Case August 2025 - IDM Cardiac Hypertrophy

Case presentation Title: Reversible Neonatal Hypertrophic Cardiomyopathy in an Infant of a Diabetic Mother: A Case Report and Review of Clinical Principles

By: Dr Animaw lingerew

MD, Pediatrician, Assistant professor of pediatrics and child health at Woldia University International

Addis Ababa, Ethiopia

Background:

Hypertrophic cardiomyopathy (HCM) in neonates is an uncommon yet significant cardiac condition, especially in infants of diabetic mothers (IDMs). Poor glycemic control during pregnancy can lead to fetal hyperinsulinemia, which is associated with myocardial hypertrophy. Although this condition is often transient, the severity of presentation may mimic other neonatal pathologies and requires careful differentiation to guide appropriate management.

Case Presentation:

We report the case of a full-term male neonate who was delivered vaginally after nine months of amenorrhea to a 27-year-old mother with poorly controlled Type 1 diabetes mellitus. The pregnancy was marked by intermittent antenatal care and persistent maternal hyperglycemia. There were no reported complications such as fetal distress or preeclampsia during gestation. At birth, the infant weighed 5 kilograms, consistent with macrosomia, and had normal Apgar scores of 8 and 9 at one and five minutes, respectively. Despite reassuring Apgar scores, he developed significant respiratory distress immediately after delivery. His vital signs revealed tachycardia with a pulse rate of 180 beats per minute, tachypnea with a respiratory rate of 82 breaths per minute, and hypoxemia with oxygen saturation measured at 80% on room air. Physical examination revealed clear lung fields upon auscultation and normal air entry bilaterally. Heart sounds were present and normal, without murmurs, rubs, or gallops. No organomegaly was detected on abdominal palpation, and peripheral perfusion was satisfactory. Initial investigations included a complete blood count, which was within normal limits, and a random blood sugar level that was also normal. A chest radiograph showed clear lungs but significant cardiomegaly, raising suspicion for a structural cardiac abnormality.

An echocardiogram was performed on the third day of life and revealed a markedly hypertrophied interventricular septum (Figure 1), with a z-score of +9.8 indicating severe thickening. Septal to posterior LV free wall ratio is estimated to be 1.8 and the left ventricular cavity was notably reduced in size, although no marked obstruction was observed in the left ventricular outflow tract. Systolic function was preserved, and valvular anatomy appeared normal.

Given the initial presentation, transient tachypnea of the newborn (TTN) was considered; however, the respiratory distress persisted beyond the typical resolution period. Upon review of echocardiographic findings and clinical progression, a diagnosis of neonatal hypertrophic cardiomyopathy was made, likely secondary to maternal diabetes-induced fetal hyperinsulinemia. Propranolol therapy was initiated during neonatal intensive care admission, with gradual clinical improvement. The neonate remained hospitalized for 20 days and was discharged on beta-blocker therapy with follow-up in the high-risk infant clinic. Over subsequent months, propranolol was tapered gradually. Serial echocardiograms demonstrated consistent regression of septal hypertrophy, and by four months of age, ventricular morphology had normalized.

Figure 1. Echocardiography at 3rd day of life showing hypertrophied IVS and reduced LV cavity.

Discussion

This case exemplifies a classical presentation of neonatal hypertrophic cardiomyopathy (HCM) in an infant born to a mother with poorly controlled Type 1 diabetes mellitus. The observed myocardial hypertrophy—predominantly affecting the interventricular septum—is consistent with the pathophysiologic changes seen in infants of diabetic mothers (IDMs). In such cases, maternal hyperglycemia stimulates fetal hyperinsulinemia, which acts as a growth factor, promoting cellular proliferation and hypertrophy of cardiomyocytes. This fetal response does not reflect a primary genetic abnormality, but rather an adaptive, and in many cases reversible, response to intrauterine metabolic stress. The initial clinical presentation of severe respiratory distress shortly after birth is not uncommon in neonates with cardiomyopathy but can easily be misinterpreted as a pulmonary condition. In this case, TTN was initially considered due to clear lung fields and absence of other defining features of cardiac compromise. However, persistent symptoms and radiographic evidence of cardiomegaly triggered a deeper cardiologic assessment, leading to the correct diagnosis. This highlights the diagnostic challenge posed by overlapping presentations and underscores the importance of maintaining a broad differential diagnosis in neonates born to high-risk mothers. Echocardiography remains the cornerstone of diagnosis in neonatal HCM, providing valuable insights into myocardial thickness, chamber dimensions, and functional parameters. The significantly elevated interventricular septal z-score (+9.8) in this infant confirmed marked hypertrophy, which was not accompanied by significant utflow tract obstruction—a finding typical of metabolic HCM rather than genetically driven forms such as sarcomeric HCM or syndromic cardiomyopathies.

Management decisions must be guided by the degree of myocardial dysfunction and clinical severity. Beta-blocker therapy, particularly with propranolol, is frequently employed in symptomatic neonates to reduce myocardial oxygen demand, enhance diastolic filling, and decrease heart rate. In this case, the initiation of propranolol was associated with gradual resolution of symptoms and eventual regression of hypertrophy, confirming the transient nature of the condition. Serial echocardiographic evaluations demonstrated progressive remodeling of the left ventricle and normalization of septal thickness, allowing for the safe discontinuation of therapy by two months of age. This course not only validates the reversibility of IDM-associated hypertrophy but also emphasizes the importance of close outpatient follow-up and structured weaning of pharmacologic agents. From a broader perspective, this case illustrates the critical need for meticulous maternal glycemic control during pregnancy. Preventing fetal hyperinsulinemia through improved glucose regulation may significantly reduce the risk of neonatal complications, including cardiac hypertrophy. Furthermore, early screening of at-risk neonates—even those with mild or nonspecific symptoms—can allow timely intervention and minimize unnecessary escalation of care.

Conclusion

Hypertrophic cardiomyopathy (HCM) associated with infants of diabetic mothers (IDMs) remains a clinically significant yet often under-recognized cause of neonatal respiratory distress. As demonstrated in this case, unexplained tachypnea and hypoxemia in the immediate postnatal period should prompt consideration of myocardial hypertrophy, particularly in neonates born to mothers with poorly controlled Type 1 diabetes mellitus. Timely recognition is crucial, as the clinical presentation may mimic more common respiratory conditions such as transient tachypnea of the newborn or neonatal sepsis, delaying appropriate management. Echocardiography plays an essential diagnostic role, allowing clinicians to distinguish metabolic cardiomyopathy from structural congenital heart disease and to monitor disease progression. Pharmacologic intervention with beta-blockers such as propranolol, when indicated, has proven effective in alleviating symptoms and facilitating myocardial remodeling. Serial imaging further supports a dynamic understanding of disease course and informs therapeutic tapering. Importantly, the reversibility observed in diabetic-associated myocardial hypertrophy emphasizes the transient nature of this condition when managed appropriately. It also reinforces the critical need for multidisciplinary care that begins with optimized maternal metabolic control during pregnancy and continues through postnatal surveillance. This case highlights the direct impact of maternal health on neonatal cardiovascular outcomes and advocates for heightened clinical vigilance in identifying and managing cardiac complications in IDMs.

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