Clinical presentations of mitochondrial cardiomyopathies

Application of left ventricular endomyocardial biopsy in the diagnosis of mitochondrial cardiomyopathy: a case report

BACKGROUND

The clinical features of mitochondrial cardiomyopathy (MCM) are diverse. It can present as hypertrophic cardiomyopathy or dilated cardiomyopathy. The diagnosis of MCM is challenging and usually based on biopsy.

CASE PRESENTATION

The 30-year-old man was admitted to hospital due to dyspnea for 1 month and edema of both lower extremities for 1 week. Echocardiography suggested a whole heart enlargement, a whole heart diminished function. Renal impairment and diabetes were observed. Coronary angiography showed single-vessel disease (90% stenosis in the ostium of a small marginal branch). Left ventricular endomyocardial biopsy was performed.

CONCLUSION

Myocardial histopathology demonstrated a large number of abnormal mitochondrial accumulation, so the diagnosis was considered as mitochondrial cardiomyopathy.

Successful catheter ablation of a left posterolateral accessory bypass tract and periinterventional management in a patient with MELAS syndrome

MELAS syndrome is defined as a combination of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes resulting from mutations in mitochondrial DNA. All medical interventions in these patients appear challenging due to a high risk of lactate acidosis or anesthesiological complications. Of note, previous reports suggest that these patients have a higher incidence of Wolff-Parkinson-White (WPW) syndrome. Here, a case of successful catheter ablation of a posteroseptal bypass tract using analgosedation in a patient with MELAS syndrome combined with WPW syndrome is presented.

Molecular Epidemiology of Mitochondrial Cardiomyopathy: A Search Among Mitochondrial and Nuclear Genes

Mitochondrial Cardiomyopathy (MCM) is a common manifestation of multi-organ Mitochondrial Diseases (MDs), occasionally present in non-syndromic cases. Diagnosis of MCM is complex because of wide clinical and genetic heterogeneity and requires medical, laboratory, and neuroimaging investigations. Currently, the molecular screening for MCM is fundamental part of MDs management and allows achieving the definitive diagnosis. In this article, we review the current genetic knowledge associated with MDs, focusing on diagnosis of MCM and MDs showing cardiac involvement. We searched for publications on mitochondrial and nuclear genes involved in MCM, mainly focusing on genetic screening based on targeted gene panels for the molecular diagnosis of the MCM, by using Next Generation Sequencing. Here we report twelve case reports, four case-control studies, eleven retrospective studies, and two prospective studies, for a total of twenty-nine papers concerning the evaluation of cardiac manifestations in mitochondrial diseases. From the analysis of published causal mutations, we identified 130 genes to be associated with mitochondrial heart diseases. A large proportion of these genes (34.3%) encode for key proteins involved in the oxidative phosphorylation system (OXPHOS), either as directly OXPHOS subunits (22.8%), and as OXPHOS assembly factors (11.5%). Mutations in several mitochondrial tRNA genes have been also reported in multi-organ or isolated MCM (15.3%). This review highlights the main disease-genes, identified by extensive genetic analysis, which could be included as target genes in next generation panels for the molecular diagnosis of patients with clinical suspect of mitochondrial cardiomyopathies.

Mitochondrial cardiomyopathy and ventricular arrhythmias associated with biallelic variants in C1QBP

Patients with biallelic mutations in the nuclear-encoded mitochondrial gene C1QBP/p32 have been described with syndromic features and autosomal recessive cardiomyopathy. We describe the clinical course in two siblings who developed cardiomyopathy and ventricular fibrillation in infancy. We provide genomic analysis and clinical-pathologic correlation. Both siblings had profound cardiac failure with ventricular arrhythmia. One child died suddenly. The second sibling survived resuscitation but required extracorporeal cardiopulmonary support and died shortly afterward. On cardiac autopsy, the left ventricle was hypertrophied in both children. Histological examination revealed prominent cardiomyocyte cytoplasmic clearing, and electron microscopy confirmed abnormal mitochondrial structure within cardiomyocytes. DNA sequencing revealed compound heterozygous variants in C1QBP (p.Thr40Asnfs*45 and p.Phe204Leu) in both children. Family segregation analysis demonstrated each variant was inherited from an unaffected, heterozygous parent. Inherited loss of C1QBP/p32 is associated with recessive cardiomyopathy, ventricular fibrillation, and sudden death in early life. Ultrastructural mitochondrial evaluation in the second child was similar to findings in engineered C1qbp-deficient mice. Rapid trio analysis can define rare biallelic variants in genes that may be implicated in sudden death and facilitate medical management and family planning. (184/200).

The Cardioprotective Mechanism of Phenylaminoethyl Selenides (PAESe) Against Doxorubicin-Induced Cardiotoxicity Involves Frataxin

Doxorubicin (DOX) is an anthracycline cancer chemotherapeutic that exhibits cumulative dose-limiting cardiotoxicity and limits its clinical utility. DOX treatment results in the development of morbid cardiac hypertrophy that progresses to congestive heart failure and death. Recent evidence suggests that during the development of DOX mediated cardiac hypertrophy, mitochondrial energetics are severely compromised, thus priming the cardiomyocyte for failure. To mitigate cumulative dose (5 mg/kg, QIW x 4 weeks with 2 weeks recovery) dependent DOX, mediated cardiac hypertrophy, we applied an orally active selenium based compound termed phenylaminoethyl selenides (PAESe) (QIW 10 mg/kg x 5) to our animal model and observed that PAESe attenuates DOX-mediated cardiac hypertrophy in athymic mice, as observed by MRI analysis. Mechanistically, we demonstrated that DOX impedes the stability of the iron-sulfur cluster biogenesis protein Frataxin (FXN) (0.5 fold), resulting in enhanced mitochondrial free iron accumulation (2.5 fold) and reduced aconitase activity (0.4 fold). Our findings further indicate that PAESe prevented the reduction of FXN levels and the ensuing elevation of mitochondrial free iron levels. PAESe has been shown to have anti-oxidative properties in part, by regeneration of glutathione levels. Therefore, we observed that PAESe can mitigate DOX mediated cardiac hypertrophy by enhancing glutathione activity (0.4 fold) and inhibiting ROS formation (1.8 fold). Lastly, we observed that DOX significantly reduced cellular respiration (basal (5%) and uncoupled (10%)) in H9C2 cardiomyoblasts and that PAESe protects against the DOX-mediated attenuation of cellular respiration. In conclusion, the current study determined the protective mechanism of PAESe against DOX mediated myocardial damage and that FXN is implicitly involved in DOX-mediated cardiotoxicity.

