fetal pulmonary trunk (PT) blood pressure may exceed aortic trunk (AoT) pressure, the specific mechanism(s) underlying this pressure difference remain undefined. To evaluate the potential role of ventricular and vascular factors in the generation of a fetal PT-AoT pressure difference, nine anesthetized late-gestation fetal sheep were instrumented with PT and AoT micromanometer catheters to measure high-fidelity pressure and transit-time flow probes to obtain blood velocity. The PT-AoT instantaneous pressure difference (IPD(PT-AoT)) was calculated from PT and AoT pressure profiles. PT and AoT wave intensity (WI) was derived from the product of the appropriate pressure and velocity rates of change. While diastolic pressures were near identical, systolic PT pressure exceeded AoT pressure (P < 0.001), with a maximal IPD(PT-AoT) of 6.5 +/- 2.5 mmHg. The comparison of IPD(PT-AoT) with wave-related PT and AoT pressure changes indicated that 1) a greater pressure-generating effect of the PT forward-running compression wave arising from impulsive right ventricular contraction in early and midsystole accounted for 2.3 +/- 2.3 mmHg (35%) of the maximal IPD(PT-AoT) and 2) a larger pressure-generating effect of a large midsystolic backward-running compression wave transmitted into the PT from the pulmonary vasculature contributed 4.0 +/- 1.5 mmHg ( approximately 60%) of the maximal IPD(PT-AoT). These results indicate that the higher PT than AoT blood pressure observed in fetal lambs is a systolic phenomenon principally related to the combination of a relatively higher level of right ventricular pump function manifest in early and midsystole and a pressure-increasing energy wave arising from the fetal pulmonary vasculature in midsystole.

Background: Recent evidence has suggested that haemodynamic information obtained from cardiac catheterisation is not essential in pre-operative assessment of children with hypoplastic left heart syndrome (HLHS) undergoing Bidirectional Cavopulmonary Connection (BCPC). Therefore our unit changed to cardiac Magnetic Resonance Imaging (MRI) in 2006. We aimed to compare peri-operative outcomes before and after this change., Methods: Children with HLHS who underwent BCPC between 2004 and 2008 were identified. Data were collected regarding pre-operative findings and peri-operative outcomes., Results: Forty patients were identified-catheterisation (n=21), MRI (n=19). Catheterisation patients were older at the time of BCPC (114.9+/-22.7 days vs. 95.4+/-11 days: p value 0.002), with no other differences in baseline data. Two patients required cardiopulmonary resuscitation during catheterisation; with no adverse events during MRI. Cardiopulmonary bypass time, ventilation time, inotrope score, and intensive care unit stay were similar. Length of hospital stay and oxygen saturations at discharge were also not significantly different., Conclusions: We have demonstrated that post-operative course and outcomes are similar in patients with HLHS who had MRI or catheterisation as their pre-BCPC investigation. Additionally the complementary data provided by echocardiography and MRI safely provides sufficient anatomic and functional information with which to plan the BCPC., (Crown Copyright (c) 2010. Published by Elsevier B.V. All rights reserved.)

Meconium aspiration syndrome (MAS) disrupts perinatal decreases in pulmonary vascular resistance (PVR) and is the commonest cause of neonatal pulmonary hypertension. The contribution of the potent vasoactive agent urotensin-II (U-II), in the pathophysiology of this condition, is unknown. In a new perinatal model of MAS, we combined measurement of circulating U-II levels with U-II receptor blockade studies. Nineteen anesthetized lambs were instrumented then randomly allocated to the following groups: 1) control (n = 5), 2) control plus specific U-II receptor blockade with palosuran (n = 5), 3) tracheal instillation of meconium (n = 5), 4) meconium instillation plus palosuran (n = 4). Hemodynamics, PVR, and plasma U-II were measured for 6 h after delivery. After birth in controls, U-II increased (p < 0.05), and PVR fell (p = 0.01) and this fall was prevented by U-II receptor blockade. By contrast, meconium lambs displayed a greater rise in U-II levels (p < 0.05 versus control) with an increase in PVR (p < 0.005) that was attenuated by U-II receptor blockade (p < 0.001). These findings suggest that U-II normally acts as a pulmonary vasodilator after birth, but in the presence of MAS, it assumes a vasoconstrictor role. U-II receptor blockade also improves pulmonary hemodynamics in this model.

Background: Poor long-term outcomes are expected after Fontan surgery, but these perspectives have been tainted by the poorly functioning Fontans suffering from arrhythmias. No predictions of outcome can be quoted to the increasing number of Fontan patients free from arrhythmic complications. The parameters determining improved exercise capacity and quality of life in this subgroup are yet unknown., Methods: Fontan survivors from our institution and living in Victoria were invited to participate in the study if they were more than 10 years of age, and free of arrhythmias. A mean of 17 +/- 4 years after Fontan, 36 patients, 23 with a classical atriopulmonary connection (AP) and 13 with a lateral tunnel (LT) underwent transthoracic echocardiography, cycloergometer exercise study, neurohumoral screening, and assessment of quality of life., Results: The only factor predicting worse exercise capacity was the type of Fontan performed; patients with LT having better exercise capacity than those with AP (percentage of predicted anaerobic threshold: 88 +/- 14% vs 72 +/- 14%, p < 0.005; percentage of predicted VO(2)max: 62 +/- 8% vs 54 +/- 7%, p < 0.005). Endothelin-1 levels were elevated in all patients (2.9 pmol/L, 2.5 to 3.7). Responses from the quality of life measures placed our Fontan cohort mainly within the normal population range. None of the preoperative and postoperative variables adversely affected patients' quality of life., Conclusions: The anaerobic threshold of arrhythmia-free Fontan patients operated with the lateral tunnel technique was relatively preserved. Despite restricted exercise capacity, Fontan patients, provided that they are free of arrhythmias, have a normal quality of life reflected in their reports of psychiatric symptoms and family relationships.

