Cardiac transplantation for pediatric restrictive cardiomyopathy: presentation, evaluation, and short-term outcome

A Review of Pediatric Cardiomyopathy

Though pediatric cardiomyopathy is rare in children, there is significant associated morbidity and mortality. Etiology varies from inborn errors of metabolism to familial genetic mutations and myocyte injury. Major classes include dilated, hypertrophic, restrictive, and non-compaction. Diagnosis generally involves a combination of clinical history and echocardiography. The use of cross-sectional imaging is gaining popularity. Management varies between subtype and may involve a combination of medical and surgical interventions depending on clinical status.

Ventricular assist device support following pediatric heart transplantation

BACKGROUND

VAD support for early graft failure after HTx is a rare event in pediatrics.

METHODS

We retrospectively describe our single-center experience with post-HTx VAD support in a cohort of patients transplanted between 01/05 and 12/20.

RESULTS

Nine patients underwent VAD insertion in the early post-HTx period [median age 6.1 years (Range 0.3-20.3), median weight 17.6 kg (Range 3.5-65.0), and congenital heart disease (67%)]. Of the nine patients with early graft failure, almost half (44%) were implanted after 2015 and all of these patients had a pre-HTx plan for possible post-transplant VAD insertion. Time to VAD implant was a median of 0 day (Range 0-11). Total time on VAD support was a median of 12 days (Range 3.0-478.0). Two-thirds (n = 6; 67%) of the patients were weaned from support, retransplanted (11%) and two patients died (22%). In all of the patients where post-HTx VAD was anticipated there was 100% survival.

CONCLUSIONS

In this small patient series, post-HTx VAD was a useful measure in selected patients especially with pre-HTx planning. However, more shared experiences to verify these findings are needed.

Pediatric heart transplantation: The past, the present, and the future

Heart transplantation (HTx) has a storied past, with origins dating back to the early twentieth century and the first pediatric orthotopic heart transplant performed in 1967 on a neonate with Ebstein abnormality. Today, approximately 500 pediatric HTx are performed annually, with survival times now measured in decades rather than days or weeks. In large part, advances in immunosuppression, critical care, dedicated transplant teams and mechanical circulatory support have paved the way for improvements in waitlist mortality and post-transplant survival, with future directions including the development of intracorporeal ventricular assist devices (VADs) for small children, expanding/standardizing donor criteria, and xenotransplantation.

Outcomes of Restrictive Cardiomyopathy in Japanese Children - A Retrospective Cohort Study

BACKGROUND

There has been no nationwide survey on the prognosis of pediatric restrictive cardiomyopathy (RCM) in Japan; therefore, this retrospective multicentered study was designed to investigate the long-term survival rate of pediatric patients with RCM in Japan.Methods and Results:A multicentered, retrospective observational study was performed between 1990 and 2014 and included patients diagnosed with RCM who were aged <18 years from 18 Japanese institutions. A total of 54 patients were diagnosed with RCM. The median age at diagnosis was 4.4 years, and the median duration of observation was 2.2 years at the time of this study. Of these patients, 54% had symptoms, including heart failure. Twelve patients died without heart transplantation, mostly due to heart failure. The median time to death from diagnosis was 2.5 years. Freedom from death at 1, 5, and 10 years was 91%, 68%, and 62%, respectively. Death occurred within 5 years of diagnosis in most patients. Twenty-two patients underwent heart transplantation. Freedom from heart transplantation at 1, 5, and 10 years was 77%, 58%, and 53%, respectively. Freedom from death or heart transplantation at 1, 5, and 10 years was 72%, 40%, and 34%, respectively. The presence of symptoms was a risk factor for death or transplantation.

CONCLUSIONS

The prognosis of pediatric RCM is poor, and the heart transplantation rate is low in Japan.

Restrictive cardiomyopathy: A rare presentation of gaucher disease

Restrictive cardiomyopathy is an unusual form of cardiomyopathy accounting only for 2%–5% of all pediatric cardiomyopathies. It is mostly idiopathic. Gaucher disease in association with restrictive cardiomyopathy is extremely rare. We herein report a case of cardiac failure in an 8-year-old male child caused by restrictive cardiomyopathy. Pathogenesis of which was attributed to Gaucher disease. In any case of restrictive cardiomyopathy, Gaucher disease should be included in differential diagnosis and investigated accordingly.

