Electrocardiographic response to enzyme replacement therapy for Pompe disease

Electrocardiographic abnormalities in patients with cardiomyopathies

Abnormalities in impulse generation and transmission are among the first signs of cardiac remodeling in cardiomyopathies. Accordingly, 12-lead electrocardiogram (ECG) of patients with cardiomyopathies may show multiple abnormalities. Some findings are suggestive of specific disorders, such as the discrepancy between QRS voltages and left ventricular (LV) mass for cardiac amyloidosis or the inverted T waves in the right precordial leads for arrhythmogenic cardiomyopathy. Other findings are less sensitive and/or specific, but may orient toward a specific diagnosis in a patient with a specific phenotype, such as an increased LV wall thickness or a dilated LV. A "cardiomyopathy-oriented" mindset to ECG reading is important to detect the possible signs of an underlying cardiomyopathy and to interpret correctly the meaning of these alterations, which differs in patients with cardiomyopathies or other conditions.

Beyond Sarcomeric Hypertrophic Cardiomyopathy: How to Diagnose and Manage Phenocopies

PURPOSE OF REVIEW

We describe the most common phenocopies of hypertrophic cardiomyopathy, their pathogenesis, and clinical presentation highlighting similarities and differences. We also suggest a step-by-step diagnostic work-up that can guide in differential diagnosis and management.

RECENT FINDINGS

In the last years, a wider application of genetic testing and the advances in cardiac imaging have significantly changed the diagnostic approach to HCM phenocopies. Different prognosis and management, with an increasing availability of disease-specific therapies, make differential diagnosis mandatory. The HCM phenotype can be the cardiac manifestation of different inherited and acquired disorders presenting different etiology, prognosis, and treatment. Differential diagnosis requires a cardiomyopathic mindset allowing to recognize red flags throughout the diagnostic work-up starting from clinical and family history and ending with advanced imaging and genetic testing. Different prognosis and management, with an increasing availability of disease-specific therapies make differential diagnosis mandatory.

The Clinical Management of Pompe Disease: A Pediatric Perspective

Pompe disease (PD) is an inherited metabolic disorder caused by a deficiency of acid α-glucosidase (GAA), leading to lysosomal accumulation of glycogen, mainly in skeletal and cardiac muscles as well as the nervous system. Patients with PD develop cellular dysfunction and muscle damage. PD can be classified into two classic forms, namely infantile-onset PD (IOPD) and late-onset PD (LOPD). Delayed treatment, particularly in IOPD, would result in significant organ damage and early death. Nonetheless, early diagnosis and timely treatment are often hampered by the rarity of PD and its wide variety of, but overlapping, symptoms. This article reviews the common clinical presentations of PD and outlines the essentials of PD management. In particular, the implications of newborn screening (NBS) and clinical performance of enzyme replacement therapy (ERT) are highlighted.

Diagnosis and Management of Rare Cardiomyopathies in Adult and Paediatric Patients. A Position Paper of the Italian Society of Cardiology (SIC) and Italian Society of Paediatric Cardiology (SICP)

Cardiomyopathies (CMPs) are myocardial diseases in which the heart muscle is structurally and functionally abnormal in the absence of coronary artery disease, hypertension, valvular disease and congenital heart disease sufficient to cause the observed myocardial abnormality. Thought for a long time to be rare diseases, it is now clear that most of the CMPs can be easily observed in clinical practice. However, there is a group of specific heart muscle diseases that are rare in nature whose clinical/echocardiographic phenotypes resemble those of the four classical morphological subgroups of hypertrophic, dilated, restrictive, arrhythmogenic CMPs. These rare CMPs, often but not solely diagnosed in infants and paediatric patients, should be more properly labelled as specific CMPs. Emerging consensus exists that these conditions require tailored investigation and management. Indeed, an appropriate understanding of these conditions is mandatory for early treatment and counselling. At present, however, the multisystemic and heterogeneous presentation of these entities is a challenge for clinicians, and time delay in diagnosis is a significant concern. The aim of this paper is to define practical recommendations for diagnosis and management of the rare CMPs in paediatric or adult age. A modified Delphi method was adopted to grade the recommendations proposed by each member of the writing committee.

Cardiac responses in paediatric Pompe disease in the ADVANCE patient cohort

Pompe disease results from lysosomal acid α-glucosidase deficiency, which leads to cardiomyopathy in all infantile-onset and occasional late-onset patients. Cardiac assessment is important for its diagnosis and management. This article presents unpublished cardiac findings, concomitant medications, and cardiac efficacy and safety outcomes from the ADVANCE study; trajectories of patients with abnormal left ventricular mass z score at enrolment; and post hoc analyses of on-treatment left ventricular mass and systolic blood pressure z scores by disease phenotype, GAA genotype, and "fraction of life" (defined as the fraction of life on pre-study 160 L production-scale alglucosidase alfa). ADVANCE evaluated 52 weeks' treatment with 4000 L production-scale alglucosidase alfa in ≥1-year-old United States of America patients with Pompe disease previously receiving 160 L production-scale alglucosidase alfa. M-mode echocardiography and 12-lead electrocardiography were performed at enrolment and Week 52. Sixty-seven patients had complete left ventricular mass z scores, decreasing at Week 52 (infantile-onset patients, change -0.8 ± 1.83; 95% confidence interval -1.3 to -0.2; all patients, change -0.5 ± 1.71; 95% confidence interval -1.0 to -0.1). Patients with "fraction of life" <0.79 had left ventricular mass z score decreasing (enrolment: +0.1 ± 3.0; Week 52: -1.1 ± 2.0); those with "fraction of life" ≥0.79 remained stable (enrolment: -0.9 ± 1.5; Week 52: -0.9 ± 1.4). Systolic blood pressure z scores were stable from enrolment to Week 52, and no cohort developed systemic hypertension. Eight patients had Wolff-Parkinson-White syndrome. Cardiac hypertrophy and dysrhythmia in ADVANCE patients at or before enrolment were typical of Pompe disease. Four-thousand L alglucosidase alfa therapy maintained fractional shortening, left ventricular posterior and septal end-diastolic thicknesses, and improved left ventricular mass z score.Trial registry: ClinicalTrials.gov Identifier: NCT01526785 https://clinicaltrials.gov/ct2/show/NCT01526785.Social Media Statement: Post hoc analyses of the ADVANCE study cohort of 113 children support ongoing cardiac monitoring and concomitant management of children with Pompe disease on long-term alglucosidase alfa to functionally improve cardiomyopathy and/or dysrhythmia.

