Heart diseases in mitochondrial encephalomyopathy, lactic acidosis, and stroke syndrome

A Case Report of a Clinically Suspected Diagnosis of Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-Like Episodes (MELAS) Syndrome With Cardiac Impairment

This case report presents a description of a hypertrophic left ventricle with reduced ejection fraction in a man in his mid-twenties with clinical, radiologic, and biochemical features of a rare syndrome called mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS). A literature review of this uncommon syndrome and MELAS cardiomyopathy has been conducted.

Acute myocardial infarction in a patient with MELAS syndrome: a possible link?

The mitochondrial encephalomyopathy, lactic acidosis, and stroke (MELAS) syndrome is a mitochondrial disorder, commonly caused by m.3243A>G mutation in the MT-TL1 gene. It encodes for the mitochondrial leucine transfer RNA (tRNA Leu [UUR]), implicated in the translation of proteins involved in the assembly and function of mitochondrial complexes in the electron transport chain. The m.3243A>G mutation determines complex I (CI) deficiency, ultimately leading to NADH accumulation, higher rates of glycolysis in order to compensate for the reduced ATP production and increase in lactates, the end-product of glycolysis. Disruption of the oxidative phosphorylation function with an inability to produce sufficient energy results in multi-organ dysfunction, with high energy demanding cells, such as myocytes and neurons, being the most affected ones. Therefore, MELAS syndrome is characterized by a heterogeneous clinical spectrum. Here we report on a case of a 55-year-old man affected by MELA syndrome with no cardiovascular risk factors. He was admitted to our department because of a non ST-segment elevation myocardial infarction (NSTEMI). A coronary angioplasty of the posterior descending artery and of the left anterior descending artery was realized. Transthoracic echocardiography showed inferior and anterior left ventricular wall hypokinesis together with a moderate left ventricle hypertrophy. Cardiac involvement is reported in about a third of the patients and left ventricular hypertrophy (LVH) is the most common phenotype, with possible dilated cardiomyopathy in end-stage disease; brady- arrhythmias and tachy-arrhythmias are also frequently reported as well as Wolff- Parkinson-White (WPW) syndrome. Organ impairment and clinical manifestations depend on the heteroplasmy level of mutant DNA in cells that can differ among individuals, explaining why some patients present a more severe disease. A clear relationship between MELAS syndrome and atherosclerosis has never been established, however recently advocated. In vitro studies in MELAS patients have shown that higher mitochondrial ROS levels and increased expression of oxidative stress-related genes, as a consequence of complex I deficiency and disrupted electron transport, allow circulating LDL to be promptly oxidized into ox-LDL, contributing to endothelial dysfunction and atherosclerosis plaque formation. In light of the recent evidence suggesting a possible link between mitochondrial disorders and atherosclerosis, we speculate that MELAS syndrome may have played a role in the pathogenesis of coronary artery disease in our patient. Further investigations are needed to confirm a pathogenetic link.

Cardiac complications in inherited mitochondrial diseases

Maternally mitochondrial dysfunction includes a heterogeneous group of genetic disorders which leads to the impairment of the final common pathway of energy metabolism. Coronary heart disease and coronary venous disease are two important clinical manifestations of mitochondrial dysfunction due to abnormality in the setting of underlying pathways. Mitochondrial dysfunction can lead to cardiomyopathy, which is involved in the onset of acute cardiac and pulmonary failure. Mitochondrial diseases present other cardiac manifestations such as left ventricular noncompaction and cardiac conduction disease. Different clinical findings from mitochondrial dysfunction originate from different mtDNA mutations, and this variety of clinical symptoms poses a diagnostic challenge for cardiologists. Heart transplantation may be a good treatment, but it is not always possible, and other complications of the disease, such as mitochondrial encephalopathy, lactic acidosis, and stroke-like syndrome, should be considered. To diagnose and treat most mitochondrial disorders, careful cardiac, neurological, and molecular studies are needed. In this study, we looked at molecular genetics of MIDs and cardiac manifestations in patients with mitochondrial dysfunction.

Heart Transplantation in Children with Mitochondrial Disease

OBJECTIVES

To compare the outcomes and comorbidities of children with mitochondrial disease undergoing heart transplantation with children without mitochondrial disease.

STUDY DESIGN

Using a unique linkage between the Pediatric Health Information System and Scientific Registry of Transplant Recipients databases, pediatric heart transplantation recipients from 2002 to 2016 with a diagnosis of cardiomyopathy were included. Post heart transplantation survival and morbidities were compared between patients with and without mitochondrial disease.