Impact of cardiovascular involvement on the clinical course of paediatric mitochondrial disorders

BACKGROUND

Primary mitochondrial disorders (PMD) are rare conditions resulting in progressive multi-organ failure. Cardiovascular involvement (CVI) has been reported in paediatric patients. However, its age-related prevalence, clinical presentation and prognostic impact are unresolved. We detailed CVI in a cohort of children diagnosed with PMD over two decades at a tertiary referral centre.

RESULTS

We enrolled 86 PMD patients (M/F = 30/56; mean age 6.4 ± 8.58 years). CVI was detected in 31 patients (36%), with mean age at onset of 5.7 ± 7.8 years including the pre- and neonatal phase in 14, often representing the first sign of PMD (42% of those with CVI). Heart disease resulted more common in males and in children with specific aetiologies (Barth, TMEM70 and MELAS syndromes). Hypertrophic, non-compaction and dilated cardiomyopathies were the prevalent disorders, although pulmonary arterial hypertension was also found. Adverse cardiac events (heart failure, resuscitated cardiac arrest, ICD/PM implantation, sudden death) occurred in 19% of children with CVI over a follow-up period of 5.4 ± 4.3 years. All-cause mortality was higher in patients with CVI compared to those without CVI (45.1% vs 21.8%; p < 0.01); female sex, age at onset < 5 years, acute heart failure at presentation and diabetes also proved independent predictors of outcome.

CONCLUSION

Cardiovascular involvement occurred in over one-third of children diagnosed with PMD, often at a very early age, and was associated with adverse prognosis. Final outcome of PMD-related CVI was influenced by the specific underlying aetiology, suggesting the need for tailored management of heart failure and sudden death prevention.

Six-year prospective follow-up study in 151 carriers of the mitochondrial DNA 3243 A>G variant

BACKGROUND

The mitochondrial DNA (mDNA) 3243A>G variant is the most common pathogenic variant of the mDNA. To interpret results of clinical trials in mitochondrial disease, it is important to have a clear understanding of the natural course of disease. To obtain more insight into the disease burden and the progression of disease in carriers of the mDNA 3243 A>G variant, we followed a cohort of 151 carriers from 61 families prospectively for up to 6 years.

METHODS

The disease severity was scored using the Newcastle Mitochondrial Disease Adult Scale (NMDAS), including SF-36 quality of life (QoL) scores. Heteroplasmy levels were measured in urinary epithelial cells (UEC), leucocytes and saliva. The progression of the disease was studied using linear mixed model analysis.

RESULTS

One hundred twenty-four carriers (out of 151) were symptomatic. Four clinical groups were identified: 1) classical mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes syndrome (n=7), 2) maternally inherited diabetes deafness syndrome (n=60), 3) 'other' (n=57) and 4) dormant carriers (n=27). A yearly increase of NMDAS score of 0.47 point was measured in the total group. Heteroplasmy levels in both leucocytes and UEC were only weakly correlated with disease severity. Physical QoL declined with age. The most important determinants of QoL decline were hearing loss, speech problems, exercise intolerance, gait instability, psychiatric problems and gastrointestinal involvement.

CONCLUSION

The mDNA 3243 A>G variant causes a slowly progressive disease, with a yearly increase of NMDAS score of ~0.5 point overall with the clinical phenotype being the only determinant of disease progression.

Cardiovascular Manifestations of Mitochondrial Disease

Genetic mitochondrial cardiomyopathies are uncommon causes of heart failure that may not be seen by most physicians. However, the prevalence of mitochondrial DNA mutations and somatic mutations affecting mitochondrial function are more common than previously thought. In this review, the pathogenesis of genetic mitochondrial disorders causing cardiovascular disease is reviewed. Treatment options are presently limited to mostly symptomatic support, but preclinical research is starting to reveal novel approaches that may lead to better and more targeted therapies in the future. With better understanding and clinician education, we hope to improve clinician recognition and diagnosis of these rare disorders in order to improve ongoing care of patients with these diseases and advance research towards discovering new therapeutic strategies to help treat these diseases.

Five non-mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes phenotype adult patients with m.3243A>G mutation after kidney transplantation: follow-up and review of the literature

Background

Renal involvement in patients with the m.3243A>G mutation may result in end-stage renal disease (ESRD) requiring renal replacement therapy. Although kidney transplantations have been performed in a small number of patients, short- and long-term follow-up data are lacking.

Methods

We describe five patients with the m.3243A<G mutation who received a kidney transplant, including follow-up data up to 13 years. We also summarize all cases (n = 13) of kidney transplantation in m.3243A>G carriers described in the literature.

Results

Proteinuria with or without renal failure was the first clinical presentation of renal involvement in 13 of 18 (72%) patients. Focal segmental glomerulosclerosis (FSGS) was found in 9 of 13 (69%) biopsies. Sixteen of 18 (84%) patients developed hearing loss. All patients were diagnosed with diabetes mellitus, of whom eight (44%) developed the disease after transplantation. All patients with reported follow-up data (13/18) had stable kidney function from 6 months to 13 years of follow-up after transplantation.

Conclusions

Renal involvement in carriers of the m.3243A>G mutation most commonly leads to proteinuria and FSGS and may lead to ESRD. Proper recognition of the mitochondrial origin of the renal disease in these patients is important for adequate treatment selection and suitable supportive care. This case series and review of the available literature on long-term follow-up after kidney transplantation shows it is feasible for non-mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes phenotype carriers of the m.3243A>G mutation to be considered for kidney transplantation in case of ESRD. These patients should not be excluded from transplant solely for their mitochondrial diagnosis.

Intra-patient variability of heteroplasmy levels in urinary epithelial cells in carriers of the m.3243A>G mutation

Background

The mitochondrial DNA m.3243A>G mutation is one the most prevalent mutation causing mitochondrial disease in adult patients. Several cohort studies have used heteroplasmy levels in urinary epithelial cells (UEC) to correlate the genotype of the patients to the clinical severity. However, the interpretation of these data is hampered by a lack of knowledge on the intra‐patient variability of the heteroplasmy levels. The goal of this study was to determine the day‐to‐day variation of the heteroplasmy levels in UEC.

Methods

Fifteen carriers of the m.3243A>G mutation collected five urine samples in a 14‐day window. Heteroplasmy levels of the m.3243A>G mutation were determined in these samples. Data from the national cohort study, including Newcastle Mitochondrial Disease Adult Scale scores and clinical diagnosis, were used.

Results

In the samples of six patients, heteroplasmy levels were within a 5% margin. In the samples collected from five patients, the margin was >20%.