Focused Update on Pulmonary Hypertension in Children-Selected Topics of Interest for the Adult Cardiologist

Pulmonary hypertensive vascular disease (PHVD), and pulmonary hypertension (PH), which is a broader term, are severe conditions associated with high morbidity and mortality at all ages. Treatment guidelines in childhood are widely adopted from adult data and experience, though big differences may exist regarding aetiology, concomitant conditions and presentation. Over the past few years, paediatric aspects have been incorporated into the common guidelines, which currently address both children and adults with pulmonary hypertension (PH). There are multiple facets of PH in the context of cardiac conditions in childhood. Apart from Eisenmenger syndrome (ES), the broad spectrum of congenital heart disease (CHD) comprises PH in failing Fontan physiology, as well as segmental PH. In this review we provide current data and novel aspects on the pathophysiological background and individual management concepts of these conditions. Moreover, we focus on paediatric left heart failure with PH and its challenging issues, including end stage treatment options, such as mechanical support and paediatric transplantation. PH in the context of rare congenital disorders, such as Scimitar Syndrome and sickle cell disease is discussed. Based on current data, we provide an overview on multiple underlying mechanisms of PH involved in these conditions, and different management strategies in children and adulthood. In addition, we summarize the paediatric aspects and the pros and cons of the recently updated definitions of PH. This review provides deeper insights into some challenging conditions of paediatric PH in order to improve current knowledge and care for children and young adults.

Restrictive Cardiomyopathy Resulting from a Troponin I Type 3 Mutation in a Chinese Family

Objective To identify the pathogenic variant responsible for restrictive cardiomyopathy (RCM) in a Chinese family.Methods Next generation sequencing was used for detecting the mutation and Results verified by sequencing. We used restriction enzyme digestion to test the mutation in the family members and 200 unrelated normal subjects without any cardiac inherited diseases when the mutation was identified.Results Five individuals died from cardiac diseases, two of whom suffered from sudden cardiac death. Two individuals have suffered from chronic cardiac disorders. Mutation analysis revealed a novel missense mutation in exon 7 of troponin I type 3 (TNNI3), resulting in substitution of serine (S) with proline (P) at amino acid position 150, which cosegregated with the disease in the family, which is predicted to be probably damaging using PolyPhen-2. The mutation was not detected in the 200 unrelated subjects we tested.Conclusion Using next generation sequencing, which has very recently been shown to be successful in identifying novel causative mutations of rare Mendelian disorders, we found a novel mutation of TNNI3 in a Chinese family with RCM.

Idiopathic Restrictive Cardiomyopathy in Children and Young Adults

Idiopathic restrictive cardiomyopathy (IRC) is a rare condition characterized by reduced ventricular compliance. Children with IRC have poor outcomes with most patients proceeding to cardiac transplantation. We sought to analyze our institutional experience and assess contemporary outcomes for children with IRC. We reviewed the medical record for patients (<21 years old) evaluated for a primary diagnosis of IRC between 1975 and 2013 at our institution. Demographic, clinical, echocardiographic, and catheterization data were abstracted. The patients were divided into 2 groups comprising a historical cohort (HC) (diagnosis: 1975 to 1993, n = 8) and a contemporary cohort (CC) (diagnosis: 1994 to 2013, n = 12). Twenty children were identified with IRC (mean age at presentation 9.7 ± 6.5 years, 55% female). Mean length of follow-up was 6.5 ± 8.4 years (range 0.1 to 35.6 years). In the CC, 7 of 12 patients (58%) progressed to cardiac transplantation (mean age of 9 ± 4 years at transplant, mean interval from diagnosis of IRC: 1.5 ± 0.9 years). Overall survival was improved significantly in the CC compared with the HC (80% vs. 38%, p = 0.02), but transplantation free survival was no different between the CC and HC over 5 years (38% vs 38%, p = 0.65). In the CC, elevation of mitral valve Doppler E/e' ratio on echocardiography was associated with increased mortality (p = 0.01). In conclusion, IRC continues has a poor prognosis. Early referral for transplantation was associated with improved overall survival in the modern era. Patients with markedly elevated E/e' ratio may have increased risk of death.

