Henry Chubb

The use of Z-scores in paediatric cardiology

Z-scores are a means of expressing the deviation of a given measurement from the size or age specific population mean. By taking account of growth or age, Z-scores are an excellent means of charting serial measurements in paediatric cardiological practice. They can be applied to echocardiographic measurements, blood pressure and patient growth, and thus may assist in clinical decision-making.

Heart and heart–lung transplantation for idiopathic restrictive cardiomyopathy in children

Objective: To review the outcome of cardiac transplantation for restrictive cardiomyopathy (RCM) in children and to assess the ability of new strategies to modulate the effects of high pulmonary vascular resistance. Design: Retrospective case note analysis of all patients receiving a transplant for RCM. Patients: 18 children with RCM referred for transplantation assessment to Great Ormond Street Hospital, London. Results: Eight boys and 10 girls were referred for assessment. Median age at presentation was 5.0 (mean (SD) 6.1 (4.0)) years. Fourteen orthotopic and two heterotopic transplantations were performed and two patients were referred for heart–lung transplantation. Mean duration from diagnosis to transplantation was 3.3 (3.0) years. Three patients with haemodynamic decompensation before transplantation had increased morbidity in the postoperative period. No patients died while awaiting a transplant. Three patients died in the first year after transplantation, one within 30 days. Five patients received pre-transplantation prostacyclin for a mean duration of 57 (18) days. Transpulmonary gradient was reduced in four of the patients. Mean transpulmonary gradient was 27 (9.8) mm Hg before and 17 (6.7) mm Hg after treatment with prostacyclin (p < 0.05). Conclusion: Most children with RCM require transplantation within four years of diagnosis. Referral for transplantation assessment should precede haemodynamic decompensation. Increase of pulmonary vascular resistance is a variable problem but can be modulated with pre-transplantation prostacyclin. With these strategies, orthotopic transplantation is possible in the majority of cases.

Long-Term Outcome Following Catheter Valvotomy for Pulmonary Atresia With Intact Ventricular Septum

OBJECTIVES This study investigated the outcome for all patients undergoing catheter valve perforation for pulmonary atresia with intact ventricular septum (PAIVS) 21 years after the first procedure at their center. BACKGROUND Catheter perforation for PAIVS is now an established procedure. However, the management of the borderline right ventricle (RV) is controversial, and there may be a place for novel techniques such as stenting of the arterial duct. METHODS There were 37 successful valve perforations (total 39 patients). Median length of follow-up was 9.2 years (range 2.2 to 21.0 years). Seventeen patients had stenting of the arterial duct. The mean (SD) initial z-score for the tricuspid valve was -5.1 (±3.4), and a further 142 sets of measurements were taken to assess the growth of the RV of survivors. RESULTS There were 8 deaths (21%), and no deaths after the first 35 days. There were no late arrhythmias or ischemic events. Twenty-five patients (83% of survivors) have a biventricular circulation. For patients who had stenting of the arterial duct, significant reductions in early reintervention (0 vs. 7 patients, p = 0.009) and hospital stay (17.4 ± 18.1 days vs. 33.8 ± 28.6 days, p = 0.012) occurred, with no increase in mortality or morbidity. There was no catch-up growth of the RV in patients who had a biventricular outcome (z-score increase +0.08/year, p = 0.26). CONCLUSIONS Long-term survival is good, and even small RVs may be amenable to this procedure. Multiple interventions may be required to achieve biventricular circulation, but stenting of the arterial duct may reduce hospital stay and repeat procedures.

Slow Conduction in the Border Zones of Patchy Fibrosis Stabilizes the Drivers for Atrial Fibrillation: Insights from Multi-Scale Human Atrial Modeling