Conclusion

Heteroplasmy levels of UEC in carriers of the m.3243A>G mutation have a significant day‐to‐day variation. The interpretation of a correlation between heteroplasmy levels in urine and disease severity is therefore not reliable. Therefore, heteroplasmy levels in UEC should not be used as a prognostic biomarker in these patients.

First description of a novel mitochondrial mutation in the MT-TI gene associated with multiple mitochondrial DNA deletion and depletion in family with severe dilated mitochondrial cardiomyopathy

Mitochondria are essential for early cardiac development and impaired mitochondrial function was described associated with heart diseases such as hypertrophic or dilated mitochondrial cardiomyopathy. In this study, we report a family including two individuals with severe dilated mitochondrial cardiomyopathy. The whole mitochondrial genome screening showed the presence of several variations and a novel homoplasmic mutation m.4318-4322delC in the MT-TI gene shared by the two patients and their mother and leading to a disruption of the tRNA^Ile secondary structure. In addition, a mitochondrial depletion was present in blood leucocyte of the two affected brother whereas a de novo heteroplasmic multiple deletion in the major arc of mtDNA was present in blood leucocyte and mucosa of only one of them. These deletions in the major arc of the mtDNA resulted to the loss of several protein-encoding genes and also some tRNA genes. The mtDNA deletion and depletion could result to an impairment of the oxidative phosphorylation and energy metabolism in the respiratory chain in the studied patients. Our report is the first description of a family with severe lethal dilated mitochondrial cardiomyopathy and presenting several mtDNA abnormalities including punctual mutation, deletion and depletion.

Myocardial Layer-Specific Strain Analysis in Children with Mitochondrial Disease

PURPOSE

Children with mitochondrial disease (MD) have clinical phenotypes that are more severe than those found in adults. In this study, we assessed cardiac function in children with MD using conventional and advanced echocardiographic measurements, explored any unique patterns present, and investigated the development of early cardiomyopathy (CMP).

MATERIALS AND METHODS

We retrospectively reviewed the medical records of 33 children with MD. All patients underwent transthoracic echocardiography with conventional and advanced myocardial analysis. We compared all data between patients and an age-matched healthy control group.

RESULTS

Conventional echocardiographic diastolic measurements of mitral E, E/A, and tissue Doppler E' were significantly lower and E/E' was significantly higher in children with MD, compared with the measurements from the control group. There was no significant difference in longitudinal and radial strain between the groups. Circumferential strain in the endocardium (p=0.161), middle myocardium (p=0.008), and epicardium (p=0.042) were lower in patients, compared to the values in controls. Circumferential strain was correlated with E' (p<0.01, r>0.60).

CONCLUSION

In children with MD, myocardial circumferential strain may develop early in all three layers, even with normally preserved longitudinal and radial strain. This may be an early diagnostic indicator with which to predict CMP in this patient population.

Chronic maternal hypercortisolemia in late gestation alters fetal cardiac function at birth

Studies in our laboratory have shown that modest chronic increases in maternal cortisol concentrations over the last 0.20 of gestation impair maternal glucose metabolism and increase the incidence of perinatal stillbirth. Previous studies had found that an increase in maternal cortisol concentrations from 115 to 130 days of gestation in sheep increased both proliferation in fetal cardiomyocytes and apoptosis in the fetal cardiac Purkinje fibers. We hypothesized that the adverse effects of excess cortisol may result in defects in cardiac conduction during labor and delivery. In the present study, we infused cortisol (1 mg·kg^-1·day^-1) into late gestation pregnant ewes and continuously monitored fetal aortic pressure and ECG through labor and delivery. We found that, although the fetuses of cortisol infused ewes had normal late gestation patterns of arterial pressure and heart rate, there was a significant decrease in fetal aortic pressure and heart rate on the day of birth, specifically in the final hour before delivery. Significant changes in the fetal ECG were also apparent on the day of birth, including prolongation of the P wave and P-R interval. We speculate that chronic exposure to glucocorticoids alters cardiac metabolism or ion homeostasis, contributing to cardiac dysfunction, precipitated by active labor and delivery.

Obstetric complications in carriers of the m.3243A>G mutation, a retrospective cohort study on maternal and fetal outcome

INTRODUCTION

The mitochondrial DNA m.3243A>G mutation is the most prevalent mutation causing mitochondrial disease in adult patients. Aside from some case reports, there are no studies on obstetric complications in a cohort of m.3243A>G carriers. We aimed to identify the prevalence of obstetric complications in a cohort of women carrying the m.3243A>G mutation.

METHODS

All female carriers of the m.3243A>G mutation known from our previous national inventory were sent a questionnaire regarding their obstetric history. Data were compared to national references. Data from the national inventory, including NMDAS (disease severity) scores and heteroplasmy levels in urinary epithelial cells (UEC) were used to stratify women.

RESULTS

Sixty women participated, the mean age was 47 years (range 20-70), mean NMDAS was 14.6 (range 0-46), and mean heteroplasmy percentage in UEC was 19.9% (range 5-85%). Ninety-eight pregnancies in 46 women were reported. Twenty-three (25.3%) had a premature delivery and five of them (5.5%) had a gestation of ≤ 32 weeks and eleven of the women (12%) suffered from preeclampsia. No different heteroplasmy level was found in the women with preeclampsia. Nine pregnancies (11%) were complicated by gestational diabetes.

DISCUSSION

Obstetric complications occur frequently in carriers of the m.3243A>G mutation. Proper guidance during pregnancies and early detection of possible obstetric complications are needed. As techniques to prevent transmission of mitochondrial mutations are studied it is important to know the possible complications patients may experience from the ensuing pregnancy.

Arrhythmia as a cardiac manifestation in MELAS syndrome

A 44-year-old female with a diagnosis of mitochondrial myopathy, encephalopathy and stroke-like episodes (MELAS) syndrome had progressive left ventricular hypertrophy (LVH) on echocardiogram. A Holter monitor demonstrated episodes of non-sustained atrial tachycardia, a finding not been previously described in this population. This unique case of MELAS syndrome demonstrates the known associated cardiac manifestation of LVH and the new finding of atrial tachycardia which may represent the potential for subclinical arrhythmia in this population.

Mitochondrial cardiomyopathy and related arrhythmias

Mitochondrial dysfunction has been shown to be involved in the pathophysiology of arrhythmia, not only in inherited cardiomyopathy due to specific mutations in the mitochondrial DNA but also in acquired cardiomyopathy such as ischemic or diabetic cardiomyopathy. This article briefly discusses the basics of mitochondrial physiology and details the mechanisms generating arrhythmias due to mitochondrial dysfunction. The clinical spectrum of inherited and acquired cardiomyopathies associated with mitochondrial dysfunction is discussed followed by general aspects of the management of mitochondrial cardiomyopathy and related arrhythmia.