Synchronized intracellular and extracellular recording of action potentials by three-dimensional nanoroded electroporation

Electrophysiological study is an essential and significant strategy to explore the biological mechanism of electrogenic cells. Current advanced nanodevices can achieve the high-fidelity intracellular electrophysiological recordings, and most of detection systems record the extracellular and intracellular action potentials (EAPs and IAPs) in an asynchronous or isolated manner, so it is demanded to develop the platform to reveal correlation between EAP and IAP recording. Here, we establish a utility strategy to achieve synchronized intracellular and extracellular recording of neonatal rat cardiomyocytes by low-voltage three-dimensional (3D) nanoroded electroporation. By integrating the advantages of nanodevice and microdevice, 3D nanoroded microdevice is developed to achieve the high-throughput large-scale synchronous intracellular and extracellular electrophysiological study. By applying low-voltage electroporation, intracellular and extracellular signals can be synchronously acquired from intracellular access and extracellular coupling, respectively. Recorded synchronized signals contain both typical EAPs and IAPs, which have good synchronicity in spatiotemporal dimensions at each recording site. Moreover, correlation between both signals is further bridged in experimental and simulated way. This intracellular electrophysiological platform presents unique advantages over the conventional system to achieve the synchronized intracellular and extracellular electrophysiological study at membrane voltage level.

Perioperative management of children with glycogen storage disease type II-Pompe disease

BACKGROUND

Pompe disease is a rare metabolic disorder caused by a deficiency of the lysosomal enzyme acid α-glucosidase. Glycogen accumulation damages skeletal, cardiac, and smooth muscles, causing a progressive and debilitating muscle weakness and cardiomyopathy. As life expectancy has much improved since the introduction of enzyme replacement therapy an increasing number of patients are referred for surgical procedures. Due to the potential cardiopulmonary complications, these patients form a high-risk group for the anesthesiologist.

AIMS

In this study, we investigated the incidence of perioperative complications in children with Pompe disease treated in our hospital since the introduction of enzyme replacement therapy.

METHODS

Anesthetic and perioperative data of children with Pompe disease treated between 1999 and 2015 in the Erasmus MC-Sophia Children's Hospital, University Medical Centre, Rotterdam, The Netherlands, were collected, retrospectively.

RESULTS

Of the 65 children with Pompe disease, 34 patients underwent in total 77, mostly low-risk, surgical procedures. Twenty-one children had the classic infantile form and 13 had a nonclassic presentation of Pompe disease. In 13 (16.8%) procedures, 1 or more perioperative complications occurred. Perioperative desaturation was the main complication (12.9%), followed by arrhythmia (3.8%) and heart failure requiring diuretic treatment (2.6%). One child died 2 days postoperatively, but this was considered unrelated to the procedure.

CONCLUSION

Despite the potentially high anesthetic risk for children with Pompe disease under enzyme replacement therapy, the incidence of perioperative complications in our study was relatively low. Our data suggest that with proper precautionary measures and a critical choice of timing of the operation, general anesthesia in children with Pompe disease could be relatively safe nowadays.

A beta-blocker, propranolol, decreases the efficacy from enzyme replacement therapy in Pompe disease

Enzyme replacement therapy (ERT) with recombinant human acid α-glucosidase (rhGAA) fails to completely reverse muscle weakness in Pompe disease. β2-agonists enhanced ERT by increasing receptor-mediated uptake of rhGAA in skeletal muscles.

PURPOSE

To test the hypothesis that a β-blocker might reduce the efficacy of ERT, because the action of β-blockers opposes those of β2-agonists.

METHODS

Mice with Pompe disease were treated with propranolol (a β-blocker) or clenbuterol in combination with ERT, or with ERT alone.

RESULTS

Propranolol-treated mice had decreased weight gain (p<0.01), in comparison with clenbuterol-treated mice. Left ventricular mass was decreased (and comparable to wild-type) in ERT only and clenbuterol-treated groups of mice, and unchanged in propranolol-treated mice. GAA activity increased following either clenbuterol or propranolol in skeletal muscles. However, muscle glycogen was reduced only in clenbuterol-treated mice, not in propranolol-treated mice. Cell-based experiments confirmed that propranolol reduces uptake of rhGAA into Pompe fibroblasts and also demonstrated that the drug induces intracellular accumulation of glycoproteins at higher doses.

CONCLUSION

Propranolol, a commonly prescribed β-blocker, reduced weight, increased left ventricular mass and decreased glycogen clearance in skeletal muscle following ERT. β-Blockers might therefore decrease the efficacy from ERT in patients with Pompe disease.

Clinical and GAA gene mutation analysis in mainland Chinese patients with late-onset Pompe disease: identifying c.2238G > C as the most common mutation

Background

Pompe disease is an autosomal recessive lysosomal glycogen storage disorder that has been reported in different ethnic populations which carry different common mutations of the acid alpha-glucosidase (GAA) gene. The GAA mutation pattern in mainland Chinese patients with late-onset Pompe disease is still not well understood.

Methods

We presented the clinical and genetic characteristics of 27 mainland Chinese late-onset Pompe patients from 24 families.

Results

GAA mutation analysis revealed 26 different mutations, including 10 that were novel. The allelic frequency of c.2238G > C (p.W746C) was found to be 27.08% in this patient group. Respiratory dysfunction was diagnosed in 10 of 11 patients who underwent pulmonary function evaluation, although only four required ventilator support at night.

Conclusions

Our findings indicate that c.2238G > C (p.W746C) is the most common mutation in mainland Chinese late-onset Pompe patients, as observed in Taiwanese patients. The novel mutations identified in this study expand the genetic spectrum of late-onset Pompe disease, and the prevalence of respiratory dysfunction highlights the importance of monitoring pulmonary function in late-onset Pompe patients.

The new frontier of genetically targeted therapies for muscle disease

This article presents the case of a 5-year-old boy with Duchenne muscular dystrophy who is eligible to enroll in a clinical trial of gene therapy for this disorder. His parents are grappling with the decision about whether to enroll him. Among the issues under consideration are the potential risks and benefits to him, the costs of participating (because frequent, partially reimbursed travel is involved), and the potential cost savings of receiving this treatment on a research basis rather than as a clinically approved therapy. His parents seek the advice of his pediatric neurologist. After careful consideration of the various factors above, the pediatric neurologist explains to the family that participating in the trial is ethically permissible but that, given the uncertain benefits and potential for substantial expenses without benefit to the child, participation should not be regarded as ethically obligatory.