Introduction: The genesis of atrial fibrillation (AF) and success of AF ablation therapy have been strongly linked with atrial fibrosis. Increasing evidence suggests that patient-specific distributions of fibrosis may determine the locations of electrical drivers (rotors) sustaining AF, but the underlying mechanisms are incompletely understood. This study aims to elucidate a missing mechanistic link between patient-specific fibrosis distributions and AF drivers. Methods: 3D atrial models integrated human atrial geometry, rule-based fiber orientation, region-specific electrophysiology, and AF-induced ionic remodeling. A novel detailed model for an atrial fibroblast was developed, and effects of myocyte-fibroblast (M-F) coupling were explored at single-cell, 1D tissue and 3D atria levels. Left atrial LGE MRI datasets from 3 chronic AF patients were segmented to provide the patient-specific distributions of fibrosis. The data was non-linearly registered and mapped to the 3D atria model. Six distinctive fibrosis levels (0–healthy tissue, 5–dense fibrosis) were identified based on LGE MRI intensity and modeled as progressively increasing M-F coupling and decreasing atrial tissue coupling. Uniform 3D atrial model with diffuse (level 2) fibrosis was considered for comparison. Results: In single cells and tissue, the largest effect of atrial M-F coupling was on the myocyte resting membrane potential, leading to partial inactivation of sodium current and reduction of conduction velocity (CV). In the 3D atria, further to the M-F coupling, effects of fibrosis on tissue coupling greatly reduce atrial CV. AF was initiated by fast pacing in each 3D model with either uniform or patient-specific fibrosis. High variation in fibrosis distributions between the models resulted in varying complexity of AF, with several drivers emerging. In the diffuse fibrosis models, waves randomly meandered through the atria, whereas in each the patient-specific models, rotors stabilized in fibrotic regions. The rotors propagated slowly around the border zones of patchy fibrosis (levels 3–4), failing to spread into inner areas of dense fibrosis. Conclusion: Rotors stabilize in the border zones of patchy fibrosis in 3D atria, where slow conduction enable the development of circuits within relatively small regions. Our results can provide a mechanistic explanation for the clinical efficacy of ablation around fibrotic regions.

The role of myocardial wall thickness in atrial arrhythmogenesis.

Changes in the structure and electrical behaviour of the left atrium are known to occur with conditions that predispose to atrial fibrillation (AF) and in response to prolonged periods of AF. We review the evidence that changes in myocardial thickness in the left atrium are an important part of this pathological remodelling process. Autopsy studies have demonstrated changes in the thickness of the atrial wall between patients with different clinical histories. Comparison of the reported tissue dimensions from pathological studies provides an indication of normal ranges for atrial wall thickness. Imaging studies, most commonly done using cardiac computed tomography, have demonstrated that these changes may be identified non-invasively. Experimental evidence using isolated tissue preparations, animal models of AF, and computer simulations proves that the three-dimensional tissue structure will be an important determinant of the electrical behaviour of atrial tissue. Accurately identifying the thickness of the atrial may have an important role in the non-invasive assessment of atrial structure. In combination with atrial tissue characterization, a comprehensive assessment of the atrial dimensions may allow prediction of atrial electrophysiological behaviour and in the future, guide radiofrequency delivery in regions based on their tissue thickness.

Systolic and Diastolic Ventricular Function Assessed by Tissue Doppler Imaging in Children with Chronic Kidney Disease

Chronic kidney disease (CKD) is associated with elevated cardiovascular risk even during childhood. Tissue Doppler is a sensitive technique for the assessment of ventricular dysfunction with relatively little data available in children with CKD. We report a prospective cross‐sectional echocardiographic study at a tertiary center. Forty‐nine patients with median (range) age 11.2 years (6.9–17.9), weight 39.6 kg (23.6–99.7) and height 146 cm (122–185). Thirty‐one patients were male. Median duration of follow‐up for CKD was 7.1 years (range 0.13–16.9). Patients were in CKD stage 3 (n = 37) or 4 (n = 12). Mitral valve E‐wave, A‐wave, and E/A ratio showed mean (SD) z‐scores of 0.08 (0.93), 0.12 (0.82) and −0.13 (0.84), respectively. Tissue Doppler imaging (TDI) at the lateral mitral valve annulus showed e′, a′, s′, and E/e′ z‐scores mean (SD) −1.10 (0.76), −0.29 (0.92), −1.2 (0.7), and 0.86 (1.1), respectively. There was a significant negative correlation of e′ and s′ z‐score with patient age. E/e′ ratio correlated positively with patient age. Blood pressure, left ventricular mass, and relative wall thickness did not correlate with tissue Doppler measurements. The e′ and s′ velocities correlated significantly with each other, suggesting an interaction of systolic and diastolic dysfunction. Children with CKD may have abnormalities of systolic and diastolic ventricular function on TDI, which are not evident on blood pool Doppler. The tissue Doppler results are consistent with worsening ventricular function in older patients.