Cardiac manifestations of primary mitochondrial disorders

OBJECTIVES

One of the most frequently affected organs in mitochondrial disorders (MIDs), defined as hereditary diseases due to affection of the mitochondrial energy metabolism, is the heart. Cardiac involvement (CI) in MIDs has therapeutic and prognostic implications. This review aims at summarizing and discussing the various cardiac manifestations in MIDs.

METHODS

Data for this review were identified by searches of MEDLINE, Current Contents, and PubMed using appropriate search terms.

RESULTS

CI in MIDs may be classified according to various different criteria. In the present review cardiac abnormalities in MIDs are discussed according to their frequency with which they occur. CI in MIDs includes cardiomyopathy, arrhythmias, heart failure, pulmonary hypertension, dilation of the aortic root, pericardial effusion, coronary heart disease, autonomous nervous system dysfunction, congenital heart defects, or sudden cardiac death. The most frequent among the cardiomyopathies is hypertrophic cardiomyopathy, followed by dilated cardiomyopathy, and noncompaction.

CONCLUSIONS

CI in MID is more variable and prevalent than previously thought. All tissues of the heart may be variably affected. The most frequently affected tissue is the myocardium. MIDs should be included in the differential diagnoses of cardiac disease.

Glucose metabolism derangements in adults with the MELAS m.3243A>G mutation

The m.3243A>G mutation in the mitochondrial gene MT-TL1 leads to a wide clinical spectrum ranging from asymptomatic carriers to MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes) at the severe end. Diabetes mellitus (DM) occurs in mitochondrial diseases, with the m.3243A>G mutation being the most common mutation associated with mitochondrial DM. The pathogenesis of mitochondrial DM remains largely unknown, with previous studies suggesting that impaired insulin secretion is the major factor. In this study we used stable isotope infusion techniques to assess glucose metabolism in vivo and under physiological conditions in 5 diabetic and 11 non-diabetic adults with the m.3243A>G mutation and 10 healthy adult controls. Our results revealed increased glucose production due to increased gluconeogenesis in both diabetic and non-diabetic subjects with the m.3243A>G mutation. In addition, diabetic subjects demonstrated insulin resistance and relative insulin deficiency, resulting in an inability to increase glucose oxidation which can explain the development of DM in these subjects. Non-diabetic subjects showed normal insulin sensitivity; and therefore, they were able to increase their glucose oxidation rate. The ability to increase glucose utilization can act as a compensatory mechanism that explains why these subjects do not have DM despite the higher rate of glucose production. These results suggest that increased gluconeogenesis is not enough to cause DM and the occurrence of combined insulin resistance and relative insulin deficiency are needed to develop DM in individuals with the m.3243A>G mutation. Therefore, multiple defects in insulin and glucose metabolism are required for DM to occur in individuals with mitochondrial diseases. The results of this study uncover previously undocumented alterations in glucose metabolism in individuals with the m.3243A>G mutation that contribute significantly to our understanding of the pathogenesis of mitochondrial DM and can have significant implications for its management.

Screening of mitochondrial mutations in Tunisian patients with mitochondrial disorders: an overview study

To investigate the spectrum of common mitochondrial mutations in Tunisia during the years of 2002-2012, 226 patients with mitochondrial disorders were clinically diagnosed with hearing loss, Leigh syndrome (LS), diabetes, cardiomyopathy, Kearns-Sayre syndrome (KSS), Pearson syndrome (PS), myopathy, mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes syndrome (MELAS) and Wolfram syndrome. Restriction fragment length polymorphism (PCR-RFLP), radioactive PCR, single specific primer-PCR (SSP-PCR) analysis and PCR-sequencing methods were used to identify the mutations. Two cases with m.1555A>G mutation and two families with the novel 12S rRNA m.735A>G transition were detected in patients with hearing loss. Three cases with m.8993T>G mutation, two patients with the novel m.5523T>G and m.5559A>G mutations in the tRNA(Trp) gene, and two individuals with the undescribed m.9478T>C mutation in the cytochrome c oxidase subunit III (COXIII) gene were found with LS. In addition, one case with hypertrophic cardiomyopathy and deafness presented the ND1 m.3395A>G mutation and the tRNA(Ile) m.4316A>G variation. Besides, multiple mitochondrial deletions were detected in patients with KSS, PS, and Wolfram syndrome. The m.14709T>C mutation in the tRNA(Glu) was reported in four maternally inherited diabetes and deafness patients and a novel tRNA(Val) m.1640A>G mutation was detected in a MELAS patient.

Cardiomyocyte specific deletion of Crif1 causes mitochondrial cardiomyopathy in mice

Mitochondria are key organelles dedicated to energy production. Crif1, which interacts with the large subunit of the mitochondrial ribosome, is indispensable for the mitochondrial translation and membrane insertion of respiratory subunits. To explore the physiological function of Crif1 in the heart, Crif1(f/f) mice were crossed with Myh6-cre/Esr1 transgenic mice, which harbor cardiomyocyte-specific Cre activity in a tamoxifen-dependent manner. The tamoxifen injections were given at six weeks postnatal, and the mutant mice survived only five months due to hypertrophic heart failure. In the mutant cardiac muscles, mitochondrial mass dramatically increased, while the inner structure was altered with lack of cristae. Mutant cardiac muscles showed decreased rates of oxygen consumption and ATP production, suggesting that Crif1 plays a critical role in the maintenance of both mitochondrial structure and respiration in cardiac muscles.

Hypertrophic Cardiomyopathy due to Mitochondrial Disease: Prenatal Diagnosis, Management, and Outcome

A case of prenatally diagnosed fetal hypertrophic cardiomyopathy is reported. The mother was referred to our department at 37 weeks' gestation because of suspected congenital heart disease. Prenatal echocardiography showed biventricular hypertrophy and pericardial effusion, without additional abnormalities. Postnatal echocardiography confirmed prenatal diagnosis. Neonatal EKG showed biventricular hypertrophy and Wolff-Parkinson-White syndrome. Skeletal muscle biopsy was consistent with mitochondrial oxidative phosphorylation defect involving a combined defect of respiratory complexes I and IV. Echocardiographic followup during the first year of life showed progressive regression of hypertrophy and evolution to left ventricular myocardial noncompaction.