Acute Ischemic Pediatric Stroke Management: An Extended Window for Mechanical Thrombectomy?

Ischemic stroke is a rare condition to afflict the pediatric population. Congenital cardiomyopathy represents one of several possible etiologies in children. We report a 9-year-old boy who developed right middle cerebral artery stroke secondary to primary restrictive cardiomyopathy. In the absence of pediatric guidelines, the child met adult criteria for mechanical thrombectomy given the small core infarct and large penumbra. The literature suggests children may benefit from mechanical thrombectomy in carefully selected cases. Our patient exemplifies specific circumstances in which acute stroke therapy with thrombolysis and thrombectomy may be safe.

Mechanical Circulatory Support in Children

The field of pediatric mechanical circulatory support has undergone a significant evolution with the advent of devices designed for children and the implementation of new strategies for deployment. With the ongoing shortage of organs the demand for new devices specifically designed for children will only increase. This review discusses the evolution of mechanical circulatory support, available devices, and the implementation of new strategies for their deployment.

Clinical Characteristics and Treatment of Cardiomyopathies in Children

Cardiomyopathies are diseases of the heart muscle, a term introduced in 1957 to identify a group of myocardial diseases not attributable to coronary artery disease. The definition has since been modified to refer to structural and or functional abnormalities of the myocardium where other known causes of myocardial dysfunction, such as systemic hypertension, valvular disease and ischemic heart disease, have been excluded. In this review, we discuss the pathophysiology, clinical assessment and therapeutic strategies for hypertrophic, dilated and hypertrophic cardiomyopathies, with a particular focus on aspects unique to children.

Pathogenesis associated with a restrictive cardiomyopathy mutant in cardiac troponin T is due to reduced protein stability and greatly increased myofilament Ca2+ sensitivity

BACKGROUND

Dilated and hypertrophic cardiomyopathy mutations in troponin can blunt effects of protein kinase A (PKA) phosphorylation of cardiac troponin I (cTnI), decreasing myofilament Ca2+-sensitivity; however this effect has never been tested for restrictive cardiomyopathy (RCM) mutants. This study explores whether an RCM cardiac troponin T mutant (cTnT-ΔE96) interferes with convergent PKA regulation and if TnT instability contributes to greatly enhanced Ca2+-sensitivity in skinned fibers.

METHODS

Force of contraction in skinned cardiac porcine fiber and spectroscopic studies were performed.

RESULTS

A decrease of -0.26 and -0.25 pCa units in Ca2+-sensitivity of contraction after PKA incubation was observed for skinned fibers incorporated with WT or cTnT-ΔE96, respectively. To further assess whether cTnT-ΔE96 interferes solely with transmission of cTnI phosphorylation effects, skinned fibers were reconstituted with PKA pseudo-phosphorylated cTnI (cTnI-SS/DD.cTnC). Fibers displaced with cTnT-WT, reconstituted with cTnI-SS/DD.cTnC decreased Ca2+-sensitivity of force (pCa50=5.61) compared to control cTnI-WT.cTnC (pCa50=5.75), similarly affecting cTnT-ΔE96 (pCa50=6.03) compared to control \cTnI-WT.cTnC (pCa50=6.14). Fluorescence studies measuring cTnC(IAANS) Ca2+-affinity changes due to cTnT-ΔE96 indicated that higher complexity (thin filament) better recapitulates skinned fiber Ca2+ sensitive changes. Circular dichroism revealed reduced α-helicity and earlier thermal unfolding for cTnT-ΔE96 compared to WT.

CONCLUSIONS

Although ineffective in decreasing myofilament Ca2+-sensitivity to normal levels, cTnT-ΔE96 does not interfere with PKA cTnI phosphorylation mediated effects; 2) cTnT-ΔE96 requires actin to increase cTnC Ca2+-affinity; and 3) deletion of E96 reduces cTnT stability, likely disrupting crucial thin filament interactions.

GENERAL SIGNIFICANCE

The pathological effect of cTnT-ΔE96 is largely manifested by dramatic myofilament Ca2+-sensitization which still persists even after PKA phosphorylation mediated Ca2+-desensitization.

