Isolated noncompaction of the left ventricular myocardium (INVM) is characterized by the presence of numerous prominent trabeculations and deep intertrabecular recesses within the left ventricle, sometimes also affecting the right ventricle and interventricular septum. Familial occurrence of this disorder was described previously. We present a family in which 6 affected individuals demonstrated X-linked recessive inheritance of this trait. Affected relatives presented postnatally with left ventricular failure and arrhythmias, associated with the pathognomonic echocardiographic findings of INVM. The usual findings of Barth syndrome (neutropenia, growth retardation, elevated urinary organic acids, low carnitine levels, and mitochondrial abnormalities) were either absent or found inconsistently. Fetal echocardiograms obtained between 24-30 weeks of gestation in 3 of the affected males showed a dilated left ventricle in one heart, but were not otherwise diagnostic of INVM in any of the cases. Four of the affected individuals died during infancy, one is in cardiac failure at age 8 months, and one is alive following cardiac transplant at age 9 months. The hearts from infants who died or underwent transplantation appeared, on gross examination, to be enlarged, with coarse, deep ventricular trabeculations and prominent endocardial fibroelastosis. Histologically, there were loosely organized fascicles of myocytes in subepicardial and midmyocardial zones of both ventricles, and the myocytes showed thin, often angulated fibers with prominent central clearing and reduced numbers of filaments. Markedly elongated mitochondria were present in some ventricular myocytes from one specimen, but this finding was not reproducible. Genetic linkage analysis has localized INVM to the Xq28 region, where other myopathies with cardiac involvement have been located.

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BACKGROUND: Hypoplastic Left Heart Syndrome is a congenital birth defect that is defined by underdevelopment of the left heart during pregnancy. This is especially dangerous as the left heart holds the systemic flow of blood- the oxygenated blood. Not enough oxygen throughout the whole body causes cyanosis, which symptoms include bluish discoloration of the skin or mucous membrane due to low oxygen saturation. Single Ventricle Palliation followed by Biventricular Conversion is the most common surgical procedural pathway to correct this defect. The goal is to convert from a single ventricle circulation during single ventricle palliation to biventricular circulation via biventricular conversion, which is the normal heart anatomy. Single Ventricle Pallation consists of three stages: Stage 1 Norwood Procedure, Bidirectional Glenn, and Fontan. Biventricular Conversion can be performed after any of the three stages. In addition, further compromise of the left ventricle includes other factors such as a thickening of fibroblast-like cells on the endocardial layer called endocardial fibroelastosis. Therefore, additional surgical procedures, also known as recruitment procedures, combat these problems. It is critical to find a correlation between a specific procedure and post surgery success in left ventricle growth and function for these patients. OBJECTIVES: Patients with Hypoplastic Left Heart Syndrome at Boston Children’s Hospital have undergone single ventricle palliation with some patients proceeding to biventricular conversion. This study aimed to study the palliation stages individually and recruitment procedures (specifically endocardial fibroelastosis resection) on the effect of left ventricle growth. METHODS: Patients with Hypoplastic Left Heart Syndrome were studied retrospectively (before 2014) and prospectively (after 2014 until December 1, 2018). Single Ventricle Palliation and Biventricular Conversion were analyzed via descriptional analysis with evidence of left ventricular growth measured by left ventricular end diastolic volume and respective z-scores. Z-scores were used to standardize end diastolic volume values across variability in age, weight, and height. RESULTS: A total of 55 patients underwent single ventricle palliation and 39 ended with biventricular circulation via biventricular conversion. Overall, there was a 9.29 ml increase in end diastolic volume between Bidirectional Glenn and Fontan and a 0.795 increase in end diastolic volume z-score between Fontan and Biventricular Conversion. Next, those who did not have recruitment procedures experienced a 135.6%, 48.8%, and 0% growth at Stage 1, Bidirectional Glenn, and Fontan, respectively, before directly proceeding to biventricular conversion. Those with recruitment experienced a 44.5%, 90.4%, and 83.0% growth at Stage 1, Bidirectional Glenn, and Fontan, respectively, before directly proceeding to biventricular conversion. Finally, there was a 50.2% and 62.3% in left ventricular growth at Bidirectional Glenn and Fontan, respectively, after endocardial fibroelastosis resection compared to only a 6.9% growth at Stage 1. CONCLUSION: Bidirectional Glenn was the most effective palliation stage for left ventricular growth. Recruitment in patients at this stage was associated with growth that exceeds those who did not have recruitment. This stage also best demonstrates the ability and success of growing a small ventricle to be adequate for biventricular conversion. Left ventricular growth at Fontan circulation holds promising results that are a point of interest for more studies. Endocardial Fibroelastosis resection is more effective on left ventricular growth at Bidirectional Glenn and Fontan compared to Stage 1.