Using Shear Wave Elastography to Characterise Ischaemic Contracture in Rodent Hearts

Abstract

Introduction: Shear wave elastography (SWE) quantifies stiffness by measuring the conduction velocity of sound waves through tissue. We hypothesised that SWE would be able to demonstrate global stiffness changes in both warm and cold isolated ischaemic hearts. Methods: Part 1 Hearts (n = 8) were explanted from anaesthetised male Sprague Dawley rats (300–400 g). Hearts were flushed with KH and immersed in a 37 °C KH bath. Organs were scanned at regular intervals to determine stiffness over 35 minutes. Part 2 Rats (n = 14) were anaesthetised, hearts excised and baseline function assessed at 37 °C on a Langendorff apparatus. After 10 minutes, hearts were flushed and stored at 4 °C with either KH (n = 6) or 4 °C STS (n = 8), and scanned for stiffness at regular intervals. Hearts were then reperfused and assessed for function. Results: Part 1 Hearts increased in stiffness over 35 mins (p = < 0.005). There was a relatively linear increment in stiffness of 0.28 m/sec/min between 13 and 28 minutes. (Fig. 1) Part 2 More hearts recovered rhythmic contraction after STS storage than KH (p = 0.06). There was no difference in stiffness between KH and STS hearts at the commencement of ischaemia (p = 0.23) or the end (p = 0.74). There was no stiffness difference in hearts that did recover compared with those that did not, at the beginning (p = 0.877) or end of ischaemia (p = 0.168). Conclusion: SWE demonstrates changes in stiffness over time in warm ischaemic hearts. This may be of use in assessing hearts donated after circulatory death. SWE could not discriminate on the basis of stiffness between preservation solution or functional recovery for cold ischaemic hearts.