Ultrafast ultrasound shear wave elastography: a novel approach for assessing myocardial stiffening in congenital aortic stenosis

Abstract Introduction Congenital aortic stenosis (ConAoS) accounts for 4-8% of all congenital heart diseases. Left ventricular (LV) diastolic dysfunction has been known as an undesirable consequence of severe pressure overload in ConAoS, as the LV becomes hypertrophied to compensate LV afterload and to normalize wall stress. Several studies suggest that advanced grades of diastolic dysfunction are associated with increased mortality and adverse events even after aortic valve replacement (AVR). Current echocardiographic parameters do not always provide a reliable representation of LV diastolic dysfunction. Ultrafast ultrasound, with its high temporal resolution (>500-1000 frames/s), enables the visualization of rapidly propagating shear waves in the myocardium. Shear waves are mechanical waves that can originate from intrinsic cardiac events such as closure of the aortic valve. As shear wave propagation velocity is directly dependent on myocardial stiffness, shear wave elastography (SWE) represents a novel, non-invasive technique for assessing LV diastolic dysfunction. Purpose This study aimed to investigate the feasibility of SWE in a clinical population with ConAoS and to assess the differences compared to healthy subjects. Methods In 68 patients with ConAoS and 19 healthy volunteers high-frame-rate images were acquired in the parasternal long axis view. The images were processed with in-house developed software to calculate the shear wave velocity (SWV) along manually placed M-lines through the interventricular septum after closure of the aortic valve. In all ConAoS patients cardiac magnetic resonance was performed. Results Shear wave elastography demonstrated an overall feasibility of 75% with a lower feasibility of 68% in patients. Significantly higher SWVs were observed in patients with moderate to severe aortic stenosis (AS) compared to healthy subjects with values of 4.7 [3.4-5.6] and 3.4 [3.0-4.4], respectively. Patients with mechanical valves demonstrated a lower feasibility of 53% and SWVs within similar range as controls. Conclusion SWE using ultrafast ultrasound is a promising new technique for the non-invasive assessment of LV diastolic dysfunction. Although further improvement is needed to reduce measurement variability, SWE is feasible in the majority of a clinical patient population. SWV represents a potential novel biomarker for the assessment of myocardial stiffening and may improve early detection in patients with ConAoS.