The effect of excessive trabeculation on cardiac rotation-A multimodal imaging study

Abstract

Background: Cardiac rotational parameters in primary symptomatic left ventricular noncompaction (LVNC) with preserved left ventricular ejection fraction (LVEF) are not well understood. We aimed to analyze cardiac rotation measured with cardiac magnetic resonance feature-tracking (CMR-FT) and speckle-tracking echocardiography (Echo-ST) in LVNC morphology subjects with preserved LVEF and different genotypes and healthy controls.

Methods: Our retrospective study included 54 LVNC subjects with preserved LVEF and 54 control individuals. We evaluated functional and rotational parameters with CMR in the total study population and with echocardiography in 39 LVNC and 40 C individuals. All LVNC subjects were genotyped with a 174-gene next-generation sequencing panel and grouped into the subgroups: benign (B), variant of uncertain significance (VUS), and pathogenic (P).

Results: In comparison with controls, LVNC subjects had reduced apical rotational degree (p = 0.004) and one-third had negative apical rotation. While the degree of apical rotation was comparable between the three genetic subgroups, they differed significantly in the direction of apical rotation (p<0.001). In contrast to control and B groups, all four studied cardiac rotational patterns were identified in the P and VUS subgroups, namely normal rotation, positive and negative rigid body rotation, and reverse rotation. When the CMR-FT and Echo-ST methods were compared, the direction and pattern of cardiac rotation had moderate to good association (p<0.001) whereas the rotational degrees showed no reasonable correlation or agreement.

Conclusion: While measuring cardiac rotation using both CMR-FT and Echo-ST methods, subclinical mechanical differences were identified in subjects with LVNC phenotype and preserved LVEF, especially in cases with genetic involvement.

Fig 1. Cardiac rotational patterns.

The normal cardiac rotational pattern is characterized by negative or CW basal and positive or CCW apical peak end-systolic rotation, and the reverse cardiac rotation is represented by positive or CCW basal and negative or CW apical rotation. RBR is defined by rotating the basal and apical parts in the same direction in a single patient: positive RBR when this rotation is positive, and negative RBR when it is negative. CCW = counterclockwise, CW = clockwise, RBR = rigid body rotation.

Fig 2

Presenting the imaging modalities used for functional analysis: CMR TB technique (1a), four-chamber CMR (1b) and echocardiography images (1c) and the rotational measurements with Echo-ST (2) and CMR-FT (3) methods at basal (2a,3a) and apical (2b,3b) segments. 1. Due to the different signal intensities, the TB algorithm (a) can differentiate the myocardial tissue from the blood volume on CMR SA images and marks it with green color within the green LV epicardial contour (LVTMi). The myocardial tissue (green) recognized within the red LV endocardial contour represents the LVTPMi. Apical LV hypertrabeculation could also be observed on four-chamber view CMR (b) and four-chamber view transthoracic 2D echocardiographic images (c) with prominent trabecular meshwork and deep intertrabecular recesses. 2,3. The interfaces of the CMR-FT and Echo-ST postprocessing software are very similar. The normal rotational pattern, which is presented on a healthy control individual’s Echo-ST images (2), is characterized by negative or CW basal (2a) and positive or CCW apical (2b) rotation. Negative RBR is frequently described in hypertrabeculation with negative or CW basal (3a) and apical (3b) rotation, which is illustrated on CMR-FT images of a VUS genotype LVNC morphology subject. CMR = cardiac magnetic resonance imaging, TB = threshold-based method, Echo-ST = speckle-tracking echocardiography, CMR-FT = CMR feature-tracking method, SA = short-axis, LV = left ventricle, LVTMi = left ventricular total myocardial mass index, LVTPMi = left ventricular trabeculated and papillary muscle mass index, CW = clockwise, CCW = counterclockwise, RBR = rigid body rotation, VUS = variant of unknown significance, LVNC = left ventricular noncompaction.

Fig 3

Cardiac rotational patterns in LVNC subjects with B, VUS and P genotypes and control individuals measured with CMR-FT (a) and Echo-ST (b) methods. LVNC = left ventricular noncompaction, B = benign, VUS = variant of uncertain significance, P = pathogenic, CMR-FT = cardiac magnetic resonance imaging feature-tracking method, Echo-ST = speckle-tracking echocardiography, RBR = rigid body rotation.

Fig 4. Comparison of the CMR-FT and Echo-ST rotation degrees in the LVNC and C groups–correlation and Bland-Altman plots with bias and LOA.

CMR-FT = cardiac magnetic resonance imaging feature-tracking method, Echo-ST = speckle-tracking echocardiography, LVNC = left ventricular noncompaction, C = control group, LOA = limit of agreement.