Two-dimensional echocardiographic assessment of right ventricular function as a predictor of outcome in hypoplastic left heart syndrome

The role of home monitoring in interstage management of infants following the Norwood procedure

Although outcomes for infants with complex single ventricle heart defects have steadily improved in recent decades, there is still a significant risk for mortality and morbidity during the interstage period between stage 1 Norwood hospitalization discharge and stage 2 palliation. Home monitoring programs, which involve parental surveillance of daily weight and oxygen saturations during the interstage period, have been shown to significantly improve survival rates. This article describes the potential risk factors or causes of interstage mortality and reviews the role of home monitoring in early detection and potential prevention of adverse outcomes.

Right ventricular systolic function in hypoplastic left heart syndrome: a comparison of velocity vector imaging and magnetic resonance imaging

AIMS

Velocity vector imaging (VVI) is an echocardiographic technique based on speckle tracking, which has been validated for the left ventricle (LV). It has not been validated to assess the systemic right ventricle (RV) in patients with hypoplastic left heart syndrome (HLHS). The aim of this study was to evaluate whether VVI measurements reliably reflect RV systolic function in patients with HLHS when compared with RV ejection fraction (EF) calculated using magnetic resonance imaging (MRI).

METHODS AND RESULTS

In this prospective study, 49 children with HLHS underwent transthoracic echocardiography and cardiac MRI under the same general anaesthetic as a part of routine assessment between the different stages of palliative surgery. Global RV fractional area change (FAC-VVI), strain (S), strain rate (SR), and peak systolic velocity (V) were analysed from the apical four-chamber view using the VVI technique. MRI-derived EF was calculated from a short-axis cine stack of images. Intra- and interobserver reproducibility was excellent for all VVI parameters (intraclass correlation coefficient >0.9). All VVI-derived parameters, except myocardial velocity, correlated with MRI-derived EF (FAC-VVI: R = 0.7, P < 0.001; S: R = -0.5, P < 0.001; SR: R = 0.5, P = 0.001, and V: R = 0.1, P = 0.4).

CONCLUSIONS

All VVI-derived parameters, except V, correlate with MRI-derived EF, with FAC being the best predictor of it. Reproducibility of all VVI parameters is excellent. VVI provides a useful tool for the follow-up of RV function during the staged treatment protocol for HLHS.

Stem cell therapy for CHD: towards translation

Stem cell therapy has the optimistic goal of regenerating the myocardium as defined by re-growth of lost or destroyed myocardium. As applied to patients with heart failure, many confuse or limit the regenerative definition to just improving myocardial function and/or decreasing myocardial scar formation, which may not be the most important clinical outcome to achieve in this promising field of molecular medicine. Many different stem cell-based therapies have been tested and have demonstrated a safe and feasible profile in adult patients with heart failure, but with varied efficacious end points reported. Although not achieved as of yet, the encompassing goal to regenerate the heart is still believed to be within reach using these cell-based therapies in adult patients with heart failure, as the first-generation therapies are now being tested in different phases of clinical trials. Similar efforts to foster the translation of stem cell therapy to children with heart failure have, however, been limited. In this review, we aim to summarise the findings from pre-clinical models and clinical experiences to date that have focussed on the evaluation of stem cell therapy in children with heart failure. Finally, we present methodological considerations pertinent to the design of a stem cell-based trial for children with heart failure, as they represent a population of patients with very different sets of issues when compared with adult patients. As has been taught by many learned clinicians, children are not small adults!

Intracoronary autologous cardiac progenitor cell transfer in patients with hypoplastic left heart syndrome: the TICAP prospective phase 1 controlled trial

RATIONALE

Hypoplastic left heart syndrome (HLHS) remains a lethal congenital cardiac defect. Recent studies have suggested that intracoronary administration of autologous cardiosphere-derived cells (CDCs) may improve ventricular function.

OBJECTIVE

The aim of this study was to test whether intracoronary delivery of CDCs is feasible and safe in patients with hypoplastic left heart syndrome.

METHODS AND RESULTS

Between January 5, 2011, and January 16, 2012, 14 patients (1.8±1.5 years) were prospectively assigned to receive intracoronary infusion of autologous CDCs 33.4±8.1 days after staged procedures (n=7), followed by 7 controls with standard palliation alone. The primary end point was to assess the safety, and the secondary end point included the preliminary efficacy to verify the right ventricular ejection fraction improvements between baseline and 3 months. Manufacturing and intracoronary delivery of CDCs were feasible, and no serious adverse events were reported within the 18-month follow-up. Patients treated with CDCs showed right ventricular ejection fraction improvement from baseline to 3-month follow-up (46.9%±4.6% to 52.1%±2.4%; P=0.008). Compared with controls at 18 months, cardiac MRI analysis of CDC-treated patients showed a higher right ventricular ejection fraction (31.5%±6.8% versus 40.4%±7.6%; P=0.049), improved somatic growth (P=0.0005), reduced heart failure status (P=0.003), and lower incidence of coil occlusion for collaterals (P=0.007).

CONCLUSIONS

Intracoronary infusion of autologous CDCs seems to be feasible and safe in children with hypoplastic left heart syndrome after staged surgery. Large phase 2 trials are warranted to examine the potential effects of cardiac function improvements and the long-term benefits of clinical outcomes.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT01273857.

Ventricular performance after surgery for a congenital heart defect as assessed using advanced echocardiography: from doppler flow to 3D echocardiography and speckle-tracking strain imaging

A varying degree of impairment of ventricular performance is observed over the long-term after surgery for a congenital heart defect (CHD). Impaired ventricular performance has been shown to be of prognostic value for increased risk of cardiovascular events in adult CHD patients. This emphasizes the importance of delineating the timing and cause of this postoperative impairment. Impairment of ventricular performance could develop over time as a consequence of residua, sequelae and complications of the CHD or surgical procedure. Yet, impaired ventricular performance has also been observed immediately after surgery and can persist and/or worsen over time. This postoperative impairment of ventricular performance is the focus of this review. This article provides an overview of echocardiographic techniques currently used to assess ventricular performance. Furthermore, we review current literature describing ventricular performance, as assessed using echocardiography, after correction of a CHD. In general, a decrease in ventricular performance is observed directly after surgery for CHD’s. Subsequent follow-up of ventricular performance is characterized by a varying degree of postoperative recovery. A consistent observation is the persistent impairment of right-ventricular performance after repair in several different subgroups of CHD patients ranging from ventricular septal defect repair to surgery for Tetralogy of Fallot.

