Category Archives: What’s New

Maria Inês Francisco Gândara

Maria Inês Francisco Gândarra

Maria Inês Francisco Gândara.

Inês joined our lab as an international graduate student from NOVA school of science & technology, Lisbon, Portugal to pursue her M.S. thesis. I had the good fortune of being her thesis advisor. I am excited and happy to report that Inês successfully defended her dissertation and is now a proud graduate of NOVA University.


Effects of spatial resolution on arrhythmia driver detection and localization


Arrhythmia is a cardiac rhythm disorder that can be fatal. Its treatment includes ab- lation of the cardiac tissue and/or defibrillation. Advances are being made for both treatment options to localize the culprit region and apply therapy directly where it is needed. However, success rates have been inconsistent, with frequent arrhythmia recurrence. A likely reason is the limited current resolution of mapping devices, that averages 4 mm. Higher resolution may improve localization of arrhythmia drivers, termed rotors, and consequently improve efficacy of treatment.

This study evaluates the effects of spa- tial resolution on arrhythmia dynamics, rotor tracking, and rotor localization. Optical data from ex vivo human hearts was used, being clinically relevant and with ultra-high spatial resolution. To simulate different resolutions, original data was downsampled by multiple factors and upsampled back to full resolution. Rotors were tracked for each sub-resolution and compared to the rotors in the original data. Further comparisons were made according to arrhythmia type, sex, anatomical region, and mapped surface. Accuracy profiles were created for both rotor detection and localization, describing how accuracy changed with spatial resolution and spatial accuracy.

Rotor detection accuracy for currently used mapping devices was found to be 57±4%. Localization accuracy is 61±7%. Detection accuracy was above 80% only for a resolution of 1.4 mm. Moreover, the detection and localization accuracies were affected by arrhythmia type, and rotor incidence was found to be higher in the endocardium. Therefore, current clinical rotor detection and localization accuracies can be expected to fall within a confidence interl,gttval of 47-67% and 46-75%, respectively. This means that a higher spatial resolution is needed in cardiac mapping devices than what is currently available.

For high accuracy, a resolution of at least 1.4 mm is required. The accuracy profiles provided in this thesis may serve as a guideline for future mapping device development.

Electrophysiology and Arrhythmogenesis in the Human RVOT

Human RVOT susceptibility to arrhythmias


  1. Right ventricular outflow tract (RVOT) is a common source of idiopathic ventricular arrhythmias (IVAs). 
  2. However, the mechanisms underlying the RVOT’s unique arrhythmia susceptibility remains not well elucidated due to lack of detailed electrophysiological and molecular studies of human RVOT.


  1. Human RVOT electrophysiology is characterized by shorter APD relative to the right ventricular apical region and drives the transmural dispersion of repolarization and transmural APD dispersion under normal physiological conditions.
  2. Cholinergic stimulation attenuates the arrhythmogenic effects of adrenergic stimulation, including increase in frequency of PVCs and shortening of wavelength.
  3. Arrhythmia in the RV is associated with weak positive spatiotemporal autocorrelation between the epicardial-endocardial arrhythmic wavefronts and reentrant rotors that are relatively more organized in the endocardium.


Aras KK, Gams A, Faye NR, Brennan JB, Goldrick K, Li J, Zhong Y, Chiang C, Smith EH, Poston MD, Chivers J, Hanna P, Mori S, Ajijola O, Shivkumar K, Hoover DB, Viventi J, Rogers JA, Bernus O, Efimov IR. Electrophysiology and Arrhythmogenesis of the human right ventricle outflow tract. Circ Arrhythm Electrophysiol. 2022. (Editor’s pick)

Book chapter: conformal electronics therapy for defibrillation


Cardiac Bioelectric Therapy: Mechanisms and Practical Applications

Chapter 38

Conformal Electronics Therapy for Defibrillation


Kedar K. Aras, John A. Rogers, Igor R. Efimov


Defibrillation remains the only effective therapy against sudden cardiac death. However, the current coil-based lead ICD devices are limited by high defibrillation threshold (DFT) and low arrhythmia sensing resolution, which can result in inappropriate and painful shocks adversely affecting the quality of life. Emerging classes of materials and mechanics concepts in the field of flexible and stretchable electronics have created new opportunities for integrating high-performance electronics with the human body and its organs and various tissues. These conformal electronics devices offer a platform for high-definition arrhythmia sensing to minimize inappropriate shocks and improve therapy and high-definition therapy delivery circuit to reduce DFT.