Clinical features and heteroplasmy in blood, urine and saliva in 34 Dutch families carrying the m.3243A > G mutation

The m.3243A>G mutation has become known as the MELAS mutation. However, many other clinical phenotypes associated with this mutation have been described,most frequently being Maternally Inherited Diabetes and Deafness (MIDD). The m.3243A>G mutation, can be detected in virtually all tissues, however heteroplasmy differs between samples. Recent reports indicate, a preference to perform mutation analysis in Urinary Epithelial Cells(UEC). To test this, and to study a correlation between the mutational load in different tissues with two mitochondrial scoring systems (NMDAS and NPMDS) we investigated 34 families carrying the m.3243A>G mutation. Heteroplasmy was determined in three non-invasively collected samples,namely leucocytes, UEC and buccal mucosa. We included 127 patients, of which 82 carried the m.3243A>G mutation.None of the children (n011) had specific complaints. In adults(n071), a median NMDAS score of 15 (IQR 10-24) was found. The most prevalent symptoms were hearing loss(68 %), gastro-intestinal problems (59 %), exercise intolerance(54 %) and glucose intolerance (52 %). Ten patients had neurologic involvement. Buccal mucosa had the best correlation with the NMDAS in all adults (r00.437, p<0.001),whereas UEC had the strongest correlation with the NMDAS in severely affected patients (r00.593, p00.002). Heteroplasmy declined significantly with increasing age in all three samples (leucocytes r0-0.705 (p<0.001), UEC r0-0.374 (p00.001), buccal mucosa r0-0.460 (p<0.001). In our cohort of 82 patients, the m.3243A>Gmutation causes a wide variety of signs and symptoms, MIDD being far more prevalent than MELAS. Looking at the characteristics of the three noninvasively available tissues for testing heteroplasmy we confirm that UEC are the preferred sample to test [corrected].

Early cardiac evaluation in children with non-specific mitochondrial disease with isolated mitochondrial respiratory chain complex I defect

AIMS

We evaluated echocardiography and electrocardiography (ECG) results in children with non-specific mitochondrial disease (MD) in order to study early cardiac involvement, a well-known complication of the disease.

METHODS

Among non-specific MD children whose isolated mitochondrial respiratory chain complex I defect was confirmed by muscle biopsy and satisfied the criteria of MD, 27 who had no cardiac symptoms were evaluated by echocardiography and ECG.

RESULTS

Three (11.1%) out of the 27 non-specific MD patients had left ventricular ejection fraction of less than 55% and two of them (7.4%) had fractional shortening of less than 26%. ECG abnormalities were observed in 16 of the non-specific MD patients (59.3%). Prolongation of heart rate-corrected QT interval was seen in 11 (40.7%) and widening of the QRS interval in eight (29.6%). Left ventricular ejection fraction and fractional shortening of the patients were significantly decreased compared with those in the control group while heart rate-corrected QT interval was prolonged in the former group. QRS interval was more widened in non-specific MD patients, but without statistical significance.

CONCLUSION

The potentially severe cardiac involvement observed in our subjects suggests that early cardiac evaluation after confirming the diagnosis of MD and regular follow-up tests should be strongly recommended in children even in cases without typical cardiac manifestations.

Inheritance of the m.3243A>G mutation

The m.3243A>G is the most prevalent pathogenic mtDNA mutation but little is known about its inheritance. We studied 34 families containing 56 mother-child relations and 82 intersibling relations to investigate its transmission. We found a significant correlation between mother and child heteroplasmy levels (r = 0.679, p < 0.001). In mothers with a heteroplasmy level of below 25% we found 30% offspring without detectable mutation, while in mothers with a heteroplasmy level of above 25%, 100% of the offspring showed the m.3243A>G mutation. Heteroplasmy levels between siblings also correlated (r = 0.512, p < ;0.001), but had limited extra predictive value because of outliers. These new data on inheritance of the m.3243A>G mutation might be of value in counseling patients and preventing transmission of the mutation.

Cardiovascular magnetic resonance imaging (CMR) reveals characteristic pattern of myocardial damage in patients with mitochondrial myopathy

BACKGROUND

Mitochondrial myopathy comprises various clinical subforms of neuromuscular disorders that are characterised by impaired mitochondrial energy metabolism due to dysfunction of the mitochondrial respiratory chain. No comprehensive and targeted cardiovascular magnetic resonance (CMR) studies have been performed so far in patients with mitochondrial disorders. The present study aimed at characterising cardiac disease manifestations in patients with mitochondrial myopathy and elucidating the in vivo cardiac damage pattern of patients with different subforms of mitochondrial disease by CMR studies.

METHODS AND RESULTS

In a prospective study, 37 patients with mitochondrial myopathy underwent comprehensive neurological and cardiac evaluations including physical examination, resting ECG and CMR. The CMR studies comprised cine-CMR, T2-weighted "edema" imaging and T1-weighted late-gadolinium-enhancement (LGE) imaging. Various patterns and degrees of skeletal myopathy were present in the participants of this study, whereas clinical symptoms such as chest pain symptoms (in eight (22%) patients) and various degrees of dyspnea (in 16 (43%) patients) were less frequent. Pathological ECG findings were documented in eight (22%) patients. T2-weighted "edema" imaging was positive in one (3%) patient with MELAS (mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes) only. LGE imaging demonstrated the presence of non-ischemic LGE in 12 (32%) patients: 10 out of 24 (42%) patients with CPEO (chronic progressive external ophthalmoplegia) or KSS (Kearns-Sayre syndrome) and 2 of 3 (67%) patients with MELAS were LGE positive. All 10 LGE-positive patients with CPEO or KSS demonstrated a potentially typical pattern of diffuse intramural LGE in the left-ventricular (LV) inferolateral segments.

CONCLUSIONS

Cardiac involvement is a frequent finding in patients with mitochondrial myopathy. A potentially characteristic pattern of diffuse intramural LGE in the LV inferolateral segments was identified in patients suffering from the subforms CPEO or KSS.

Mitochondrial tRNA valine as a recurrent target for mutations involved in mitochondrial cardiomyopathies

The aim of this study was to identify the genetic defect in two patients having cardiac dysfunction accompanied by neurological symptoms, and in one case MRI evidence of cortical and cerebellar atrophy with hyperintensities in the basal ganglia. Muscle biopsies from each patient revealed single and combined mitochondrial respiratory chain deficiency. The complete mtDNA sequencing of both patients revealed two transitions in the mitochondrial tRNA(Val) gene (MT-TV) (m.1628C>T in Patient 1, and m.1644G>A in Patient 2). The functional and molecular analyses reported here suggest that the MT-TV gene should be routinely considered in the diagnosis of mitochondrial cardiomyopathies.

