Elamipretide for Barth syndrome cardiomyopathy: gradual rebuilding of a failed power grid

Barth syndrome is a rare and potentially fatal X-linked disease characterized by cardiomyopathy, skeletal muscle weakness, growth delays, and cyclic neutropenia. Patients with Barth syndrome are prone to high risk of mortality in infancy and the development of cardiomyopathy with severe weakening of the immune system. Elamipretide is a water-soluble, aromatic-cationic, mitochondria-targeting tetrapeptide that readily penetrates and transiently localizes to the inner mitochondrial membrane. Therapy with elamipretide facilitates cell health by improving energy production and inhibiting excessive formation of reactive oxygen species, thus alleviating oxidative stress. Elamipretide crosses the outer membrane of the mitochondrion and becomes associated with cardiolipin, a constituent phospholipid of the inner membrane. Elamipretide improves mitochondrial bioenergetics and morphology rapidly in induced pluripotent stem cells from patients with Barth syndrome and other genetically related diseases characterized by pediatric cardiomyopathy. Data with elamipretide across multiple models of disease are especially promising, with results from several studies supporting the use of elamipretide as potential therapy for patients with Barth syndrome, particularly where there is a confirmed diagnosis of cardiomyopathy. This review highlights the challenges and opportunities presented in treating Barth syndrome cardiomyopathy patients with elamipretide and addresses evidence supporting the durability of effect of elamipretide as a therapeutic agent for Barth syndrome, especially its likely durable effects on progression of cardiomyopathy following the cessation of drug treatment and the capability of elamipretide to structurally reverse remodel the failing left ventricle at the global, cellular, and molecular level in a gradual manner through specific targeting of the mitochondrial inner membrane.

Hypertrophic cardiomyopathy in infant newborns of diabetic mother: a heterogeneous condition, the importance of anamnesis, physical examination and follow-up

Background Hypertrophic cardiomyopathy (HCM) in neonates is a rare and heterogeneous disorder. HCM accounts for 25 to 40% of all pediatric cardiomyopathy cases and the highest incidence in pediatric population is reported in children < 1 year. Case presentation we report two clinical cases of neonates, born to mothers respectively with a pre-pregnancy insulin-dependent diabetic mellitus type 2 and a suspected diabetes, with inadequate prenatal glycemic control for the first and underestimated glycemic control for the second case, with a different evolution. In the first case, a slow evidence of improvement of the HCM was observed, persuading us to the diagnosis of a diabetes-related HCM; In the second case the progressive worsening of the HCM during follow-up in association with further investigations, resulted in the diagnosis of Pompe disease. Conclusions Hypertrophic cardiomyopathy in newborns can be the clinical expression of different underlying disorders. We aim to show the importance both to reassess maternal and family history and critically evaluate the physical examination in order to address the correct differential diagnosis. Furthermore it is important to continue a regular cardiologic follow-up for this pathology with neonatal onset to prevent a poor prognosis.

Investigating Insulin Resistance in Pediatric Cardiomyopathy - A Pilot Study

Children with cardiomyopathy are a vulnerable population and understanding the factors that contribute to cardiac dysfunction are of great importance. At the biochemical level, energy utilization by cardiomyocytes during stress may provide insight into the progression of cardiomyopathy. There is a large body of literature that describes insulin resistance in adults with cardiomyopathy (1,2). Extensive literature on the topic in adult individuals exists however investigation in the pediatric population is sparse. The pathophysiology of disease in children and adolescents is unique. To study the role of insulin resistance in pediatric cardiomyopathy, we measured the homeostasis model assessment-estimated insulin resistance (HOMA-IR) at baseline in pre-pubertal patients (age 13-18 years old; mean 16 years old; n = 8) with either hypertrophic cardiomyopathy (HCM) or dilated cardiomyopathy (DCM). In patients with HCM, greater insulin resistance was positively correlated with greater left ventricular (LV) septal thickness (r = 0.55; p = 0.33; n = 5) and LV posterior wall thickness (r = 0.7; p = 0.19; n = 5) during diastole. As expected, insulin resistance was strongly correlated with BMI (r = 0.84; p = 0.08; n = 5) though greater BMI was not as strongly associated with LV septal thickness (r = 0.59; p = 0.3; n = 5) or posterior wall thickness (r = 0.59; p = 0.3; n = 5). In patients with DCM, insulin resistance was positively correlated with LV end diastolic volume (r = 0.59; p = 0.59; n = 3). Interestingly, there was an observed inverse association between insulin resistance and BMI in DCM (r = -0.85; p = 0.34; n =3). Though our sample population is limited, thus affecting statistical significance, results showed that there was a trend towards greater insulin resistance in patients with poorer cardiac measurements. These findings are consistent with adult literature and the proposition that cardiac dysfunction is an insulin resistant state. References: (1) Riehle C, Abel ED. Insulin Signaling and Heart Failure. Circulation research. 2016;118(7):1151-1169. (2) Shah A, Shannon RP. Insulin resistance in dilated cardiomyopathy. Reviews in cardiovascular medicine. 2003;4 Suppl 6:S50-57

Genetic Causes of Cardiomyopathy in Children: First Results From the Pediatric Cardiomyopathy Genes Study

Background Pediatric cardiomyopathy is a genetically heterogeneous disease with substantial morbidity and mortality. Current guidelines recommend genetic testing in children with hypertrophic, dilated, or restrictive cardiomyopathy, but practice variations exist. Robust data on clinical testing practices and diagnostic yield in children are lacking. This study aimed to identify the genetic causes of cardiomyopathy in children and to investigate clinical genetic testing practices. Methods and Results Children with familial or idiopathic cardiomyopathy were enrolled from 14 institutions in North America. Probands underwent exome sequencing. Rare sequence variants in 37 known cardiomyopathy genes were assessed for pathogenicity using consensus clinical interpretation guidelines. Of the 152 enrolled probands, 41% had a family history of cardiomyopathy. Of 81 (53%) who had undergone clinical genetic testing for cardiomyopathy before enrollment, 39 (48%) had a positive result. Genetic testing rates varied from 0% to 97% between sites. A positive family history and hypertrophic cardiomyopathy subtype were associated with increased likelihood of genetic testing ( P =0.005 and P =0.03, respectively). A molecular cause was identified in an additional 21% of the 63 children who did not undergo clinical testing, with positive results identified in both familial and idiopathic cases and across all phenotypic subtypes. Conclusions A definitive molecular genetic diagnosis can be made in a substantial proportion of children for whom the cause and heritable nature of their cardiomyopathy was previously unknown. Practice variations in genetic testing are great and should be reduced. Improvements can be made in comprehensive cardiac screening and predictive genetic testing in first‐degree relatives. Overall, our results support use of routine genetic testing in cases of both familial and idiopathic cardiomyopathy. Registration URL: https://www.clinicaltrials.gov ; Unique identifier: NCT01873963.

Hypertension masquerading as Pediatric Cardiomyopathy: an exercise in cognitive biases

Heuristics and cognitive biases constantly influence clinical decision-making and often facilitate judgements under uncertainty. They can frequently, however, lead to diagnostic errors and adverse outcomes, particularly when considering rare disease processes that have common, masquerading presentations. Herein, we present two such cases of newborn infants with hypertensive renal disorders that were initially thought to have cardiomyopathy.