Genetics and metabolic cardiomyopathies

Metabolic disorders encompass a heterogeneous group of conditions that commonly affect the heart and contribute adversely to cardiovascular outcomes. As the heart is a metabolically active organ, inborn errors in metabolism (IEMs) often present with cardiac manifestations such as cardiomyopathy, arrhythmia, and valvular dysfunction. More than 40 IEMs are reported to cause cardiomyopathy, including fatty acid oxidation defects, glycogen, lysosomal and perioxisome storage diseases, mitochondrial cardiomyopathies, organic acidaemias, aminoacidopathies and congenital disorders of glycosylation. Studies suggest that IEM account for only 5% of cardiomyopathies; however, their diagnosis is imperative to enable the effective institution of disease-specific management strategies. This review describes the more common genetic defects that affect metabolic pathways and give rise to heart muscle disease.

Pulmonary interstitial glycogenosis associated with pulmonary hypertension and hypertrophic cardiomyopathy

A neonate with pulmonary interstitial glycogenosis, pulmonary hypertension, and hypertrophic cardiomyopathy is described. The fatal outcome for this patient contrasts with the reported favorable prognosis associated with isolated pulmonary interstitial glycogenosis. To the authors' knowledge, the association of pulmonary interstitial glycogenosis and hypertrophic cardiomyopathy has not been reported previously. The authors have broadened the phenotype of pulmonary interstitial glycogenosis and demonstrate the diagnostic value of lung biopsy in cases of unexplained neonatal pulmonary hypertension.

Ethical issues in neurogenetic disorders

The field of neurogenetics is moving so rapidly that new discoveries are announced almost weekly. The tools available for the diagnosis of neurogenetic disorders have become powerful and complex, and raise new ethical dilemmas that did not exist just a few years ago. In addition to previous concerns about presymptomatic genetic testing and carrier testing, the widening availability of next-generation sequencing raises concerns about the reporting of incidental findings of unclear significance. Genetically targeted therapies have now been proven to be efficacious for a few neurogenetic diseases, and it is likely that gene therapies and cell-based therapies will soon be applied to other neurologic disorders. These therapies are generally quite expensive compared to other treatments. Given the cost constraints that will be needed in the healthcare system in the United States and other countries, and the likelihood that new genetically targeted therapies will be introduced, society will face difficult questions regarding its obligations to fund expensive therapies both for large populations and for small numbers of patients with rare diseases. Potential conflicts of interest involving both individuals and institutions will need ongoing vigilance. Scientific advances will continue to raise consequential ethical questions in the field of neurogenetics.

The emerging phenotype of long-term survivors with infantile Pompe disease

PURPOSE

Enzyme replacement therapy with alglucosidase alfa for infantile Pompe disease has improved survival creating new management challenges. We describe an emerging phenotype in a retrospective review of long-term survivors.

METHODS

Inclusion criteria included ventilator-free status and age ≤6 months at treatment initiation, and survival to age ≥5 years. Clinical outcome measures included invasive ventilator-free survival and parameters for cardiac, pulmonary, musculoskeletal, gross motor, and ambulatory status; growth; speech, hearing, and swallowing; and gastrointestinal and nutritional status.

RESULTS

Eleven of 17 patients met study criteria. All were cross-reactive immunologic material-positive, alive, and invasive ventilator-free at most recent assessment, with a median age of 8.0 years (range: 5.4-12.0 years). All had marked improvements in cardiac parameters. Commonly present were gross motor weakness, motor speech deficits, sensorineural and/or conductive hearing loss, osteopenia, gastroesophageal reflux, and dysphagia with aspiration risk. Seven of 11 patients were independently ambulatory and four required the use of assistive ambulatory devices. All long-term survivors had low or undetectable anti-alglucosidase alfa antibody titers.

CONCLUSION

Long-term survivors exhibited sustained improvements in cardiac parameters and gross motor function. Residual muscle weakness, hearing loss, risk for arrhythmias, hypernasal speech, dysphagia with risk for aspiration, and osteopenia were commonly observed findings.

Infantile Pompe disease: clinical and genetic characteristics with an experience of enzyme replacement therapy

Pompe disease is an autosomal recessive disorder caused by lysosomal acid α-glucosidase deficiency. Infantile-onset Pompe disease presents with cardiomyopathy and hypotonia, leading to premature death. This article describes 7 infantile Pompe disease cases and provides their molecular bases and clinical outcomes after enzyme replacement therapy for the first time in Korea. Molecular genetic analyses revealed the presence of 9 different mutations, including 5 novel mutations (c.2171C>A, c.2774C>T, c.1582_3de12, c.1261_1263Tms, and c.1322_1326+9de114). The most common mutation in these 7 patients was c.1316T>A (28%). Four patients received intravenous recombinant human acid α-glucosidase therapy for 2 years, on average, without significant side effects during the treatment course. They all exhibited increased muscle power, with considerable improvement in cardiac function. Pompe disease is heterogeneous regarding both clinical features and molecular characteristics. Early identification of Pompe disease is very important, considering that enzyme replacement therapy is a safe and effective treatment for early-onset patients.

Cardiac Pathology in Glycogen Storage Disease Type III

PURPOSE

To investigate the distribution and clinical impact of glycogen accumulation on heart structure and function in individuals with GSD III.

METHODS

We examined cardiac tissue and the clinical records of three individuals with GSD IIIa who died or underwent cardiac transplantation. Of the two patients that died, one was from infection and the other was from sudden cardiac death. The third patient required cardiac transplantation for end-stage heart failure with severe hypertrophic cardiomyopathy.

RESULTS

Macro- and microscopic examination revealed cardiac fibrosis (n = 1), moderate to severe vacuolation of cardiac myocytes (n = 3), mild to severe glycogen accumulation in the atrioventricular (AV) node (n = 3), and glycogen accumulation in smooth muscle cells of intramyocardial arteries associated with smooth muscle hyperplasia and profoundly thickened vascular walls (n = 1).

CONCLUSION

Our findings document diffuse though variable involvement of cardiac structures in GSD III patients. Furthermore, our results also show a potential for serious arrhythmia and symptomatic heart failure in some GSD III patients, and this should be considered when managing this patient population.