Neonatal cardiomyopathies and metabolic crises due to oxidative phosphorylation defects

Neonatal cardiomyopathies due to mitochondrial oxidative phosphorylation (OXPHOS) defects are extremely severe conditions which can be either isolated or included in a multi-organ disease, with or without metabolic crises, of which profound lactic acidosis is the prominent feature. Cardiomyopathy is more often hypertrophic than dilated. Antenatal manifestations such as fetal cardiomyopathy, arrhythmia and/or hydrops have been reported. Pathophysiological mechanisms are complex, going beyond ATP deficiency of the high-energy-consuming neonatal myocardium. Birth is a key metabolic period when the myocardium switches ATP production from anaerobic glycolysis to mitochondrial fatty acid oxidation and OXPHOS. Heart-specificity of the defect may be related to the specific localization of the defect, to the high myocardium dependency on OXPHOS, and/or to interaction between the primary genetic alteration and other factors such as modifier genes. Therapeutic options are limited but standardized diagnostic procedures are mandatory to confirm the OXPHOS defect and to identify its causal mutation, allowing genetic counseling and potential prenatal diagnosis.

The genetics of conduction disease

Conduction diseases (CD) include defects in impulse generation and conduction. Patients with CD may manifest a wide range of clinical presentations, from asymptomatic to potentially life-threatening arrhythmias. The pathophysiologic mechanisms underlying CD are diverse and may have implications for diagnosis, treatment, and prognosis. Known causes of functional CD include cardiac ion channelopathies or defects in modifying proteins, such as cytoskeletal proteins. Progress in molecular biology and genetics along with development of animal models has increased the understanding of the molecular mechanisms of these disorders. This article discusses the genetic basis for CD and its clinical implications.

Electrocardiography as an early cardiac screening test in children with mitochondrial disease

Purpose

To evaluate myocardial conductivity to understand cardiac involvement in patients with mitochondrial disease.

Methods

We performed retrospective study on fifty-seven nonspecific mitochondrial encephalopathy patients with no clinical cardiac manifestations. The patients were diagnosed with mitochondrial respiratory chain complex defects through biochemical enzyme assays of muscle tissue. We performed standard 12-lead electrocardiography (ECG) on all patients.

Results

ECG abnormalities were observed in 30 patients (52.6%). Prolongation of the QTc interval (>440 ms) was seen in 19 patients (33.3%), widening of the corrected QRS interval in 15 (26.3%), and bundle branch block in four (7.0%). Atrioventricular block, premature atrial contraction and premature ventricular contraction were seen in two patients each (3.5%) and Wolff-Parkinson-White syndrome in one patient (1.8%).

Conclusion

Given this finding, we recommend active screening with ECG in patients with mitochondrial disease even in patients without obvious cardiac manifestation.

Mitochondrial DNA analysis by multiplex denaturing high-performance liquid chromatography and selective sequencing in pediatric patients with cardiomyopathy

PURPOSE

Mitochondrial DNA testing is typically performed by targeted mutation analysis only. We applied a more comprehensive approach to study the mitochondrial genome in 24 pediatric patients with idiopathic cardiomyopathy.

METHODS

Patients in the cohort did not show overt multisystemic disease and were previously tested for mutations in a subset of structural genes associated with cardiomyopathy. Mutation screening of the mitochondrial DNA by multiplex denaturing high-performance liquid chromatography was complemented by sequence analysis.

RESULTS

We identified 130 individual (unique) sequence changes. Among several potentially pathogenic changes, a novel heteroplasmic mutation in nicotinamide adenine dinucleotide dehydrogenase subunit 4 (10677G>A) was identified in one fraternal twin with worse clinical symptoms than his sibling. Another proband carried homoplasmic mutation 13708G>A (in nicotinamide adenine dinucleotide dehydrogenase subunit 5) that has been associated with Leber's hereditary optic neuropathy.

CONCLUSIONS

Changes in mitochondrial DNA may represent a relatively rare cause of idiopathic pediatric cardiomyopathies and/or influence their phenotypic expression. Interpretation of variants with uncertain pathogenicity, however, currently impedes clinical diagnostic use of comprehensive mitochondrial DNA testing. Whereas combined use of multiplex denaturing high-performance liquid chromatography and sequencing is more comprehensive than targeted mutation analysis, measurement of additional functional parameters, such as tissue respiratory chain activity, remains important to establishing a definitive diagnosis.

Muscle 3243A-->G mutation load and capacity of the mitochondrial energy-generating system

OBJECTIVE

The mitochondrial energy-generating system (MEGS) encompasses the mitochondrial enzymatic reactions from oxidation of pyruvate to the export of adenosine triphosphate. It is investigated in intact muscle mitochondria by measuring the pyruvate oxidation and adenosine triphosphate production rates, which we refer to as the "MEGS capacity." Currently, little is known about MEGS pathology in patients with mutations in the mitochondrial DNA. Because MEGS capacity is an indicator for the overall mitochondrial function related to energy production, we searched for a correlation between MEGS capacity and 3243A-->G mutation load in muscle of patients with the MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes) syndrome.

METHODS

In muscle tissue of 24 patients with the 3243A-->G mutation, we investigated the MEGS capacity, the respiratory chain enzymatic activities, and the 3243A-->G mutation load. To exclude coinciding mutations, we sequenced all 22 mitochondrial transfer RNA genes in the patients, if possible.

RESULTS

We found highly significant differences between patients and control subjects with respect to the MEGS capacity and complex I, III, and IV activities. MEGS-related measurements correlated considerably better with the mutation load than respiratory chain enzyme activities. We found no additional mutations in the mitochondrial transfer RNA genes of the patients.

INTERPRETATION

The results show that MEGS capacity has a greater sensitivity than respiratory chain enzymatic activities for detection of subtle mitochondrial dysfunction. This is important in the workup of patients with rare or new mitochondrial DNA mutations, and with low mutation loads. In these cases we suggest to determine the MEGS capacity.

A novel G3337A mitochondrial ND1 mutation related to cardiomyopathy co-segregates with tRNALeu(CUN) A12308G and tRNAThr C15946T mutations

We describe a novel mutation in human mitochondrial NADH dehydrogenase 1 gene (ND1), a G to A transition at nucleotide position 3337, which is co-segregated with two known mutations in tRNALeu(CUN) A12308G and tRNAThr C15946T. These mutations were detected in two unrelated patients with different clinical phenotypes, exhibiting cardiomyopathy as the common symptom. The ND1 G3337A mutation that was detected was found almost homoplasmic in the two patients and it was absent in 150 individuals that were tested as control group. Mitochondrial respiratory chain complex I activity of the patients platelets was also tested and found decreased compared to those of controls. We suggest that the co-existence of mutations in tRNA and ND1 genes may act synergistically affecting the clinical phenotype. Our study highlights the enormous phenotypic diversity that exists among pathogenic mtDNA mutations and re-emphasizes the need for a more careful clinical approach.