RESULTS

A total of 1330 patients were included, including 47 (3.5%) with mitochondrial disease. Survival after heart transplantation was similar between patients with and without mitochondrial disease over a median follow-up of 4 years. Patients with mitochondrial disease were more likely to have a stroke after heart transplantation (11% vs 3%; P = .009), require a longer duration of mechanical ventilation after heart transplantation (3 days vs 1 day; P < .001), and have a longer intensive care unit stay after heart transplantation (10 vs 6 days; P = .007). The absence of a hospital readmission within the first post-transplant year was similar among patients with and without mitochondrial disease (61.7% vs 51%; P = .14). However, patients with mitochondrial disease who were readmitted demonstrated a longer length of stay compared with those without (median, 14 days vs 8 days; P = .03).

CONCLUSIONS

Patients with mitochondrial disease can successfully undergo heart transplantation with survival comparable with patients without mitochondrial disease. Patients with mitochondrial disease have greater risk for post-heart transplantation morbidities including stroke, prolonged mechanical ventilation, and longer intensive care unit and readmission length of stay. These results suggest that the presence of mitochondrial disease should not be an absolute contraindication to heart transplantation in the appropriate clinical setting.

The MELAS mutation m.3243A>G promotes reactivation of fetal cardiac genes and an epithelial-mesenchymal transition-like program via dysregulation of miRNAs

The pathomechanisms underlying oxidative phosphorylation (OXPHOS) diseases are not well-understood, but they involve maladaptive changes in mitochondria-nucleus communication. Many studies on the mitochondria-nucleus cross-talk triggered by mitochondrial dysfunction have focused on the role played by regulatory proteins, while the participation of miRNAs remains poorly explored. MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes) is mostly caused by mutation m.3243A>G in mitochondrial tRNA^Leu(UUR) gene. Adverse cardiac and neurological events are the commonest causes of early death in m.3243A>G patients. Notably, the incidence of major clinical features associated with this mutation has been correlated to the level of m.3243A>G mutant mitochondrial DNA (heteroplasmy) in skeletal muscle. In this work, we used a transmitochondrial cybrid model of MELAS (100% m.3243A>G mutant mitochondrial DNA) to investigate the participation of miRNAs in the mitochondria-nucleus cross-talk associated with OXPHOS dysfunction. High-throughput analysis of small-RNA-Seq data indicated that expression of 246 miRNAs was significantly altered in MELAS cybrids. Validation of selected miRNAs, including miR-4775 and miR-218-5p, in patient muscle samples revealed miRNAs whose expression declined with high levels of mutant heteroplasmy. We show that miR-218-5p and miR-4775 are direct regulators of fetal cardiac genes such as NODAL, RHOA, ISL1 and RXRB, which are up-regulated in MELAS cybrids and in patient muscle samples with heteroplasmy above 60%. Our data clearly indicate that TGF-β superfamily signaling and an epithelial-mesenchymal transition-like program are activated in MELAS cybrids, and suggest that down-regulation of miRNAs regulating fetal cardiac genes is a risk marker of heart failure in patients with OXPHOS diseases.

Mitochondrial Heteroplasmy

Genetic polymorphisms, in concert with well-characterized etiology and progression of major pathologies, plays a significant role in aberrant processes afflicting human populations. Mitochondrial heteroplasmy represents a dynamically determined co-expression of inherited polymorphisms and somatic pathology in varying ratios within individual mitochondrial DNA (mtDNA) genomes with repetitive patterns of tissue specificity. The ratios of the MtDNA genomes represent a balance between healthy and pathological cellular outcomes. Mechanistically, cardiomyopathies have profound alterations of normative mitochondrial function. Certain allele imbalances in the nuclear mitochondrial genome are associated with key energy mitochondrial proteins. Mitochondrial heteroplasmy may manifest itself at critical protein expression points, e.g., cytochrome c oxidase (COX). Pathological mtDNA mutations also are associated with the development of congestive heart failure. Interestingly, mitochondrial 'normal vs. abnormal' ratios of various heteroplasmic populations may occur in families. In the translational context of human health and disease, we discuss the need for determining critical foci to probe multiple biological roles of mitochondrial heteroplasmy in cardiomyopathy.

