The MRI exams allowed the researchers to observe the cardiovascular changes involved in the diving reflex in real time. During apnea, the amount of blood flowing to the brain through the carotid arteries increased and then leveled off.
"At the beginning of the apnea period, the heart pumped more strongly than when the heart was at rest," Dr. Dörner said. "Over time, the heart dilated and began to struggle."
Ad Statistics
Times Displayed: 50213
Times Visited: 1424 Ampronix, a Top Master Distributor for Sony Medical, provides Sales, Service & Exchanges for Sony Surgical Displays, Printers, & More. Rely on Us for Expert Support Tailored to Your Needs. Email info@ampronix.com or Call 949-273-8000 for Premier Pricing.
By the end of the apnea period, Dr. Dörner said the divers' heart function began to fail.
"At that point, not enough blood is being pumped to the brain," he said. "The heart is unable to pump against the high resistance of the blood vessels."
Although the changes in the divers' systolic heart function during apnea are similar to those in patients with systolic heart failure, Dr. Dörner said that the condition was transient in the divers.
"The divers' heart function recovered within minutes of breathing again," said Claas Nähle, M.D., head of this cardiac magnetic resonance research group. "It appears that elite divers develop compensatory mechanisms that help them adapt to the cardiovascular changes that occur during apnea."
However, for individuals with less training, free diving may be problematic.
"As a recreational activity, free diving could be harmful for someone who has heart or other medical conditions and is not well trained for the activity," said one of the study's leaders, Lars Eichhorn, M.D., from the Department of Anesthesiology and Intensive Care Medicine at the University Hospital of Bonn.
Dr. Eichhorn added that deaths among highly trained divers are mostly seen in the discipline called deep diving, a special type of apnea diving that combines the risk of prolonged apnea with changes of ambient pressure.
Other co-authors on the study are Jean-Marc Lunkenheimer, Julian A. Luetkens, M.D., Juergen Gieseke, D.Sc., Rainer Meyer, Ph.D., Andreas Hoeft, M.D., and Hans H. Schild, M.D.
Note: Copies of RSNA 2015 news releases and electronic images will be available online at RSNA.org/press15 beginning Monday, Nov. 30.
RSNA is an association of more than 54,000 radiologists, radiation oncologists, medical physicists and related scientists, promoting excellence in patient care and health care delivery through education, research and technologic innovation. The Society is based in Oak Brook, Ill. (RSNA.org)
For patient-friendly information on cardiac MRI, visit RadiologyInfo.org.
SOURCE Radiological Society of North America (RSNA)
Back to HCB News
