Hypertrophic Cardiomyopathy in a Fetus: A Rare Presentation Case Report

ABSTRACT

A 34‐year‐old pregnant woman at 23 weeks of gestation was referred for fetal cardiomegaly, later diagnosed as fetal hypertrophic cardiomyopathy with left ventricular outflow tract obstruction. The neonate, delivered vaginally at 39 weeks, was treated with propranolol and has shown favorable progress under regular follow‐up.

1. Introduction

Hypertrophic cardiomyopathy (HCM) is a rare and heterogeneous condition that accounts for 25%–40% of pediatric cardiomyopathy patients, with the highest prevalence observed in infants under 1 year of age [1, 2]. It involves both histological and functional disruptions of myocardial structure, often presenting with interventricular septal hypertrophy and left ventricular outflow tract obstruction on imaging. While HCM is primarily genetic in etiology, secondary causes such as maternal diabetes or inborn errors of metabolism are also recognized [3, 4].

Prenatal detection of hypertrophic cardiomyopathy (HCM) through advanced echocardiographic imaging is crucial for early diagnosis and management [5, 6]. This condition, characterized by abnormal thickening of the heart muscle, particularly the interventricular septum, can often be identified during fetal life using high‐resolution imaging techniques [7].

Key echocardiographic features include interventricular septal hypertrophy, which serves as a primary diagnostic marker [8]. This thickening may present in isolation or alongside other structural or functional abnormalities, such as altered cardiac dimensions, impaired ventricular function, or abnormalities in the outflow tract [9]. Additionally, Doppler imaging may reveal altered flow patterns, which can further support the diagnosis of HCM [9, 10].

This case report presents the diagnosis and management of fetal hypertrophic cardiomyopathy, emphasizing the importance of prenatal imaging and its role in predicting postnatal outcomes.

2. Case Presentation

A 34‐year‐old pregnant woman, with no significant medical history, was referred to our hospital at 23 weeks of gestation due to fetal cardiomegaly detected on routine ultrasonography. She had no family or obstetric history of congenital heart disease and no prior history of abortion or pregnancy complications. Fasting blood glucose levels (84 mg/dL) and HbA1c (5.8%) were within normal ranges throughout the pregnancy, and there was no evidence of gestational diabetes.

3. Methods and Treatment

Fetal echocardiography confirmed hypertrophic cardiomyopathy (HCMP) in the fetus. The septal view revealed significant interventricular septal hypertrophy and cardiomegaly (Figure 1A). The ventricular short‐axis view showed pronounced biventricular hypertrophy with asymmetry in the interventricular septum (Figure 1B). Color Doppler imaging demonstrated flow acceleration in the left ventricular outflow tract (LVOT), indicating narrowing (Figure 2A). Doppler spectral imaging further confirmed LVOT obstruction (Figure 2B).

FIGURE 1.

(A) Axial view of the fetal heart demonstrates significant hypertrophy of the interventricular septum (IVS) and cardiomegaly, with clear visualization of the right ventricle (RV) and left ventricle (LV). (B) Short‐axis view of both ventricles reveals marked asymmetric hypertrophy of the interventricular septum.

FIGURE 2.

(A) Color Doppler imaging in the five‐chamber view displays flow acceleration in the left ventricular outflow tract (LVOT) and aorta (yellow arrow), consistent with LVOT narrowing or obstruction. (B) Doppler spectral imaging of the LVOT reveals high‐velocity flow, confirming LVOT obstruction.

The pregnancy was closely monitored with serial fetal evaluations, and the patient delivered vaginally at 39 weeks of gestation without complications. The neonate was born in good general condition. No respiratory support or emergency interventions were needed. Postnatal echocardiographic findings supported the prenatal observations. The parasternal long‐axis view showed significant and asymmetric interventricular septal hypertrophy (1.04 cm) (Figure 3A), as well as thickening of the anterior mitral valve leaflet (AML) and the presence of endocardial plaques, both consistent with systolic anterior motion (SAM) and the Venturi effect (Figure 3B). Color Doppler imaging revealed mitral regurgitation (Figure 3C). The five‐chamber view with color Doppler demonstrated flow acceleration (Figure 4A), and Doppler spectral imaging confirmed mild LVOT obstruction (Figure 4B).

FIGURE 3.

(A) Postnatal two‐dimensional transthoracic echocardiography in the parasternal long‐axis view demonstrates significant hypertrophy of the interventricular septum (IVS). (B) The same parasternal long‐axis view shows thickening of the anterior mitral valve leaflet (AML) (yellow arrow). Additionally, thickening of the left ventricular endocardium at the point of contact with the AML, indicative of an endocardial plaque, is observed (red arrow). (C) Color Doppler imaging in the parasternal long‐axis view highlights significant mitral regurgitation (MR).

FIGURE 4.

(A) The five‐chamber view with color Doppler imaging displays significant aliasing in the LVOT, indicative of turbulent flow. (B) Doppler spectral imaging of the LVOT postnatally shows no significant LVOT obstruction (LVOTO).

4. Conclusion and Result

Following initial postnatal evaluation, oral beta‐blocker therapy with propranolol at a dose of 1 mg/kg was initiated. The infant has been under regular follow‐up, showing favorable progress to date. Moreover, periodic follow‐ups were done every 3 months. The neonate's chest X‐ray showed obvious cardiomegaly due to biventricular hypertrophy. Additionally, the electrocardiogram indicated increased voltage in R waves and inverted T waves (in left precordial leads) which demonstrated left ventricular hypertrophy (Figure 5A,B). Notably, genetic testing was not conducted as the parents were financially unable to afford it. Although RASopathy was ruled out based on clinical assessment, no characteristic phenotypic features or symptomatic indications were observed [11].