In midsystole, fetal pulmonary trunk (PT) and arterial (PA) blood flows characteristically fall, despite pulmonary blood pressure increasing, while ductus arteriosus (DA) flow continues to rise to a delayed peak. Wave intensity (WI) analysis indicates that midsystolic fetal PT and PA flow reductions are related to a very large midsystolic PA backward-running compression wave (BCW(ms)), which originates in the pulmonary microvasculature and is partially transmitted into the PT. This study tested the hypothesis that midsystolic augmentation of DA blood flow was related to transmission of the PA BCW(ms) into the DA. DA, PT, and PA WI analysis was performed in eight anesthetized late-gestation fetal sheep instrumented with DA, PT, and left PA micromanometer catheters to measure pressure (P) and transit-time flow probes to obtain blood velocity (U). In a subgroup (n = 5), the main PA was briefly occluded to abolish wave transmission from the lungs. WI was calculated as the product of P and U rates of change. PA and PT WI profiles both contained a prominent BCW(ms), approximately 5-fold larger in the PA (P < 0.005), which increased P but decreased U. By contrast, the DA WI profile demonstrated a large midsystolic forward-running compression wave (FCW(ms)), which increased DA P and U, and occurred 5 ms after PA BCW(ms). Furthermore, both DA FCW(ms) and PT BCW(ms) were abolished by main PA occlusion. These results suggest that the fetal PA BCW(ms) undergoes retrograde transmission into the PT as a BCW(ms), but antegrade transmission into the DA as a FCW(ms) that augments midsystolic DA flow.

Steady-state wave intensity (WI) analysis indicates that characteristic midsystolic falls in fetal pulmonary trunk (PT) and artery (PA) blood flow are due to an extremely large backward-running compression wave (BCW(ms)) that 1) originates from the pulmonary microvasculature by a combination of cyclical pulmonary vasoconstriction and vascular reflection of the forward-running compression wave (FCW(is)) associated with impulsive right ventricular ejection, and 2) is transmitted into the PT. However, no information is available about the dynamic properties of PA BCW(ms) and its contribution to beat-to-beat regulation of pulmonary hemodynamics. Accordingly, beat-by-beat WI analysis was performed during brief increases in ventricular contractility accompanying an extrasystole (ES) in nine anesthetized late-gestation fetal sheep instrumented with PT and left PA micromanometer catheters to measure pressure (P) and transit-time flow probes to obtain blood velocity (U). WI was calculated as the product of P and U rates of change. At steady state, the magnitude of PA BCW(ms), and its associated P and U changes (DeltaP and DeltaU, respectively), were similar to those of FCW(is). The PA FCW(is) and BCW(ms), and their accompanying DeltaP and DeltaU, were all transiently potentiated after an ES. Beat-by-beat PA FCW(is)-BCW(ms) wave area, DeltaP and DeltaU relationships were highly linear (R(2) > or = 0.91) with slopes of 1.36-1.47 (P < 0.001), consistent with the presence of a vasoconstrictor component in PA BCW(ms). PA-PT BCW(ms) area and DeltaP and DeltaU relationships were also linear (R(2) > or = 0.77) with slopes of 0.23-0.64 (P < 0.001). These results indicate that the fetal PA BCW(ms) contributes to beat-to-beat regulation of not only PA but also PT hemodynamics.

Objectives: The aim of this study was to relate changes in energy expenditure and growth in infants with congenital heart disease (CHD), to the timing of corrective cardiac surgery., Methods: Prospective cohort study of infants less than 1 year with CHD admitted for cardiac surgery to Royal Children's Hospital, between January to September 2005. Infants were assessed using anthropometry and indirect calorimetry and compared to healthy age-matched controls., Results: Infants (38) underwent corrective (n=25) or palliative (n=13) cardiac surgery either at < or = 10 days or at >10 days. Infants undergoing corrective surgery after 10 days had deficits in z-scores for weight compared with infants undergoing early surgery (-1.15+/-1.02 vs -0.24+/-0.98; CI 95%: -1.736 to -0.085; P<0.05) and height (-1.47+/-1.16 vs -0.12+/-0.66; CI 95%: -2.262 to -0.428; P<0.01). However, 6 months following surgery, weight and height were similar in both groups. Resting energy expenditure was increased before surgery compared to healthy controls (247+/-36 vs 210+/-22 kJ kg(-1 )day(-1); 95% CI: -57.29 to -16.71; P<0.001) however, normalized 1 week following cardiac surgery. Standard equations did not accurately predict measured REE., Conclusion: Increased REE observed in infants with CHD normalizes within 1 week following corrective cardiac surgery. Deficits in weight and growth were greater in infants undergoing corrective cardiac surgery>10 days of age compared with infants undergoing surgery in the first 10 days of life.

Aim: Antenatal diagnosis of severe congenital heart disease enables planning of perinatal care of affected infants. Congenital heart surgery is highly centralised in Australia, and surgery for hypoplastic left heart syndrome (HLHS) currently takes place at a single institution, in order to ensure case volume. The study aims to review the impact of antenatal diagnosis on the early clinical course of infants with HLHS in Australia., Methods: Retrospective review was performed on all neonates who were admitted for management of HLHS between 2001 and 2005 at the Paediatric Cardiac Surgical Unit, The Royal Children's Hospital, Melbourne, Australia., Results: Sixty neonates with HLHS were admitted, in whom an antenatal diagnosis was present in 46 (77%). Treatment was withdrawn in seven infants, of whom three had prenatal, and 4 had post-natal diagnoses. Antenatally diagnosed infants were commenced on prostaglandin earlier than post-natally diagnosed infants (age 1 h and 55 h respectively), and on paediatric intensive care unit admission had a higher pH (7.31 vs. 7.20), a lower lactate (3.0 vs. 6.7), a lower inspired oxygen fraction (0.21 vs. 0.96) and were less likely to be ventilated (10.8% vs. 92.9%). Infants with an antenatal diagnosis had lower peak creatinine (70 vs. 120) and alanine aminotransferase (29 vs. 242). The survival to intensive care discharge and stage 2 palliation was 74% and 68% respectively, and was not influenced by timing of diagnosis., Conclusions: Antenatal diagnosis of HLHS was strongly associated with a superior pre-operative clinical status, but did not influence early survival after surgical palliation.