Assessment of right ventricular volumes in hypoplastic left heart syndrome by real-time three-dimensional echocardiography: comparison with cardiac magnetic resonance imaging

BACKGROUND

Accurate assessment of right ventricular (RV) volumes and function is important in patients with hypoplastic left heart syndrome (HLHS). We prospectively sought to determine the reproducibility of three-dimensional (3D) echocardiography and its agreement with cardiac magnetic resonance imaging (CMR) in HLHS.

METHODS AND RESULTS

Twenty-eight patients underwent CMR followed immediately by transthoracic 3D echocardiography under general anaesthesia. Semi-automated border detection software was used to determine echocardiographic RV volumes. Inter- and intra-observer variability, correlation and levels of agreement between techniques were determined. The median age was 0.37 years (0.18-9.28 years) and weight 6.24 kg (3.42-32.50 kg). Intra- and inter-observer variability was excellent for both techniques. Median (range) measurements for 3D echocardiography and CMR were; end-diastolic volume (EDV) 23.6 mL (6.5-63.2) and 30.6 mL (11.8-87.9), end-systolic volume (ESV) 12.6 mL (3.7-37.0) and 14.9 mL (5.8-33.9), stroke volume (SV) 11.2 mL (2.8-33.0) and 17.1 mL (6.0-54.1), ejection fraction (EF) 48.2% (31.2-64.9), and 56.5% (42.7-72.2). Correlation coefficients were r = 0.85, 0.84, 0.83, and 0.74, respectively (P < 0.01 for all). Volumetric data were expressed as a percentage of the echocardiographic volume to CMR volume. When compared with CMR, 3D echocardiography underestimated EDV, ESV and SV by 26.7% (SD ± 20.2), 10.6% (±28.1), and 37.5% (±20.1), respectively. The difference in volume appeared largest at low ventricular volumes. EF was 8.3% (±7.3) lower by 3D echocardiography compared with CMR.

CONCLUSION

Both 3D echocardiography and CMR volumes appear highly reproducible. Measurements obtained by 3D echocardiography are significantly lower than those obtained by CMR, with wide limits of agreement such that these two methods cannot be used interchangeably.

Pressure-overload hypertrophy of the developing heart reveals activation of divergent gene and protein pathways in the left and right ventricular myocardium

Right ventricular (RV) and left ventricular (LV) myocardium differ in their pathophysiological response to pressure-overload hypertrophy. In this report we use microarray and proteomic analyses to identify pathways modulated by LV-aortic banding (AOB) and RV-pulmonary artery banding (PAB) in the immature heart. Newborn New Zealand White rabbits underwent banding of the descending thoracic aorta [LV-AOB; n = 6]. RV-PAB was achieved by banding the pulmonary artery (n = 6). Controls (n = 6 each) were sham-manipulated. After 4 (LV-AOB) and 6 (RV-PAB) wk recovery, the hearts were removed and matched RNA and proteins samples were isolated for microarray and proteomic analysis. Microarray and proteomic data demonstrate that in LV-AOB there is increased transcript expression levels for oxidative phosphorylation, mitochondria energy pathways, actin, ILK, hypoxia, calcium, and protein kinase-A signaling and increased protein expression levels of proteins for cellular macromolecular complex assembly and oxidative phosphorylation. In RV-PAB there is also an increased transcript expression levels for cardiac oxidative phosphorylation but increased protein expression levels for structural constituents of muscle, cardiac muscle tissue development, and calcium handling. These results identify divergent transcript and protein expression profiles in LV-AOB and RV-PAB and provide new insight into the biological basis of ventricular specific hypertrophy. The identification of these pathways should allow for the development of specific therapeutic interventions for targeted treatment and amelioration of LV-AOB and RV-PAB to ameliorate morbidity and mortality.

Reduced ascending aorta distensibility relates to adverse ventricular mechanics in patients with hypoplastic left heart syndrome: noninvasive study using wave intensity analysis

OBJECTIVE

To evaluate the aortic arch elastic properties and ventriculoarterial coupling efficiency in patients with single ventricle physiology, with and without a surgically reconstructed arch.

METHODS

We studied 21 children with single ventricle physiology after bidirectional superior cavopulmonary surgery: 10 with hypoplastic left heart syndrome, who underwent surgical arch reconstruction, and 11 with other types of single ventricle physiology but without arch reconstruction. All children underwent pre-Fontan magnetic resonance imaging. No patient exhibited aortic recoarctation. Data on aortic wave speed, aortic distensibility and wave intensity profiles were all extracted from the magnetic resonance imaging studies using an in-house-written plug-in for the Digital Imaging and Communications in Medicine viewer OsiriX.

RESULTS

Children with hypoplastic left heart syndrome had significantly greater wave speed (P = .002), and both stiffer (P = .004) and larger (P < .0001) ascending aortas than the patients with a nonreconstructed arch. Aortic distensibility was not influenced by ventricular stroke volume but depended on a combination of increased aortic diameter and abnormal wall mechanical properties. Those with hypoplastic left heart syndrome had a lower peak wave intensity and reduced energy carried by the forward compression and the forward expansion waves, even after correction for stroke volume, suggesting an abnormal systolic and diastolic function. Lower wave energy was associated with an increased aortic diameter.

CONCLUSIONS

Using a novel, noninvasive technique based on image analysis, we have demonstrated that aortic arch reconstruction in children with hypoplastic left heart syndrome is associated with reduced aortic distensibility and unfavorable ventricular-vascular coupling compared with those with single ventricle physiology without aortic arch reconstruction.

Subjective evaluation of right ventricular systolic function in hypoplastic left heart syndrome: how accurate is it?

Background

The geometry and heterogeneity of the right ventricle in hypoplastic left heart syndrome makes objective echocardiographic assessment of systolic function challenging. Consequently, subjective echocardiographic assessment of right ventricular (RV) function is still routinely undertaken. The aims of this study were to compare this with magnetic resonance imaging (MRI), investigate the impact of experience and training on the accuracy of subjective assessment, and critically analyze the role of echocardiography to detect impaired systolic function.

Methods

A retrospective analysis of prospectively acquired data was performed. Children with hypoplastic left heart syndrome underwent routine preoperative cardiac MRI and echocardiography under the same general anesthetic. Echocardiograms were reviewed, and members of the congenital heart disease team with differing echocardiography experience subjectively graded RV systolic function (good, moderate, or poor). This was compared with MRI-derived ejection fraction.

Results

Twenty-eight patients at different palliative stages were included. Twenty-eight observers were divided into five experience categories (congenital heart disease junior trainees to attending cardiologists). Median agreement was 47.6% (range, 31.4%–58.2%), with the lowest agreement among junior trainees and the highest among attending cardiologists. When used as a screening test for poor RV systolic function, the median sensitivity of echocardiography was 0.89 (range, 0.86–0.96), and median specificity was 0.45 (range, 0.26–0.55). The highest sensitivity was observed among junior trainees but with the lowest specificity. The highest specificity was observed among attending cardiologists (0.55).

