Capturing complex right ventricular wall motion abnormalities in arrhythmogenic right ventricular cardiomyopathy by combining longitudinal and radial myocardial dynamics in feature-tracking MRI

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): INSERM Liliane Bettencourt doctoral grant

Background

Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) is ass­­ociated with complex spatial and temporal right ventricular (RV) wall motion abnormalities. While cardiac magnetic resonance (CMR) is the gold-standard imaging technique, its diagnosic performance remains suboptimal and additional CMR biomarkers reflecting ARVC pathophysiology are needed.

Purpose

To evaluate the performance of a CMR feature-tracking (FT)-derived parameter combining both longitudinal and radial RV deformation and motion for the characterization of RV wall motion abnormalities in ARVC.

Methods

Thirty-nine patients with definite or borderline ARVC (median age 45 years, interquartile range 31–51, 56% males) were compared to 20 healthy controls with comparable age, sex and weight distributions. All subjects had 1.5T CMR including short axis and 4-chamber views steady-state free precession acquisitions. A custom FT software adapted to RV wall segmentation and tracking was used to assess RV wall deformation and motion in the 3 space directions resulting in: 1) global longitudinal strain (GLS) estimated on the 4 chamber view from the RV free wall, 2) basal circumferential strain (BCS) and radial motion fraction (BRMF) estimated as an average of short-axis slices comprised in the RV third basal portion. To capture the complex RV motion in ARCV, a longitudinal to radial strain loop (LRSL) was displayed and its area was calculated.

Results

The ARVC group comprised 28 (72%) patients with definite and 11 (28%) with borderline diagnosis . As compared to controls, LVEF and RVEF were significantly lower in ARVC patients (61(interquartile range (IQR) 52-71) vs. 71%(IQR 55-88) , p = 0.03 and 47%(IQR 16-63) vs. 57%(IQR 49-63) , p = 0.02, respectively), LVEF remaining within normal range limits. While there was no significant difference in RV GLS between ARVC patients and controls (median -17.7%(IQR -24–15) vs. -17.5%(IQR -20.1–15.2), p = 0.67) , BCS and BRMF were significantly lower in ARVC patients vs. controls [-7.5%(IQR -12.3–8.4.) vs. -9.8%(IQR -13.8–8.6.), p = 0.004 and -12.2(IQR -14.4–8.7.) vs. -14.9%(IQR -16.6–13.2) p = 0.0007, respectively] . The LRSL area was significantly and markedly lower in ARVC patients vs. controls [70.6 (IQR 16.3-63.1) vs. 144.1 (IQR 110.4-251.3), p = 0.0002] . LRSL area outperformed RVEF, BCS and BRS in separating ARVC from controls (area under receiving operator characteristics curve 0.82 vs. 0.78, 0.73 and 0.78, respectively).

Conclusion

In ARVC, a FT-derived parameter combining longitudinal and radial RV wall deformation and motion provided better discrimination of ARVC patients from controls than conventional FT measurements. Its implementation in clinical practice may bolster CMR performance to characterize ARVC wall motion abnormalities.

Abstract Figure

Wave decomposition applied to LA phasic longitudinal strain evaluated from MRI feature tracking to estimate a true LA booster strain index

Funding Acknowledgements

Type of funding sources: None.

Background. Feature tracking (FT) is an emerging approach for the evaluation of both left atrium (LA) and left ventricular (LV) myocardial strain from the same cine MRI dataset. We hypothesized that the LA active contraction longitudinal strain, is a merge of an intrinsic LA booster contraction with the early diastolic LA emptying, especially when this latter is extended because of a poor LV relaxation (Figure 1, bottom). Such index can be estimated through LA phasic strain wave-decomposition as conventionally done for pressure curves to estimate forward and reflected components.

Purpose. To compare the newly proposed LA intrinsic or "true" booster index (Sla_fit) against the conventional index (Sla) in terms of associations with LV remodeling (LV mass/ LV volume), LV systolic longitudinal strain (LV_GLS), and transmitral LV filling indices in healthy controls and aortic valve stenosis (AVS) patients with preserved LV ejection fraction.

Methods. We studied 55 patients (34 AVS:71 ± 11years, 21 controls:66 ± 9years) who had an MRI exam with cine SSFP and phase contrast (PC) images. FT was applied to cine images to extract LV and LA phasic longitudinal strain and strain rates. Transmitral flow early (E, cm/s) and late (A, cm/s) filling peak velocities were calculated from PC data. To estimate intrinsic LA booster index, the LA longitudinal strain curve corresponding to the reservoir and conduit phases was fitted using two half cosine waves, to account for an eventual LA filling to LA early emptying asymmetry, while fitting the LA contraction with a full cosine wave (Figure 1). The peak of this latter wave was defined as the intrinsic LA booster strain index (Sla_fit), while the second peak of the measured LA strain was defined as the conventional LA booster strain (Sla).

Results. While conventional Sla was significantly higher than intrinsic LA booster Sla_fit in AVS patients (13.55 ± 4.26 vs. 8.09 ± 6.07, p = 0.0002), it was nearly equivalent in controls (14.34 ± 4.30 vs.13.43 ± 4.23, p =.49). But the newly proposed LA booster strain index was significantly related to LV_GLS (r=-48,p=.0004); to LV remodeling (r=-.44,p = 0.0012) as well as to transmitral flow A wave ( r=-.49, p=.0005) none of these associations were significant when considering conventional LA booster strain. Interestingly our intrinsic LA booster index Sla_fit was significantly associated with LV longitudinal strain in both controls (r=-.55,p = 0.009) and asymptomatic AVS (N = 10) (r=-.77,p = 0.0081) but not in symptomatic AVS (N = 24) (p>.70). This may reveal a maintained LA-LV coupling in the asymptomatic phase and an uncoupling in the symptomatic phase, caused by elevated LV filling pressures.

Conclusions. A promising index for the quantitative evaluation of intrinsic LA booster function was proposed and its consistency was demonstrated through its significant associations with LV remodeling, LV longitudinal strain and transmitral late filling peak.

Abstract Figure.