Assessing disease severity in Pompe disease: the roles of a urinary glucose tetrasaccharide biomarker and imaging techniques

Defining disease severity in patients with Pompe disease is important for prognosis and monitoring the response to therapies. Current approaches include qualitative and quantitative assessments of the disease burden, and clinical measures of the impact of the disease on affected systems. The aims of this manuscript were to review a noninvasive urinary glucose tetrasaccharide biomarker of glycogen storage, and to discuss advances in imaging techniques for determining the disease burden in Pompe disease. The glucose tetrasaccharide, Glcα1-6Glcα1-4Glcα1-4Glc (Glc(4) ), is a glycogen-derived limit dextrin that correlates with the extent of glycogen accumulation in skeletal muscle. As such, it is more useful than traditional biomarkers of tissue damage, such as CK and AST, for monitoring the response to enzyme replacement therapy in patients with Pompe disease. Glc(4) is also useful as an adjunctive diagnostic test for Pompe disease when performed in conjunction with acid alpha-glucosidase activity measurements. Review of clinical records of 208 patients evaluated for Pompe disease by this approach showed Glc(4) had 94% sensitivity and 84% specificity for Pompe disease. We propose Glc(4) is useful as an overall measure of disease burden, but does not provide information on the location and distribution of excess glycogen accumulation. In this manuscript we also review magnetic resonance spectroscopy and imaging techniques as alternative, noninvasive tools for quantifying glycogen and detailing changes, such as fibrofatty muscle degeneration, in specific muscle groups in Pompe disease. These techniques show promise as a means of monitoring disease progression and the response to treatment in Pompe disease. © 2012 Wiley Periodicals, Inc.

Cardiovascular abnormalities in late-onset Pompe disease and response to enzyme replacement therapy

PURPOSE

We evaluated the prevalence of cardiovascular abnormalities and the efficacy and safety of enzyme replacement therapy in patients with late-onset Pompe disease.

METHODS

Ninety patients were randomized 2:1 to enzyme replacement therapy or placebo in a double-blinded protocol. Electrocardiograms and echocardiograms were obtained at baseline and scheduled intervals during the 78-week study period. Baseline cardiovascular abnormalities, and efficacy and safety of enzyme replacement therapy were described. Three pediatric patients were excluded.

RESULTS

Eighty-seven patients were included. Median age was 44 years; 51% were men. At baseline, a short PR interval was present in 10%, 7% had decreased left ventricular systolic function, and 5% had elevated left ventricular mass on echocardiogram (all in mild range). There was no change in cardiovascular status associated with enzyme replacement therapy. No significant safety concerns related to enzyme replacement therapy were identified.

CONCLUSIONS

Although some patients with late-onset Pompe disease had abnormalities on baseline electrocardiogram or echocardiogram, those classically seen in infantile Pompe disease, such as significant ventricular hypertrophy, were not noted. Cardiovascular parameters were not impacted by enzyme replacement therapy, and there were no cardiovascular safety concerns. The cardiovascular abnormalities identified may be related to Pompe disease or other comorbid conditions.

Pompe's Disease in Childhood: A Metabolic Myopathy

BACKGROUND

Myopathy of metabolic origin in childhood occurs due to a variety of conditions. Pompe's Disease also known as Glycogen storage disease Type II, is a rare storage disorder with clinical presentation akin to spinal muscular atrophy.

METHODS

A series of patients with suspected metabolic myopathy were reviewed at a tertiary care service hospital over a period of three years. The diagnosis was confirmed by estimation of acid alpha glucosidase activity.

RESULT

At our centre, these cases presented with generalized hypotonia, organomegaly (hepatomegaly, cardiomegaly) and congestive cardiac failure. Infantile onset, the most severe form of Pompe's disease, was the commonest form accounting for 75% of the cases. Four of the babies with infantile onset Pompe's disease expired, three due to refractory heart failure and one to fulminant respiratory infection before 15 months of age.

CONCLUSION

Pompe's Disease is now being increasingly diagnosed, due to definitive enzyme estimation facilities. With the recent availability of enzyme replacement therapy with Myozyme, the prognosis is likely to change for the better.

Improvement of cardiac fibrosis in dystrophic mice by rAAV9-mediated microdystrophin transduction

Duchenne muscular dystrophy (DMD) is the most common form of the progressive muscular dystrophies characterized by defects of the dystrophin gene. Although primarily characterized by degeneration of the limb muscles, cardiomyopathy is a major cause of death. Therefore, the development of curative modalities such as gene therapy is imperative. We evaluated the cardiomyopathic features of mdx mice to observe improvements in response to intravenous administration of recombinant adeno-associated virus (AAV) type 9 encoding microdystrophin. The myocardium was extensively transduced with microdystrophin to significantly prevent the development of fibrosis, and expression persisted for the duration of the study. Intraventricular conduction patterns, such as the QRS complex duration and S/R ratio in electrocardiography, were also corrected, indicating that the transduced microdystrophin has a protective effect on the dystrophin-deficient myocardium. Furthermore, BNP and ANP levels were reduced to normal, suggesting the absence of cardiac dysfunction. In aged mice, prevention of ectopic beats as well as echocardiographic amelioration was also demonstrated with improved exercise performance. These findings indicate that AAV-mediated cardiac transduction with microdystrophin might be a promising therapeutic strategy for the treatment of dystrophin-deficient cardiomyopathy.

Use of cardiac magnetic resonance imaging to evaluate cardiac structure, function and fibrosis in children with infantile Pompe disease on enzyme replacement therapy

BACKGROUND

Pompe disease (acid α-glucosidase deficiency) is one of several lysosomal storage diseases amenable to treatment with enzyme replacement therapy (ERT). While echocardiography (echo) has been the standard method to evaluate the cardiac response to ERT, cardiac magnetic resonance imaging (CMR) has the advantage of a better tissue definition and characterization of myocardial fibrosis. However, CMR for Pompe disease is not frequently performed due to a high risk of sedation. We report the first use of CMR in a feasible protocol to quantify left ventricular (LV) mass, function, and the presence of myocardial fibrosis in the Pompe population.

METHODS

Children with Pompe disease on ERT were assessed with transthoracic echo and CMR over a 3 year period at a single institution. Echocardiography was performed using standard techniques without sedation. CMR was performed using retrospectively gated and real-time imaging, with and without sedation. LV mass indexed to body surface area (LVMI) and ejection fraction (EF) were measured by both echo and CMR, and evaluated for change over time. Myocardial fibrosis was assessed by CMR with delayed enhancement imaging 5-10 min after gadolinium contrast using single shot inversion recovery sequences with inversion time set to null the signal from normal myocardium.