MELAS Syndrome with Cardiac Involvement: A Multimodality Imaging Approach

A 49-year-old man presented with chest pain, dyspnea, and lactic acidosis. Left ventricular hypertrophy and myocardial fibrosis were detected. The sequencing of mitochondrial genome (mtDNA) revealed the presence of A to G mtDNA point mutation at position 3243 (m.3243A>G) in tRNA^Leu(UUR) gene. Diagnosis of cardiac involvement in a patient with Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes syndrome (MELAS) was made. Due to increased risk of sudden cardiac death, cardioverter defibrillator was implanted.

The phenotypic spectrum of fifty Czech m.3243A>G carriers

BACKGROUND

Mitochondrial myopathy, Encephalopathy, Lactic Acidosis and Stroke-like episodes syndrome (MELAS) is a common mitochondrial disorder with varying multisystemic clinical manifestation. We present a comprehensive clinical picture of 50 Czech m.3243A>G carriers with emphasis on the sequence of symptoms in symptomatic patients.

RESULTS

Symptoms developed in 33 patients (66%) and 17 carriers remained unaffected (34%). The age of onset varied from 1month to 47years of age, with juvenile presentation occurring in 53% of patients. Myopathy was the most common presenting symptom (18%), followed by CPEO/ptosis and hearing loss, with the latter also being the most common second symptom. Stroke-like episodes (SLE) occurred in fourteen patients, although never as a first symptom, and were frequently preceded by migraines (58%). Rhabdomyolysis developed in two patients. The second symptom appeared 5.0±8.3years (range 0-28years) after the first, and the interval between the second and third symptom was 2.0±6.0years (range 0-21years). Four of our patients remained monosymptomatic up to 12years of follow-up. The sequence of symptoms according to their time of manifestation was migraines, myopathy, seizures, CPEO/ptosis, SLE, hearing loss, and diabetes mellitus. The average age at death was 32.4±17.7years (range 9-60years) in the juvenile form and 44.0±12.7years (range 35-53years) in the adult form. Some patients with SLE harboured very low heteroplasmy levels in various tissues. No threshold for any organ dysfunction could be determined based on these levels.

CONCLUSIONS

Sufficient knowledge of the timeline of the natural course of MELAS syndrome may improve the prediction and management of symptoms in patients with this mitochondrial disease.

[Cardiac manifestations of mitochondrial diseases]

Mitochondrial diseases are multi-system disorders in relation with mitochondrial DNA and/or nuclear DNA abnormalities. Clinical pictures are heterogeneous, involving endocrine, cardiac, neurologic or sensory systems. Cardiac involvements are morphological and electrical disturbances. Prognosis is worsened in case of cardiac impairment. Treatments are related to the type of cardiac dysfunction including medication or pacemaker implantation.

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.

Genetic Cardiomyopathies Causing Heart Failure

Despite the striking advances in medical and surgical therapy, the morbidity, mortality, and economic burden of heart failure (HF) remain unacceptably high. There is increasing evidence that the risk and course of HF depend on genetic predisposition; however, the genetic contribution to HF is heterogeneous and complex. At one end of the spectrum are the familial monogenic HF syndromes in which causative mutations are rare but highly penetrant. At the other, HF susceptibility and course may be influenced by more common, less penetrant genetic variants. As detailed in this review, efforts to unravel the basis of the familial cardiomyopathies at the mendelian end of the spectrum already have begun to deliver on the promise of informative mechanisms, novel gene-based diagnostics, and therapies for distinct subtypes of HF. However, continued progress requires the differentiation of pathogenic mutations, disease modifiers, and rare, benign variants in the deluge of data emerging from increasingly accessible novel sequencing technologies. This represents a significant challenge and demands a sustained effort in analysis of extended family pedigrees, diligent clinical phenotyping, and systematic annotation of human genetic variation.

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].

Characteristics of intestinal pseudo-obstruction in patients with mitochondrial diseases

AIM: To reveal the frequency, characteristics and prog-nosis of chronic intestinal pseudo-obstruction (CIP) in mitochondrial disease patients.

METHODS: Between January 2000 and December 2010, 31 patients (13 males and 18 females) were diagnosed with mitochondrial diseases at our hospital. We conducted a retrospective review of the patients’ sex, subclass of mitochondrial disease, age at onset of mitochondrial disease, frequency of CIP and the age at its onset, and the duration of survival. The age at onset or at the first diagnosis of the disorder that led to the clinical suspicion of mitochondrial disease was also examined.

