Compaction ratio for diagnosis of LVNC

Compaction ratio for diagnosis of LVNC.

Epicardium- to- trabecular- trough thickness is termed compacted myocardium (C), and trabecular- peak- to- trough thickness is termed non- compacted myocardium (NC).

LVNC is considered when NC/ C is greater than 2 by echocardiography and 2.3 by magnetic resonance imaging.

Compaction Ratio for Diagnosis of Left Ventricular Non-Compaction (LVNC)

Overview

Left Ventricular Non-Compaction (LVNC) cardiomyopathy is a structural myocardial disorder characterized by a two-layered left ventricular (LV) wall consisting of a thin, compacted (C) epicardial layer and an abnormally thickened non-compacted (NC) trabecular layer with deep recesses communicating with the LV cavity. LVNC is considered a genetic or primary cardiomyopathy, though increased trabeculation alone may also be seen in healthy individuals, athletes, or pregnancy, making accurate diagnosis essential. 

Compaction Ratio Criteria

The main imaging modalities used to assess LVNC are transthoracic echocardiography (TTE) and cardiac magnetic resonance imaging (CMR). A central quantitative diagnostic parameter across many criteria is the ratio of non-compacted (NC) to compacted (C) myocardial layer thickness (NC:C), typically measured in specific views and phases of the cardiac cycle. 

1. Petersen’s CMR Criterion

NC:C ratio > 2.3 at end-diastole on CMR is one of the most widely cited and validated cut-offs for diagnosing LVNC. This diastolic measurement distinguishes pathological non-compaction from normal trabeculation with high specificity and sensitivity. 

2. Jenni’s Echocardiographic Criterion

On echocardiography, some criteria (e.g., Jenni et al.) define LVNC by a NC:C ratio > 2.0 measured at end-systole in the parasternal short-axis view. 

3. Alternate Imaging Thresholds and Modalities

Computed tomography criteria have proposed a NC:C ratio ≥ 1.8 at end-diastole as discriminating LVNC from normal hearts. 

Some refined CMR approaches also consider segmental thresholds, where a NC:C ≥ 3:1 in non-apical segments offers excellent sensitivity and specificity when combined with other measurements like trabeculated LV mass. 

Why Timing and Modality Matter

Measurements are phase-dependent:

CMR Petersen’s criteria use diastolic images for optimal layer delineation. 

Echocardiographic ratios are more often reported in end-systole to improve layer distinction. 

Strengths and Limitations of NC:C Ratio

The NC:C ratio is simple and quantitative, but has limitations:

Marked trabeculation can be found in individuals without cardiomyopathy, especially athletes and some ethnic groups. 

Different imaging modalities and measurement standards yield varying cut-offs, so correlation with clinical and functional findings remains important. 

Summary of Typical Cut-Offs

Modality Measurement Phase NC:C Diagnostic Threshold

CMR (Petersen) End-diastole >2.3:1 

Echocardiography (Jenni) End-systole >2:1 

CT (Low-dose) End-diastole ≥1.8:1 

CMR Segmental criteria End-diastole ≥3:1 in specified segments 

Conclusion

The NC:C compaction ratio remains a pivotal quantitative tool in diagnosing LVNC, with typical thresholds of >2.3 in diastole by CMR and >2 in systole by echocardiography forming the basis of many established diagnostic criteria. However, interpretation should be integrated with clinical context and other imaging findings due to overlapping features with normal variants and other cardiomyopathies.