Left Ventricular Non-Compaction (LVNC)

There is no gene specific to non-compaction. Where trabeculation accompanies a cardiomyopathy phenotype, the genes implicated are those of the associated condition, principally the sarcomeric and cytoskeletal genes seen in dilated and hypertrophic cardiomyopathy.^[1]

Genetic testing is therefore directed by the phenotype rather than by the trabeculation. Trabeculation alone, in a person with normal ventricular function and no family history, is not on its own an indication for a cardiomyopathy gene panel.^[1]

Reported prevalence varies by more than tenfold depending on imaging modality and criteria used. A systematic review and meta-analysis of 59 studies found a pooled prevalence of 14.79% in cohorts assessed by cardiac MRI against 1.28% by echocardiography.^[2]

Athletic cohorts sit higher still, at 3.16% by echocardiography and 27.29% by MRI in the same analysis.^[2] The authors concluded that LVNC in adults is a poorly defined entity that likely encompasses both physiological adaptation and pathological disease, with significant potential for overdiagnosis, overtreatment and unnecessary follow-up.^[2]

This site's NDLVC page covers the related 2023 ESC category for non-ischaemic scar or isolated LV dysfunction without dilatation.

Several criteria are in use. They were derived in small selected cohorts and none has been validated as a threshold for disease.

Criterion	Modality	Threshold
Jenni	Echocardiography	Non-compacted to compacted ratio greater than 2, measured at end-systole[6]
Petersen	Cardiac MRI	Non-compacted to compacted ratio greater than 2.3, measured at end-diastole[5]

Specificity is the problem. In 1,480 adults over 40 with no cardiovascular disease and a low 10-year risk, 14.8% met at least one MRI criterion, 7.9% met two, 4.3% met three and 1.3% met all four. Long-axis ratios were the least specific of the measures tested.^[3]

Meeting a ratio threshold therefore says relatively little on its own, and a criterion met on a single long-axis slice says least of all.

The practical question is not whether the trabeculation meets a ratio, but whether there is a cardiomyopathy present.

Features that make the finding clinically meaningful:

• Impaired LV systolic function or LV dilatation
• Late gadolinium enhancement on cardiac MRI
• Ventricular arrhythmia, unexplained syncope, or thromboembolism
• A family history of cardiomyopathy or premature sudden death
• A pathogenic variant in a cardiomyopathy gene^[1]

Physiological and reversible causes to consider first: athletic training, pregnancy, sickle cell disease and other chronic anaemias, and chronic kidney disease. In a longitudinal study of 102 primigravid women, 25.4% developed increased trabeculation during pregnancy and 8 met criteria for non-compaction; trabeculation resolved completely in 73% during postpartum follow-up.^[4] Trabeculation appearing under increased loading conditions is not evidence of cardiomyopathy.^[4]

• Echocardiography: first-line. Assess function and dimensions, not only the trabecular layer
• Cardiac MRI: the key test, less for the ratio than for late gadolinium enhancement and accurate volumes and function^[1]
• ECG and ambulatory monitoring: where there are symptoms, arrhythmia or a relevant family history
• Family history and, where indicated, first-degree relative screening: driven by the presence of a cardiomyopathy phenotype rather than by the trabeculation itself^[1]

When reporting, describing the appearance (for example "increased LV trabeculation") is more useful than applying a disease label that the finding may not support.^[2]

There is no treatment for trabeculation itself. Management follows whatever cardiomyopathy or complication is present.

1. General measures: assess and treat reversible loading conditions and anaemia; review training load where the person is an athlete.

2. Medical therapy: where there is LV systolic dysfunction, standard heart failure therapy applies as it would for the corresponding cardiomyopathy.^[1]

3. Anticoagulation: not indicated by trabeculation alone. It follows the usual indications, namely atrial fibrillation, LV thrombus or a prior embolic event.^[1]

4. Device therapy: ICD decisions follow the risk assessment for the associated cardiomyopathy phenotype, not the trabecular appearance.^[1]

Where there is an associated cardiomyopathy, follow-up is that of the cardiomyopathy.

Where trabeculation is an isolated finding with normal ventricular function, no scar, no arrhythmia, no symptoms and no relevant family history, indefinite surveillance is difficult to justify and carries its own costs, including insurance and occupational consequences and the anxiety of carrying a disease label. Discharge with clear advice on what would warrant re-referral is a reasonable position.^[2]

• Do not treat a ratio as a diagnosis. A ratio threshold is met by a substantial minority of healthy adults, and by 1.3% even when all four MRI criteria are required.^[3]
• Check the loading conditions before labelling. Pregnancy, athletic training and chronic anaemia all induce trabeculation that can resolve.^[4]
• The label follows the phenotype. Function, scar, arrhythmia and family history determine what this means, not the trabecular layer.^[1]
• Beware the modality effect. Prevalence is roughly ten times higher by MRI than by echocardiography, so a finding that appears on MRI alone should be interpreted with that in mind.^[2]
• Consider the cost of the label. Overdiagnosis here carries downstream consequences for insurance, occupation and lifelong follow-up.^[2]