Impact of loading, heart rate, and short episodes of ischaemia on myocardial stiffness assessed using shear wave elastography in an open-chest animal model.

Abstract

Aims: Shear wave elastography (SWE) is a new promising ultrasound modality that enables non-invasive measurement of the dynamic myocardial stiffness. The impact of varying physiological conditions on SWE measurement of left ventricular (LV) myocardial stiffness remains poorly investigated.

Methods and results: Nineteen sheep were evaluated during open-chest surgery. Epicardial multiframe SWE acquisitions were performed in short-axis view simultaneously with haemodynamic acquisitions during inferior vena cava occlusion, aortic clamping, atrial pacing, and ischaemia-reperfusion. The cyclic variation in the median value of LV myocardial stiffness ranged from 1.1 m/s in diastole (C_min) to 2.4 m/s in systole (C_max). At steady state, intra-animal reproducibility was good for C_min [intraclass correlation coefficient ICC = 0.77 (0.54, 0.90), P < 0.001] and C_max [ICC = 0.92 (0.84, 0.96), P < 0.001]. C_min was independent of loading conditions, heart rate, and short 15-minute episodes of ischaemia and reperfusion. C_max was independent of loading conditions and moderate increase in heart rate but decreased significantly during ischaemia and reperfusion. Compared with baseline, percentage changes in C_max was correlated to percentage changes in dP/dt_max (R = 0.47, P = 0.001) and in LV systolic pressure (R = 0.35, P = 0.013) and SW (R = 0.31, P = 0.026).

Conclusion: In this study, LV diastolic myocardial stiffness C_min assessed using SWE demonstrated the characteristics of a potentially useful clinical marker of LV diastolic function linked to the intrinsic elastic properties of the myocardium, whereas C_max was an indicator of LV contractility.