The Weiss Lab, which features a multi-disciplinary team at Johns Hopkins as well as at Cedars Sinai Medical Center in Los Angeles, is dedicated to identifying the most important clinical, genetic, structural, contractile and metabolic causes of sudden cardiac death as well as the means to reverse the underlying pathology and lower risk. Current projects include research into energy metabolism in human heart failure and creatine kinase metabolism in animal models of heart failure. Robert G. Weiss, MD, is professor of medicine, Radiology and Radiological Science, at the Johns Hopkins University.

The Arking Lab studies the genomics of complex human disease, with the primary goal of identifying and characterizing genetics variants that modify risk for human disease. The group has pioneered the use of genome-wide association studies (GWAS), which allow for an unbiased screen of virtually all common genetic variants in the genome. The lab is currently developing improved GWAS methodology, as well as exploring the integration of additional genome level data (RNA expression, DNA methylation, protein expression) to improve the power to identify specific genetic influences of disease. The Arking Lab is actively involved in researching: • autism, a childhood neuropsychiatric disorder • cardiovascular genomics, with a focus on electrophysiology and sudden cardiac death (SCD) • electrophysiology is the study of the flow of ions in biological tissues Dan E. Arking, PhD, is an associate professor at the McKusick-Nathans Institute of Genetic Medicine and Department of Medicine, Division of Cardiology, Johns Hopkins University.

Dr. Wu leads a multi-disciplinary team with collaborators from the Bloomberg School of Public Health, JHU Whiting School of Engineering, and JHU Krieger School of Arts and Sciences. She conducts ongoing investigations with the Multicenter AIDS Cohort Study and Women’s Inter-agency Health Study. Her lab’s goals are to develop, implement, and validate novel imaging-based metrics of cardiac structure and function to improve risk prediction and stratification at the individual patient-level. Research Focuses: Predictors of Sudden Cardiac Death by Magnetic Resonance Imaging Subclinical myocardial disease in people living with HIV Individualized risk prediction Cardiac structural and mechanical modeling

The Post Lab is involved in the Multi-Ethnic Study of Atherosclerosis (MESA), a collaborative study of the characteristics of subclinical cardiovascular disease (that is, disease detected non-invasively before it has produced clinical signs and symptoms) and the risk factors that predict progression to clinically overt cardiovascular disease or progression of the subclinical disease. As MESA researchers, we study a diverse, population-based sample of 6,814 asymptomatic men and women aged 45-84. Approximately 38 percent of the recruited participants are white, 28 percent African-American, 22 percent Hispanic, and 12 percent Asian, predominantly of Chinese descent. Participants were recruited from six field centers across the United States, including Johns Hopkins University. Each participant received an extensive physical exam to determine a number of conditions, including coronary calcification, ventricular mass and function, flow-mediated endothelial vasodilation, standard coronary risk factors, sociodemographic factors, lifestyle factors, and psychosocial factors. Selected repetition of subclinical disease measures and risk factors at follow-up visits have allowed study of the progression of disease. Participants are being followed for identification and characterization of cardiovascular disease events, including acute myocardial infarction and other forms of coronary heart disease (CHD), stroke, and congestive heart failure; for cardiovascular disease interventions; and for mortality. Wendy S. Post, MD, MS, is an associate faculty, Welch Center for Prevention, Epidemiology, and Clinical Research, Johns Hopkins University, and a professor of medicine.

The Cardiology Bioengineering Laboratory, located in the Johns Hopkins Hospital, focuses on the applications of advanced imaging techniques for arrhythmia management. The primary limitation of current fluoroscopy-guided techniques for ablation of cardiac arrhythmia is the inability to visualize soft tissues and 3-dimensional anatomic relationships. Implementation of alternative advanced modalities has the potential to improve complex ablation procedures by guiding catheter placement, visualizing abnormal scar tissue, reducing procedural time devoted to mapping, and eliminating patient and operator exposure to radiation. Active projects include • Physiological differences between isolated hearts in ventricular fibrillation and pulseless electrical activity • Successful ablation sites in ischemic ventricular tachycardia in a porcine model and the correlation to magnetic resonance imaging (MRI) • MRI-guided radiofrequency ablation of canine atrial fibrillation, and diagnosis and intervention for arrhythmias • Physiological and metabolic effects of interruptions in chest compressions during cardiopulmonary resuscitation Henry Halperin, MD, is co-director of the Johns Hopkins Imaging Institute of Excellence and a professor of medicine, radiology and biomedical engineering. Menekhem M. Zviman, PhD is the laboratory manager.

The O’Rourke Lab uses an integrated approach to study the biophysics and physiology of cardiac cells in normal and diseased states. Research in our lab has incorporated mitochondrial energetics, Ca2+ dynamics, and electrophysiology to provide tools for studying how defective function of one component of the cell can lead to catastrophic effects on whole cell and whole organ function. By understanding the links between Ca2+, electrical excitability and energy production, we hope to understand the cellular basis of cardiac arrhythmias, ischemia-reperfusion injury, and sudden death. We use state-of-the-art techniques, including single-channel and whole-cell patch clamp, microfluorimetry, conventional and two-photon fluorescence imaging, and molecular biology to study the structure and function of single proteins to the intact muscle. Experimental results are compared with simulations of computational models in order to understand the findings in the context of the system as a whole. Ongoing studies in our lab are focused on identifying the specific molecular targets modified by oxidative or ischemic stress and how they affect mitochondrial and whole heart function. The motivation for all of the work is to understand • how the molecular details of the heart cell work together to maintain function and • how the synchronization of the parts can go wrong Rational strategies can then be devised to correct dysfunction during the progression of disease through a comprehensive understanding of basic mechanisms. Brian O’Rourke, PhD, is a professor in the Division of Cardiology and Vice Chair of Basic and Translational Research, Department of Medicine, at the Johns Hopkins University.