Much debate remains regarding the genetic association of this condition. The unique character of the resulting myocardium suggests a distinct CM, but the significant genetic heterogeneity with sarcomere protein gene mutations associated with several other CMs, including hypertrophic and dilated CM, suggests that LVNC may simply exist on a phenotypic continuum with these other conditions.4 Inheritance shows additional similarities to these other known CMs with autosomal-
dominant and X-linked modes of transmission shown with familial forms in about 25% of patients.5,7 This has led many to believe that screening of first-degree relatives of clinically affected patients may be appropriate.
The prevalence of LVNC in adults referred for echocardiography is about 0.014% to 1.3%.5 A recent increase in the rate of recognition has raised concerns of possible overdiagnosis, with attempts now made to develop specific imaging diagnostic criteria. Diagnosis of LVNC is most commonly suspected (but can be missed) on echocardiography using 2-D and color Doppler imaging modalities. Echocardiographic findings supporting the diagnosis of LVNC suggested by Oechslin and colleague include:
• Presence of multiple trabeculations, particularly in the LV apex and free wall;
• Multiple deep trabeculation recesses in communication with the LV cavity, usually seen on color Doppler imaging;
• A 2-layered structure of the endomyocardium with ratio of end systolic, noncompacted endocardial layer to compacted epicardial layer > 2 in adults; and
• Absence of other congenital or acquired heart disease, particularly those causing LV outflow obstruction.8
Another proposed standardized method for identifying LVNC via echocardiography by Chin and colleagues focuses on trabeculae at the LV apex on the parasternal short axis and apical views.2,3 LVNC is defined by a ratio of X/Y of ≤ 0.5, where X is the distance from the epicardial surface to the trough of the trabecular recess, and Y is the distance from the epicardial surface to the peak of the trabeculations.
Cardiac MRI is now a more common mode of imaging used for diagnosis of LVNC and often has better imaging characteristics than those of echocardiography. Using a ratio of noncompacted to compacted CM in diastole > 2.3 is suggestive of LVNC with sensitivity and specificity of 86% and 99%.9
The management of LVNC focuses primarily on treatment of complications, including heart failure, rhythm disturbances, and thromboembolic events. Treatment of heart failure is typically the same as for other CMs and includes medical therapy with salt restriction, diuretics, beta-blockers, and ACE inhibitors. In addition, exercise training, as tolerated, is beneficial to improve clinical status.3,10 Electrophysiology studies are often performed in these patients, and implantation of an AICD is typically done in cases of documented, sustained VT, presyncope with inducible VT or severally depressed ejection fraction of < 35%.4,10 Deep intertrabecular recesses and impaired blood flow increase the risk of thrombus formation. Hence, anticoagulation with warfarin (international normalized ratio target 2.3) for those with an impaired LV ejection fraction (< 40%) should be considered for the prevention of cardioembolic events.3,4,6,10
Summary
An active-duty solider with a history of battlefield trauma and multiple hospitalizations was admitted for symptomatic heart failure with cardiac MRI suggestive of LVNC. This condition is a phenotypic result of genetic heterogeneity with significant variability in clinical presentation and a predisposition for heart failure, ventricular arrhythmias, and systemic embolic events. The etiology of this patient’s clinical presentation remains unclear, and additional research is needed to understand whether his recent trauma and multiple hospitalizations played a role in the manifestation of his disease.
Author disclosures
The authors report no actual or potential conflicts of interest with regard to this article.
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