By using sound waves Mayo Clinic researchers have described subtle changes in the motion of the heart that are measurable by ultrasound and may improve understanding of heart function, and possibly be a noninvasive aid in predicting impending heart damage including heart attacks.
The study could also contribute to optimal adjustment of cardiac pacemakers or perhaps better design of artificial hearts. The findings, published in the current Journal of Applied Physiology, are based on "snapshots" of the mechanical transitions that occur between the main relaxation and contraction phases of the heartbeat. During these split-second transitions, the heart muscle "shifts gears" or prepares for the upcoming phase.
"This is only a start and much work is needed, but we are optimistic that our research will ultimately lead to development of noninvasive, broadly clinically available methods in diagnostic ultrasonography," says Marek Belohlavek, M.D., Ph.D., Mayo Clinic ultrasound imaging specialist and senior researcher of the study. "These methods could improve our chances in predicting cardiac events, so that preventive measures could be taken. And in patients with an existing heart condition, a detailed analysis of cardiac function could contribute to therapeutic optimization of heart performance." A patent application has been filed based on this research.
Researchers at the Mayo Clinic Translational Ultrasound Research Unit study the mechanical, biochemical and electrical aspects of these transitions which occur between phases of relaxation -- when the heart ventricles fill with a volume of blood -- and contraction -- when the heart ejects most of the blood volume into body circulation. Recently advanced, high-resolution ultrasound tissue Doppler imaging allowed them to experimentally measure these transitional tissue deformations, which last only milliseconds and are unnoticeable to the human eye. The technology allows slow-motion comparisons of these events separately between the inner and outer layers of the cardiac left ventricle. The researchers' published measurements demonstrate how a rapid succession of motions occurring within tissue of the ventricular wall can appear chaotic if not observed closely and with high temporal resolution. The data also show how these transitions "reorganize" the ventricle to best perform its cycles of filling and ejection.