RESULTS

Seventeen CMR scans were successfully performed in 10 subjects with Pompe disease (median age at first CMR is 9 months, range 1-38 months, 80% male), with sedation only performed in 4 studies. There was a median interval of 5 months (range 0-34 months) from the start of ERT to first CMR (baseline). At baseline, the median indexed LVMI by CMR (140.0 g/m(2), range 43.8-334.0) tended to be lower than that assessed by echo (median 204.0 g/m(2), range 52.0-385.0), but did not reach statistical significance. At baseline, CMR EF was similar to that assessed by echo (55% vs. 55%). Overall, there was no significant decrease in CMR measured LVMI over time (CMR median LVMI at baseline 94 g/m(2) (range 43.8-334) vs. CMR median at most recent study 44.5 g/m(2) (range 34-303), p=0.44). In 5 patients with serial CMR scans over time, LVMI decreased in 2, was similar in 2, and increased in 1 patient with high sustained antibodies to exogenous enzyme. Delayed enhancement was noted in only l separate patient who also had high sustained antibodies to exogenous enzyme.

CONCLUSION

CMR is an imaging tool that is feasible to use to serially follow LVMI and EF in children with Pompe disease on ERT. Real-time imaging is adequate for quantification purposes in these patients and minimizes the need for sedation. Quantitative CMR LVMI is generally lower than echo derived LVMI. Delayed enhancement appears to be a rare finding by CMR in Pompe disease. A further follow-up is necessary to better understand the long term effects of ERT in infantile Pompe survivors, especially those with high sustained antibody titers or advanced cardiac disease at treatment outset.

Antenatal diagnosis of pompe disease by fetal echocardiography: impact on outcome after early initiation of enzyme replacement therapy

Hypertrophic cardiomyopathy (HCM) affects most infants with Pompe disease (PD), and may serve as a marker for its antenatal diagnosis (ANDx) by fetal echocardiography (FE). Fetuses diagnosed with HCM between 2006 and 2009 were included in this study. HCM, defined as Z-score of mean left ventricular wall thickness (LVWT) and/or mass (LVM) above 2, was detected in 5/1,268 fetuses (0.39%) carried by 1,137 pregnant women referred for FE. Three fetuses (0.24%) had postnatal confirmation of PD. Their gestational age and fetal weight at diagnosis was (mean ± standard deviation) 31 ± 3.6 weeks and 1.9 ± 0.2 kg, respectively. Fetal Z-score of LVM and LVWT was 3.8 ± 0.9 and 3.1 ± 0.6, respectively. Postnatally, acid α-glucosidase (GAA) enzyme activity was nearly absent in all patients, 2 were homozygous for the mutation 1327-2A>G in the GAA gene, and 1 was homozygous for 340insT. Enzyme replacement therapy (ERT) was initiated 4.9 ± 7.8 days after birth (range 2 h-14 days), and continued every 2 weeks. Two infants are alive at 4 and 31 months, and one died of aspiration pneumonia at 19 months. Cardiac hypertrophy resolved after 10-12 weeks of ERT in all patients, and none required any respiratory support. One patient had normal neurodevelopmental assessment at 25 months, and one had severe global delay at 15 months before death. ANDx of PD by FE is feasible based on fetal HCM. It promotes early initiation of ERT which may improve outcome in some patients. However, larger studies and longer follow-ups are required.

Long-term follow-up results in enzyme replacement therapy for Pompe disease: a case report

Pompe disease (PD) is a metabolic myopathy caused by a deficiency of acid-alpha glucosidase (GAA), a lysosomal enzyme that cleaves glycogen. The classic infantile-onset form is characterised by severe hypotonia and cardiomyopathy. Untreated patients usually die within the first year of life due to cardiorespiratory failure. Several studies involving patients with infantile-onset PD have shown that enzyme replacement therapy (ERT) with alglucosidase alfa, recombinant human GAA (rhGAA), significantly prolongs survival, decreases cardiomegaly, and improves cardiac function and conduction abnormalities. However, the efficacy on motor, cognitive and social milestones appears to be more related to the condition of the patient before the start of treatment. To date, the sample of early diagnosed and treated patients is small and the length of follow-up is still limited. We report the results of a long-term follow-up of one patient presenting severe bradycardia and cardiomyopathy at birth, diagnosed in the third day of life and successfully treated by ERT. Serum muscle enzymes at diagnosis were AST 200 U/L, ALT 99 U/L and CPK 731 U/L (n.v. 0-295); the molecular study identified the homozygous missense mutation c.1933 G> A p.Asp645Asn (GAA exon 14). Left Ventricular Mass Index (LVMI) at baseline was 171 g/m(2) (Z-score = 4.3) and decreased to normal values since the 3-month follow-up. A muscle biopsy performed at 18 months after the start of therapy, showed only a low degree of muscle involvement. To our knowledge, this is the longest ERT treatment follow-up in a symptomatic neonatal patient with Pompe disease.

Cross-reactive immunologic material status affects treatment outcomes in Pompe disease infants

Deficiency of acid alpha glucosidase (GAA) causes Pompe disease, which is usually fatal if onset occurs in infancy. Patients synthesize a non-functional form of GAA or are unable to form native enzyme. Enzyme replacement therapy with recombinant human GAA (rhGAA) prolongs survival in infantile Pompe patients but may be less effective in cross-reactive immunologic material (CRIM)-negative patients. We retrospectively analyzed the influence of CRIM status on outcome in 21 CRIM-positive and 11 CRIM-negative infantile Pompe patients receiving rhGAA. Patients were from the clinical setting and from clinical trials of rhGAA, were 6 months of age, were not invasively ventilated, and were treated with IV rhGAA at a cumulative or total dose of 20 or 40 mg/kg/2 weeks. Outcome measures included survival, invasive ventilator-free survival, cardiac status, gross motor development, development of antibodies to rhGAA, and levels of urinary Glc(4). Following 52 weeks of treatment, 6/11 (54.5%) CRIM-negative and 1/21 (4.8%) CRIM-positive patients were deceased or invasively ventilated (p<0.0001). By age 27.1 months, all CRIM-negative patients and 4/21 (19.0%) CRIM-positive patients were deceased or invasively ventilated. Cardiac function and gross motor development improved significantly more in the CRIM-positive group. IgG antibodies to rhGAA developed earlier and serotiters were higher and more sustained in the CRIM-negative group. CRIM-negative status predicted reduced overall survival and invasive ventilator-free survival and poorer clinical outcomes in infants with Pompe disease treated with rhGAA. The effect of CRIM status on outcome appears to be mediated by antibody responses to the exogenous protein.