Pediatric heart transplantation-indications and outcomes in the current era

Pediatric heart transplantation (HTx) remains an important treatment option in the care of children with end-stage heart disease, whether it is secondary to cardiomyopathy or congenital heart disease (CHD). As surgical outcomes for CHD have improved, the indications for pediatric HTx have had to be dynamic, not only for children with CHD but also for the growing population of adults with CHD. As the field of pediatric HTx has evolved, the outcomes for children undergoing HTx have improved. This is undoubtedly due to the continued research efforts of both single-center studies, as well as research collaboratives such as the International Society for Heart and Lung Transplantation (ISHLT) and the Pediatric Heart Transplant Study (PHTS) group. Research collaboratives are increasingly important in pediatric HTx as single center studies for a limited patient population may not elicit strong enough evidence for practice evolution. Similarly, complications that limit the long term graft survival may occur in a minority of patients thus pooled experience is essential. This review focuses on the indications and outcomes for pediatric HTx, with a special emphasis on studies generated by these research collaboratives.

Pediatric heart transplantation-indications and outcomes in the current era

Pediatric heart transplantation (HTx) remains an important treatment option in the care of children with end-stage heart disease, whether it is secondary to cardiomyopathy or congenital heart disease (CHD). As surgical outcomes for CHD have improved, the indications for pediatric HTx have had to be dynamic, not only for children with CHD but also for the growing population of adults with CHD. As the field of pediatric HTx has evolved, the outcomes for children undergoing HTx have improved. This is undoubtedly due to the continued research efforts of both single-center studies, as well as research collaboratives such as the International Society for Heart and Lung Transplantation (ISHLT) and the Pediatric Heart Transplant Study (PHTS) group. Research collaboratives are increasingly important in pediatric HTx as single center studies for a limited patient population may not elicit strong enough evidence for practice evolution. Similarly, complications that limit the long term graft survival may occur in a minority of patients thus pooled experience is essential. This review focuses on the indications and outcomes for pediatric HTx, with a special emphasis on studies generated by these research collaboratives.

Nature of the underlying heart disease affects survival in pediatric patients undergoing extracorporeal cardiopulmonary resuscitation

OBJECTIVE

To describe the use of extracorporeal membrane oxygenation (ECMO) in acute resuscitation after cardiac arrest in pediatric patients with heart disease, with reference to patient selection and predictors of outcome.

METHODS

A retrospective medical record review was performed of all patients aged ≤21 years with heart disease who had undergone ECMO for cardiopulmonary resuscitation (ECPR) at Texas Children's Hospital from January 2005 to December 2012. The most recent Pediatric Overall Performance Category score was determined from the patients' medical records.

RESULTS

During the study period, 62 episodes of ECPR occurred in 59 patients, with 27 (46%) surviving to hospital discharge and 25 (43%) alive at the most recent follow-up visit. The overall survival to discharge for patients with myocardial failure (myocarditis, cardiomyopathy, or after transplantation) and structural heart disease was similar (40% vs 50%, P=.6). No patient with restrictive cardiomyopathy survived; 1 patient (13%) in ECPR group after late cardiac graft failure survived to discharge. Survival to discharge was greater for patients who were intubated (70%) at cardiac arrest (P=.001). The presence of pre-existing acute kidney injury at cardiac arrest (62%) was associated with greater mortality (P=.059). A Pediatric Overall Performance Category score of ≤2 (indicating good neurologic performance) was present in 68% of the survivors; 7 patients (87%) with a score>2 had abnormal imaging findings (P=.01).

CONCLUSIONS

ECPR was associated with modest survival in pediatric patients with heart disease; however, this was associated in part with the underlying disease and pre-existing comorbidities, including the presence of acute kidney injury.

Conduction abnormalities in pediatric patients with restrictive cardiomyopathy

BACKGROUND

Pediatric restrictive cardiomyopathy carries a poor prognosis secondary to a high risk of sudden death previously attributed to ventricular tachyarrhythmias. The extent of conduction abnormalities in this population and their relationship to life-threatening events has not been previously reported.

