Development and prevention of ischemic contracture ("stone heart") in the pig heart

Mei Li; Zhi Qin; Erik Steen; Ann Terry; Bowen Wang; Björn Wohlfart; Stig Steen; Anders Arner

doi:10.3389/fcvm.2023.1105257

Development and prevention of ischemic contracture ("stone heart") in the pig heart

Front Cardiovasc Med. 2023 Feb 20:10:1105257. doi: 10.3389/fcvm.2023.1105257. eCollection 2023.

Authors

Mei Li^{1

2}, Zhi Qin², Erik Steen², Ann Terry³, Bowen Wang², Björn Wohlfart¹, Stig Steen¹, Anders Arner¹

Affiliations

¹ Department of Clinical Sciences, Lund, Lund University, Lund, Sweden.
² Igelösa Life Science AB, Lund, Sweden.
³ MAX IV Laboratory, Lund University, Lund, Sweden.

Abstract

Stone heart (ischemic contracture) is a rare and serious condition observed in the heart after periods of warm ischemia. The underlying mechanisms are largely unknown and treatment options are lacking. In view of the possibilities for cardiac donation after circulatory death (DCD), introducing risks for ischemic damage, we have investigated stone heart in pigs. Following cessation of ventilation, circulatory death (systolic pressure <8 mmHg) occurred within 13.1 ± 1.2 min; and a stone heart, manifested with asystole, increased left ventricular wall thickness and stiffness, established after a further 17 ± 6 min. Adenosine triphosphate and phosphocreatine levels decreased by about 50% in the stone heart. Electron microscopy showed deteriorated structure with contraction bands, Z-line streaming and swollen mitochondria. Synchrotron based small angle X-ray scattering of trabecular samples from stone hearts revealed attachment of myosin to actin, without volume changes in the sarcomeres. Ca²⁺ sensitivity, determined in permeabilized muscle, was increased in stone heart samples. An in vitro model for stone heart, using isolated trabecular muscle exposed to hypoxia/zero glucose, exhibited the main characteristics of stone heart in whole animals, with a fall in high-energy phosphates and development of muscle contracture. The stone heart condition in vitro was significantly attenuated by the myosin inhibitor MYK-461 (Mavacamten). In conclusion, the stone heart is a hypercontracted state associated with myosin binding to actin and increased Ca²⁺ sensitivity. The hypercontractile state, once developed, is poorly reversible. The myosin inhibitor MYK-461, which is clinically approved for other indications, could be a promising venue for prevention.

Keywords: Ca2+-sensitivity; Mavacamten; donation after circulatory death (DCD); ischemic contracture; stone heart; transplantation.

Grants and funding

This study was supported by grants from the Hans-Gabriel and Alice Trolle-Wachtmeisters Foundation. The electron microscopy was performed at the Microscopy Facility at Department of Biology, Lund University with excellent help from Ola Gustafsson. The experiments with small angle X-ray diffraction were performed at the CoSAXS beamline, MAX IV Laboratory, Lund, and supported by a beam-time grant.