Redefining How Heart Functions
Contrary to the widely accepted explanation that the human heart is simply a pump, Mayo Clinic researchers have uncovered novel findings on how cardiac muscle operates. The findings appear in the Jan. 3, 2006, issue of the Journal of the American College of Cardiology.
"Redefining how the heart functions is one of the first steps that could lead to revolutionary approaches to treating patients who have heart failure - 5 million and growing in the U.S. - or better yet, preventing the heart failure from developing," says Bijoy Khandheria, M.D., chair of the Division of Cardiology at Mayo Clinic in Arizona and one of the co-authors of the study.
The heart is often thought as a "piston pump." Contraction (systole) occurs when the heart moves blood from its left ventricular cavity into the body's circulatory system, and relaxation (diastole) is when the heart fills with new blood.
According to Marek Belohlavek, M.D.,Ph.D., senior author of the study, "This research focuses on the cardiac left ventricle. Results show that the left ventricle ejects blood into the body's blood vessels through well synchronized electrical and mechanical waves traveling from the heart's tip (apex) towards the base of the heart."
Dr. Belohlavek, a scientist at Mayo Clinic in Rochester, Minn., engaged in more accurately defining how the heart functions, explains, "Relaxation (diastole) is much more important than we previously realized. Diastole is actually comprised of active and passive expansion phases, which efficiently fill the pumping chamber with blood. The newest discovery is the fact that there is an additional contribution to the active relaxation phase by muscle layers close to the outer surface of the pumping chamber."
Partho Sengupta, M.D., lead author of the study who designed the project under the mentorship of Drs. Belohlavek and Khandheria, notes further: "By a brief shortening, cardiac muscle in these outer layers helps to 'unwrap' the rest of the left ventricle after each twisting contraction. We plan to study whether impairment of this active 'unwrapping' in some heart diseases could contribute to left ventricular failure - and, if yes, we hope to find ways to prevent such impairment."