METHODS AND RESULTS

A retrospective study of pediatric patients with restrictive cardiomyopathy diagnosed between April 1994 and May 2011 was performed. Demographic, cardiac, and ECG characteristics and the mechanisms of serious arrhythmic events (death or episode of acute hemodynamic compromise thought to be secondary to arrhythmia) were evaluated. Sixteen patients (1-17 years of age) were reviewed, with 5 sudden cardiac events noted, including 4 deaths. Two deaths were caused by development of acute heart block; another patient with syncope had intermittent heart block and survived as the result of pacing features of an implanted defibrillator system. The median PR interval (222 versus 144 ms; P<0.01) and the QRS duration (111 versus 74; P=0.01) were significantly longer in those who had an acute cardiac event. Older age at presentation was associated with sudden cardiac events (P<0.01). No other functional or echocardiographic variables were associated with a sudden cardiac event.

CONCLUSIONS

Pediatric patients with restrictive cardiomyopathy are at risk for acute high-grade heart block, and, in this cohort, bradycardic events represented a significant portion of all arrhythmic events. Aggressive ECG monitoring strategies looking for conduction system disease should be ongoing in all patients with restrictive cardiomyopathy. Implantation of a defibrillator/pacemaker should be considered as prophylactic management.

Pediatric heart transplantation: demographics, outcomes, and anesthetic implications

The evolving demographics, outcomes, and anesthetic management of pediatric heart transplant recipients are reviewed. As survival continues to improve, an increasing number of these patients will present to our operating rooms and sedation suites. It is therefore important that all anesthesiologists, not only those specialized in cardiac anesthesia, have a basic understanding of the physiologic changes in the transplanted heart and the anesthetic implications thereof.

Restrictive cardiomyopathy in childhood

Depending on the part of the world one lives in, restrictive cardiomyopathy is either one of the rarest forms of cardiomyopathy in childhood, with no cause usually identified, or it is secondary to a poorly understood disease, endomyocardial fibrosis, that is endemic in some populations. Regardless of the underlying cause, the outcome is poor once symptoms develop. This article reviews the definitions, epidemiology, etiologies, genetics, "overlap" phenotypes, clinical presentation, diagnostic evaluation, outcome, and management of pediatric patients with restrictive cardiomyopathy.

Cardiac troponin mutations and restrictive cardiomyopathy

Mutations in sarcomeric proteins have recently been established as heritable causes of Restrictive Cardiomyopathy (RCM). RCM is clinically characterized as a defect in cardiac diastolic function, such as, impaired ventricular relaxation, reduced diastolic volume and increased end-diastolic pressure. To date, mutations have been identified in the cardiac genes for desmin, α-actin, troponin I and troponin T. Functional studies in skinned muscle fibers reconstituted with troponin mutants have established phenotypes consistent with the clinical findings which include an increase in myofilament Ca²⁺ sensitivity and basal force. Moreover, when RCM mutants are incorporated into reconstituted myofilaments, the ability to inhibit the ATPase activity is reduced. A majority of the mutations cluster in specific regions of cardiac troponin and appear to be mutational “hot spots”. This paper highlights the functional and clinical characteristics of RCM linked mutations within the troponin complex.

Acute right ventricular failure after pediatric cardiac transplant: predictors and long-term outcome in current era of transplantation medicine

OBJECTIVES

To identify pretransplant factors associated with postprocedural right ventricular failure and the relationship between right ventricular failure and long-term survival in children.

METHODS

Records were reviewed for children having heart transplantation from 2000 to 2006.

RESULTS

Right ventricular failure was identified by clinical and echocardiographic parameters in 33/129 (25%) recipients: dilated cardiomyopathy in 14/90 (15%), congenital heart disease in 11/27 (41%), and restrictive cardiomyopathy in 8/12 (66%). In 9 of 12 (75%), known elevated (reactive) pulmonary vascular resistance progressed to right ventricular failure. In a further 23/117 (20%) recipients, pulmonary vascular resistance within predefined acceptable range progressed to right ventricular failure. Multiple logistic regression analyses indicated elevated pulmonary vascular resistance (odds ratio 12.30; 95% confidence interval 2.73, 55.32; P = .001) and primary diagnosis, restrictive cardiomyopathy (odds ratio 9.21; 95% confidence interval 2.07, 41.12; P = .004), and congenital heart disease (odds ratio 4.07; 95% confidence interval 1.36, 12.19; P = .012) were strongly associated with right ventricular failure, but duration of heart failure, pretransplant mechanical support, donor status, and ischemic times were not. Treatment included inhaled nitric oxide in 28 (84%), mechanical support in 10 (31%), hemofiltration in 13 (40%), and retransplantation in 2. A Cox multiple regression model including: primary diagnosis, right ventricular failure, and elevated pulmonary vascular resistance indicated that only the latter was independently linked with eventual mortality (hazards ratio 5.45; 95% confidence interval 1.36, 21.96; P = .017).

