Comparison of biplane manual, automated volumetric and MRI methods for assessment of left ventricle volumes and function in a series of three left ventricle non-compaction patients

Non-compaction of the ventricular myocardium (LVNC) is a rare genetically determined heart defect. The disease is most frequently detected during accidental echocardiography. There is no golden rule examination for LVNC diagnosis. In our study, we aimed to compare the measurements of the left ventricle volumes and function obtained with the two-dimensional, and three-dimensional echo based on the results from MR imaging in a series of three left ventricle non-compaction cardiomyopathy patients. and multi-beat electrocardiography-gated volumetric analysis from apical view was performed. The three-dimensional pyramidal volume was reduced from an initial 90 ◦ x 90 ◦ angle to achieve a temporal resolution of 20 volumes per second. Moreover, we have characterized myocardial displacement using global, circumferential, and radial strains presenting values for the endocardial layer. We present circumferential and radial strains measured at mid-cavity.


Introduction
Non-compaction of the ventricular myocardium (LVNC) is a genetically determined heart defect, sometimes co-occurring with congenital heart defects (1). The multiple excessively prominent trabeculations and deep inter-trabecular recesses within the left ventricle myocardium characterize this rare cardiomyopathy (2). During fetal growth, the heart develops from a linear myocardial tube lined by the endocardium. The construction is then reminiscent of a mesh composed of muscle bers and divided by inter-trabecular recesses. These recesses communicate with the chamber cavity. However, after the formation of coronary circulation, the ventricular myocardium begins to undergo the process of compaction, and the recesses transform into capillaries. Consecutively, between 6 and eight weeks of fetal age, trabeculations should begin to merge, starting from the base of the heart to the apex and from epi-to endocardium (2,3). Among patients with LVNC, this process is disturbed and results in multiple deep trabeculations within the left ventricular myocardium (2,3). The disease is most frequently detected during accidental echocardiography. There is no golden rule examination for LVNC diagnosis. Jenni et al. criteria are the most common (4). Among the essential features in echocardiography, we can distinguish: 1) thick, double-layer myocardium composed of a compacted layer (C) and non-compacted endocardial layer (NC) with deep recesses; 2) maximum end-systolic NC/C indicator > 2; 3) the recesses between the trabeculations are deeply perfused, and this is visible in color-coded Doppler imaging; 4) The non-compacted layer predominates in apical, and at mid-cavity segments (2,3).
Various echocardiographic methods of assessment of ejection fraction have been compared to magnetic resonance imaging (MRI), and there is no doubt that the 3D echo, with optimal image quality, offers the closest approximation to the quantities coming from MRI. There are also data about the limited value of 3D echo among patients with decreased ejection fraction, and when the endocardial border between compacted myocardium and the LV cavity is not well de ned (5). In our study, we aimed to compare the measurements of the left ventricle volumes and function obtained with the 2D and 3D echo based on the results from MR imaging.

Materials And Methods
We have performed left ventricle volumes and function assessment using echocardiography and magnetic resonance imaging in three left ventricle non-compaction cardiomyopathy patients. For echocardiographic assessment, we have used Siemens Acuson SC2000 Prime machine equipped with 4Z1c, and 4V1c transducers and integrated software packages Left Ventricle Analysis (LVA) and Vector Velocity Imaging (VVI). Automated left ventricle volumes, and function analysis software derives from different physical properties and different abilities of solid tissues, blood, pericardial uid, and air to re ect ultrasound. It segments the borders after setting a threshold of echo intensity with blood as reference. The endocardial contour is automatically traced from equidistant points on the border of blood and tissue. Transthoracic echocardiographic examination was started up with two-dimensional acquisition following standard views, then multi-beat electrocardiography-gated volumetric analysis from apical view was performed. The three-dimensional pyramidal volume was reduced from an initial 90• x 90• angle to achieve a temporal resolution of 20 volumes per second. Moreover, we have characterized myocardial displacement using global, circumferential, and radial strains presenting values for the endocardial layer. We present circumferential and radial strains measured at mid-cavity.