Conclusions

Agreement between echocardiographic and MRI RV ejection fraction improves with experience but remains suboptimal. When used as a screening test for poor RV function, echocardiography is sensitive, but specificity is heavily influenced by operator experience.

Right ventricular function in fetal hypoplastic left heart syndrome

BACKGROUND

The systemic right ventricle in palliated hypoplastic left heart syndrome (HLHS) has relatively reduced longitudinal compared with circumferential deformation, a pattern of contraction more akin to the normal left ventricle, which presumably improves right ventricular (RV) pumping efficiency. The aim of this study was to test the hypothesis that these changes in the RV contraction pattern in infants with HLHS are present prenatally.

METHODS

Echocardiograms from 48 fetuses with HLHS were retrospectively compared with those from appropriately grown RV and left ventricular controls. Ventricular function was assessed using Velocity Vector Imaging velocity, tissue deformation, two-dimensional echocardiography, and Doppler flow parameters.

RESULTS

Fetuses with HLHS demonstrated reduced peak global RV longitudinal velocity (P < .01), strain (P < .001), and displacement (P < .05), while radial displacement was increased (P < .001) compared with the normal fetal right ventricle. Mean RV diameter was increased in HLHS (P < .001), but length was unchanged. The ratio of longitudinal to circumferential deformation was reduced in HLHS compared with the normal right ventricle (P < .001) and equivalent to the normal left ventricle. Tricuspid inflow peak A-wave velocity (P < .01), A-wave duration, A-wave inflow fraction, RV Tei index (P < .05 for all), and inferior vena cava A-wave reversal (P < .0001) were increased in HLHS.

CONCLUSIONS

The fetal right ventricle in HLHS becomes more spherical because of increased RV diameter. It has relatively reduced longitudinal compared with circumferential deformation and an increased reliance on atrial contraction for ventricular filling. These findings are similar to postnatal changes observed in the systemic right ventricle in palliated congenital heart disease, suggesting that ventricular remodeling is initiated in fetal life.

Graft survival is better without prior surgery in cardiac transplantation for functionally univentricular hearts

BACKGROUND

The effect of surgical history on graft outcomes in patients with functionally univentricular hearts (UH) is not well understood. We compared graft outcomes after heart transplantation in children with a UH between patients who received allografts without prior cardiac surgery (Group A) and patients who underwent transplantation after prior cardiac surgery (Group B).

METHODS

We reviewed all patients who received allografts for UH at our institution from 1990 to 2009. Differences in the probability of acute rejection (AR), incidence of graft vasculopathy (GV), and incidence of death or retransplantation were compared between Group A and Group B. Student's t-test, Mann-Whitney U-test, the log-rank test, logistic regression, and Cox proportional hazards modeling were used as appropriate.

RESULTS

During the study period, 180 patients with a UH received allografts: 105 in Group A and 75 in Group B at a median (interquartile range) age of 84 (47-120) days vs 584 (168-2,956) days, respectively (p < 0.001). The odds of AR were higher in Group B (odds ratio, 2.7, 95% confidence interval, 1.3-5.4). Group A had lower univariable risks of GV (p = 0.034) and graft loss (p = 0.003). Median graft survival was 18 years in Group A vs 8 years in Group B. The risk of graft loss after 5 years post-transplant was higher in Group B patients who were aged ≥ 1 year at time of transplant (p < 0.001).

CONCLUSIONS

Heart transplantation without prior cardiac surgery in patients with a UH was associated with better graft survival and lower probability of AR. The effect of age is complex and time-dependent, with age affecting outcomes after 5 years.

Outcomes of infants undergoing superior cavopulmonary connection in the presence of ventricular dysfunction

Outcomes in patients with ventricular dysfunction undergoing superior cavopulmonary connection (SCPC) are not well known. We reviewed records of patients undergoing SCPC at our center from December 2005 to October 2009 and studied those whose pre-SCPC echocardiograms demonstrated at least moderate systemic ventricular dysfunction. Of the 213 patients undergoing SCPC, 19 (9%) met inclusion criteria. Diagnoses were hypoplastic left heart syndrome (n = 18) and rightward unbalanced atrioventricular canal with pulmonary stenosis (n = 1). In those surviving >2 months after SCPC, ventricular function was assessed by echocardiography 4.9 (range 3.5 to 9.7) months after SCPC and was improved in ten of 17 (59%), unchanged in six of 17 (35%), and worsened in one of 17 (16%) patients. After SCPC, three patients died, and one underwent heart transplant 21.9 months after SCPC. Transplant-free survival was attained by 15 of 19 (79%) patients during follow-up of 33.0 months (range 10.8 to 51.4). Fontan completion was performed on six survivors on reaching an appropriate age. Ventricular dysfunction before SCPC is not uncommon and occurs primarily in patients with a morphologic right ventricle. Ventricular performance improves in the majority of patients after SCPC, and midterm outcomes are comparable with previous reports, suggesting that these patients remain candidates for staged palliation.

Myocardial alternative RNA splicing and gene expression profiling in early stage hypoplastic left heart syndrome

Hypoplastic Left Heart Syndrome (HLHS) is a congenital defect characterized by underdevelopment of the left ventricle and pathological compensation of the right ventricle. If untreated, HLHS is invariably lethal due to the extensive increase in right ventricular workload and eventual failure. Despite the clinical significance, little is known about the molecular pathobiological state of HLHS. Splicing of mRNA transcripts is an important regulatory mechanism of gene expression. Tissue specific alterations of this process have been associated with several cardiac diseases, however, transcriptional signature profiles related to HLHS are unknown. In this study, we performed genome-wide exon array analysis to determine differentially expressed genes and alternatively spliced transcripts in the right ventricle (RV) of six neonates with HLHS, compared to the RV and left ventricle (LV) from non-diseased control subjects. In HLHS, over 180 genes were differentially expressed and 1800 were differentially spliced, leading to changes in a variety of biological processes involving cell metabolism, cytoskeleton, and cell adherence. Additional hierarchical clustering analysis revealed that differential gene expression and mRNA splicing patterns identified in HLHS are unique compared to non-diseased tissue. Our findings suggest that gene expression and mRNA splicing are broadly dysregulated in the RV myocardium of HLHS neonates. In addition, our analysis identified transcriptome profiles representative of molecular biomarkers of HLHS that could be used in the future for diagnostic and prognostic stratification to improve patient outcome.

