Shall a pilot with left ventricular hypertrabeculation/noncompaction fly passengers?

Quantification of left ventricular trabeculae using fractal analysis

BACKGROUND

Left ventricular noncompaction (LVNC) is a myocardial disorder characterized by excessive left ventricular (LV) trabeculae. Current methods for quantification of LV trabeculae have limitations. The aim of this study is to describe a novel technique for quantifying LV trabeculation using cardiovascular magnetic resonance (CMR) and fractal geometry. Observing that trabeculae appear complex and irregular, we hypothesize that measuring the fractal dimension (FD) of the endocardial border provides a quantitative parameter that can be used to distinguish normal from abnormal trabecular patterns.

METHODS

Fractal analysis is a method of quantifying complex geometric patterns in biological structures. The resulting FD is a unitless measure index of how completely the object fills space. FD increases with increased structural complexity. LV FD was measured using a box-counting method on CMR short-axis cine stacks. Three groups were studied: LVNC (defined by Jenni criteria), n=30(age 41±13; men, 16); healthy whites, n=75(age, 46±16; men, 36); healthy blacks, n=30(age, 40±11; men, 15).

RESULTS

In healthy volunteers FD varied in a characteristic pattern from base to apex along the LV. This pattern was altered in LVNC where apical FD were abnormally elevated. In healthy volunteers, blacks had higher FD than whites in the apical third of the LV (maximal apical FD: 1.253±0.005 vs. 1.235±0.004, p<0.01) (mean±s.e.m.). Comparing LVNC with healthy volunteers, maximal apical FD was higher in LVNC (1.392±0.010, p<0.00001). The fractal method was more accurate and reproducible (ICC, 0.97 and 0.96 for intra and inter-observer readings) than two other CMR criteria for LVNC (Petersen and Jacquier).

CONCLUSIONS

FD is higher in LVNC patients compared to healthy volunteers and is higher in healthy blacks than in whites. Fractal analysis provides a quantitative measure of trabeculation and has high reproducibility and accuracy for LVNC diagnosis when compared to current CMR criteria.

[Isolated noncompaction cardiomyopathy with special emphasis on arrhythmia complications]

Isolated noncompaction cardiomyopathy (NCCM) is a rare genetically determined myocardial disease caused by abnormal fetal development of the myocardium resulting in a thin compacted and a thicker noncompacted layer of the affected left ventricular (LV) wall. The genetic basis of NCCM is heterogenous. Diagnosis can be made using echocardiography or magnetic resonance imaging. The diagnostic criteria for NCCM are still under discussion. Afflicted patients may present with various symptoms caused by arrhythmias, heart failure and cardioembolic events. Severely reduced LV function as well as left bundle branch block and atrial fibrillation were shown to be linked to worse outcomes. Treatment in patients with NCCM should be targeted at individual symptoms and clinical findings. Therapy includes pharmacological treatment, and in individual cases ablation or device therapy, as well as consideration for heart transplantation in selected cases. Aside from regular clinical follow-up of patients with NCCM screening of first degree family members with assessment of medical history, physical examination, ECG recording, and echocardiography are recommended.

Refinement of echocardiographic criteria for left ventricular noncompaction

BACKGROUND

Left ventricular hypertrabeculation/noncompaction (LVNC) is a cardiac abnormality whose echocardiographic criteria are still controversial. Cooperation between echocardiographic laboratories may contribute to uniformly accepted criteria, as illustrated by the following pilot study.

METHODS AND RESULTS

Echocardiograms proposed for inclusion into a registry were reviewed. Three experts with 17-26 years experience with LVNC agreed on a common definition of LVNC: 1. >3 prominent trabeculous formations along the left ventricular endocardial border visible in end-diastole, distinct from papillary muscles, false tendons or aberrant bands; 2. trabeculations move synchronously with the compacted myocardium, 3. trabeculations form the noncompacted part of a two-layered myocardial structure, best visible at end-systole; and 4. perfusion of the intertrabecular spaces from the ventricular cavity is present at end-diastole on color-Doppler echocardiography or contrast echocardiography. During 3 sessions 115 cases (37% females, mean 57 years) were reviewed. Eleven patients (18% females, mean 60 years) were excluded because of <4 trabeculations (n=5), lack of a two-layered myocardial structure (n=1) and poor image quality (n=5). The observers agreed on inclusion or exclusion in all cases. Consensus was achieved that measurements of the thickness of the myocardial layers, and calculation of the noncompacted:compacted ratio is not feasible due to a lack of uniformly accepted standards for measurements.

CONCLUSIONS

When diagnosing LVNC, end-systolic as well as end-diastolic images have to be considered. The presence of more than three trabeculations as well as a two-layered myocardium are required. Since these criteria are not anatomically controlled, a comparison of echocardiographic images with pathoanatomic findings for assessing sensitivity and specificity is urgently needed.