Mayo scientists: There's a twist to heartbeats
CORRECTION RAN TUESDAY (12/27/05)
A Dec. 20 story on Page 2A about heart function should have listed Dr. Partho Sengupta as lead author, Dr. Marek Belohlavek as senior author and Dr. Bijoy Khandheria as senior author of a journal article about a study showing the heart "wrings" instead of pumps.
By Jeff Hansel
Hold on to your heart.
Scientists at Mayo Clinic in Scottsdale, Ariz., and Rochester say they have found a twist, literally and figuratively, in the way the heart works.
It does not behave like an engine; using a piston as a pump, the conventional view. Instead, the heart muscle twists. Patterns of muscle fibers in the heart resemble spirals found in nature, said Dr. Bijoy Khandheria, chair of the Division of Cardiology at Mayo in Arizona.
"Movements of (these) counter-directional muscle layers produce cyclic propulsion and suction of blood in and out of the left ventricular cavity -- the main chamber of the heart," said Khandheria, who has a double appointment, meaning he also sees patients in Rochester.
Khandheria said the heart squeezes blood kind of like someone trying to wring out a sopping-wet towel. Muscles in the tip of the heart, called the apex, turn in a clockwise direction, while muscles at the opposite end of the heart twist counterclockwise, he said. This creates a suction vortex that forces blood to circulate.
"It's kind of almost like a tornado that is created in the heart every time the heart beats," Khandheria said.
The findings have implications for heart surgery, medical-device makers and cardiology research.
"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 United States -- or better yet, preventing the heart failure from developing," Khandheria said in a clinic statement.
The Jan. 3 issue of the Journal of the American College of Cardiology includes an article by Khandheria and several other Mayo researchers, including lead author Dr. Marek Belohlavek of Rochester. Publication was hastened due to the study's implications.
Researchers implanted multiple miniature crystals that emit ultrasonic waves and mapped the muscle movement. They found that heart muscle moved in waves from the apex to the base of the heart.
"During diastole, the period when (the) heart stops ejecting and starts relaxing, the muscle layers close to the outer surface of the pumping chamber remain contracted. This activity helps the chamber to relax faster, generating a suction force. With this brief shortening, cardiac muscle in the outer layers 'unwraps' and enlarges the rest of the left ventricle after each twisting contraction, resulting in blood being actively sucked into the left ventricular cavity rather than filling passively," Khandheria said.
Khandheria said he believes heart specialists will quickly accept the new concept. Two other research groups independently reached similar conclusions, he said.
"A fairly inexpensive ultrasound can allow us to measure the (vortex) strength. It's like measuring the strength of the tornado," Khandheria said. Mayo researchers are developing medical devices based on the findings.