Association of feeding modality with interstage mortality after single-ventricle palliation

OBJECTIVE

Interstage mortality has been reported in 10% to 25% of hospital survivors after single-ventricle palliation. The purpose of this study was to examine the impact of feeding modality at discharge after single-ventricle palliation on interstage mortality.

METHODS

We conducted a retrospective review of all neonates undergoing single-ventricle palliation from January 2003 to January 2010. A total of 334 patients (90%) survived to hospital discharge, comprising the study group. Preoperative, operative, and postoperative variables were examined, including feeding method at discharge. Multivariate Poisson regression models were constructed to estimate the relative risk of interstage mortality.

RESULTS

Of 334 patients, 56 (17%) underwent gastrostomy tube ± Nissen. There was a statistically significant increase in interstage mortality for patients who underwent gastrostomy tube ± Nissen compared with patients who did not (relative risk, 2.38; 95% confidence interval, 1.05-5.40; P = .04]). Of the 278 patients who were not fed via a gastrostomy tube ± Nissen, 190 (68%) were fed with nasogastric feedings and 88 (32%) were fed entirely by mouth. There was no difference in interstage mortality between these 2 groups (relative risk, 0.92; 95% confidence interval, 0.31-2.73; P = .89).

CONCLUSIONS

Neonates undergoing single-ventricle palliation who require gastrostomy tube ± Nissen are at an increased risk of interstage mortality. The need for gastrostomy tube ± Nissen in this population may be a marker for other unmeasured comorbidities that place them at an increased risk of interstage mortality. Discharge with nasogastric feeds does not increase the risk of interstage mortality.

Lessons from inter-stage cardiac magnetic resonance imaging in predicting survival for patients with hypoplastic left heart syndrome

This study describes single-unit experience and explores risk stratification, with protocolised inter-stage cardiac magnetic resonance imaging for infants with hypoplastic left heart syndrome. Survival was retrospectively analysed among the cohort of locally followed survivors of Norwood Stage I procedure, who underwent magnetic resonance imaging under general anaesthesia from 2003 to 2008. This included 32 patients: 17 with Sano conduit and 15 with arterio-pulmonary shunt. The median (inter-quartile range) age and weight at scan were 3.1 (2.6-4.6) months and 5.0 (4.5-5.3) kilograms, respectively. Using morphologic definitions, the median coarctation index was 0.71 (0.57-0.83). The degree of proximal right and left pulmonary artery narrowing was 25% (14-44%) and 25% (11-50%), respectively. The median right ventricular ejection fraction was 54% (48-59%). The ejection fraction was not related to the coarctation index or to pulmonary artery narrowing. Patients were followed up for a median of 19.2 (10.8-46.0) months, during which 13 (41%) had an intervention in addition to routine Norwood Stage II surgery and seven died. Risk of death was related to reduced right ventricular ejection fraction, with a hazard ratio of 0.91 (95% confidence interval 0.85-0.98, p = 0.02), and the cumulative number of focal stenoses of neo-aortic arch and pulmonary arteries (hazard ratio 2.71, 95% confidence interval 1.14-6.44, p = 0.02).

CONCLUSIONS

In addition to comprehensive three-dimensional morphologic imaging, inter-stage cardiac magnetic resonance imaging provides a ventricular functional index that may predict outcome in patients with hypoplastic left heart syndrome. Measures to preserve right ventricular systolic function and relieve stenoses are paramount within the complex management strategies for these patients.

Acute Cardiac Resynchronization Therapy for the Failing Left, Right, or Single Ventricle After Repaired Congenital Heart Disease

Use of cardiac resynchronization in children and young adults with congenital heart disease has been described in a variety of anecdotal cases and pooled institutional summaries which report mid-term results. This manuscript addresses use of cardiac resynchronization and/or multisite pacing in children in the acute postoperative period with a failing right, left, or single ventricle.

Cardiac resynchronization therapy in children

Cardiac Resynchronization therapy has become an important management tool in adults with heart failure and dilated cardiomyopathy. The role of CRT in children with CHF is still unclear. Evidence is slowly emerging in the pediatric cardiology literature that CRT may have an important and useful role in certain select populations with CHF. These include patients with complete heart block who develop pacing-induced cardiomyopathy, certain forms of congenital heart disease associated with systemic ventricular failure (even if the systemic ventricle is a morphologic RV) and in patients with idiopathic dilated cardiomyopathy. Studies in children supporting the use of CRT include many case reports, a few studies of CRT in post-operative patients, and one multi-center registry reporting the use of CRT in children. These papers will be summarized.

Norwood with right ventricle-to-pulmonary artery conduit is more effective than Norwood with Blalock-Taussig shunt for hypoplastic left heart syndrome: mathematic modeling of hemodynamics

OBJECTIVE

The introduction of right ventricle to pulmonary artery (RV-PA) conduit in the Norwood procedure for hypoplastic left heart syndrome resulted in a higher survival rate in many centers. A higher diastolic aortic pressure and a higher mean coronary perfusion pressure were suggested as the hemodynamic advantage of this source of pulmonary blood flow. The main objective of this study was the comparison of two models of Norwood physiology with different types of pulmonary blood flow sources and their hemodynamics.

METHOD

Based on anatomic details obtained from echocardiographic assessment and angiographic studies, two three-dimensional computer models of post-Norwood physiology were developed. The finite-element method was applied for computational hemodynamic simulations. Norwood physiology with RV-PA 5-mm conduit and Blalock-Taussig shunt (BTS) 3.5-mm shunt were compared. Right ventricle work, wall stress, flow velocity, shear rate stress, energy loss and turbulence eddy dissipation were analyzed in both models.

RESULTS

The total work of the right ventricle after Norwood procedure with the 5-mm RV-PA conduit was lower in comparison to the 3.5-mm BTS while establishing an identical systemic blood flow. The Qp/Qs ratio was higher in the BTS group.

CONCLUSIONS

Hemodynamic performance after Norwood with the RV-PA conduit is more effective than after Norwood with BTS. Computer simulations of complicated hemodynamics after the Norwood procedure could be helpful in establishing optimal post-Norwood physiology.

