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Severe diastolic filling restriction secondary to rigid myocardial tissue describes restrictive cardiomyopathy (RCM). In RCM, the myocardium becomes stiff and non-compliant, impairing ventricular relaxation and diastolic filling while systolic contractile function often remains relatively preserved initially. This is not the primary mechanism of dilated cardiomyopathy.

Dynamic subaortic obstruction caused by asymmetric septal hypertrophy is the cardinal hallmark of hypertrophic cardiomyopathy (HCM). HCM involves disarrayed, hypertrophied cardiac myocytes, most prominently in the interventricular septum, which impedes left ventricular outflow during systole.

Replacement of right ventricular myocytes with fibrofatty adipose tissue describes arrhythmogenic right ventricular cardiomyopathy (ARVC). ARVC is a genetic disease of cell adhesion proteins (desmosomes) that leads to ventricular arrhythmias and right-sided heart failure, rather than post-viral dilated cardiomyopathy.

Restrictive cardiomyopathy is an exceptionally rare pediatric cardiomyopathy characterized primarily by severe diastolic filling impairment due to rigid, non-compliant ventricular walls, while systolic pump function remains relatively preserved until late stages. Metabolic storage diseases (such as glycogen storage disease or lysosomal disorders) typically present with progressive developmental delay, skeletal muscle hypotonia, organomegaly, and distinctive dysmorphic features rather than an acute post-viral onset of acute congestive heart failure.

Hypertrophic obstructive cardiomyopathy secondary to maternal diabetes presents in the early neonatal period (typically within the first few days to weeks of life) due to fetal hyperinsulinemia stimulating cardiac myocyte hypertrophy, particularly of the interventricular septum. While it causes dynamic left ventricular outflow tract obstruction, it is a congenital metabolic phenomenon observed immediately post-partum rather than an acquired heart failure presentation following a viral respiratory illness in a 6-month-old infant.

Left ventricular non-compaction is a genetic congenital cardiomyopathy characterized by deep intertrabecular recesses and a prominent two-layered myocardium resulting from arrested embryological compaction. While affected infants can develop heart failure, the clinical presentation is structural and congenital rather than triggered by a preceding acute viral illness. Furthermore, clients presenting with classic symptomatic infant heart failure demonstrate significantly impaired, rather than preserved, ventricular systolic function.

Severe impairment of myocardial systolic contractility with chamber dilation is the defining characteristic of dilated cardiomyopathy (DCM). In DCM, weakened myocytes fail to generate adequate stroke volume, leading to compensatory chamber enlargement and systolic pump failure, whereas early RCM exhibits preserved systolic squeezing with impaired diastolic filling.

Massive asymmetrical septal hypertrophy causing dynamic subaortic obstruction describes hypertrophic obstructive cardiomyopathy (HCM). In HCM, disarrayed myocytes and asymmetric thickening of the interventricular septum create an outflow tract obstruction during systole, which is a distinctly different structural anomaly than RCM.

Replacement of right ventricular myocardium with fibrofatty tissue is the hallmark of arrhythmogenic right ventricular cardiomyopathy (ARVC). ARVC is a genetic desmosomal disorder leading to localized right ventricular akinesis, aneurysms, and ventricular arrhythmias, rather than diffuse rigid ventricular diastolic dysfunction.

Diffuse dilation of all four cardiac chambers with reduced wall thickness describes dilated cardiomyopathy (DCM). DCM is characterized by thin, stretched ventricular walls and impaired systolic contractile force, resulting in a low ejection fraction rather than severe asymmetrical septal hypertrophy.

Marked bi-atrial enlargement paired with normal ventricular wall thickness is the characteristic structural finding of restrictive cardiomyopathy (RCM). In RCM, rigid ventricular walls severely restrict diastolic filling, forcing the atria to dilate significantly under elevated backpressure while ventricular wall thickness remains relatively normal.

Excessive non-compacted endocardial trabeculations with deep intertrabecular recesses describes left ventricular non-compaction (LVNC). LVNC is a distinct congenital cardiomyopathy resulting from arrested intrauterine endomyocardial morphogenesis, creating a porous, spongy appearance of the left ventricular myocardium.

Maternal folate deficiency during early gestation is linked to neural tube defects. Deficient folic acid impairs embryonic DNA synthesis and neurulation during 3 to 4 weeks post-conception. It does not cause hypertrophic cardiomyopathy or septal wall thickening. Supplementation of 400 mcg daily prevents cranioschisis and spina bifida.

Intrauterine varicella zoster virus infection leads to congenital varicella syndrome. Manifestations include cutaneous cicatricial scarring, limb hypoplasia, chorioretinitis, and microcephaly rather than structural cardiac hypertrophy. Exposure during the late third trimester poses risks for neonatal varicella pneumonia. It does not alter fetal myocardial glycogen stores.

Inadequate thyroid hormone during pregnancy typically correlates with congenital hypothyroidism. Levothyroxine therapy restores maternal euthyroid status, preventing fetal neurodevelopmental impairment and low birth weight. Maternal hypothyroidism does not cause asymmetric ventricular hypertrophy or muscular outflow obstruction. Unmanaged hypothyroidism primary increases preeclampsia risk.