The price of myocardial complexity: excessive trabeculation of the left ventricle and resuscitated sudden cardiac death

Description of Clinical Presentation: A 55-year-old hypertensive woman without previous relevant medical history was admitted following an out-of-hospital cardiac arrest due to ventricular fibrillation. After a single defibrillation shock, spontaneous circulation was restored. A 12-lead electrocardiogram obtained post–cardiac arrest demonstrated sinus rhythm, left bundle branch block morphology, diffuse T-wave inversions in leads V1–V6, II, III, and aVF, with a corrected QT interval of 505 ms. Transthoracic echocardiography revealed severe left ventricular systolic dysfunction with marked hypertrabeculation, while right ventricular size and function were preserved (Figure 1).

Diagnostic Techniques and Their Most Important Findings: Cardiac magnetic resonance (CMR) was performed on a 1.5 T scanner. The study demonstrated a severely dilated left ventricle with prominent hypertrabeculation in the mid and apical segments of the lateral and inferior walls, and severe systolic dysfunction (LVEF 25%) (Figure 2). End-diastolic SSFP sequences revealed a hypertrabeculated myocardium and a thin, compacted myocardial layer measuring 4.5 mm. The end-diastolic ratio between the so-called “noncompacted” and “compacted” myocardium was 3.0, and trabeculated mass in short axis accounted for 50% of the total LV mass. The right ventricle was of normal size and wall thickness, with borderline global systolic function (RVEF 49%). A small jet of mitral regurgitation was present. Both atria were mildly enlarged. Rest perfusion was normal, and no late gadolinium enhancement was detected (Figure 3).

Learning Points from this Case: This patient met two diagnostic criteria for the hypertrabeculation phenotype: Petersen criterion: end-diastolic noncompacted-to-compacted ratio of 3 ( >2.3 diagnostic threshold), and Jacquier criterion: trabeculated LV mass >50% of total LV mass ( >20% diagnostic threshold). Given the CMR findings, in association with malignant arrhythmia (ventricular fibrillation and cardiac arrest), QT prolongation, and severe LV systolic dysfunction, a diagnosis of left ventricular noncompaction cardiomyopathy (LVNC) was established. Implantation of an implantable cardioverter-defibrillator was recommended for secondary prevention, and guideline-directed medical therapy for heart failure with reduced ejection fraction was initiated. Left ventricle excessive trabeculation may represent more than an innocent morphological finding. While it can be a benign anatomical variant in some populations, when combined with LV systolic dysfunction, malignant arrhythmias, systemic embolization, or a positive family/genetic background, it defines the formerly called LVNC and mandates careful arrhythmic risk stratification. There is no pathognomonic pattern of late gadolinium enhancement in LVNC, as intramyocardial enhancement similar to dilated cardiomyopathy may be observed. Recent studies suggest that LV dysfunction may correlate more strongly with the thickness of the compacted myocardium ( < 5 mm in ≥2 segments, sensitivity 100%, specificity 60%) rather than the degree of trabeculation.

Figure 1. Transthoracic echocardiography. A. Parasternal short-axis view showing prominent LV trabeculation. B. Four-chamber color Doppler demonstrating mitral regurgitation. C. Continuous-wave Doppler of mild-to-moderate mitral regurgitation. D. Four-chamber view showing LV hypertrabeculation and dilation. E. TAPSE measurement. F. Parasternal short-axis view with echo contrast, highlighting trabeculation and absence of thrombi.
Figure 2. Cardiac magnetic resonance SSFP sequences. A. Three-chamber view. B. Two-chamber view. C. Four-chamber view. D. Short-axis view. Arrows point to marked LV hypertrabeculation in mid-apical lateral and inferior segments.
Figure 3. Cardiac magnetic resonance. A. Short-axis SSFP showing end-diastolic noncompacted-to-compacted ratio of 3 (>2.3 per Petersen criteria). B–C. Short-axis, with trabeculated LV mass >50% of global LV mass (>20% diagnostic threshold per Jacquier criteria). D. Perfusion images: no resting perfusion defects. E. Late gadolinium enhancement: no focal fibrosis.