Local reflection coefficients (R) provide important insights into the influence of wave reflection on vascular haemodynamics. Using the relatively new time-domain method of wave intensity analysis, R has been calculated as the ratio of the peak intensities (R(PI)) or areas (R(CI)) of incident and reflected waves, or as the ratio of the changes in pressure caused by these waves (R(DeltaP)). While these methods have not yet been compared, it is likely that elastic non-linearities present in large arteries will lead to changes in the size of waves as they propagate and thus errors in the calculation of R(PI) and R(CI). To test this proposition, R(PI), R(CI) and R(DeltaP) were calculated in a non-linear computer model of a single vessel with various degrees of elastic non-linearity, determined by wave speed and pulse amplitude (DeltaP(+)), and a terminal admittance to produce reflections. Results obtained from this model demonstrated that under linear flow conditions (i.e. as DeltaP(+)-->0), R(DeltaP) is equivalent to the square-root of R(PI) and R(CI) (denoted by R(PI)(p) and R(CI)(p)). However for non-linear flow, pressure-increasing (compression) waves undergo amplification while pressure-reducing (expansion) waves undergo attenuation as they propagate. Consequently, significant errors related to the degree of elastic non-linearity arise in R(PI) and R(CI), and also R(PI)(p) and R(CI)(p), with greater errors associated with larger reflections. Conversely, R(Delta)(P) is unaffected by the degree of non-linearity and is thus more accurate than R(PI) and R(CI).

Precise identification of end-diastole (ED), corresponding to the end of diastole and start of systole, is crucial for accurate assessment of cardiac function. The aims of this study were to develop a new algorithm based on peak curvature (kappa(p)) for detecting ED as a "corner" in left ventricular pressure (LVP) signals, and to compare this approach with "gold-standard" ED obtained by manual annotation (ED(man)) and ED calculated with previously described algorithms that use an LVP first-derivative threshold (dP/dt(0) or dP/dt(100)), the peak LVP second-derivative (d(2)P/dt(2)(p)) or ECG R-wave peak (ECG(R)). Using customized software, all algorithms were applied to data derived from 213 large animal studies spanning a wide range of animal ages (fetus to adult), heart rates, inotropic states, and loading conditions. Differences between ED(man) and each algorithm were then compared after defining an acceptance region for the ED detection based on ED(man) interobserver variability. ED detected with kappa(p) was the most accurate (p < 0.001) and least variable (p < 0.001), with 97% of measurements within the acceptance region and difference from ED(man) of (1.5 +/- 4.2) ms. By contrast, ED was often detected early with dP/dt(0) and dP/dt(100) , and late with d(2)P/dt(2)(p) and ECG(R). These results indicate that the peak curvature algorithm using LVP provides accurate and reliable detection of ED.

Background: Rheumatic heart disease (RHD) is an important problem in developing countries; however, many cases are detected only when the disease has progressed to cardiac failure. Screening can detect cases earlier, but there are no screening guidelines., Methods: We performed a cross-sectional screening study in Tonga among 5,053 primary school children, in whom auscultation followed by echocardiography of those with heart murmurs were used to identify RHD. We also analyzed whether a three-stage screening protocol of auscultation performed by a medical student to detect any heart murmur, second-stage auscultation performed by a local pediatrician to differentiate pathological from innocent murmurs and echocardiography of those with pathological murmurs altered outcomes., Results: The prevalence of definite RHD was 33.2 per 1,000. The prevalence of RHD increased significantly with age, peaking at 42.6 per 1,000 in children aged 10-12 years. Most valve lesions (91 [54%] of 169) were mild. Auscultation to detect pathological murmurs was poorly sensitive (46.4%), and the finding of any murmur on auscultation did not affect the likelihood of detecting pathology on echocardiography. The finding of a pathological murmur did significantly increase the likelihood of detecting pathology on echocardiography, but still missed 54% of those with pathology (mainly RHD) detected on echocardiography., Conclusions: Screening is a useful method for detecting asymptomatic RHD in regions of high prevalence and we report a high echocardiographically confirmed prevalence. The most appropriate screening strategy remains to be confirmed, however, and implementation will depend on the availability of echocardiography and trained staff.

The physiological basis of a characteristically low blood flow to the fetal lungs is incompletely understood. To determine the potential role of pulmonary vascular interaction in this phenomenon, simultaneous wave intensity analysis (WIA) was performed in the pulmonary trunk (PT) and left pulmonary artery (LPA) of 10 anesthetized late-gestation fetal sheep instrumented with PT and LPA micromanometer catheters to measure pressure (P) and transit-time flow probes to obtain blood velocity (U). Studies were performed at rest and during brief complete occlusion of the ductus arteriosus to augment pulmonary vasoconstriction (n = 4) or main pulmonary artery to abolish wave transmission from the lungs (n = 3). Wave intensity (dI(W)) was calculated as the product of the P and U rates of change. Forward and backward components of dI(W) were determined after calculation of wave speed. PT and LPA WIA displayed an early systolic forward compression wave (FCW(is)) increasing P and U, and a late systolic forward expansion wave decreasing P and U. However, a marked midsystolic fall in LPA U to near-zero was related to an extremely prominent midsystolic backward compression wave (BCW(ms)) that arose approximately 5 cm distal to the LPA, was threefold larger than the PT BCW(ms) (P < 0.001), of similar size to FCW(is) at rest (P > 0.6), larger than FCW(is) following ductal occlusion (P < 0.05) and abolished after main pulmonary artery occlusion. These findings suggest that the absence of pulmonary arterial midsystolic forward flow which accompanies a low fetal lung blood flow is due to a BCW(ms) generated in part by cyclical vasoconstriction within the pulmonary microcirculation.