CONCLUSIONS

Primary diagnosis and pretransplant elevated reactive pulmonary vascular resistance are both linked to the evolution of right ventricular failure. Pulmonary vascular resistance assessment in end-stage heart failure is challenging; therefore, avoidance of right ventricular failure may not always be possible. Aggressive early treatment may mitigate the effects of right ventricular failure: pretransplant elevated pulmonary vascular resistance was independently associated with long-term survival, but right ventricular failure was not.

A de novo mutation of the beta cardiac myosin heavy chain gene in an infantile restrictive cardiomyopathy

Here we report the first pediatric case of restrictive cardiomyopathy secondary to a de novo mutation in the cardiac myosin heavy chain gene MYH7. The clinical course is characterized by an early onset of disease, mild hypertrophy of the left ventricle and a very short evolution to death. Because of the location of the mutation in the hinge region between the rod part and the globular head of the myosin molecule, it is possible that restrictive cardiomyopathy resulted from an impairment of flexion/extension of myosin heads during the contraction/relaxation cycle.

Restrictive cardiomyopathy in a child

Restrictive cardiomyopathy in young children is rare and carries a poor prognosis. We report an 18-month-old girl with poor feeding and abdominal distension. Except for hepatomegaly, no other gastrointestinal abnormalities were found. She had normal-sized ventricles but biatrial enlargement. Echocardiography demonstrated normal systolic but impaired diastolic function. Cardiac catheterization revealed a characteristic dip-and-plateau configuration of the right ventricular pressure tracing. The diagnosis turned out to be typical restrictive cardiomyopathy. The patient was maintained on aspirin while awaiting cardiac transplant.

Twenty-year experience with heart transplantation for infants and children with restrictive cardiomyopathy: 1986-2006

Idiopathic restrictive cardiomyopathy (RCM) is a rare cardiomyopathy in children notable for severe diastolic dysfunction and progressive elevation of pulmonary vascular resistance (PVR). Traditionally, those with pulmonary vascular resistance indices (PVRI) >6 W.U. x m(2) have been precluded from heart transplantation (HTX). The clinical course of all patients transplanted for RCM between 1986 and 2006 were reviewed. Preoperative, intraoperative and postoperative variables were evaluated. A total of 23 patients underwent HTX for RCM, with a mean age of 8.8 +/- 5.6 years and a mean time from listing to HTX of 43 +/- 60 days. Preoperative and postoperative (114 +/- 40 days) PVRI were 5.9 +/- 4.4 and 2.9 +/- 1.5 W.U. x m(2), respectively. At time of most recent follow-up (mean = 5.7 +/- 4.6 years), the mean PVRI was 2.0 +/- 1.0 W.U. x m(2). Increasing preoperative mean pulmonary artery pressure (PA) pressure (p = 0.04) and PVRI > 6 W.U. x m(2) (chi(2)= 7.4, p < 0.01) were associated with the requirement of ECMO postoperatively. Neither PVRI nor mean PA pressure was associated with posttransplant mortality; 30-day and 1-year actuarial survivals were 96% and 86%, respectively. Five of the seven patients with preoperative PVRI > 6 W.U. x m(2) survived the first postoperative year. We report excellent survival for patients undergoing HTX for RCM despite the high proportion of high-risk patients.