FIGURE 5.

(A) Electrocardiogram showing increased R wave voltage and T wave inversion, indicative of left ventricular hypertrophy. (B) Chest radiograph of a neonate showing cardiomegaly with prominence of the left heart border, suggestive of left ventricular hypertrophy. A nasogastric tube is also visible in situ.

5. Discussion

HCM in the fetal and neonatal periods represents a rare, complex, and heterogeneous condition, with significant implications for both prenatal and postnatal management. Current literature on fetal hypertrophic cardiomyopathy is limited by a paucity of longitudinal data (due to a rarity of this abnormality) and the absence of standardized management guidelines [12]. This case contributes to the existing body of knowledge by providing comprehensive prenatal imaging findings. In this case, HCM was diagnosed based on echocardiographic findings of marked interventricular septal hypertrophy, biventricular hypertrophy, and left ventricular outflow tract obstruction (LVOTO). These findings are consistent with established diagnostic criteria for HCM and underscore the importance of fetal echocardiography in early detection and monitoring [13].

Although Doppler echocardiography demonstrated mild left ventricular outflow tract obstruction (LVOTO), the pressure gradient across the LVOT was not significantly elevated. This finding may be partially explained by normal systemic blood pressure levels during evaluation, which could have minimized dynamic obstruction. In this case, the obstruction was likely functional rather than fixed and has been influenced by interventricular septal hypertrophy and systolic anterior motion (SAM) of the mitral valve [14]. Diagnosing HCM in utero is technically difficult due to fetal movement, small cardiac size, and evolving myocardial patterns. Differentiating HCM from other causes of cardiomegaly also presents a diagnostic challenge, making serial imaging and careful interpretation crucial for appropriate treatment planning [15]. Accordingly, the prenatal diagnosis of HCM is critical, as it enables clinicians to anticipate potential complications such as LVOTO, arrhythmias, and heart failure, which may manifest shortly after birth [16]. Previous studies have demonstrated that interventricular septal thickness measured during fetal life is a reliable predictor of postnatal outcomes, with a threshold of ≥ 4.5 mm associated with a higher risk of perinatal morbidity and mortality [17]. In this case, close prenatal surveillance allowed for a timely initiation of postnatal therapy, including beta‐blockade with propranolol, which is widely used to manage LVOTO and reduce myocardial oxygen demand. Additionally, fetal echocardiography was the primary imaging modality. Cardiac MRI was not pursued due to its limited resolution in small fetuses and reduced availability compared to echocardiography, which remains the gold standard for in utero cardiac assessment [18].

The etiology of HCM in the fetal period is diverse, with genetic mutations in sarcomere proteins accounting for approximately 50% of cases in children [9]. Secondary causes, such as maternal diabetes, inborn errors of metabolism, and other systemic conditions, contribute to a substantial proportion of cases. Notably, the absence of maternal diabetes or a family history of HCM in this case highlights the idiopathic nature of the condition and the need for thorough genetic and metabolic evaluations to identify potential underlying causes [19].

Postnatal echocardiographic findings in this case revealed progressive regression of septal hypertrophy and LVOTO under beta‐blocker therapy. This outcome aligns with prior evidence suggesting that neonatal HCM often shows improvement with pharmacologic management, particularly in cases without significant metabolic or genetic abnormalities [20]. However, the long‐term prognosis for such cases remains variable and depends on factors such as the severity of myocardial involvement, the presence of fibrosis, and the underlying etiology [21].

While advancements in fetal imaging and neonatal care have improved the prognosis for HCM, challenges persist in differentiating between transient and progressive forms of the disease. Serial imaging and regular follow‐up are essential to monitor myocardial function, assess the risk of sudden cardiac death, and guide therapeutic decisions [22].

Long‐term outcomes of fetal HCM are influenced by underlying etiology, severity of myocardial hypertrophy, and treatment response [9]. Genetic counseling is essential for cases involving pathogenic sarcomere mutations, as these are associated with an increased risk of progressive hypertrophy, arrhythmias, and heart failure [23]. Such tests may impose a financial burden on the parents. Family counseling should emphasize recurrence risk, the implications of genetic findings, and signs of potential complications [24]. For idiopathic cases without confirmed genetic or metabolic abnormalities, the prognosis may be more favorable, yet continued monitoring is warranted due to the potential for late‐onset cardiac events [25]. Individualized follow‐up plans, incorporating patient education on activity modifications and early symptom recognition, are recommended to mitigate the risk of adverse outcomes.

6. Conclusion

This case underscores the value of an integrated approach to managing fetal HCM, incorporating detailed prenatal imaging, timely postnatal interventions, and a multidisciplinary care model. Further research into the genetic and molecular mechanisms underlying HCM in the fetal period may provide new insights into early diagnosis, targeted therapies, and personalized management strategies.

Author Contributions

Alireza Golbabaei: conceptualization, methodology, supervision, writing – original draft. Elham sadat Alavi Moghaddam: data curation, methodology, supervision. Mahsa Naemi: conceptualization, data curation, writing – original draft. Hooman Mohammad Talebi: conceptualization, data curation, methodology, software, supervision, writing – original draft, writing – review and editing.

Consent

A written informed consent was obtained from the patient.

Golbabaei A., Moghaddam E. s. A., Naemi M., and Mohammad Talebi H., “Hypertrophic Cardiomyopathy in a Fetus: A Rare Presentation Case Report,” Clinical Case Reports 13, no. 7 (2025): e70599, 10.1002/ccr3.70599.

Data Availability Statement

Data are available via direct email and request from the corresponding author.