A proportion of symptomatic neonates with congenital heart disease have lesions requiring urgent stabilisation. Despite increasing antenatal diagnoses, the importance of early recognition of symptomatic neonates is highlighted by the fact that up to 10% of all deaths in congenital heart disease continue to occur in children undiagnosed at the time of death. Specific anatomical knowledge of the many complex lesions is not required for good early management. The focus of this article is the specific symptom complexes in critically ill neonates with congenital heart disease, initial management strategies for stabilization and transfer to specialist centres, and issues in the ongoing preoperative care.

This study undertook a detailed examination of the ventricular-vascular interaction of the predominant beta-adrenergic agonist dobutamine using wave intensity analysis. Eight anesthetized open-chest ewes were instrumented with an aortic micromanometer to measure central aortic blood pressure (P) and an ultrasonic flow probe to obtain ascending aortic blood velocity (U). Hemodynamics were recorded during incremental dobutamine infusion (0.5, 1, 2.5, 5, 7.5, and 10 microg.kg(-1).min(-1)). Wave intensity (dI(W)) was calculated as the product of the rates of change of P and U with customized software using ensemble-averaged signals. Forward and backward components of dI(W), P, and U were determined after calculation of wave speed. As well as the typical initial forward compression wave (FCW), midsystolic backward compression wave (BCW), and late-systolic forward expansion wave (FEW(es)), two minor and previously unheralded waves were also detectable in the wave intensity profile at baseline. The first was an early systolic backward expansion wave (BEW), which reduced P but increased peak U. The second was a mid-systolic forward expansion wave (FEW(ms)), which reduced P and U. During dobutamine infusion FCW dI(W) increased 18-fold (P < 0.001), but BCW dI(W) rose 12-fold (P < 0.001) while FEW(es) dI(W) fell by 70% (P < 0.001). However, the latter changes were accompanied by a 44-fold increase in BEW dI(W) (P = 0.005) that augmented the initial aortic forward flow and a >100-fold rise in FEW(ms) dI(W) (P < 0.001) that produced earlier and enhanced aortic blood deceleration. These findings provide new insights into the ventricular-vascular interaction of dobutamine.

Objective: The congenitally bicuspid aortic valve is the most common etiologic factor associated with clinically significant aortic stenosis and/or regurgitation in pediatric patients. Beyond infancy, surgical intervention typically involves valve repair with cusp thinning and commissurotomy or valve replacement, primarily with pulmonary autograft in the current era. An aortic valve repair technique using tricuspidization with cusp extension was introduced in 1999. This study compares the midterm clinical outcome in patients undergoing valve repair by tricuspidization with cusp extension with those receiving a pulmonary autograft (Ross)., Methods: A retrospective study was performed on all consecutive patients with symptomatic bicuspid aortic valve disease who underwent tricuspidization with cusp extension or a Ross procedure between 1999 and 2005. In both groups, all patients were at least 1 year of age at time of the operation., Results: During this period, 21 children (median age 12.6 years, range 2.6-18 years) underwent tricuspidization with cusp extension (TCE group) and 25 children (median age 10.2 years, range 11.5 months-20.1 years) underwent the Ross procedure. Prior balloon valvuloplasty was performed in 5 (24%) of the children in the TCE group and 16 (64%) of the children in the Ross group. Prior surgical commissurotomy was performed in 4 (19%) TCE patients and in 9 (36%) Ross patients. During a median follow-up period of 36.4 months (range 2.5 months-7.4 years), 2 (10%) patients in the TCE group required valve-preserving early revision of the repair, 2 (10%) TCE patients required subsequent aortic valve replacement at 16 and 33 months, 1 (4%) Ross patient required subsequent valve repair at 5 years, and 1 (4%) Ross patient underwent cardiac transplantation at 46 months. At 36 months, the actuarial freedom from reintervention on the aortic valve or autograft was 90% in the TCE group, with 11 patients at risk, and 100% in Ross patients, with 13 patients at risk (P = .39); the freedom from moderate valve dysfunction or reintervention was 66% for TCE patients and 95% for Ross patients (P = .07). There were no deaths, and all but 1 Ross patient remain in New York Heart Association class I., Conclusions: Reintervention rates in patients undergoing tricuspidization with cusp extension or a primary Ross procedure are similar. Valve performance in the TCE group is satisfactory at midterm follow-up, but the Ross repair appears to provide greater stability of valve function. These results suggest that repair with valve tricuspidization and cusp extension provides reliable palliation of the symptomatic bicuspid aortic valve.

