Laurine Wouters

Wouters L, et al. Korean Circ J. 2025 Dec;56:e32. https://doi.org/10.4070/kcj.2025.0420

Cardiac shear wave elastography (SWE) is a non-invasive technique to assess myocardial stiffness, based on the speed of waves that travel through the heart after valve closure. The wave physics underlying natural SWE remains incompletely understood. Therefore, we investigated the impact of wave excitation sources on 3 wave propagation aspects – wave amplitude (determined as wave acceleration magnitude), temporal wave width and speed. SWE was applied to 17 patients with aortic stenosis (AS), 13 AS patients that underwent transcatheter aortic valve implantation (TAVI), 10 AS patients that underwent surgical aortic valve replacement (AVR) and 18 age-matched healthy volunteers (HV). Absolute wave acceleration was lower in AS, TAVI and AVR patients compared to HV (1.5±0.60 vs 2.8±1.1 m/s²; p=0.001; 1.6±0.78 vs 2.8±1.1 m/s²; p=0.010; 1.7±0.66 vs 2.8±1.1 m/s²; p=0.015). Wave acceleration amplitude (measured as negative peak acceleration of the tissue) correlated with wave speed (r=0.388; p=0.003), implying that absolute wave acceleration is smaller in a stiffer heart. Subgroup analysis showed that the correlation between wave peak acceleration and speed is less steep in AS patients vs. HV (slopes: 0.23 vs 0.47 s). This implies that stenotic valves generate a wave with a lower acceleration magnitude compared to native valves. Further, temporal wave width was lower in TAVI patients vs. HV (8.7±2.3 vs 12.5±3.0 ms; p=0.002) and there was no difference in wave speed after aortic valve closure (AVC) between the groups. To conclude, wave acceleration magnitude and width offer additional insights into SWE physics next to wave speed and should be verified in a larger cohort.

Most clinical studies use a 2D parasternal long-axis view to measure natural shear waves after valve closure for myocardial stiffness assessment. However, its 3D wave propagation direction and its alignment with the 2D imaging plane are not well understood. Previous 3D research has mainly focused on wave propagation from an apical view, primarily tracking the longitudinal component of wave motion instead of the transverse component observed in the parasternal view. Therefore, this work aims to bridge this gap by using 3D high-frame-rate imaging in the parasternal view in 6 healthy volunteers (~750 volumes/s), and compared its results to 2D measurements (~1000 frames/s). We found a more complex wave propagation pattern after mitral valve closure encompassing two wave excitation sources, whereas the wave propagation after aortic valve closure clearly originated near the left ventricular outflow tract. The extent of the wave excitation region varied across volunteers. For the septal wall – tracked in 2D shear wave imaging, the overall wave propagation was from base to apex, which is theoretically in line with the 2D imaging plane orientation. However, wave speed estimations were lower for 3D measurements than for 2D (-0.7 m/s for mitral valve and -0.5 m/s for AVC, on average), potentially due to misalignment of the 2D imaging plane with the longitudinal direction of the heart.

Background and aim: The presence of mechanical dyssynchrony on echocardiography is associated with reverse remodelling and decreased mortality after cardiac resynchronization therapy (CRT). Contrarily, myocardial scar reduces the effect of CRT. This study investigated how well a combined assessment of different markers of mechanical dyssynchrony and scarring identifies CRT responders. Methods: In a prospective multicentre study of 170 CRT recipients, septal flash (SF), apical rocking (ApRock), systolic stretch index (SSI), and lateral-to-septal (LW-S) work differences were assessed using echocardiography. Myocardial scarring was quantified using cardiac magnetic resonance imaging (CMR) or excluded based on a coronary angiogram and clinical history. The primary endpoint was a CRT response, defined as a ≥15% reduction in LV end-systolic volume 12 months after implantation. The secondary endpoint was time-to-death. Results: The combined assessment of mechanical dyssynchrony and septal scarring showed AUCs ranging between 0.81 (95%CI: 0.74–0.88) and 0.86 (95%CI: 0.79–0.91) for predicting a CRT response, without significant differences between the markers, but significantly higher than mechanical dyssynchrony alone. QRS morphology, QRS duration, and LV ejection fraction were not superior in their prediction. Predictive power was similar in the subgroups of patients with ischemic cardiomyopathy. The combined assessments significantly predicted all-cause mortality at 44 ± 13 months after CRT with a hazard ratio ranging from 0.28 (95%CI: 0.12–0.67) to 0.20 (95%CI: 0.08–0.49). Conclusions: The combined assessment of mechanical dyssynchrony and septal scarring identified CRT responders with high predictive power. Both visual and quantitative markers were highly feasible and demonstrated similar results. This work demonstrates the value of imaging LV mechanics and scarring in CRT candidates, which can already be achieved in a clinical routine.