Fetal aortic valve stenosis: a critique of case selection criteria for fetal intervention

Selection of fetuses with aortic stenosis (AS) for prenatal intervention has been influenced by published scoring systems. This study aimed to test these scoring systems by retrospective application to consecutive cases of fetal AS.

Real-time MRI guidance of cardiac interventions

Cardiac magnetic resonance imaging (MRI) is appealing to guide complex cardiac procedures because it is ionizing radiation‐free and offers flexible soft‐tissue contrast. Interventional cardiac MR promises to improve existing procedures and enable new ones for complex arrhythmias, as well as congenital and structural heart disease. Guiding invasive procedures demands faster image acquisition, reconstruction and analysis, as well as intuitive intraprocedural display of imaging data. Standard cardiac MR techniques such as 3D anatomical imaging, cardiac function and flow, parameter mapping, and late‐gadolinium enhancement can be used to gather valuable clinical data at various procedural stages. Rapid intraprocedural image analysis can extract and highlight critical information about interventional targets and outcomes. In some cases, real‐time interactive imaging is used to provide a continuous stream of images displayed to interventionalists for dynamic device navigation. Alternatively, devices are navigated relative to a roadmap of major cardiac structures generated through fast segmentation and registration. Interventional devices can be visualized and tracked throughout a procedure with specialized imaging methods. In a clinical setting, advanced imaging must be integrated with other clinical tools and patient data. In order to perform these complex procedures, interventional cardiac MR relies on customized equipment, such as interactive imaging environments, in‐room image display, audio communication, hemodynamic monitoring and recording systems, and electroanatomical mapping and ablation systems. Operating in this sophisticated environment requires coordination and planning. This review provides an overview of the imaging technology used in MRI‐guided cardiac interventions. Specifically, this review outlines clinical targets, standard image acquisition and analysis tools, and the integration of these tools into clinical workflow.

Myocardial Deformation Measured by 3-Dimensional Speckle Tracking in Children and Adolescents With Systemic Arterial HypertensionNovelty and Significance

Systemic arterial hypertension predisposes children to cardiovascular risk in childhood and adult life. Despite extensive study of left ventricular (LV) hypertrophy, detailed 3-dimensional strain analysis of cardiac function in hypertensive children has not been reported. The aim of this study was to evaluate LV mechanics (strain, twist, and torsion) in young patients with hypertension compared with a healthy control group and assess factors associated with functional measurements. Sixty-three patients (26 hypertension and 37 normotensive) were enrolled (mean age, 14.3 and 11.4 years; 54% men and 41% men, respectively). All children underwent clinical evaluation and echocardiographic examination, including 3-dimensional strain. There was no difference in LV volumes and ejection fraction between the groups. Myocardial deformation was significantly reduced in those with hypertension compared with controls. For hypertensive and normotensive groups, respectively, global longitudinal strain was −15.1±2.3 versus −18.5±1.9 (P<0.0001), global circumferential strain −15.2±3 versus −19.9±3.1 (<0.0001), global radial strain +44.0±11.3 versus 63.4±10.5 (P<0.0001), and global 3-dimensional strain −26.1±3.8 versus −31.5±3.8 (P<0.0001). Basal clockwise rotation, apical counterclockwise rotation, twist, and torsion were not significantly different. After multivariate regression analyses blood pressure, body mass index and LV mass maintained a significant relationship with measures of LV strain. Similar ventricular volumes and ejection fraction were observed in hypertensive and normotensive children, but children with hypertension had significantly lower strain indices. Whether reduced strain might predict future cardiovascular risk merits further longitudinal study.

Tachyarrhythmias and catheter ablation in adult congenital heart disease.

Advances in surgical technique have had an immense impact on longevity and quality of life in patients with congenital heart disease. However, an inevitable consequence of these surgical successes is the creation of a unique patient population whose anatomy, surgical history and haemodynamics result in the development of a challenging and complex arrhythmia substrate. Furthermore, this patient group remains susceptible to the arrhythmias seen in the general adult population. It is through a thorough appreciation of the cardiac structural defect, the surgical corrective approach, and haemodynamic impact that the most effective arrhythmia care can be delivered. Catheter ablation techniques offer a highly effective management option but require a meticulous attention to the real-time integration of anatomical and electrophysiological information to identify and eliminate the culprit arrhythmia substrate. This review describes the current approach to the interventional management of patients with tachyarrhythmias in the context of congenital heart disease.