Objectives: Ultrasound-based screening is widely employed for the detection of congenital malformations in utero including congenital heart disease (CHD), but there is widespread variability in the efficacy of screening programs. We aimed to evaluate current antenatal detection rates of selected congenital heart defects in Victoria., Methods: Data were collected from the Victorian Perinatal Data Collection Unit and Birth Defects Registry. There were 631 209 births in Victoria (1993-2002), of which 4897 cases had CHD. Cases included live births, stillbirths and termination of pregnancies because of CHD. We reviewed all cases from 1999 to 2002 with atrioventricular septal defect, simple coarctation of the aorta, double-inlet or -outlet ventricle, hypoplastic left heart syndrome, simple transposition of the great arteries (TGA), tetralogy of Fallot and truncus arteriosus. Outcome measures were antenatal diagnosis, pregnancy outcome and associated malformations., Results: The overall birth prevalence of CHD from 1993 to 2002 in Victoria was 7.8/1000. The antenatal detection rate for the seven selected defects from 1999 to 2002 was 52.8%. All but 4.8% of the cases had an ultrasound examination at > 13 weeks' gestation. Antenatal detection was highest for hypoplastic left heart syndrome (84.6%) and lowest for simple TGA (17.0%)., Conclusions: This study shows wide variation in the antenatal detection rate of CHD in Victoria. The low antenatal detection rate of TGA, a defect that should be detected easily, demonstrates suboptimal routine obstetric anomaly scanning.

Specific features of hemodynamic signals are invaluable for elucidating ventricular and vascular function. A semi-automatic algorithm is presented that enables accurate detection of any feature in any hemodynamic signal, using feature extraction from local maxima and minima in signal curvature. A particular feature is selected manually in the first beat and then detected automatically in subsequent beats.

Aim: Antenatal diagnosis of congenital heart disease (CHD) facilitates prenatal treatment and optimal perinatal care. This has been demonstrated to improve perinatal mortality and morbidity in neonates with CHD. Thus, antenatal diagnosis of CHD is most likely to benefit patients who require surgery in early infancy. We aimed to examine the frequency of antenatal diagnosis in neonates presenting to The Royal Children's Hospital severe CHD., Methods: Main outcome measures were antenatal diagnosis and whether the individual lesion would have been expected to be detected on a four-chamber view or four-chamber and outflow tract view during a routine obstetric anomaly ultrasound. Poisson regression was used to estimate the average trend over the study period., Results: A total of 610 patients met the inclusion criteria, of whom 164 had an antenatal diagnosis (26.8%). If routine ultrasound screening was ideal, we would have expected 63.9% of cases to be detected on four-chamber view and 83.6% on four-chamber and outflow tract view. Trend analysis demonstrated an annual rate of improvement of 9% in actual versus expected antenatal diagnosis of CHD. Malformation-specific analysis showed that antenatal detection was the highest for double inlet/outlet ventricle (51.3%, 95% confidence interval 34.8-67.6%) and the lowest for simple transposition of the great arteries (15.6%, 95% confidence interval 9.0-24.5)., Conclusion: Despite mass screening for congenital malformations in Victoria with routine antenatal ultrasounds, a large proportion of neonates with severe congenital heart disease still present without an antenatal diagnosis.

Sildenafil is becoming increasingly popular for the treatment of pulmonary hypertension. However, there are potential concerns regarding its effects on oxygenation and systemic hemodynamics that could theoretically reduce its utility in the neonatal population. We performed a prospective cumulative dose-response study of increasing doses of i.v. sildenafil (0.4, 1, and 3 mg/kg) on hemodynamics and oxygenation in 32 anesthetized piglets, of which 17 had meconium-induced pulmonary hypertension and lung injury, and 15 did not. Sildenafil caused a reduction in mean pulmonary artery pressure and pulmonary vascular resistance (PVR) at all doses, in non-lung-injured animals. There was no difference in pulmonary hemodynamics between doses. Oxygenation index [OI = mean airway pressure (cm H2O) * FiO2 * 100/PaO2 (mm Hg)] did not reach critical levels at any dose. In lung-injured animals, sildenafil also reduced mean pulmonary artery pressure and PVR by 30%. Again, this effect was achieved at the lowest dose, without subsequent changes at higher doses. However, in lung-injured animals, sildenafil produced a dose-related increase in oxygenation index. Sildenafil reduced the systemic vascular resistance (SVR) at the lowest dose in lung-injured animals, but this occurred only at higher doses in non-lung-injured animals. In conclusion, sildenafil is a potent pulmonary vasodilator. However, it should be administered with caution in the presence of lung injury because of a dose-related increase in oxygenation index and concomitant systemic vasodilatation.

Since September 2001, 7 consecutive patients with childhood idiopathic pulmonary arterial hypertension (IPAH), a rapidly progressive and fatal condition, have been treated with combinations of bosentan, and other therapies (sildenafil/warfarin/epoprostenol), at our institution. Survival and clinical status in these patients were compared with a group of 12 historic control patients who were diagnosed prior to 1997 and received only conventional medical therapy. Survival in the bosentan-treated subjects was better than among historic controls with comparable disease severity (log rank, p = 0.04). Our findings indicate treatment with bosentan permits a delay in IPAH disease progression and, in combination with other therapies, improves survival compared with historic control patients.

Background: Improved survival in young people with congenital heart disease (CHD) alters the significance of a range of developmentally important subjects, such as sexual and reproductive health. The aim of this study was to determine the level of knowledge about sexual and reproductive health issue in young people with CHD., Methods: We undertook a systematic review of the literature from 1966 to March 2004, searching Medline, Psych Info, and Em base using a broad range of search terms. Additionally, we searched the literature for published guidelines on standards of care for young people with CHD., Results: We identified ten articles that examined patients,' understanding of their heart disease. Seven of them specifically investigated knowledge of sexual and reproductive health as it related to cardiac disease., Conclusions: In general, young people have a poor understanding of their heart disease. They appear to have a particularly poor grasp of sexual and reproductive health issues, yet they are interested in these issues. Therefore, health care programs for young people with CHD should incorporate sexual and reproductive health information and include anticipatory counseling and health risk screening.