The in-depth evaluation of suspected mitochondrial disease

Mitochondrial disease confirmation and establishment of a specific molecular diagnosis requires extensive clinical and laboratory evaluation. Dual genome origins of mitochondrial disease, multi-organ system manifestations, and an ever increasing spectrum of recognized phenotypes represent the main diagnostic challenges. To overcome these obstacles, compiling information from a variety of diagnostic laboratory modalities can often provide sufficient evidence to establish an etiology. These include blood and tissue histochemical and analyte measurements, neuroimaging, provocative testing, enzymatic assays of tissue samples and cultured cells, as well as DNA analysis. As interpretation of results from these multifaceted investigations can become quite complex, the Diagnostic Committee of the Mitochondrial Medicine Society developed this review to provide an overview of currently available and emerging methodologies for the diagnosis of primary mitochondrial disease, with a focus on disorders characterized by impairment of oxidative phosphorylation. The aim of this work is to facilitate the diagnosis of mitochondrial disease by geneticists, neurologists, and other metabolic specialists who face the challenge of evaluating patients of all ages with suspected mitochondrial disease.

A follow-up study in a Taiwanese family with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes syndrome

BACKGROUND/PURPOSE

MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes) syndrome is often associated with A3243G point mutation of mitochondrial DNA (mtDNA). We previously described a MELAS family characterized by harboring an additional approximately 260 bp tandem duplication in the D-loop and a novel C3093G point mutation in the 16S rRNA gene of mtDNA in the proband. We studied the clinical progression and fluctuation of mtDNA mutations in this Taiwanese MELAS family.

METHODS

We followed up the clinical course in all members of this family (1 proband, her mother and 3 sons) for 12 years. Mutations of mtDNA in serial muscle biopsies of the proband and blood samples and hair follicles taken at different time points from the members of this family were analyzed.

RESULTS

The proband developed repeated stroke-like episodes, chronic intestinal pseudo-obstruction, polyneuropathy, progressive renal failure and dilated cardiomyopathy with heart failure. During the follow-up period, the mother and one of the siblings of the proband developed stroke-like episodes at age 62 and 12, respectively. There was no significant difference in the proportions of mtDNA with A3243G mutation among five serial muscle biopsies of the proband. In one carrier (I-2), the proportion of A3243G mutated mtDNA in blood cells was slightly increased with disease progression.

CONCLUSION

This study underlines the importance of early detection of extraneuromuscular symptoms in the members of a family with MELAS syndrome by adequate follow-up. The age of onset of stroke-like episode in MELAS syndrome may be as late as 62 years. We suggest that the manifestations of MELAS syndrome in this family might be associated with the additional approximately 260 bp tandem duplication in the D-loop region and the coexistence of C3093G mutation in the 16S rRNA gene with the A3243G mutation of mtDNA.

Cardiac manifestations in oxidative phosphorylation disorders of childhood

OBJECTIVE

To determine the frequency, type, and severity of cardiac involvement in pediatric patients with oxidative phosphorylation (OXPHOS) disorders.

STUDY DESIGN

Retrospective review of clinical and laboratory records of all patients with definitive OXPHOS disorders diagnosed and treated at the Royal Children's Hospital in Melbourne between 1984 and 2005.

RESULTS

Of a total of 89 patients (male:female ratio 1.5:1) 29 (33%) had cardiac involvement: 9 as presenting symptoms, 9 developing on follow-up, and 11 with subclinical cardiac findings. Leigh or Leigh-like syndrome and complex I and combined complex I, III, and IV deficiencies were the most common clinical and laboratory diagnoses, respectively. Clinically symptomatic patients had hypertrophic cardiomyopathy (5 patients), dilated cardiomyopathy (4 patients), combined ventricular hypertrophy and systolic dysfunction (3 patients), and left ventricular noncompaction (3 patients) at first assessment. A change in the type of cardiomyopathy was noted on follow-up in 2 patients. Conduction and rhythm abnormalities were present in 7 symptomatic patients.

CONCLUSIONS

Cardiac assessment in children with OXPHOS disorders may reveal subclinical abnormalities of cardiac function. Patients who present with primary cardiac features have a poor prognosis. OXPHOS disorders should be considered in the differential diagnosis of children presenting with otherwise unexplained cardiomyopathy.

Mitochondrial diseases: a nosological update

Mitochondrial diseases are disorders caused by impairment of the mitochondrial respiratory chain, characterized by clinical-genetic heterogeneity and frequent multisystemic involvement. It is difficult to establish a precise genotype/phenotype correlation and obtain a definitive nosology. Today's genetic classification distinguishes disorders caused by defects in the mitochondrial genome (sporadic or maternally-inherited) from disorders caused by defects in the nuclear genome (autosomally-inherited). We report an updated classification, briefly review the main clinical syndromes and describe the most recent genetic knowledge.

Cardiac features of a novel autosomal recessive dilated cardiomyopathic syndrome due to defective importation of mitochondrial protein

Dilated cardiomyopathy as seen in children is clinically and genetically heterogeneous, with an increasing proportion of cases known to be caused by disorders of single genes. An autosomal recessive syndrome with a high incidence of dilated cardiomyopathy was recently described in the Canadian Dariusleut Hutterite population. It is caused by homozygous mutations in a novel gene, DNAJC19, presumed to play a role in importation of mitochondrial proteins. We discuss the cardiac features of this syndrome, and its relationship to cardiac mitochondrial function.

Early cardiac involvement in children carrying the A3243G mtDNA mutation

The phenotypic spectrum of the mitochondrial A3243G DKA mutation is highly variable, particularly when occuring in childhood. In contrast to the classical presentation in adulthood (MELAS syndrome; mitochondria! myopathy, encephalopathy, lactic acidosis and stroke-like episodes) children show a different pattern of symptoms, often without the typical encephalopathy or psychomotor regression. We present six children carrying the A3243G mtDNA mutation with a heteroplasmy above 50 % in muscle tissue. The age of diagnosis ranged from 2 weeks up to 14.5 years. The clinical presentation was rather non-specific including muscle weakness, developmental delay and epilepsy. In this small pediatric group we detected presymptomatic cardiac involvement in five out of six children already at an early stage of disease. The cardiac pathology included cardiomyopathy and biventricular hypertrophy with rhythm disturbances (for example long QT-syndrome). The observed cardiac changes do not always increase the risk of cardiac deterioration; however, two of our patients died early on.

