While there have been numerous studies of abnormalities in the human heart, there have not been studies of the electromechanics of healthy adult hearts — until now. Yoram Rudy, the Fred Saigh Distinguished Professor of Engineering in the McKelvey School of Engineering, and Christopher Andrews, a postdoctoral research scholar in the Department of Biomedical Engineering, have completed the first study to combine electrocardiographic imaging (ECGI), a noninvasive method developed in the Rudy lab, with tagged MRI to study the electromechanics of healthy hearts in living humans.
ECGI is a noninvasive imaging method that maps the heart's electrical activity using electrocardiographic measurements from about 250 body surfaces together with the heart-torso geometry from anatomical MRI or computed tomography (CT) scans. The electrocardiographic measurements and geometrical information are combined mathematically to create maps of the cardiac electrical excitation. Tagged MRI measures displacement of heart-muscle regions, providing a 3D image of cardiac strain during contraction.
The study conducted ECGI and tagged MRI on 20 healthy adult volunteers at Washington University in St. Louis, making it the largest ECGI study of healthy adults to date and the first study of electromechanics coupling in living normal human hearts.
In the study, Rudy and Andrews, along with Brian Cupps, a senior scientist in the Department of Surgery, and Michael K. Pasque, MD, professor of surgery, both at Washington University School of Medicine, found that electrical excitation was very fast compared to mechanical contraction; it started at the antero-lateral region of the right ventricle and ended in the base of the left ventricle. There was a difference in the duration of local electrical excitation between men and women subjects; women had a longer mean activation-recovery interval than men by about 30 milliseconds. This highlights the sensitivity of ECGI in measuring cardiac repolarization.
The data could be helpful in designing and validating mathematical models of the heart's electromechanics for the study of human cardiac electrophysiology and mechanics.
"The ability to image noninvasively the electrical and mechanical function in the same human heart in vivo carries great promise for clinical diagnosis and guidance of treatment in various cardiac disorders, such as heart failure," Rudy said.