A troponin T mutation that causes infantile restrictive cardiomyopathy increases Ca2+ sensitivity of force development and impairs the inhibitory properties of troponin

Restrictive cardiomyopathy (RCM) is a rare disorder characterized by impaired ventricular filling with decreased diastolic volume. We are reporting the functional effects of the first cardiac troponin T (CTnT) mutation linked to infantile RCM resulting from a de novo deletion mutation of glutamic acid 96. The mutation was introduced into adult and fetal isoforms of human cardiac TnT (HCTnT3-DeltaE96 and HCTnT1-DeltaE106, respectively) and studied with either cardiac troponin I (CTnI) or slow skeletal troponin I (SSTnI). Skinned cardiac fiber measurements showed a large leftward shift in the Ca(2+) sensitivity of force development with no differences in the maximal force. HCTnT1-DeltaE106 showed a significant increase in the activation of actomyosin ATPase with either CTnI or SSTnI, whereas HCTnT3-DeltaE96 was only able to increase the ATPase activity with CTnI. Both mutants showed an impaired ability to inhibit the ATPase activity. The capacity of the CTnI.CTnC and SSTnI.CTnC complexes to fully relax the fibers after TnT displacement was also compromised. Experiments performed using fetal troponin isoforms showed a less severe impact compared with the adult isoforms, which is consistent with the cardioprotective role of SSTnI and the rapid onset of RCM after birth following the isoform switch. These data indicate that troponin mutations related to RCM may have specific functional phenotypes, including large leftward shifts in the Ca(2+) sensitivity and impaired abilities to inhibit ATPase and to relax skinned fibers. All of this would account for and contribute to the severe diastolic dysfunction seen in RCM.

Prevalence, clinical significance, and genetic basis of hypertrophic cardiomyopathy with restrictive phenotype

OBJECTIVES

The purpose of this study was to determine the prevalence, clinical significance, and genetic basis of hypertrophic cardiomyopathy (HCM) with "restrictive phenotype" characterized by restrictive filling and minimal or no left ventricular hypertrophy.

BACKGROUND

Hypertrophic cardiomyopathy is a heterogeneous myocardial disorder with a broad spectrum of clinical presentation and morphologic features. Recent reports indicated that some patients with restrictive cardiomyopathy, which is an uncommon condition defined by restrictive filling and reduced diastolic volumes with normal or near normal left ventricular wall thickness and contractile function, have features suggestive of HCM with mutations in cardiac troponin I, myocyte disarray at explant/autopsy, and relatives with HCM. Systematic evaluation of the restrictive phenotype in HCM patients has not been performed.

METHODS

We evaluated 1,226 patients from 688 consecutive HCM families to identify individuals who fulfilled diagnostic criteria for "restrictive phenotype."

RESULTS

Nineteen of 1,226 affected individuals (1.5%) from 16 families (2.3%) had the "restrictive phenotype." During follow up (53.7 +/- 49.2 months), 17 patients (89%) experienced dyspnea (New York Heart Association functional class > or =2). The 5-year survival rate from all-cause mortality, cardiac transplantation, or implantable cardioverter-defibrillator discharge was 56.4%. Mutation analysis for 5 sarcomere genes was feasible in 15 of 16 probands. Mutations were found in 8: 4 in beta-myosin heavy chain, and 4 in cardiac troponin I.

CONCLUSIONS

The "restrictive phenotype" in isolation is an uncommon presentation of the clinical spectrum of HCM and is associated with severe limitation and poor prognosis. This phenotype may be associated with beta-myosin heavy chain and cardiac troponin I mutations.

Indications for Heart Transplantation in Pediatric Heart Disease

Background— Since the initial utilization of heart transplantation as therapy for end-stage pediatric heart disease, improvements have occurred in outcomes with heart transplantation and surgical therapies for congenital heart disease along with the application of medical therapies to pediatric heart failure that have improved outcomes in adults. These events justify a reevaluation of the indications for heart transplantation in congenital heart disease and other causes of pediatric heart failure.

Methods and Results— A working group was commissioned to review accumulated experience with pediatric heart transplantation and its use in patients with unrepaired and/or previously repaired or palliated congenital heart disease (children and adults), in patients with pediatric cardiomyopathies, and in pediatric patients with prior heart transplantation. Evidence-based guidelines for the indications for heart transplantation or retransplantation for these conditions were developed.

Conclusions— This evaluation has led to the development and refinement of indications for heart transplantation for patients with congenital heart disease and pediatric cardiomyopathies in addition to indications for pediatric heart retransplantation.

