Ventricular hypertrabeculation, also known as ventricular noncompaction, is a myocardial phenotype characterized by excessive trabeculation and deep intertrabecular recesses caused by incomplete myocardial compaction during embryonic development. The earliest reported cases were associated with congenital heart defects, including ventricular outflow tract obstruction, complex cyanotic congenital heart disease, and coronary artery anomalies.^1,2

The clinical presentation is highly heterogeneous and may include heart failure (HF), arrhythmias, thromboembolic events, and sudden cardiac death. In addition to ventricular structural abnormalities, ventricular hypertrabeculation may be associated with cardiac conduction disorders, atrial arrhythmias, and functional valvular regurgitation (FVR) secondary to cardiac chamber dilatation, all of which contribute to greater clinical complexity and a poorer prognosis.³

Furthermore, ventricular hypertrabeculation is a well-recognized feature of several neuromuscular disorders, suggesting a shared genetic basis and a syndromic phenotype in a subset of patients. Diagnosis may be challenging because of its marked phenotypic variability and overlap with other cardiomyopathies. Cardiac magnetic resonance (CMR) plays a particularly important role in confirming the diagnosis and providing detailed anatomical characterization.⁴

We report the case of a young patient with biventricular noncompaction associated with significant valvular heart disease, cardiac conduction disease requiring permanent pacemaker implantation, who is undergoing investigation for an underlying neuromuscular disorder. The patient is enrolled in a study approved by the Human Research Ethics Committee of the Universidade do Estado do Amazonas (approval no. 7,108,530; CAAE no. 55200322.5.3009.516).

A 21-year-old woman from the city of Tefé, state of Amazonas, Brazil, was referred to a specialized cardiomyopathy clinic with a diagnosis of biventricular noncompaction associated with severe mitral regurgitation (MR) and tricuspid regurgitation (TR) secondary to annular dilatation. Her medical history included permanent atrial fibrillation (AF) (CHA₂DS₂-VA score = 3; HAS-BLED score = 0), complete atrioventricular (AV) block with prior implantation of a dual-chamber permanent pacemaker, and a previous episode of compensated cardiogenic ascites. A neuromuscular disorder under investigation was the most relevant comorbidity.

Her clinical history revealed symptom onset during childhood, beginning with progressive ascites at 11 years of age. She was initially managed at a local health care facility but showed no satisfactory response to medical therapy. At that time, both cardiac and hepatic etiologies were considered, prompting referral to a tertiary referral center, where she remained hospitalized for approximately 3 months. Thereafter, outpatient follow-up was irregular, partly because it relied on telemedicine.

At 20 years of age, she experienced recurrent massive ascites refractory to diuretic therapy, with subsequent clinical improvement following evaluation at a private health care facility. At 21 years of age, she developed another episode of decompensation characterized by ascites and dyspnea, requiring hospitalization and referral to a tertiary care center. During this admission, the diagnosis of biventricular noncompaction cardiomyopathy was established.

On physical examination, the patient appeared underweight, with normal skin coloration, no cyanosis, and hypotension (blood pressure: 88/58 mmHg; heart rate: 71 bpm), without signs of peripheral congestion. Cardiac auscultation revealed a regular two-sound rhythm and a systolic murmur best heard at the pulmonary area. Pulmonary auscultation demonstrated normal vesicular breath sounds without adventitious findings, and no lower-extremity edema was present. Electrocardiography showed a junctional rhythm, extreme axis deviation, and left bundle branch block (Figure 1).

Transthoracic echocardiography demonstrated biatrial enlargement and mild eccentric left ventricular (LV) hypertrophy. Global LV systolic function was preserved (left ventricular ejection fraction [LVEF], 51%). Additional findings included myxomatous degeneration with prolapse of the anterior mitral leaflet, resulting in severe MR, mild pulmonary hypertension, spontaneous echo contrast in the right atrium, and ventricular hypertrabeculation.

CMR demonstrated biventricular chamber enlargement (Figure 3), with indexed LV and right ventricular (RV) end-diastolic volumes of 110.33 mL/m² and 119.37 mL/m², respectively. Prominent LV myocardial trabeculation was observed, with a noncompacted-to-compacted myocardium ratio > 2.3, meeting the Petersen diagnostic criterion. LVEF was preserved (56%), whereas the RV exhibited systolic dysfunction (ejection fraction, 30%), accompanied by biatrial enlargement, functional MR, and a small pericardial effusion, without evidence of late gadolinium enhancement or intracardiac thrombi.

Neurological evaluation revealed a motor deficit syndrome involving all four limbs, muscle atrophy, and findings suggestive of a neuromuscular disorder with probable X-linked inheritance. Emery-Dreifuss muscular dystrophy (EDMD) was considered the leading diagnostic hypothesis. As part of the etiological investigation, G-banded karyotyping was performed and demonstrated a normal female chromosomal complement without detectable abnormalities.

At 25 years of age, the patient underwent dual-chamber permanent pacemaker implantation because of complete AV block. At her most recent outpatient follow-up, she reported occasional palpitations but denied chest pain, dyspnea, or peripheral edema. She also reported good adherence to guideline-directed medical therapy, consisting of enalapril, carvedilol, dapagliflozin, furosemide, and spironolactone, together with anticoagulation with rivaroxaban and fluid restriction.

Ventricular hypertrabeculation predominantly affects the LV, whereas biventricular involvement is less common and is generally associated with greater clinical complexity and a higher incidence of adverse outcomes. In the present case, cardiac chamber dilatation, FVR, and evidence of RV dysfunction underscore the phenotypic heterogeneity of the disease and the potential for a more severe clinical course when both ventricles are involved.^5,6

Cardiac chamber dilatation in ventricular hypertrabeculation may lead to FVR, particularly MR and TR, as observed in this patient. This mechanism is driven by annular dilatation and distortion of ventricular geometry, contributing to worsening HF symptoms and an increased risk of clinical decompensation.⁶

Patients with ventricular hypertrabeculation have a high prevalence of arrhythmias and cardiac conduction abnormalities, including AF and advanced AV block. The need for permanent pacemaker implantation at a young age, together with permanent AF, highlights the arrhythmogenic potential of this condition and the impact of myocardial remodeling on the cardiac conduction system.^7,8

The American College of Medical Genetics and Genomics recommends genetic evaluation in patients with cardiomyopathies, particularly in the presence of early disease onset, an arrhythmic phenotype, or concomitant neuromuscular disorders.⁹ Ventricular hypertrabeculation has been associated with muscular dystrophies, myotonic dystrophy, EDMD, and mitochondrial myopathies. In the present case, the patient remains under etiological investigation for her neuromuscular disorder, and G-banded karyotyping has not identified any chromosomal abnormalities to date.¹⁰

Biventricular hypertrabeculation is a rare manifestation of the disease. Previous reports have described adults presenting with HF and a family history suggestive of cardiomyopathy, patients in whom the diagnosis was established only after CMR, and young individuals presenting with severe arrhythmias or initially noncardiac manifestations.^11–13 These findings highlight the marked phenotypic variability of biventricular involvement, its substantial arrhythmogenic potential, and the pivotal role of advanced cardiac imaging in establishing the diagnosis.

This case highlights the diagnostic complexity of biventricular hypertrabeculation and its association with neuromuscular manifestations, emphasizing the importance of a comprehensive etiological investigation and a multidisciplinary approach. Early recognition of the disease and follow-up at specialized centers are essential to optimize treatment, facilitate monitoring for disease-related complications, and expand our understanding of the clinical spectrum of this condition, particularly in patients with neuromuscular disorders that remain under etiological investigation.