Ventriculocoronary artery connections with the hypoplastic left heart: a 4-year prospective study: incidence, echocardiographic and clinical features

Ventriculocoronary connections (VCCs), also called sinusoids, occur with hypoplastic left heart (HLH). Previous reports are limited to case reports, pathologic series, and surgical series with limited detail, which may underestimate the incidence and overestimate the severity of VCCs in HLH. A study was conducted to determine the incidence VCCs in HLH, their effect on survival, and their echocardiographic and clinical features. The echocardiograms and medical records of 100 consecutive neonatal HLH cases were analyzed. All had an aortic and a mitral valve diameter and a left ventricular (LV) volume less than Z-3. For palliation, Norwood, Sano, or hybrid procedures were used, and if the patient was alive, subsequent bidirectional Glenn and extracardiac Fontan procedures were applied. Cases were classified as manifesting mitral and aortic atresia (MAAA), mitral and aortic stenosis (MSAS), or mitral stenosis and aortic atresia (MSAA). All other diagnoses or any case with additional cardiac anomalies were excluded from the study. Overall, VCCs were found in 15% of the cases. They occurred in 56% of the MSAA subtype cases and were not statistically associated with a high mortality rate. However, in one case, large and multiple VCCs definitely caused or contributed to early death. All VCCs had a transmyocardial course, a turbulent color-Doppler flow, and a dominant usually retrograde systolic coronary artery flow pattern. The VCCs were associated (p < 0.05) with MSAA, endocardial fibroelastosis, and ascending aortic size less than 2 mm. As shown by the findings, 15% of the HLH patients had MSAA with VCCs. Unless the VCCs were large or extensive, they did not contribute to mortality. Detailed echocardiographic analysis of VCCs in HLH was feasible. Recent reports emphasize more severe cases.

Comparison of Norwood shunt types: do the outcomes differ 6 years later?

BACKGROUND

A modification to the Norwood procedure involving a right ventricle-to-pulmonary artery (RV-PA) shunt may improve early postoperative outcomes. Concerns remain about the effect of the right ventriculotomy required with this shunt on long-term ventricular function.

METHODS

Between January 2000 and April 2005, 76 patients underwent the Norwood procedure, 35 with a modified Blalock-Taussig shunt (mBTS) and 41 with a RV-PA shunt. Patients were monitored until death or September 1, 2009, with an average follow-up of 6.8 years. Cardiac catheterization, echocardiograms, perioperative Fontan courses, and need for cardiac transplantation were compared between groups.

RESULTS

Cumulative survival was 63% (22 of 35) in the mBTS group vs 78% (32 of 41) in the RV-PA group (p = 0.14). Pre-Fontan echocardiography revealed poorer ventricular function in RV-PA patients (p = 0.03). Cardiac transplantation was required in 6 of 32 (19%) patients with a prior RV-PA shunt vs 1 of 23 (4%) in the mBTS group (p = 0.06). This results in an almost identical cumulative transplant-free survival between groups; 60% (21 of 35) in the mBTS group and 63% (26 of 41) in the RV-PA group (p = 0.95).

CONCLUSIONS

Neither shunt offers a clear survival advantage through an average follow-up of 6.8 years. The RV-PA shunt results in impaired late ventricular function that may result in an increased need for cardiac transplantation.

Differential changes in TGF-β/BMP signaling pathway in the right ventricular myocardium of newborns with hypoplastic left heart syndrome

BACKGROUND

Hypoplastic left heart syndrome (HLHS) is characterized by underdevelopment of the left ventricle (LV) and increased biomechanical stress on the right ventricle (RV) from single ventricle physiology. Despite the clinical significance, the signaling pathways active during RV remodeling and disease progression are not known. To address this, we examined differential changes in expression of genes associated with transforming growth factor-beta (TGF-beta)/bone morphogenetic protein (BMP) signaling in RV tissue isolated from HLHS patients relative to RV and LV tissue from control subjects.

METHODS AND RESULTS

Quantitative real-time polymerase chain reaction was used to detect changes in expression of 84 genes involved in TGF-beta/BMP-mediated cardiac development, cell growth, and differentiation in RV tissue collected from 6 neonates with HLHS undergoing stage 1 Norwood procedure (age, 1-7 days; mean, 4 days) and RV and LV tissue obtained from 5 infants with noncardiac pathology (age range, 1-135 days: mean, 85 days) that served as controls. Analysis of gene expression profiles between control-LV and control-RV revealed significant depression of TGF-beta/BMP signaling in RV compared with LV. Of the 84 genes analyzed, 38 were differentially expressed between HLHS-RV and control-RV, whereas only 22 compared with control-LV. Significant changes were observed in: tissue remodeling genes including Activin receptor type IIA (ACVR2A) (+2.13) and Activin receptor-like kinase 1 (ACVRL1) (+2.22); and cell survival, growth, and differentiation genes including CDC25A (+2.18), p21 (-3.64), p15 (+2.15), BMP5 (+4.58), BMP3 (+2.16), GDF3 (+8.59), NODAL (+2.32), and BMP binding endothelial regulator (BMPER) (+4.58). The most significant changes common to HLHS-RV versus control-RV and control-LV sample groups is observed for Anti müllerian hormone receptor 2 (AMHR2) (+18.79 control-RV, +3.38 control-LV), and the BMP antagonist Inhibin alpha (INHA) (+11.47 control-RV, +5.73 control-LV).

CONCLUSIONS

Although this descriptive study does not allow cause-effect inferences, our results suggest changes in cardiac development pathways and upregulation of genes associated with cell growth and differentiation in the neonatal RV of children with HLHS. These molecular profiles are more closely related to those observed in the normal LV rather than normal RV at similar maturational age. This work provides the basis for future mechanistic studies to elucidate the molecular mechanisms regulating RV remodeling in HLHS.

Two-dimensional speckle strain and dyssynchrony in single right ventricles versus normal right ventricles

BACKGROUND

Patients with single-right ventricle (RV) physiology are at increased risk for myocardial dysfunction and mechanical dyssynchrony. Newer echocardiographic modalities may be better able to quantitate right ventricular function in this unique population. The aim of this study was to use two-dimensional speckle analysis of strain and strain rate to quantify systolic function and dyssynchrony in single-RV post-Fontan patients and compare them with values for controls.

METHODS

Patients with single RV who underwent Fontan palliation and patients with normal biventricular anatomy were studied. Two-dimensional speckle echocardiography was used to measure strain, strain rate, time to peak, and longitudinal displacement in a 6-segment model of the RV. Independent t tests were used to compare group means. P values < .05 were considered significant.

