Towards a rhythmic heart

SCDs usually occur due to cardiac arrhythmias, with 80 % attributed to ventricular fibrillation (VF). VF refers to uncoordinated heart muscle contraction due to erratic electrical impulses that cause severe cardiac dysfunction.

Recently, researchers discovered that electrical activity from a specialised cell-type in the heart called Purkinje fibres precedes VF. Ablating such areas in the heart noticeably reduced recurrence of VF in patients.

Under the aegis of the project PSCD (Establishing the role of Purkinje fibres in the development of arrhythmias for the prevention of sudden cardiac death: Insights from a combined in vivo and ex vivo study), researchers combined ex vivo optical imaging with in vivo electrophysiological techniques to elucidate the function of Purkinje fibres.

Early on in the project, researchers investigated the electrical propagation and repolarisation patterns in the heart to determine factors contributing to electrical abnormalities.

A first, researchers investigated and experimentally verified that Purkinje fibres impact electrical activation and propagation in heart muscles. Electrical coupling, tissue architecture and action potential morphology were found to be key contributing factors in arrhythmias. These findings were published in the Frontiers in Physiology journal.

PSCD developed a novel global activation map approach using optical signals, which was presented and published in conference proceedings of the 35th Annual International conference of the IEEE. This tool proved invaluable in reconstructing electrical activity in 3D in large animal hearts ex vivo. The researcher was awarded third prize for the Young Investigator's award at the 40th International Congress of Electrocardiology in the United Kingdom.

This same researcher also identified a novel pathway that sustains ventricular tachycardia in sheep with normal healthy heart muscle. Ventricular tachycardia is a condition where the heartbeat per minute exceeds 100. The pathway consisted of a muscular area called moderator band that was found to contain some structures of the Purkinje network.

Project activities uncovered novel target sites for ablation therapy to treat arrhythmias. This should improve ablation accuracy, surgery time and success rates, and thus improve patient outcome. Moreover, the novel tools developed can be used to study different experimental models, species and electrophysiological activation patterns.