Development of a pro-arrhythmic ex vivo intact human and porcine model: cardiac electrophysiological changes associated with cellular uncoupling

Abstract

We describe a human and large animal Langendorff experimental apparatus for live electrophysiological studies and measure the electrophysiological changes due to gap junction uncoupling in human and porcine hearts. The resultant ex vivo intact human and porcine model can bridge the translational gap between smaller simple laboratory models and clinical research. In particular, electrophysiological models would benefit from the greater myocardial mass of a large heart due to its effects on far-field signal, electrode contact issues and motion artefacts, consequently more closely mimicking the clinical setting. Porcine (n = 9) and human (n = 4) donor hearts were perfused on a custom-designed Langendorff apparatus. Epicardial electrograms were collected at 16 sites across the left atrium and left ventricle. A total of 1 mM of carbenoxolone was administered at 5 ml/min to induce cellular uncoupling, and then recordings were repeated at the same sites. Changes in electrogram characteristics were analysed. We demonstrate the viability of a controlled ex vivo model of intact porcine and human hearts for electrophysiology with pharmacological modulation. Carbenoxolone reduces cellular coupling and changes contact electrogram features. The time from stimulus artefact to (-dV/dt)max increased between baseline and carbenoxolone (47.9 ± 4.1–67.2 ± 2.7 ms) indicating conduction slowing. The features with the largest percentage change between baseline and carbenoxolone were fractionation + 185.3%, endpoint amplitude − 106.9%, S-endpoint gradient + 54.9%, S point − 39.4%, RS ratio + 38.6% and (-dV/dt)max − 20.9%. The physiological relevance of this methodological tool is that it provides a model to further investigate pharmacologically induced pro-arrhythmic substrates.

Development of a cardiovascular magnetic resonance‐compatible large animal isolated heart model for direct comparison of beating and arrested hearts

“…Future studies may include investigation of the effectiveness of motion compensation provided by the STEAM sequence by comparing the phase images between equivalent beating and arrested heart data, in a manner similar to Stoeck et al 47 Beyond the investigation of CMR methods, we believe this CMR-compatible isolated perfused beating large animal heart model has potential use in assessing myocardial tissue engineering methods, cardiac regeneration therapy and in joint imaging-electrophysiology studies. 48 There are a number of limitations to this study, in addition to the myocardial oedema and apparent failure to achieve microstructural relaxation, as discussed above. Eight out of 10 hearts were used in refining the methods and a full protocol was only performed in one heart, so a full statistical analysis would therefore be of little value.…”

“…Beyond the investigation of CMR methods, we believe this CMR‐compatible isolated perfused beating large animal heart model has potential use in assessing myocardial tissue engineering methods, cardiac regeneration therapy and in joint imaging–electrophysiology studies. 48 …”

Transthoracic ultrasound localization microscopy of myocardial vasculature in patients

“…For the ex vivo experiment, two porcine hearts were explanted from two large white pigs (65–75 kg, 4–5 months old). Each heart was extracted as previously described 37 under anaesthesia using a human donor heart retrieval protocol. Animal studies were reviewed by the Royal Veterinary College Animal and Ethics Review Board and carried out in accordance with ethics standards (European Commission 2010, the Animal Welfare Act 2006 and the Welfare for Farm Animals (England) Regulations 2007).…”

Immunohistochemical characteristics of local sites that trigger atrial arrhythmias in response to high-frequency stimulation

“…A custom-built Langendorff apparatus was used for whole porcine heart preparation. 8 The apparatus consisted of a 5 L solution reservoir (custom supply from Radnoti Ltd.), an oxygen supply to oxygenate the physiological solution to maximal saturation, a heating coil to maintain optimal temperature of 37 ± 0.5°C (custom supply from Radnoti Ltd.) of the physiological solution, a bubble trap to remove air pockets from the system (custom supply from Radnoti Ltd.) and a high flow peristaltic pump to circulate solution around the system at a constant rate (Cole Parmer, UK). The physiological solution used was oxygenated Tyrode’s solution (10–3 moL/L: NaCl, 130; KCl, 4.05; MgCl 2 , 1.0; NaHCO 3 , 20; NaH 2 PO 4 , 1.0; glucose, 5.5; and CaCl 2 , 1.35; pH = 7.4).…”