Cases presentation
Patient # 1-44-year-old female, presenting with ventricular arrhythmia. She had two ablations with no clinical improvement. In a 7-day long ECG Holter monitoring, ventricular premature beats formed 20% of all analyzed complexes. She has not had any symptoms of heart failure. Non-compacted myocardium was present in apex, apical, and latero-medial segments. The proportion of thickness of non-compacted to compacted layers exceeded 2.3 in MRI.
Patient # 2-54-year old male admitted to the hospital with symptomatic heart failure. The patient's medical history was irrelevant. Magnetic resonance imaging has disclosed non-compaction cardiomyopathy with intensi ed trabeculation distributed diffusely in the left ventricle. The proportion of thickness of non-compacted to compacted layers exceeded 2.9. The patient has an implantable cardioverter/de brillator implanted.
Patient # 3-43-year old female presented with severely decompensated heart failure. In the electrocardiogram left bundle branch block was present. Coronary angiography revealed healthy coronary arteries. Cardiac MRI revealed a non-compacted myocardium in the anterior, posterior, inferior, and lateral walls of the left ventricle. The proportion of thickness of non-compacted to compacted layers exceeded 3.6. The patient has a CRTD implanted.
Written informed consent for publication of their clinical details and/or clinical images was obtained from the patients.

Results And Discussion
Three-dimensional real-time echocardiography (3DRTE) with automated volumetric analysis of left ventricle volumes and function has revealed substantially higher volumes (up to 34%) in comparison with two-dimensional biplane measurement, yet not as high as observed in magnetic resonance imaging (Table 1). 3DRTE assessment of left ventricle volumes and function is free of errors resulting from geometrical assumptions of manual biplane measurements. Moreover, the algorithm employed for automated tracking of the blood -endocardium border seems to have particular applicability in the assessment of left ventricle volumes and function in patients with non-compacted myocardium. As the phenotype of LVNC is highly heterogeneous with different proportions of compacted to non-compacted myocardium, the different architecture of trabeculae and recesses, manual tracking of the endocardial border may often be challenging. 3D transducer visualizes the complex morphology of the noncompacted layer (6) simultaneously and facilitates precise segmenting of the left ventricle cavity border at the bottom of recesses (Fig. 1). Results of left ventricle volume and function assessment in our patients indicate its dilation with varying degrees of dysfunction (7)(8)(9). The underestimation of left ventricle end-diastolic and end-systolic volumes by two-dimensional or three-dimensional echocardiography in comparison to magnetic resonance imaging is already documented (9). A comparison of left ventricle volumes and function assessed with two-and three-dimensional echocardiography in healthy subjects indicates comparable results (7,9). However, left ventricle assessment in a pediatric population with three-dimensional vendor-speci c (QLab), and vendor-independent (TomTec 30 , TomTec 75 ) software provided information on substantial intertechnique variability (10).
The strain enables one to recognize the mechanism of contractility and plays a signi cant role in early detection of subclinical left ventricular dysfunction, before a decline in ejection fraction. All our patients have signi cantly reduced global longitudinal, circumferential, and radial strains in comparison to reference values reported for the NORRE (Normal Reference Ranges for Echocardiography) healthy population (11). The reduced deformation of non-compacted myocardium has been reported at the very early age of LVNC in the pediatric population (12). Comparing the subpopulation of pediatric patients, who survived with a subpopulation of patients who died or were transplanted, the latter has a signi cantly lower strain in all segments (12).

Conclusion
Real-time three-dimensional echocardiography with automated left ventricle analysis offers more information on the assessment of left ventricle in patients with left ventricle non-compaction in comparison to two-dimensional echocardiography. Speckle tracking analysis may add prognostic information in this speci c group of patients.

Declarations
Ethics approval and consent to participate Ethical Board of Medical University of Silesia waived the approval.

Consent for publication
Written informed consent for publication of their clinical details and/or clinical images was obtained from the patients.

Availability of data and materials
We declare the availability of complete data and materials.

Competing interests
We declare no competing interests.

Funding
Study has no funding.