Background A genetic cause can be identified in 30% of noncompaction cardiomyopathy patients (NCCM) with clinical features ranging from asymptomatic cardiomyopathy to heart failure with major adverse cardiac events (MACE). Methods and Results To investigate genotype-phenotype correlations, the genotypes and clinical features of genetic NCCM patients were collected from the literature. We compared age at diagnosis, cardiac features and risk for MACE according to mode of inheritance and molecular effects for defects in the most common sarcomere genes and NCCM subtypes. Geno- and phenotypes of 561 NCCM patients from 172 studies showed increased risk in children for congenital heart defects (P<0.001) and MACE (P<0.001). In adult NCCM patients the main causes were single missense mutations in sarcomere genes. Children more frequently had an X-linked or mitochondrial inherited defect (P=0.001) or chromosomal anomalies (P<0.001). MYH7 was involved in 48% of the sarcomere gene mutations. MYH7 and ACTC1 mutations had lower risk for MACE than MYBPC3 and TTN (P=0.001). The NCCM/dilated cardiomyopathy cardiac phenotype was the most frequent subtype (56%; P=0.022) and was associated with an increased risk for MACE and high risk for left ventricular systolic dysfunction (<0.001). In multivariate binary logistic regression analysis MYBPC3, TTN, arrhythmia -, non-sarcomere non-arrhythmia cardiomyopathy-and X-linked genes were genetic predictors for MACE. Conclusions Sarcomere gene mutations were the most common cause in adult patients with lower risk of MACE. Children had multi-systemic disorders with severe outcome, suggesting that the diagnostic and clinical approaches should be adjusted to age at presentation. The observed genotype-phenotype correlations endorsed that DNA diagnostics for NCCM is important for clinical management and counseling of patients.

Systematic Review of Genotype-Phenotype Correlations in Noncompaction Cardiomyopathy

To discuss the association of left ventricular hypertrabeculation/noncompaction (LVHT/LVNC/NCCM) with genetic disease and to outline the therapeutic options for non-symptomatic and symptomatic LVHT. A number of new mutated genes have been recently detected being associated with LVHT. There are indications that microtubules changing cell polarity, the transcription factor Nkx2-5, and NOTCH-1 signaling are involved in the pathogenesis of LVHT. There are also indications that the PKC signaling pathway, which is involved in the regulation of gap junction intercellular communication, is disturbed in LVHT. LVHT is the same as LVNC and is associated with pathogenic variants in > 110 mtDNA or nDNA genes. LVHT has been also reported in > 15 chromosomal defects. However, a causal relation between any of these variants and LVHT has not been proven. There is no general agreement on the treatment of LVHT. According to expert opinions, LVHT patients require anticoagulation if they meet the criteria for anticoagulation or an ICD if they meet the appropriate criteria. Heart failure therapy is equal to patients with other causes of heart failure.

Left Ventricular Noncompaction Syndrome: Genetic Insights and Therapeutic Perspectives.

Objectives: Disappearance of left ventricular hypertrabeculation (LVHT) over time has been occasionally recognized, but absence on echocardiography and autopsy and presence on histological examination after autopsy has not been reported. Methods: Routine investigations such as chocardiography, cardiac MRI and coronary angiography were applied. Autopsy studies included macroscopic inspection and dissection but also histological work-up. Results: In a 64-year-old male, LVHT was diagnosed at age 51 years during diagnostic work-up for hypertrophic cardiomyopathy. He had a history of mitochondrial myopathy which was diagnosed long before the cardiac problem became evident. Thickening of the left ventricular myocardium increased over years, resulting also in thickening of the trabeculations and the disappearance of the intertrabecular recesses. This is why LVHT was no longer visible on echocardiography shortly before death at age 64 years. The autopsy revealed that macroscopically no LVHT was visible but upon histological work-up the preformed recesses were still visible but had become unfolded. Conclusions: This case shows that LVHT may disappear due to thickening of the trabeculations but may remain visible on postmortem histological examination in patients with hypertrophic cardiomyopathy from a mitochondrial myopathy.

Noncompaction in mitochondrial myopathy: visible on microscopy but absent on macroscopic inspection.

https://www.internationaljournalofcardiology.com/article/S0167-5273(13)01183-2/pdf

Noncompaction predisposing for recurrent Takotsubo syndrome in myotonic dystrophy 1

https://www.internationaljournalofcardiology.com/article/S0167-5273(13)00764-X/pdf

Mitochondrial myopathy with disappearance of noncompaction within a thickening myocardium

Left ventricular hypertrabeculation/noncompaction is associated with various neuromuscular and other rare genetic disorders. In a 53-year-old man with a Turner mosaic karyotype, regression of left ventricular hypertrabeculation/noncompaction was documented by cardiac magnetic resonance imaging and echocardiography after 7 years. During that time, coronary 3-vessel disease and severe left ventricular dys function developed, necessitating coronary bypass surgery. Postoperatively, left ventricular systolic function recovered to an ejection fraction of 40%. The patient died suddenly 6 months postoperatively. In conclusion, the disappearance of left ventricular hypertrabeculation/noncompaction was most likely due to scar formation.

Johann Altenberger

Papers

Disappearance of left ventricular hypertrabeculation/noncompaction and sudden death in a patient with Turner mosaic syndrome.