The heart beat is driven by a wave of electrical activity that sweeps through the heart and triggers contraction. Disturbances of this electrical rhythm (cardiac arrhythmias) are relatively common, may impair health and can lead to sudden death.

Cardiac electrophysiology is an important medical discipline that identifies and treats heart rhythm disturbances. The cardiac electrophysiology group at the ABI consists of bioengineers, physiologists and clinicians. We are seeking to understand better how the structure of the heart influences its electrical activity and how both are altered in heart disease. The group uses state-of-the-art imaging methods to reconstruct the 3D architecture of the heart at scales ranging from the cell to the whole organ. It simulates electrical activity using detailed computer models based on these these images and is also actively involved in studies where high-resolution maps of cardiac electrical activity are acquired experimentally. Comparison of experimental data with image-based modelling predictions provides new insights into the factors that give rise to heart rhythm disturbance. Finally, we are also developing new ways of identifying drivers of cardiac arrhythmia.

Cardiac electrophysiology is an important medical discipline that identifies and treats heart rhythm disturbances. The cardiac electrophysiology group at the ABI consists of bioengineers, physiologists and clinicians. We are seeking to understand better how the structure of the heart influences its electrical activity and how both are altered in heart disease. The group uses state-of-the-art imaging methods to reconstruct the 3D architecture of the heart at scales ranging from the cell to the whole organ. It simulates electrical activity using detailed computer models based on these these images and is also actively involved in studies where high-resolution maps of cardiac electrical activity are acquired experimentally. Comparison of experimental data with image-based modelling predictions provides new insights into the factors that give rise to heart rhythm disturbance. Finally, we are also developing new ways of identifying drivers of cardiac arrhythmia.

Dr Jichao Zhao is leading research on mechanisms responsible for persistent atrial fibrillation (AF). This work is supported by grants from the Health Research Council of New Zealand (HRCNZ) and the US National Institutes of Health (NIH), and involves collaborations with groups in the UK, Europe, China, Australia and the US. With Professor Vadim Federov and his team at Ohio State University, Jichao has for the first time elucidated how structural remodelling of the atria in failing human hearts contributes to initiation and maintenance of AF. This work has important implications for identification and ablation of atrial regions that drive AF. Other active research areas include the use of machine-learning methods for automated image segmentation and arrhythmia classification, and why metabolic syndrome increases AF risk.

The ABI cardiac electrophysiology group is also studying how structural remodelling of the ventricles contributes to ventricular arrhythmia and sudden cardiac death. This work is funded by the Leducq Foundation Transatlantic Network of Excellence programme grant RHYTHM, which has a specific focus on repolarisation abnormalities in the human heart. RHYTHM links us with researchers from George Washington University, Johns Hopkins University, Northwestern University, Illinois, AMC, Amsterdam and the cardiac electrophysiology research institute LIRYC in Bordeaux. Our roles are to:

1. Develop high-throughput imaging systems that enable structural remodelling in large heart specimens to be characterised at cell and tissue levels
2. Establish new ways of incorporating this information into computer models of electrical activation.

Dr Greg Sands, has extended and refined recent optical technologies developed for brain imaging. Specimens are labelled with fluorescent probes and optically cleared by refractive index matching so that structures >1mm below the surface can be visualised. Four channels of co-registered fluorescence images can be acquired at submicron resolution with a purpose-developed high speed (up to 40 Mpixels/second/channel) confocal microscope.

In parallel, Dr Mark Trew has established a novel modelling framework which allows factors such as cell dimension, cell orientation, intra- and extracellular electrical coupling to be incorporated directly into network representations that reflect the discontinuity inherent at the cell and tissue levels. This enables computationally efficient image-based modelling of electrical activation across a range of spatial scales. We are particularly excited by these developments and believe that our methods are applicable to a wide range of problems in computational physiology. These include modelling of the cardiac neural plexus and its role in modulating rhythm in normal and diseased hearts.

Finally, we are working on a new intracardiac approach for panoramic mapping of 3D electrical electrical activity in AF. This research, led by Professor Bruce Smaill and Associate Professor David Budget, is funded by an Endeavour grant from the NZ Ministry of Business Innovation and Enterprise (MBIE) and by the Centre for Research Excellence in Medical Technology. We have demonstrated that accurate real-time maps of 3D global and regional atrial electrical activity can be recovered from open multi-electrode basket catheters where some or all electrodes are not in contact with the heart surface using appropriate inverse methods.

Currently, we are developing an interactive in silico test bed that will be used to demonstrate the utility and accuracy of the method to clinical cardiac electrophysiologists and device companies. The system is also being used to optimise the design of specialised catheters intended for AF mapping. This work is being carried out by Dr Shu Meng, Dr Nick Sunderland and Dr Emma Ordono with additional input from Dr Jichao Zhao.

The Cardiac Electrophysiology gratefully acknowledges the support of its funding partners:

• Health Research Council of New Zealand
• National Institutes of Health
• Fondation Leducq
• Ministry of Business Innovation & Employment Endeavour Fund
• The Royal Society of New Zealand
• National Heart Foundation of New Zealand
  
• The Wellcome Trust
• Auckland Medical Research Foundation
• Auckland Uniservices Ltd
• National Health and Medical Research Council (Australia)
• Lottery Health Research  

Academics

Shu Meng
Greg Sands
Bruce Smaill
Nick Sunderland
Mark Trew
Jichao Zhao

Clinical Associates

Nigel Lever
Martin Stiles

Students

Shaleka Agrawal
Sarah Fong
Kevin Jamart
Andy (Chun Yip) Lo
Emma Ordono
Girish Ramlugun
Christine Sy
Belvin Thomas
Vibujithan Vigneshwaran
Zhaohan Xiong

Casual

Elizabeth Cheng
Helen Fu
Roshan Sharma
Aaqel Nalar