Reversal of cardiac dysfunction after enzyme replacement in patients with infantile-onset Pompe disease

OBJECTIVE

To compare the effects of enzyme replacement therapy (ERT) on cardiac performance in symptomatic and symptom-free infants with Pompe disease.

STUDY DESIGN

Patients diagnosed between 1983 and 2008 were identified. Before the initiation of ERT, systolic dysfunction appeared only in patients > or = 5 months; thus we used this cut-point in age to divide clinically symptomatic patients into early and late treatment groups (Clin-E and Clin-L). Newborn screening (NBS) identified symptom-free patients.

RESULTS

Among a total of 40 patients, 14 received ERT: 5 in the Clin-L, 4 in the Clin-E, and 5 in the NBS groups. All patients showed cardiomegaly, hypertrophic myocardium, and elevated B-type natriuretic peptide (measured in the Clin-E and NBS groups). ERT improved the survival and outcomes. Regressed myocardial hypertrophy and lowered B-type natriuretic peptide level occurred after 1 to 6 months of ERT. Nonetheless, there were 2 deaths and 2 survivors requiring ventilator support in the Clin-L group. Despite the regressed QRS voltage and shortened QT dispersion, life-threatening arrhythmias were still observed in 3, but none in the NBS group.

CONCLUSION

ERT may restore the cardiac function in both symptomatic and symptom-free patients, but the beneficial effect may be unpredictable if given after the age of 5 months.

Early administration of enzyme replacement therapy for Pompe disease: short-term follow-up results

Pompe disease (glycogen storage disease II, OMIM # 232300), is a hereditary lysosomal disorder. It is characterized by deficiency of acid alpha-glucosidase enzyme (acid maltase, GAA, OMIM *606800, EC 3.1.26.2), secondary to mutations in the GAA gene (HGNC:4065) on chromosome 17q25.2-q25.3. Absent enzyme activity in the infantile form of Pompe disease results in abnormal glycogen deposition in the skeletal, cardiac, and smooth muscles, leading to hypertrophic cardiomyopathy, feeding abnormalities, hypotonia, weakness, respiratory insufficiency, and ultimately death. Prenatal diagnosis is accomplished by enzyme assay, mutation analysis or electron microscopy of amniotic fluid cells or chorionic villus sample. However, these techniques may not always be available, and can result in perinatal morbidity and fetal loss. Early diagnosis of Pompe disease results in early institution of enzyme replacement therapy (ERT), which minimizes morbidity and prolongs survival. We report the case of a 35-week part-of-twin neonate, whose older sibling died earlier because of infantile Pompe disease. At 32 weeks of gestation, fetal echocardiography showed hypertrophic cardiomyopathy in twin 1, which persisted until birth at 35 weeks of gestation. Diagnosis was confirmed after birth by enzyme assay, and mutation analysis showing homozygosity for the sequence change 1327-2A>G (GAA intr 8). Administration of ERT at 18 h of age, resulted in normalization of cardiac abnormalities within 21 weeks of therapy, and normal neurodevelopmental assessment at 46 weeks, using Griffiths Mental Development Scales. To our knowledge, this is the youngest patient reported to receive ERT for Pompe disease, and the first report of prenatal diagnosis of Pompe disease by fetal echocardiography.

[Enzyme replacement therapy in a boy with infantile Pompe disease: cardiac follow-up]

Pompe disease is an autosomal recessive glycogen storage disorder caused by acid-alpha-glucosidase deficiency. The infantile form is usually fatal by 1 year of age in the absence of specific therapy. We report the cardiac follow-up of a 4-month-old boy treated with enzyme replacement therapy (ERT) for 8 months. The patient had no cardiac failure at the age of 1 year. Before starting ERT, ECG showed a shortened PR interval, with huge QRS complexes and biventricular hypertrophy; echocardiography demonstrated major hypertrophic cardiomyopathy. The QRS voltage (SV1+RV6) decreased from 13 to 2.9 mV after 32 weeks of ERT, suggesting a progressive reduction of cardiac hypertrophy and intracellular glycogen excess. The PR interval increased from 60 to 90 ms. A block of the right bundle branch appeared after 13 weeks of treatment. The indexed left ventricular mass decreased from 240 to 90 g/m2 after 30 weeks of ERT. The left ventricular ejection fraction decreased transitorily between the 5th and the 15 th weeks of treatment. In summary, ERT is an efficient therapeutic approach for the cardiomyopathy of infantile Pompe disease. However, the possible occurrence of a right bundle branch block and a transitory alteration in the ejection fraction highlight the importance of cardiac follow-up.

Cardiac remodeling after enzyme replacement therapy with acid alpha-glucosidase for infants with Pompe disease

BACKGROUND

Infantile Pompe disease (glycogen storage disease type 2) is a fatal disorder caused by deficiency of acid alpha-glucosidase. This deficiency results in glycogen accumulation in the lysosomes of many tissues including cardiac muscle. The disease is characterized by profound hypotonia, poor growth, organomegaly, and cardiomegaly. Severe hypertrophic cardiomyopathy often is present in early infancy, and most patients die of cardiac or respiratory failure in the first year of life. This report describes the cardiac response of infants with Pompe disease to a phase 2 trial of enzyme replacement therapy (ERT).

METHODS

Eight patients with classical infantile Pompe disease were given intravenous recombinant human GAA (rhGAA) for 1 year. Cardiac monitoring included echocardiography, electrocardiograms (ECGs), chest radiographs, and clinical cardiac evaluation at 4, 8, 12, 24, 36, and 52 weeks. At 52 weeks, 6 patients were alive.

RESULTS

Most of the treated patients had rapid regression of ventricular hypertrophy in response to ERT, with near normalization of posterior wall thickness, ventricular mass, and ventricular size. Systolic ventricular function was preserved despite rapid changes in ventricular mass and size. Concomitantly, ECGs documented lengthening of the PR interval and decreased ventricular voltages, whereas chest radiographs documented a decreased cardiothoracic ratio. Symptoms of pulmonary congestion were diminished, and survival was improved.

CONCLUSION

The cardiovascular system responds quickly and strikingly to ERT with rhGAA, suggesting rapid reversal of excessive glycogen storage in cardiac muscle cells. Changes in ventricular mass and function are maintained throughout 1 year of follow-up evaluation and associated with decreased morbidity and prolonged survival.

