Cardiac Device Electrophysiology Projects

Principal Investigators:
Felipe Aguel, Ph.D.
Dulciana Chan, B.S.
Richard A. Gray, Ph.D.
Jayna Stohlman, M.S. 

Intramural Collaborators:
Victor Krauthamer, Ph.D.
Soma Kalb, Ph.D. ODE/DCD 

Extramural Collaborators:
Mark Haigney, M.D. & Matie Shou, M.D. (USUHS Department of Cardiology)
John Wikswo, Ph.D. (Vanderbilt Univ. Dept. of Biomedical Engineering)
Andy Bachtel, B.S. (Univ. of Alabama at Birmingham Dept. of Biomedical Engineering)
Michele Triventi, M.S.; Eugenio Mattei, M.S.; Federica Censi, Ph.D.; & Giovanni Calcagnini, Ph.D. (Italian National Institute of Health)
Natalia Trayanova, Ph.D. (Johns Hopkins University Department of Biomedical Engineering) 

Background:
Heart disease is the number one cause of death in the United States. The use of implantable cardioverter defibrillator (ICD) has greatly expanded in the past several years to clinically prevent conditions leading to sudden cardiac death (affecting 330,000 Americans annually).  In 2009, over 11,000 ICDs were implanted monthly in the U.S> (JAMA 2009; 301:1713-1714).  The growing usage of this device is in part due to the expansion in recommendations by the American College of Cardiology in indications for heart failure patients, and increased reimbursements by the Center for Medicare and Medicaid Services. The Cardiac Device Electrophysiology group has conducted several research initiatives aimed at addressing the safety and effectiveness of ICDs.  Specifically, the group studied focused on the biophysical mechanisms of cardiac electrical stimulation; device issues associated with over-the counter automatic external cardiac defibrillators; the effectiveness of new defibrillation waveforms; and the effects of combined mechanical and electrical stimulation therapies.

This group also engaged in studies of heart failure (HF).  HF is estimated to cost $37.2 billion annually (2009).  It is the one form of heart disease on the rise in the U.S. with a 171% increase between 1979 and 2006.  Between 1993 and 2003 there was a 20% increase in deaths due to heart failure, even as the overall death rate declined by 2.0%.  The group has targeted efforts in evaluating biomarkers for HF which is in part supported through the FDA Critical Path Initiative. 

Mission:
The overall goal of the Cardiac Device Electrophysiology (CDEP) group is to provide scientific research regarding the safety and efficacy of cardiac electrophysiological medical devices. Our approach is to develop and use a wide variety of scientifically rigorous methods and expertise to respond to a broad range of issues related to the mission of FDA. Our group provides a flexible framework to address premarket, postmarket, innovation, total product life cycle (TPLC), and “Critical Path” issues related to cardiac electrophysiological devices. 

Resources:
Our group conducts research on a wide range of topics in CDEP and thus has developed a very unique set of scientific resources and expertise. We employ advanced experimental, numerical, and theoretical scientific and engineering methods in conducting research at various spatial scales that is directly applicable to cardiac electrophysiological medical devices. 

We have implemented a number of in-vitro and ex-vivo models for the study of cardiac electrophysiology using optical mapping techniques. These include single cells (cardiac myocytes), organotypic myo-balls, monolayers of cultured neonatal ventricular myocytes, porcine tissue wedge preparations, and isolated whole Langendorff-perfused rabbit hearts. We are using these models to study a range of issues related to electrical stimulation devices used in treating cardiac disease including pacemakers, defibrillators, and radiofrequency ablation catheters.

(Top) Fluorescent signal (ΔF) of transmembrane potential at one site during ventricular fibrillation (V-fib). (Bottom) False color image of a snapshot of ΔF at 16x16 sites during ventricular fibrillation.

"(Left) Greyscale image of fluorescent signal (F) of transmembrane potential during reentrant ventricular arrhythmia in the rabbit heart. (Right) Phase map of the same image, where the color indicates the phase angle (O).

 

We perform a variety of numerical simulations and theoretical analyses to complement our experimental studies. These simulation studies span the scale from cell to whole body and are used to provide insight into a variety of cardiac electrophysiological device issues including cellular excitability, stability of action potential propagation, effect of heart geometry on arrhythmias, and electrical stimulation of cardiac tissue.