RESULTS

Thirteen patients were studied in each group. There was no significant difference in age between single-RV patients and controls (6.60 +/- 2.07 vs 5.75 +/- 1.83 years, respectively). Single-RV strain values were significantly lower in all 6 segments compared with values in controls (basal interventricular septum [IVS], -14.28 +/- 7.78% vs -22.00 +/- 2.36%; mid IVS, -17.70 +/- 4.54% vs -22.99 +/- 2.71%; apical IVS, -19.46 +/- 4.97% vs -25.42 +/- 4.06%; basal RV, -22.40 +/- 5.7% vs -41.42 +/- 5.42%; mid RV, -21.20 +/- 3.21% vs -39.67 +/- 6.04%; apical RV, -20.70 +/- 4.90% vs -33.68 +/- 3.90%). Systolic strain rate and longitudinal displacement were also lower in the free wall and apical IVS in single-RV patients compared with controls. The modified Yu index for strain time to peak was longer in the single-RV patients (43.16 +/- 13.63 vs 21.72 +/- 7.25 ms).

CONCLUSION

Significant differences in strain analysis between single-RV patients and patients with biventricular physiology exist at a relatively young age. Future studies are needed to determine the clinical significance of these differences.

Improved reproducibility of right ventricular volumes and function estimation from cardiac magnetic resonance images using level-set models

This study aims to assess whether an alternative method, that is based on volumetric surface detection (VoSD) without tracing and is totally free of geometric assumptions, can improve the reproducibility of right ventricular (RV) volume quantification from cardiac magnetic resonance (CMR) images, in comparison with a conventional disk-area technique. In a sample of 23 patients, with wide variability of RV end-diastolic volume (EDV: 47-131 ml), end-systolic volume (ESV: 20-76 ml), and ejection fraction (EF: 29-73%), using the standard method (Argus, Siemens) as the reference, the VoSD method showed good agreement for EDV, ESV, and EF estimations (correlation coefficient: 0.91, 0.94, and 0.94; Bland-Altman biases: 1 ml, 1 ml, and 0%; limits of agreement: +/-16 ml, +/-11 ml, and +/-11%, respectively). An analysis of the reproducibility of the two methods showed lower intraobserver variability for the VoSD method than for the conventional method, as evidenced by the coefficient of variability (CoV) values (2-6% vs. 8-15%; P < 0.05). In addition, the VoSD method showed improved interobserver reproducibility (7-10% vs. 8-15%), but the difference was statistically significant only for EF estimation variability (8 vs. 15%, P < 0.05). In conclusion, the newly developed VoSD technique allows accurate measurements of RV volumes and function, and appears to be more reproducible than the conventional methodology.

The effect of left ventricular size on right ventricular hemodynamics in pediatric survivors with hypoplastic left heart syndrome

BACKGROUND

Outcome status in patients with hypoplastic left heart syndrome (HLHS) is partially dependent on right ventricular (RV) systolic function. In other disease states, ventricular function is impacted by anatomy and physiology of the contralateral ventricle. In HLHS, it is suggested that a relatively larger left ventricular (LV) size may negatively impact RV function because it becomes a "passenger" without providing any systolic or diastolic physiologic benefit. The purpose of this study was to determine whether LV size adversely affects RV systolic function in surviving patients with HLHS.

METHODS

The hospital database was searched for all patients with HLHS and technically adequate echocardiograms born in the last 6 years and who had survived at least the Norwood procedure. LV size was assessed by echocardiographic measurement of LV end-diastolic short-axis and apical area. RV function was assessed by short-axis and apical fractional area change as well as the myocardial performance index (Tei). Measurements were made at up to 4 time points depending on duration of follow-up (1 - pre-Norwood; 2 - pre-Glenn; 3 - pre-Fontan; and 4- post-Fontan).

RESULTS

A total of 48 patients were studied. LV size showed sufficient variability in the patient population (1.0-21 cm(2)/body surface area, pre-Norwood). RV function tended to worsen across the time periods but these changes did not reach statistical significance. Regression analysis showed no effect of LV size on RV function before Norwood operation. Significant correlations existed between LV size indices and RV functional indices before Glenn shunt but these were inconsistent in the direction of their effect. Only before Fontan operation did the correlation between LV size and RV function become both consistent and statistically significant; specifically larger LV size correlated significantly with poor RV systolic function (short-axis RV fractional area change vs LV area r = -0.4, P = .03 and RV Tei vs LV area r = 0.5, P = .02). These relationships were not apparent after Fontan operation.

CONCLUSION

In surviving patients with HLHS, larger LV size does not seem to negatively impact RV function before or after Norwood procedure nor does it seem to have an adverse effect on RV function chronically (after Fontan). However, further study with larger population size will be necessary to see whether these findings remain negative and are true for nonsurvivors as well.

Intra-observer and interobserver reproducibility of right ventricle volumes, function and mass by cardiac magnetic resonance

OBJECTIVES

Cardiac magnetic resonance (CMR) allows quick and non-invasive evaluation both of right ventricle (RV) volume and function, which are important in many heart diseases. We have evaluated CMR intra- and interobserver reproducibility in different conditions of RV dimension and function.

METHODS

We have analysed CMR exams of 45 subjects, randomly selected from our database according to RV end-diastolic volume (EDV; 15-subject groups with EDV < 25th, 25-75th and > 75th percentiles of a normal control population). Selected subjects were of both sexes (male/female 33/12) and of variable age (8-83 years) and body surface (0.9-2.3 m). RV end-diastolic and end-systolic volumes (ESV), ejection fraction (EF) and mass were blindly evaluated by two operators. Bland-Altman bias and coefficient of variability (CoV) were used to assess intra- and interobserver reproducibility.

RESULTS

A wide range of EDV (range = 46-239 ml), ESV (20-129 ml) and EF (6-64%) was observed. The intra-observer bias was -5 ml for EDV, -2 ml for ESV, -1% for EF and 5 g for mass, with a CoV of 7-12%. The interobserver bias was 5 ml for EDV, 2 ml for ESV, 2% for EF and 6 g for mass, with a CoV of 8-13%. Analysis by tertiles showed EF assessment variability to be higher in the lower tertiles at intra-observer (P < 0.036) and, above all, at interobserver (P < 0.000) analysis. Mass assessment variability was higher in the upper tertile (P < 0.004) at intra-observer analysis.

CONCLUSIONS

Intra- and interobserver reproducibility of RV parameters assessed by CMR are adequate in a wide range of RV dimensions and function. However, caution is required with respect to the significance of small changes of EF and mass in the case of poor function and hypertrophy of the RV, respectively.