CONCLUSION

We hypothesize that the A3243G mutation might be underdiagnosed, as patients could suffer from an unexplained cardiac death before the diagnosis is made. We advise performing regular repeated ECGs and echocardiography in all children carrying a A3243G mtDNA mutation independently from the presence of cardiac symptoms.

Cardiac involvement over 10 years in myotonic and Becker muscular dystrophy and mitochondrial disorder

BACKGROUND

Little is known about the long-term development and outcome of cardiac involvement (CI) in patients with myotonic dystrophy type 1 (MD), Becker muscular dystrophy (BMD), and mitochondrial myopathy (MMP).

OBJECTIVE

To assess the progression of "definite", "possible" or "absent" CI, based on the history, clinical examination, electrocardiography, 24-h ambulatory electrocardiography, and transthoracic echocardiography, over 10 years in MD, BMD, and MMP patients.

METHODS

Included were 13 MD patients, aged 29-60 years, 5 BMD patients, aged 23-68 years, and 9 MMP patients, aged 24-73 years. Main outcome measures were the muscular disability score, the CI-classification, and the sum of abnormality score.

RESULTS

Since seven patients (2 MD, 2 BMD, 3 MMP) died during the observational period and 2 MMP patients refused the 10 year-follow-up, 11 MD, 3 BMD, and 4 MMP patients were actually investigated. At baseline/10 year later CI was "definite" in 12/11, 4/3, 6/4, "possible" in 1/0, 1/0, 3/0, and "absent" in 0/0, 0/0, 1/0 of the MD, BMD and MMP patients respectively. The most frequently abnormal investigations at baseline and follow-up were the history, electrocardiography, and the echocardiography. The mean number of abnormalities per MD, BMD, MMP patient at baseline/10y later was 4.5/5.1, 5.6/7.3, and 4.1/3.5 respectively. Cardiac medication required 25% of the MMP, 27% of the MD, and 100% of the BMD patients.

CONCLUSION

CI becomes "definite" in all patients with MD, BMD, and MMP, but progresses markedly only in BMD patients within 10 years. MD, BMD, or MMP patients should be cardiologically investigated as soon as the neurological diagnosis is established and treated if CI becomes symptomatic, or in case of severe ECG or echocardiographic abnormalities.

Cardiac involvement in adults with m.3243A>G MELAS gene mutation

Cardiac data in adults with mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes (MELAS syndrome) or asymptomatic gene carriers with the mitochondrial deoxyribonucleic acid adenine-to-guanine point mutation at nucleotide pair 3243 are scarce. Twelve subjects (mean age 35 +/- 13 years), 8 with MELAS syndrome (patients) and 4 asymptomatic gene carriers (carriers), were enrolled in the study. Each subject underwent electrocardiography, exercise testing, Holter monitoring, echocardiography, and genetic and biochemical analysis for respiratory chain enzyme activity (complex I rest activity) in skeletal muscle. On electrocardiography and Holter monitoring, none of the subjects had evidence of preexcitation, cardiac arrhythmias, or conduction abnormalities. Patients had significantly lower (42 +/- 17% from normal vs 103 +/- 14%, p <0.02) exercise tolerance. All but 1 of the patients and none of the gene carriers had ragged red fibers on muscle biopsy. The mean percentage of gene mutation in skeletal muscle tended to be higher in patients (53 +/- 19%, range 19% to 73%) compared with carriers (33 +/- 20%, range 15% to 62%). Mean complex I rest activity in patients (36 +/- 18%, range 10% to 58%) was significantly (p <0.01) lower compared with carriers (120 +/- 60%, range 72% to 205%). Left ventricular (LV) abnormalities were confined to patients with MELAS syndrome. Two patients had LV hypertrophy, 5 had LV systolic abnormalities, and 5 had LV diastolic dysfunction. Apart from 1 patient with an isolated LV diastolic abnormality, all patients with LV abnormalities had ragged red fibers. Patients with abnormal systolic LV function had a trend toward a higher percentage of mutated skeletal muscle (59.7 +/- 10.7% vs 35.8 +/- 21.3%, p <0.10) and significantly lower complex I rest activity (26.7 +/- 14.0% vs 97.8% +/- 57.9, p <0.01). In conclusion, none of the MELAS gene carriers had cardiac abnormalities, whereas most patients with the MELAS phenotype, particularly those with ragged red fibers, had LV involvement.

Successful heart failure therapy in mitochondrial disorder with noncompaction cardiomyopathy

OBJECTIVE

Effective heart failure therapy with angiotensin-converting enzyme inhibitors and beta-blockers in a patient with mitochondrial disorder and asymptomatic previously stable hypertrophic cardiomyopathy and left ventricular noncompaction (NCCMP) has not been reported.

CASE REPORT

In a 58-year-old male with juvenile seizures, impaired hearing, recurrent pancreatitis, diabetes, recurrent emesis and diarrhea, discrete weakness for hip flexion, general wasting, and reduced tendon reflexes, elevated muscle-enzymes, abnormal lactate-stress-test, and mitochondrial dysfunction on muscle biopsy, mitochondrial disorder was diagnosed at age 51 year. Echocardiography revealed myocardial thickening and NCCMP. Cardiac abnormalities did not progress upon repeated follow-ups. At age 57 year he developed acute heart failure during respiratory infection. Echocardiography additionally revealed reduced left ventricular systolic function, and a restrictive filling pattern. Within seven weeks of therapy with ramipril (2.5 mg/day) and bisoprolol (1.25 mg/day) the restrictive filling pattern disappeared and fractional shortening normalized.

CONCLUSION

This case shows that heart failure in a patient with mitochondrial disorder and previously stable hypertrophic cardiomyopathy and NCCMP promptly resolves under therapy with angiotensin-converting enzyme inhibitors and beta-blockers.

Heart Transplantation for Progressive Cardiomyopathy as a Manifestation of MELAS Syndrome

Mitochondrial diseases represent a heterogeneous group of disorders associated with a wide array of clinical manifestations. The presentation of patients with mitochondrial pathology largely depends upon the dysfunction of organ systems with large metabolic/energy requirements, including cardiac, neurologic, and musculoskeletal. In particular, mitochondrial myocardial disease can be progressive resulting in congestive heart failure and end-stage heart disease. This article reviews the role of heart transplantation for a particular variant of mitochondrial disorder, mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome, and discusses perioperative management issues related to transplantation for mitochondrial cardiomyopathies.