In neonates with coarctation of the aorta, left ventricular function may be impaired due to an increased afterload and an associated endocardial fibroelastosis. Repair of the coarctation usually results in improvement in left ventricular function over the postoperative weeks. We report a patient in whom, despite successful repair of coarctation, left ventricular performance continued to deteriorate. Investigation revealed the unusual coincidental finding of anomalous left coronary artery from the right pulmonary artery.

Objective: Success in treatment of premature infants has resulted in increased numbers of neonates who have bronchopulmonary dysplasia (BPD) and require surgical palliation or repair of congenital heart disease (CHD). We sought to investigate the impact of BPD on children with CHD after heart surgery., Methods: This was a retrospective, multicenter study of patients who had BPD, defined as being oxygen dependent at 28 days of age with radiographic changes, and CHD and had cardiac surgery (excluding arterial duct ligation) between January 1991 and January 2002. Forty-three infants underwent a total of 52 cardiac operations. The median gestational age at birth was 28 weeks (range: 23-35 weeks), birth weight was 1460 g (range: 431-2500 g), and age at surgery was 2.7 months (range: 1.0-11.6 months). Diagnoses included left-to-right shunts (n = 15), conotruncal abnormalities (n = 13), arch obstruction (n = 6), univentricular hearts (n = 4), semilunar valve obstruction (n = 3), Shone syndrome (n = 1), and cor triatriatum (n = 1)., Results: Thirty-day survival was 84% with 6 early and 6 late postoperative deaths. Survival to hospital discharge was 68%. There was 50% mortality for patients with univentricular hearts and severe BPD. The median duration of preoperative ventilation was 76 days (range: 2-244 days) and of postoperative ventilation was 15 days (range: 1-141 days). The median duration of cardiac ICU stay was 7.5 days (range: 1-30 days) and of hospital stay was 115 days (range: 35-475 days). Current pulmonary status includes on room air (n = 14), O2 at home (n = 4), and ventilated at home (n = 4) or in hospital (n = 4), and 5 patients were lost to follow-up., Conclusions: BPD has significant implications for children who have CHD and undergo cardiac surgery, leading to prolonged ICU and hospital stays, although most survivors are not O2 dependent. Postoperative mortality was highest among patients with univentricular hearts and severe BPD. Optimal timing of surgery and strategies to improve outcome remains to be delineated.

We describe a newborn girl with incontinentia pigmenti (IP, MIM308300), unilateral acheiria, and fatal primary pulmonary hypertension. Limb deficiency has not been described previously in IP and pulmonary hypertension only on two previous occasions. A review of the cause of IP shows that these rare manifestations may not be unexpected, given the many roles of the underlying gene product.

We tested the agreement between non-invasive measurement of intrapulmonary shunt, using oxygen uptake and pulmonary capillary blood flow measurement obtained by nitrous oxide rebreathing, with that measured using mixed venous blood sampling. Nine patients were recruited pre- and post-cardiac surgery resulting in 20 sets of measurements overall. Mean shunt fraction was 12.5%, and bias between methods (+/-95% confidence limits) was -0.7% (+/-0.8%). The standard deviation of the difference was 1.7% with limits of agreement between the two methods of +2.6% and -3.9%. Correlation coefficient r was 0.90. Agreement with the invasive standard was less accurate and precise where cardiac output was measured by bolus thermodilution (mean bias +1.6%, standard deviation of the difference 2.2%, limits of agreement between the two methods of +5.8% and -2.8%, r = 0.86). Good agreement was demonstrated between the non-invasive method and the invasive reference standard.

Acute neonatal pulmonary hypertension is associated with increased activation of the endogenous endothelin pathway. We investigated the role of selective endothelin-A receptor blockade using i.v. BQ-123 in a piglet model of meconium aspiration syndrome. Meconium aspiration was induced in 18 anesthetized piglets. Six controls received no further intervention. Six piglets received 1 mg/kg BQ-123 at 120 min, with the addition of 20 ppm inhaled nitric oxide at 240 min. Six commenced nitric oxide therapy at 120 min, and were given i.v. BQ-123 at 240 min. The total study duration was 360 min. Meconium aspiration resulted in acute pulmonary hypertension and elevated endothelin-1 levels in all animals. There were no changes in pulmonary hemodynamics or endothelin-1 levels beyond 120 min in controls. In the group receiving BQ-123 first, this agent alone reduced the pulmonary artery pressure and pulmonary vascular resistance, and the subsequent addition of inhaled nitric oxide further reduced pulmonary artery pressure. In the group first receiving nitric oxide alone, this reduced the pulmonary artery pressure, and the addition of BQ-123 resulted in a fall in pulmonary vascular resistance. Endothelin-1 levels increased with both agents. BQ-123 was found to be a highly effective pulmonary vasodilator and augmented the effects of nitric oxide in this model of acute pulmonary hypertension.

Objective: We sought to assess the effects of insulin-like growth factor 1 on the balance between systemic oxygen consumption and oxygen delivery after cardiopulmonary bypass in piglets., Methods: Twelve piglets weighing 4.5 to 8.3 kg undergoing hypothermic (28 degrees C) cardiopulmonary bypass for 70 to 120 minutes with 40 minutes of aortic crossclamping were studied before and during the first 6 hours after cardiopulmonary bypass. Oxygen consumption was continuously measured by an indirect calorimeter, Deltatrac II MBM-200 Metabolic Monitor (Datex Division Instrumentarium, Helsinki, Finland). Oxygen delivery and cardiac output were calculated from oxygen consumption and the arterial and mixed venous oxygen contents sampled before and every 30 minutes after cardiopulmonary bypass. Oxygen extraction ratio was derived by the ratio of oxygen consumption to oxygen delivery. Arterial blood lactate was measured before and every 30 minutes after cardiopulmonary bypass. Six animals were randomly assigned to receive an intravenous infusion of insulinlike growth factor 1 at 1.2 mg/h from 1 to 6 hours after cardiopulmonary bypass; the remaining 6 served as a control group., Results: Relative to the control group, intravenous infusion of insulin-like growth factor 1 significantly reduced oxygen consumption (P =.02) and increased cardiac output (P =.016) and oxygen delivery (P =.049) during the first 6 hours after surgery with hypothermic cardiopulmonary bypass. As a result, oxygen extraction was significantly decreased (P =.012)., Conclusions: Intravenous infusion of insulin-like growth factor 1 improved oxygen transport by reducing oxygen consumption as well as increasing cardiac output and oxygen delivery during the first 6 hours after cardiopulmonary bypass in piglets. This may have important clinical implications for the care of critically ill children after surgery with cardiopulmonary bypass.