Bidirectional cavopulmonary anastomosis: impact on diastolic ventricular function indices

Systolic ventricular function has been demonstrated to remain unchanged following bidirectional cavopulmonary anastomosis (BCPA). The effects of BCPA on diastolic ventricular performance have not been critically assessed. The objective of this study was to evaluate the changes in diastolic ventricular function indices early after BCPA. Nineteen patients were enrolled prospectively. Transthoracic echocardiograms were performed at a median of 4 days prior to and 5 days subsequent to BCPA. Diastolic and systolic echocardiographic indices of ventricular performance were measured for the dominant ventricle. End diastolic volume decreased postoperatively (71.1 +/- 21.1 vs 68.08 +/- 17.9 ml/m2, p = 0.05). Tei index increased postoperatively (0.51 +/- 0.2 vs 0.62 +/- 0.1, p = 0.002), whereas inflow Doppler E velocity (70.3 +/- 13 vs 56.3 +/- 24.7 cm/sec, p = 0.04), E/A ratio (1.18 +/- 0.52 vs 0.84 +/- 0.2, p = 0.02), tissue Doppler E' velocity (9.5 +/- 2.5 vs 6.4 +/- 3.2 cm/sec, p = 0.03) and diastolic flow propagation velocity (56.5 +/- 12 vs 52.8 +/- 11 cm/sec, p = 0.04) all decreased. There was no change in ventricular mass, area change fraction, heart rate, or inflow Doppler A or tissue Doppler A' and S' velocities. This study demonstrated that diastolic indices of ventricular performance are altered indicating decreased diastolic function early following BCPA. Whether this observation is a result of a change in ventricular mass:volume ratio, loading conditions of the ventricle, ventricular geometry, or the effects of cardiopulmonary bypass remains to be determined.

Right Ventricular Mechanical Dyssynchrony in Children with Hypoplastic Left Heart Syndrome

BACKGROUND

Mechanical dyssynchrony predicts response to cardiac resynchronization therapy in adults with heart failure. Children with hypoplastic left heart syndrome (HLHS) are susceptible to right ventricular (RV) failure; however, mechanical dyssynchrony has not been studied in this population with newly available methodologies. We investigated RV mechanical dyssynchrony in children with HLHS using vector velocity imaging.

METHODS

We used vector velocity imaging to quantify the SD of time to peak velocity, strain, and strain rate among 6 RV segments to define intraventricular RV synchrony in 16 children with HLHS and RV and left ventricular (LV) synchrony in 16 healthy age-matched control subjects. We further investigated relations between QRS duration and mechanical dyssynchrony and between mechanical dyssynchrony and systolic function.

RESULTS

Children with HLHS had significant RV mechanical dyssynchrony versus LV and RV control subjects (strain 37 +/- 35 vs 8 +/- 8 milliseconds, P = .003 [LV], 9 +/- 11 milliseconds, P = .005 [RV]; strain rate 31 +/- 37 vs 10 +/- 13 milliseconds, P = .04 [LV], 14 +/- 15 milliseconds, P = .09 [RV]). There was no significant relationship between QRS duration and mechanical dyssynchrony and no obvious relation between the degree of mechanical dyssynchrony and the RV fractional area of change.

CONCLUSIONS

Children with HLHS have RV mechanical dyssynchrony unrelated to surface electrocardiographic QRS duration. This may contribute to RV dysfunction and may indicate the usefulness of cardiac resynchronization therapy in this population.

The Systolic to Diastolic Duration Ratio in Children with Hypoplastic Left Heart Syndrome: A Novel Doppler Index of Right Ventricular Function

BACKGROUND

Right ventricular (RV) function is an important determinant of clinical status in children with hypoplastic left heart syndrome (HLHS). However, assessment of RV function remains challenging because of its complex morphology. We investigated the S/D duration ratio in children with HLHS as a novel index of global RV function.

METHODS

We measured systolic (S) and diastolic (D) duration using tricuspid regurgitation duration from Doppler flow, to calculate the S/D ratio in 33 children with HLHS and 33 control subjects matched for age and sex. We compared the S/D ratio between patients with HLHS and control subjects, between patients with HLHS and normal and abnormal RV function, and between patients with HLHS at different stages of palliation. We further correlated the S/D ratio with catheterization data.

RESULTS

Patients and control subjects were well matched for age (3.12 +/- 4.5 vs 3 +/- 4.5 years, not significant) sex, and heart rate (cycle length 524 +/- 179 vs 575 +/- 162 milliseconds, not significant). Patients with HLHS had a significantly higher S/D ratio than control subjects (1.65 +/- 0.85 vs 0.85 +/- 0.2, P < .0001). The S/D ratio became increasingly elevated in HLHS at higher heart rates, but not in control subjects. The S/D ratio was significantly higher in patients with HLHS and decreased RV function as compared with patients with HLHS and normal RV function (2.2 +/- 0.7 vs 1.5 +/- 0.47, P = .006), and significantly increased in patients with Norwood stage 1 versus patients with Norwood stages 2 and 3 HLHS (2.16 vs 1.4 and 1.32, respectively, P < .01 and P < .001, respectively). The S/D ratio did not correlate with catheterization-derived RV end-D pressure or cardiac index.

CONCLUSIONS

Patients with HLHS have an increased S/D ratio as a result of a shortened D and prolonged S. Measurement of the S/D duration ratio using Doppler flow is a novel method to augment assessment of global RV function in HLHS.

Does a ventriculotomy have deleterious effects following palliation in the Norwood procedure using a shunt placed from the right ventricle to the pulmonary arteries?

INTRODUCTION

A recent modification to the Norwood procedure involving a shunt placed directly from the right ventricle to the pulmonary arteries may improve postoperative haemodynamics. Concerns remain, however, about the potential problems produced by the required ventriculotomy.

METHODS

We compared 76 patients with hypoplastic left heart syndrome who underwent the Norwood procedure, 35 receiving a modified Blalock-Taussig shunt and the remaining 41 a shunt placed directly from the right ventricle to the pulmonary arteries. We reviewed their subsequent progress through the second stage of palliation. A single observer graded right ventricular function, and the severity of tricuspid regurgitation, based on blinded review of the most recent echocardiograms prior to the second stage of palliation.

RESULTS

At the time of catheterization prior to the second stage, patients with a shunt placed from the right ventricle to the pulmonary arteries, rather than a modified Blalock-Taussig shunt, had higher arterial diastolic blood pressure, at 44 versus 40 millimetres of mercury, p equal to 0.02, lower ventricular end diastolic pressures, at 8 versus 11 millimetres of mercury, p equal to 0.0002, and larger pulmonary arteries as judged using the Nakata index, at 270 versus 188 millimetres squared per metres squared, p equal to 0.009. There was no difference in qualitative ventricular systolic function or tricuspid regurgitation between groups. No differences were found between groups during the hospitalization following the second stage of palliation. A trend towards improved survival to the second stage was seen following the construction of a shunt from the right ventricle to the pulmonary arteries.