Pompe's disease

Pompe's disease, glycogen-storage disease type II, and acid maltase deficiency are alternative names for the same metabolic disorder. It is a pan-ethnic autosomal recessive trait characterised by acid alpha-glucosidase deficiency leading to lysosomal glycogen storage. Pompe's disease is also regarded as a muscular disorder, but the generalised storage of glycogen causes more than mobility and respiratory problems. The clinical spectrum is continuous and broad. First symptoms can present in infants, children, and adults. Cardiac hypertrophy is a key feature of classic infantile Pompe's disease. For a long time, there was no means to stop disease progression, but the approval of enzyme replacement therapy has substantially changed the prospects for patients. With this new development, the disease is now among the small but increasing number of lysosomal storage disorders, for which treatment has become a reality. This review is meant to raise general awareness, to present and discuss the latest insights in disease pathophysiology, and to draw attention to new developments about diagnosis and care. We also discuss the developments that led to the approval of enzyme replacement therapy with recombinant human alpha-glucosidase from Chinese hamster ovary cells (alglucosidase alfa) by the US Food and Drug Administration and European Medicines Agency in 2006, and review clinical practice.

Arrhythmias in patients receiving enzyme replacement therapy for infantile Pompe disease

PURPOSE

Enzyme replacement therapy in infants with Pompe disease prolongs survival, decreases cardiomegaly, and improves muscle function. Because ectopy has been previously described in these patients, we sought to determine the prevalence and types of arrhythmias.

METHODS

Thirty-eight children with infantile Pompe disease received enzyme replacement therapy in two open-label, multicenter, international, clinical trials. Data were reviewed on a retrospective basis. The corrected QT interval, ejection fraction, and indexed left ventricular mass were measured on a scheduled basis from electrocardiograms and echocardiograms. Arrhythmias were identified and characterized from electrocardiograms, ambulatory electrocardiograms, and point-of-care monitoring. Electrocardiogram and echocardiogram measurements were compared in children with and without arrhythmias.

RESULTS

Seven children (18%) experienced arrhythmias. The QT interval, ejection fraction, indexed left ventricular mass, and rate of reduction of indexed left ventricular mass were not statistically different in those seven versus the other 31 children. Two children with life-threatening arrhythmias had among the highest combined baseline maximum indexed left ventricular mass and QT interval. Their arrhythmias occurred during severe metabolic stress from noncardiac illness.

CONCLUSIONS

There was a high incidence of arrhythmias in our cohort. The relationship of arrhythmias with enzyme replacement therapy, myocardial fibrosis, or simply longer survival is unknown. Therefore, further characterization of specific arrhythmia risk factors and continued vigilance regarding screening for arrhythmias in children receiving enzyme replacement therapy is warranted.

Cardiac involvement in adults with Pompe disease

BACKGROUND

Glycogen storage disease type II or Pompe disease is a neuromuscular disorder caused by deficiency of lysosomal acid alpha- glucosidase. Classic infantile Pompe disease results in massive left ventricular (LV) hypertrophy and failure. Although Pompe disease is often included in the differential diagnosis of LV hypertrophy the true frequency of cardiac involvement in adults with Pompe disease is not known.

METHODS

Forty-six consecutive adult patients (mean age 48 +/- 12, 22 men) with Pompe disease were included. Each patient underwent a clinical examination, electrocardiography, and rest and low-dose dobutamine (in 20 patients) two-dimensional echocardiography including contrast and tissue Doppler imaging.

RESULTS

All patients had limited exercise tolerance; a rollator walking aid was used in seven patients (15%), a wheelchair in 13 patients (28%), and assisted ventilation in 14 patients (30%). Prior to this study, one patient was known with permanent atrial fibrillation, His-bundle ablation and a VVI pacemaker and another patient was known with fluid retention. The first patient had increased LV end-diastolic diameter, impaired LV ejection fraction, low systolic mitral annular velocities and diastolic dysfunction grade II. The patient with fluid retention was wheelchair bound and dependent on 24-h assisted ventilation and showed right ventricular and LV hypertrophy (septum 16 mm, posterior wall 15 mm). LV hypertrophy was not seen in any of the other patients. One woman of advanced age had isolated low systolic mitral annular velocities. Mean global systolic LV function, including contractile reserve, was not decreased in patients with Pompe disease. Eight patients (17%) had mild diastolic dysfunction grade I, related to hypertension in four and advanced age in seven.

CONCLUSIONS

In adult patients with Pompe disease without objective signs of cardiac affection by 12-leads electrocardiography or physical examination, echocardiographic screening for LV hypertrophy seems not effective.

Primary myopathies and the heart

Myopathies are frequently not confined to the skeletal muscles but also involve other organs or tissues. One of the most frequently affected organ in addition to the skeletal muscle is the heart (cardiac involvement, CI). CI manifests as impulse generation or conduction defects, focal or diffuse myocardial thickening, dilation of the cardiac cavities, relaxation abnormality, hypertrophic, dilated, restrictive cardiomyopathy, apical form of hypertrophic cardiomyopathy, noncompaction, Takotsubo phenomenon, secondary valve insufficiency, intra-cardiac thrombus formation, or heart failure with systolic or diastolic dysfunction. CI occurs in dystrophinopathies, Emery-Dreifuss muscular dystrophy, facioscapulohumeral muscular dystrophy, limb girdle muscular dystrophies, laminopathies, congenital muscular dystrophies, myotonic dystrophies, congenital myopathies, metabolic myopathies, desminopathies, myofibrillar myopathy, Barth syndrome, McLeod syndrome, Senger's syndrome, and Bethlem myopathy. Patients with myopathy should be cardiologically investigated as soon as their neurological diagnosis is established, since supportive cardiac therapy is available, which markedly influences prognosis and outcome of CI in these patients.

Cardiac arrhythmias following anesthesia induction in infantile-onset Pompe disease: a case series

BACKGROUND

Patients with infantile-onset Pompe disease suffer from marked hypertrophic cardiomyopathy and an increased risk of arrhythmia. A noncompliant left ventricle predisposes these infants to diastolic heart failure with elevated left ventricular enddiastolic pressure (LVEDP); these patients also commonly develop systolic heart failure. Given this baseline cardiac physiology, coronary perfusion pressure becomes highly sensitive to abrupt changes in diastolic blood pressure (DBP).

METHODS

We retrospectively reviewed the experiences of 139 patients enrolled in clinical trials investigating the treatment of infantile-onset Pompe disease with recombinant human acid alpha-glucosidase (rhGAA). Adverse events were screened for those involving anesthesia.