RESULTS: Twenty patients were sub-classified with mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS), 8 with chronic progressive external ophthalmoplegia (CPEO), and 3 with myoclonus epilepsy associated with ragged-red fibers (MERRF). Nine patients were diagnosed with CIP, 8 of the 20 (40.0%) patients with MELAS, 0 of the 8 (0.0%) patients with CPEO, and 1 of the 3 (33.3%) patients with MERRF. The median age (range) at the diagnosis and the median age at onset of mitochondrial disease were 40 (17-69) and 25 (12-63) years in patients with CIP, and 49 (17-81) and 40 (11-71) years in patients without CIP. During the survey period, 5 patients (4 patients with MELAS and 1 with CPEO) died. The cause of death was cardiomyopathy in 2 patients with MELAS, cerebral infarction in 1 patient with MELAS, epilepsy and aspiration pneumonia in 1 patient with MELAS, and multiple metastases from gastric cancer and aspiration pneumonia in 1 patient with CPEO.

CONCLUSION: Patients with CIP tend to have disorders that are suspected to be related to mitochondrial diseases at younger ages than are patients without CIP.

Risk factors for symptomatic hyperlactatemia and lactic acidosis among combination antiretroviral therapy-treated adults in Botswana: results from a clinical trial

Nucleoside analogue reverse transcriptase inhibitors are an integral component of combination antiretroviral treatment regimens. However, their ability to inhibit polymerase-γ has been associated with several mitochondrial toxicities, including potentially life-threatening lactic acidosis. A total of 650 antiretroviral-naive adults (69% female) initiated combination antiretroviral therapy (cART) and were intensively screened for toxicities including lactic acidosis as part of a 3-year clinical trial in Botswana. Patients were categorized as no lactic acidosis symptoms, minor symptoms but lactate <4.4 mmol/liter, and symptoms with lactate ≥ 4.4 mmol/liter [moderate to severe symptomatic hyperlactatemia (SH) or lactic acidosis (LA)]. Of 650 participants 111 (17.1%) developed symptoms and/or laboratory results suggestive of lactic acidosis and had a serum lactate drawn; 97 (87.4%) of these were female. There were 20 events, 13 having SH and 7 with LA; all 20 (100%) were female (p<0.001). Cox proportional hazard analysis limited to the 451 females revealed that having a higher baseline BMI was predictive for the development of SH/LA [aHR=1.17 per one-unit increase (1.08-1.25), p<0.0001]. Ordered logistic regression performed among all 650 patients revealed that having a lower baseline hemoglobin [aOR=1.28 per one-unit decrease (1.1-1.49), p=0.002] and being randomized to d4T/3TC-based cART [aOR=1.76 relative to ZDV/3TC (1.03-3.01), p=0.04] were predictive of the symptoms and/or the development of SH/LA. cART-treated women in sub-Saharan Africa, especially those having higher body mass indices, should receive additional monitoring for SH/LA. Women presently receiving d4T/3TC-based cART in such settings also warrant more intensive monitoring.

Anesthetic considerations in mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes syndrome: a case series

PURPOSE

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes syndrome (MELAS) is a rare inherited mitochondrial disorder associated with severe multiorgan pathology and stress-induced episodes of metabolic decompensation and lactic acidosis. The purpose of this case series is to review the medical records of patients with MELAS who underwent anesthetic care at the Mayo Clinic to observe their perioperative responses to anesthesia and to assess outcomes.

PRINCIPAL FINDINGS

From September 1997 to October 2010, nine patients with MELAS were identified who underwent 20 general anesthetics, 12 prior to MELAS diagnosis. Debilitating neurologic symptoms involved eight patients, and three patients had substantial cardiac comorbidities. The patients tolerated commonly used anesthetics and muscle relaxants, including succinylcholine. Lactated Ringer's solution was used frequently. One patient was noted to have elevated postoperative serum lactate, but his serum lactate was chronically elevated. Metabolic acidosis was not observed in any patient. Hyponatremia and hyperkalemia, sometimes profound, were observed in seven patients, but these abnormalities also occurred at times remote from surgery. Two patients developed renal dysfunction following cardiac surgery and abdominal surgery for severe sepsis.

CONCLUSION

The MELAS patients developed episodes of hyponatremia and hyperkalemia of variable severity unrelated to the timing of surgery, suggesting these patients are prone to major electrolyte disturbances. Given the propensity to develop acid-base disturbances and lactacidemia, it is prudent to review and normalize electrolyte abnormalities and to adjust the anesthetic plan accordingly. Fortunately, the limited data suggest that patients with MELAS tolerate commonly used anesthetic drugs well.