CONCLUSIONS

Construction of a shunt from the right ventricle to the pulmonary arteries is associated with lower right ventricular end diastolic pressures, larger pulmonary arterial size, and higher systemic arterial diastolic pressures. No apparent deleterious effects of the right ventriculotomy were observed in terms of qualitative ventricular systolic function or tricuspid regurgitation.

Results of staged palliation for hypoplastic left heart syndrome: a complete population-based series

AIM

To study the outcome of staged palliation for classic hypoplastic left heart syndrome.

METHODS

Retrospective chart review. Risk factors for mortality were analysed using Cox's proportional hazard regression modelling.

RESULTS

From 1993 to 2004, 55 infants underwent Norwood stage I procedure at a median age of 8 d (range 1-19 d). Hospital survival was 39/55 (71%), and there were six late deaths (before stage II). Birthweight, circulatory arrest time and cardiopulmonary bypass time were independent risk factors for stage I hospital mortality (p=0.029, p=0.001 and p=0.003, respectively). Poor right ventricular function prior to stage I was a significant predictor for interstage mortality (p=0.02). Thirty-two patients underwent bidirectional cavopulmonary anastomosis, at a median age of 6.5 mo (range 2.0-9.5 mo), with seven late deaths. Two patients had a heart transplant after stage II. Total cavopulmonary connection (TCPC) was performed in 13 patients, at a median age of 33 mo (range 21-45 mo), without mortality. Kaplan-Meier survival was 58%, 52% and 45% at 6, 12 and 48 mo, respectively.

CONCLUSION

Low birthweight, long time on circulatory arrest and cardiopulmonary bypass were risk factors for stage I mortality. Poor right ventricular function was detrimental to intermediate outcome.

Outcomes after the stage I reconstruction comparing the right ventricular to pulmonary artery conduit with the modified Blalock Taussig shunt

BACKGROUND

Recent reports advocate that a right ventricular to pulmonary artery (RV-PA) conduit improves outcome after the stage I reconstruction.

METHODS

We retrospectively compared the outcomes of all neonates who underwent a stage I reconstruction between January 1, 2002, and October 1, 2004, with use of the RV-PA conduit and modified Blalock-Taussig shunt (mBTS) interspersed over this time period.

RESULTS

In all, 149 infants underwent a stage I reconstruction (95 mBTS, 54 RV-PA) for hypoplastic left heart syndrome (HLHS) or variants. There was a preference for the RV-PA conduit in patients with aortic atresia (mBTS 30% versus RV-PA 67%, p < 0.01). There was no difference in surgical mortality (mBTS 14% versus RV-PA 17%, p = 0.67), time to extubation (mBTS 4.5 +/- 4.8 days versus RV-PA 3.9 +/- 3.5 days, p = 0.47), or length of hospital stay (mBTS 25 +/- 29 days versus RV-PA 21 +/- 23 days, p = 0.52). There was an increased incidence of shunt reinterventions in the patients with the RV-PA conduit (mBTS 17% versus RV-PA 32%, p = 0.04). Patients with RV-PA conduit returned earlier for stage II reconstruction (mBTS 6.5 +/- 2.5 months versus RV-PA 5.6 +/- 1.7 months, p = 0.05). There was no difference in overall mortality (mBTS 32% versus RV-PA 30%, p = 0.45) with a median duration of follow-up of 18 +/- 8 months.

CONCLUSIONS

Comparing shunt strategies (mBTS versus RV-PA) over the same time period, we found no difference in outcome. These data support the need for a larger prospective, randomized trial.

Impaired Power Output and Cardiac Index With Hypoplastic Left Heart Syndrome: A Magnetic Resonance Imaging Study

BACKGROUND

Unfavorable cardiac mechanics in children with hypoplastic left heart syndrome (HLHS) when compared with other single-ventricle defects may affect long-term morbidity and outcome. Using noninvasive phase contrast magnetic resonance imaging (PC MRI), we examined cardiac mechanics in children with HLHS and compared the results to other single-ventricle defects.

METHODS

Eighteen children with HLHS and 18 children with other single-ventricle defects were studied after the Fontan operation. Phase contrast MRI scans were obtained perpendicular to the ascending aorta, and flow was quantified using an in-house segmentation and reconstruction scheme. The total power output was determined using the modified Bernoulli equation along with cardiac output and systemic vascular resistance index.

RESULTS

Compared with non-HLHS congenital heart defects, children with HLHS had significantly lower power output (1.40 +/- 0.39 versus 1.78 +/- 0.38 W/m2, p < 0.004) and cardiac index (3.15 +/- 0.97 versus 4.09 +/- 1.23 L x Min(-1) x m(-2), p < 0.009) with a concomitant higher systemic vascular resistance index (28.94 +/- 11.5 versus 22.7 +/- 8.53 WU, p < 0.03) despite generating similar systolic blood pressures (112.9 +/- 22.4 versus 115.2 +/- 23 mm Hg, p > 0.05).

CONCLUSIONS

Minimally invasive measurements with PC MRI in children with HLHS showed significantly lower power output and cardiac index when compared with other single-ventricle physiologies. Abnormal aortic flow patterns may contribute to power loss and may have long-term survival and morbidity implications associated with the Fontan procedure. Elevated systemic vascular resistance index despite similar blood pressure opens avenues for therapeutic intervention for afterload reduction.

Cardiac resynchronization therapy in congenital heart disease

While cardiac resynchronization therapy (CRT) is of proven benefit in selected patients with severe ischemic or dilated cardiomyopathy, refractory symptoms, and conduction delay, extrapolation to congenital heart disease is not straightforward. This rapidly expanding patient population commonly suffers from heart failure, particularly in the presence of a single or systemic right ventricle. Surgical repair may also contribute to ventricular asynchrony. In this systematic review, the current state of knowledge regarding CRT in congenital heart disease is presented. Issues specific to congenital heart disease including right bundle branch block, right (pulmonary) ventricular dysfunction, systemic right ventricular dysfunction, and single ventricle dysfunction are explored. Evidence-based CRT applications for each of these particular conditions are reviewed. Initial experience with CRT in the acute postoperative setting and longer-term, including our own, is elaborated. Unlike standard indications based on multiple randomized clinical trials, supporting evidence for CRT in congenital heart disease is limited to case reports, case series, and small experimental crossover studies in the acute postoperative setting. The heterogeneous patient population, technical limitations from patient size, vascular access issues, and unique forms of ventricular asynchrony further obscure the selection of potential beneficiaries. Despite these limitations, experience thus far has been favorable. Quality of current data precludes definitive evidence-based recommendations, but optimistic initial results suggest that research endeavors in this field should be pursued. Multicenter prospective collaborative efforts are to be encouraged.