There has been recent interest in the use of the phosphodiesterase-5 inhibitor sildenafil for treating pulmonary hypertension. We examined the interaction between inhaled nitric oxide (iNO) and i.v. sildenafil in 12 piglets with acute pulmonary hypertension and lung injury secondary to meconium aspiration. Six animals (controls) received no intervention after meconium instillation, and six received iNO (20 ppm) from 120 min, with the addition at 240 min of an i.v. sildenafil infusion (2 mg/kg over 2 h). Meconium instillation increased mean pulmonary artery (PA) pressure from 16.0 +/- 3.1 to 24.8 +/- 4.6 mm Hg (p < 0.01) and pulmonary vascular resistance (PVR) from 0.047 +/- 0.008 to 0.089 +/- 0.027 mm Hg. ml(-1). min(-1). kg(-1) (p < 0.01). Oxygenation index increased from 3 +/- 0.8 to 8.3 +/- 3.0 (p < 0.01). There were no further changes beyond 120 min in controls. iNO reduced PA pressure and PVR to baseline values, without influencing oxygenation. The addition of sildenafil further reduced PA pressure, tended to increase the cardiac output, and reduced PVR from 0.049 +/- 0.02 to 0.028 +/- 0.01 mm Hg. ml(-1). min(-1). kg(-1) (p < 0.05). Sildenafil lowered the systemic blood pressure and systemic vascular resistance and produced profound arterial hypoxemia, reducing arterial Po(2) from 69 +/- 23 mm Hg to 49 +/- 15 mm Hg, despite substantial increases first in inspired oxygen fraction and subsequently in mean airway pressures. Consequently, the oxygenation index increased by 13.9 +/- 4.8 (p = 0.01). When given in addition to iNO, sildenafil at a dose of >0.5 mg/kg produced profound pulmonary vasodilation, but this was coupled with an unacceptable deterioration in oxygenation and systemic vasodilation in this model of pulmonary hypertension with acute parenchymal lung disease.

Regional mechanical and electrophysiological changes accompany most ventricular arrhythmias and, it has been suggested, by mechanoelectric feedback. We hypothesized that an intervention producing regional mechanical dispersion was associated with regional, proarrhythmic electrical dispersion and studied the regional mechanoelectric feedback in the right ventricle (RV) of anesthetized lambs. Ten lambs were deeply anesthetized, and their hearts were exposed. Three tripodal devices, each incorporating three monophasic action potential electrodes and an integrated strain-gauge system, were placed on the RV apex outflow and inflow regions. Measurements were made before, during, and after 10-s pulmonary arterial occlusion. Pulmonary arterial occlusion increased RV pressure and overall regional segment length. Length excursion became out of phase with RV pressure beats immediately after occlusion, and the strain patterns were different in the three regions at the peak of occlusion. The occlusion resulted in different alterations in regional monophasic action potential morphology, including reduction in monophasic action potential amplitude and duration by different amounts and early afterdepolarizations that were unevenly distributed in the monophasic action potential recordings. This was associated with dispersion of repolarization and recovery time. The combination of electromechanical events precipitated a variety of arrhythmias. Acute RV distension is proarrhythmic, possibly through a causal relationship among mechanically induced afterdepolarizations, dispersion (heterogeneity) of mechanical strain, and dispersion of electrical recovery. The relationship among the different wall motions, the dispersion of repolarization, and arrhythmia underscored mechanoelectric feedback as an important part of arrhythmogenesis in pulmonary embolism and commotio cordis.

Objective: To quantify non-invasively right ventricular (RV) performance in infants after stage 1 palliation for hypoplastic left heart syndrome (HLHS)., Design: Prospective, observational study with two dimensional and strain Doppler echocardiography., Setting: Single tertiary paediatric cardiology centre., Patients: Convenience sample of nine consecutive infants with HLHS. Four whose surgery involved a systemic to pulmonary artery (S-PA) shunt were compared with five whose surgery incorporated a right ventricle to pulmonary artery (RV-PA) conduit., Methods: Basal RV free wall longitudinal strain rate, systolic strain (epsilon), and RV percentage area change were calculated during a single assessment between 27-50 days after surgery., Results: Cardiopulmonary bypass time was longer in patients who underwent RV-PA (226 (30) minutes v 181 (18) minutes, p = 0.03), but cross clamp time, duration of ventilation, and inotrope use did not differ. Two patients in the S-PA group died, on days 29 and 60 after surgery. Peak systolic strain rate (-1.24 (0.19)/s v -0.91 (0.21)/s, p = 0.048), peak epsilon (-17.8 (1.8)% v -13.4 (2.0)%, p = 0.01), and RV percentage area change (56 (6)% v 25 (6)%, p < 0.01) were all greater among RV-PA patients. These indices also tended to be greater in survivors as a group. Ventricular loading conditions (oxygen saturations, diuretic treatment, and blood pressure) were similar in both groups., Conclusion: Strain Doppler echocardiography shows improved RV longitudinal systolic contractility in patients during convalescence after the RV-PA modification of stage 1 palliation for HLHS compared with those with an S-PA shunt.