Heart transplantation in pediatric age

Heart transplantation, formerly the final option for terminally ill children, has now become the treatment of choice for a number of serious acquired or congenital cardiac conditions, which cannot be treated conservatively. Nevertheless, several problems remain unsolved. First of all the shortage of donors, mainly in the first months and years of life, which has become more and more significant with time, regardless of the country, religious belief or culture of the people. Secondly, the long-term impact of immunosuppression in a developing organism, and its possible inter-relation with the primary disorder, which leads to intractable heart failure. Whether a heart transplant is a cure or an ongoing disease for both the child and the family is another matter of concern. These and other topics are covered in this article.

Electrocardiographic and Clinical Characteristics of Idiopathic Restrictive Cardiomyopathy in Children

BACKGROUND

Idiopathic restrictive cardiomyopathy (RCM) is not a single disease and is rare.

METHODS AND RESULTS

The clinical features and clinical course of 12 pediatric patients with RCM seen between 1978 and 2005 were retrospectively analyzed. The age at diagnosis ranged from 4 months to 12 years (median 4 years). The age of 7 patients diagnosed because of an abnormal electrocardiogram (ECG) ranged from 4 to 12 years. Three infants less than 2 years old presented with cardiomegaly. Obliquely elevated ST-T segments and the late peak T waves on 12-lead ECG were present in 8 patients (67%). Three patients with ST depression during exercise had no perfusion defects on radioisotope myocardial perfusion imaging. Two patients underwent orthotopic heart transplantation. Of the remaining 10 patients, 7 have died: 4 died suddenly and 3 died of right heart failure. Three patients with a hypertrophic left ventricular wall had a prolonged survival. The probability of survival at 1, 2 and 3 years was 78%, 52% and 26%, respectively.

CONCLUSIONS

Obliquely elevated ST-T segments and the late peak T wave on ECG are characteristic, and reflect the restrictive physiology, which may indicate abnormalities of repolarization of ventricular muscle. The mode of death was either heart failure from pulmonary hypertension or sudden death from presumed ventricular arrhythmia.

Infantile restrictive cardiomyopathy resulting from a mutation in the cardiac troponin T gene

Here we report the first infantile case of restrictive cardiomyopathy caused by a de novo mutation of the cardiac troponin T gene. The patient presented with an apparent life-threatening event. She developed malignant arrhythmias and hemodynamic instability, requiring initial rescue support with extracorporeal membrane oxygenation, and subsequently underwent insertion of a biventricular assist device (VAD). She successfully received an orthotopic heart transplant 172 days after VAD implantation.

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.

Idiopathic restrictive cardiomyopathy in children

OBJECTIVE

To define the natural history of idiopathic restrictive cardiomyopathy in a paediatric population and to identify any factors predictive of outcome.

DESIGN

Retrospective analysis of patients born between 1970 and 2002 were identified from the Children's Hospital of Pittsburgh cardiology database. Demographic data, mode of presentation, echocardiographic and haemodynamic findings at diagnosis, survival time, and manner of death were evaluated.

SETTING

Tertiary referral and transplant centre for paediatric patients with cardiac disease.

PATIENTS

All local and referred patients with idiopathic restrictive cardiomyopathy born after 1970 and under 21 years of age at time of diagnosis.

RESULTS

21 patients were identified. Probability of survival at 1, 5, and 10 years was 80.5% (95% confidence interval (CI) 58 to 100), 39% (95% CI 17 to 61), and 20% (95% CI 0 to 42), respectively. Median age of presentation was 3.8 years (mean (SD) 5.7 (6.1) years). Median survival without transplantation was 2.2 years (mean (SD) 4.6 (5.4) years). Age at presentation, sex, and presence or absence of heart failure symptoms at presentation were not associated with clinical course. Right (p = 0.05) and left ventricular end diastolic pressures (p = 0.04) and ratio of left atrial to aortic root dimensions (LA:Ao) (p = 0.03) at presentation had a significantly negative correlation with survival time after diagnosis.

CONCLUSIONS

Without transplantation, most children with restrictive cardiomyopathy have a very poor prognosis. Longer survival from diagnosis was correlated with lower LA:Ao and cardiac filling pressures at diagnosis. Survival time was not influenced by the symptoms present at diagnosis.