RESULTS

Nine patients (6%) with infantile-onset Pompe disease experienced an arrhythmia or cardiopulmonary arrest soon after the induction of general anesthesia. Of these events, propofol was involved in four arrhythmias; sevoflurane without propofol was associated with an additional two. Deaths resulting from arrhythmia appeared to correlate with left ventricular mass indices >350 g x m(-2).

CONCLUSIONS

With the advent of enzyme replacement therapy (ERT) using rhGAA, and increased survivability, more infantile Pompe patients will likely present for surgical procedures. Additional care in maximizing coronary perfusion pressure and minimizing arrhythmia risk must be given. For these reasons, it is recommended that anesthesia for infantile Pompe patients specifically avoid propofol or high concentrations of sevoflurane and, instead, use an agent such as ketamine as the cornerstone for induction in order to better support coronary perfusion pressure and to avoid decreasing DBP with vasodilatory agents.

Acid alpha-glucosidase deficiency (Pompe disease)

The development and recent approval of recombinant acid alpha-glucosidase for enzyme replacement therapy have been major milestones in Pompe disease research. Acid alpha-glucosidase is the enzyme responsible for degradation of glycogen polymers to glucose in the acidic milieu of the lysosomes. Cardiac and skeletal muscles are the two major tissues affected by the accumulation of glycogen within the lysosomes. Both cardiomyopathy and skeletal muscle myopathy are observed in patients with complete enzyme deficiency; this form of the disease is fatal within the first year of life. Skeletal muscle myopathy eventually leading to respiratory insufficiency is the predominant manifestation of partial enzyme deficiency. The recombinant enzyme alglucosidase alfa is the first drug ever approved for this devastating disorder. This review discusses the benefits and the shortcomings of the new therapy.

Physiological Correction of Pompe Disease by Systemic Delivery of Adeno-associated Virus Serotype 1 Vectors

Pompe disease is caused by a lack of functional lysosomal acid alpha-glucosidase (GAA) and can ultimately lead to fatal hypertrophic cardiomyopathy and respiratory insufficiency. Previously, we demonstrated the ability of recombinant adeno-associated virus serotype 1 (rAAV2/1) vector to restore the therapeutic levels of cardiac and diaphragmatic GAA enzymatic activity in vivo in a mouse model of Pompe disease. We have further characterized cardiac and respiratory function in rAAV2/1-treated animals 1 year post-treatment. Similar to the patient population, electrocardiogram measurements (P-R interval) are significantly shortened in the Pompe mouse model. In rAAV2/1-treated mice, we show a significant improvement in cardiac conductance with prolonged P-R intervals of 39.34+/-1.6 ms, as compared to untreated controls (35.58+/-0.57 ms) (P</=0.05). In addition, we note a significant decrease in cardiac left ventricular mass from 181.99+/-10.70 mg in untreated controls to 141.97+/-19.15 mg in the rAAV2/1-treated mice. Furthermore, the mice displayed an increased diaphragmatic contractile force of approximately 90% of wild-type peak forces with corresponding improved ventilation (particularly in frequency, minute ventilation, and peak inspiratory flow). These results demonstrate that in addition to biochemical and histological correction, rAAV2/1 vectors can mediate sustained physiological correction of both cardiac and respiratory function in a model of fatal cardiomyopathy and muscular dystrophy.

Characterization of pre- and post-treatment pathology after enzyme replacement therapy for Pompe disease

In Pompe disease, a genetic deficiency of lysosomal acid alpha-glucosidase, glycogen accumulates abnormally in the lysosomes of skeletal, cardiac and smooth muscle, and contributes to clinically progressive and debilitating muscle weakness. The present study involved 8 infantile-onset Pompe patients, treated weekly with 10 mg/kg of recombinant human acid alpha-glucosidase (rhGAA). Muscle biopsies were obtained at baseline, 12 and 52 weeks post-treatment to establish an indicator of efficacy. Several histologic strategies were employed to characterize changes in pre- and post-treatment samples, including high-resolution light microscopy and digital histomorphometry, electron microscopy, capillary density and fiber type analysis, and confocal microscopy for satellite cell activation analysis. Histomorphometric analysis was performed on muscle samples to assess glycogen depletion in response to enzyme replacement therapy (ERT). The extent of glycogen clearance varied widely among these patient samples, and correlated well with clinical outcome. Low glycogen levels, mild ultrastructural damage, a high proportion of type I fibers, and young age at baseline were all features associated with good histologic response. There was no correlation between capillary density and glycogen clearance, and activated satellite cell levels were shown to be higher in post-treatment biopsies with poor histologic responses. This histopathologic study of infantile Pompe disease provides detailed insight into the cellular progression of the disease and its response to therapy while highlighting a number of methodologies which may be employed to assess regression or progression of the associated pathology. As enzyme replacement therapy becomes more prevalent for the treatment of lysosomal storage diseases, such evaluation of post-treatment pathology will likely become a more common occurrence in the daily practice of pathologists.

Ambulatory electrocardiogram analysis in infants treated with recombinant human acid α-glucosidase enzyme replacement therapy for Pompe disease

PURPOSE

Infantile Pompe disease is caused by deficiency of lysosomal acid alpha-glucosidase. Trials with recombinant human acid alpha-glucosidase enzyme replacement therapy (ERT) show a decrease in left ventricular mass and improved function. We evaluated 24-hour ambulatory electrocardiograms (ECGs) at baseline and during ERT in patients with infantile Pompe disease.

METHODS

Thirty-two ambulatory ECGs were evaluated for 12 patients with infantile Pompe disease from 2003 to 2005. Patients had a median age of 7.4 months (2.9-37.8 months) at initiation of ERT. Ambulatory ECGs were obtained at determined intervals and analyzed.

RESULTS

Significant ectopy was present in 2 of 12 patients. Patient 1 had 211 and 229 premature ventricular contractions (0.2% of heart beats) at baseline and at 11.5 weeks of ERT, respectively. Patient 2 had 10,445 premature ventricular contractions (6.7% of heart beats) at 11 weeks of therapy.

CONCLUSION

Infantile Pompe disease may have preexisting ectopy; it may also develop during the course of ERT. Therefore, routinely monitoring patients using 24-hour ambulatory ECGs is useful. Periods of highest risk may be early in the course of ERT when there is a substantial decrease in left ventricular mass and an initial decrease in ejection fraction.