Recent decades have witnessed dramatic advances in the care of adults with heart disease. However, equally significant advances have occurred in the care of children. In this review we describe some of the advances, which have been made in the care of children with heart disease, focusing not only on technological advances, but also on developments in team-based care, which together have resulted in significant improvements in outcomes.

Aim: Mechanically induced early afterdepolarization (EAD) is morphologically similar but different in the mechanisms with drug-induced EAD, which lead to arrhythmia. Pacing suppresses the drug-induced EAD and arrhythmia, however the effect of pacing on mechanically induced EAD and arrhythmia is not clear. This study addressed this issue in right ventricle (RV) of anaesthetized lambs., Methods: Six lambs were anaesthetized, and their hearts exposed. Nine monophasic action potential (MAP) electrodes were placed on RV apex, outflow and inflow regions, and recorded before, during, and after a 10 s occlusion of pulmonary artery at a number of pacing rates., Results: Pacing significantly reduced the baseline MAP duration at 90% repolarization (MAPD90), decreased the reduction of MAPD at early repolarization at the peak of occlusion. Nonetheless, the percentage of reduction was not significantly different among them. Pacing was able to reduce the frequencies, size of mechanically induced EADs. MAPD90 at the peak of occlusion was all shortened during pacing rather than some lengthened at intrinsic rate. Therefore, the dispersion of MAPD90 at the peak of occlusion reduced from 86 +/- 6 ms at intrinsic rate to 42 +/- 4 ms at 120 beats min-1, 38 +/- 3 ms at 150 beats min-1 and 26 +/- 3 ms at 170 beats min-1. Ultimately, pacing reduced/suppressed mechanically induced premature ventricular beats. These alterations were inversely related to heart rates., Conclusion: Pacing reduces/suppresses both stretch-induced EADs and arrhythmia. These modulations are remarkably similar to those on other EADs by the pacing.

Objective: To investigate the acute effects of intravenous sildenafil on haemodynamics and oxygenation, and its interaction with inhaled nitric oxide (iNO) in infants at risk of pulmonary hypertension early after cardiac surgery., Design: Prospective, randomised trial., Setting: Paediatric intensive care unit of a children's hospital., Patients and Participants: Sixteen ventilated infants early after closure of ventricular or atrioventricular septal defects, were randomly assigned to one of two groups. The study was completed in 15 infants., Interventions: Studies were commenced within 7 h of separation from bypass. Seven infants received iNO (20 ppm) first, with the addition of intravenous sildenafil (0.35 mg/kg over 20 min) after 20 min. Eight infants received sildenafil first, iNO was added after 20 min. Vascular pressures, cardiac output and a blood gas were recorded at 0, 20 and 40 min., Measurements and Results: In infants receiving iNO first, iNO lowered the pulmonary vascular resistance index (PVRI) from 3.45 to 2.95 units (p=0.01); sildenafil further reduced PVRI to 2.45 units p<0.05). In those receiving sildenafil first, PVRI was reduced from 2.84 to 2.35 units (p<0.05) with sildenafil, and fell to 2.15 units (p=0.01) with the addition of iNO. In both groups, sildenafil reduced the systemic blood pressure and systemic vascular resistance (p<0.01) and worsened arterial oxygenation and the alveolar-arterial gradient (p<0.05)., Conclusion: Intravenous sildenafil augmented the pulmonary vasodilator effects of iNO in infants early after cardiac surgery. However, sildenafil produced systemic hypotension and impaired oxygenation, which was not improved by iNO.

In neonates with severe aortic or pulmonary stenosis, the obstructed circulation is usually supported through patency of the arterial duct. We describe a neonate in whom an aortopulmonary window supported a critically obstructed pulmonary circulation.

Patients after repair of tetralogy of Fallot are at increased risk of arrhythmic death. Clinical data suggest that pulmonary regurgitation predisposes to these arrhythmias, although the cellular electrophysiologic effects of pulmonary regurgitation are unknown. We induced pulmonary regurgitation in lambs, and 3 mo later, having quantified the pulmonary regurgitant (PR) fraction, studied right ventricular mechanical and electrophysiologic properties in vivo and in vitro. The PR fraction was greater in PR (75 +/- 10%) than in sham-operated animals (8 +/- 4%; p < 0.01). In vivo, monophasic action potential duration and activation time, at rest and during acute right ventricular stretch, were similar in both groups. However, the dispersion of activation time was greater in PR animals at rest (13 +/- 1.1 versus 8 +/- 1.1 ms; p < 0.05). Furthermore, the dispersion of activation increased during right ventricular stretch in PR, but not in sham-operated animals. In vitro, myocardial force-frequency responses were similar in both groups, indicating preserved systolic performance, but mechanical restitution studies showed a prolonged refractory period (447 +/- 22 versus 370 +/- 26 ms; p < 0.05) and a decreased recovery time constant (184 +/- 19 versus 265 +/- 20 ms; p < 0.001) in PR animals, indicating altered calcium cycling. Furthermore, the myocardial conduction velocity was reduced in PR animals (31 +/- 3.58 versus 47.9 +/- 5.1 cm/s; p < 0.01), resulting from a 2-fold increase in intracellular resistance (437.25 +/- 125.93 versus 194 +/- 43.27 Omega. cm; p = 0.025). Chronic PR leads to inhomogeneity of right ventricular activation, alters myocardial calcium cycling, reduces conduction velocity, and increases intracellular resistivity. These may contribute to the development of arrhythmias associated with PR, including those in patients after tetralogy repair.