Reporter's Notebook: News From RSNA 2016
Vol. 18 No. 1 P. 8
Editor's note: This article is based on materials distributed for the press conferences at RSNA 2016 in Chicago.
Alcohol Consumption Shows No Effect on Coronary Arteries
Researchers using coronary CT angiography (CCTA) have found no association between light to moderate alcohol consumption and coronary artery disease (CAD), according to a study presented at the annual meeting of RSNA.
Some previous studies have suggested that light alcohol consumption may actually reduce the risk for CAD. However, data regarding regular alcohol consumption and its association with the presence of CAD remains controversial. For the new study, researchers looked at alcohol consumption, type of alcohol consumed, and presence of coronary plaques using CCTA.
"CCTA is an excellent diagnostic modality to noninvasively depict the coronary wall and identify atherosclerotic lesions," said study author Júlia Karády, MD, from the MTA-SE Cardiovascular Imaging Research Group, Heart and Vascular Center at Semmelweis University in Budapest, Hungary. "Furthermore, we're able to characterize plaques and differentiate between several types. Prior studies used cardiovascular risk factors—like high cholesterol levels—and cardiovascular outcomes to study the effects of alcohol, but our study is unique in that we analyzed both drinkers and nondrinkers using CCTA, which may shed some light on how alcohol may or may not contribute to the development of fatty plaques in the arteries of the heart."
The researchers studied 1,925 consecutive patients referred for CCTA with suspected CAD. Information on alcohol consumption habits was collected using questionnaires about the amount and type of alcohol consumed. Using an in-house reporting platform that contained the patients' clinical and CCTA data, researchers were able to assess the relationship between atherosclerosis, clinical risk factors, and patient drinking habits.
"About 40% of our patients reported regular alcohol consumption, with a median of 6.7 alcohol units consumed weekly," Karády said.
One unit translates to approximately 2 deciliters (dl) or 6.8 fluid ounces of beer, 1 dl or 3.4 ounces of wine, or 4 centiliters (cl) or 1.35 ounces of hard liquor.
The results showed that the amount of weekly alcohol consumption, whether light or moderate, was not associated with the presence of CAD. In addition, when researchers looked at different types of alcohol and the presence of coronary atherosclerosis, no associations were found.
"When we compared consumption between patients who had coronary artery plaques and those who had none, no difference was detected," Karády said. "Evaluating the relationship between light alcohol intake (maximum of 14 units per week) and presence of CAD, we again found no association. Furthermore, we analyzed the effect of different types of alcohol (beer, wine, and hard liquor) on the presence of CAD, but no relationship was found."
Karády added that while no protective effect was detected among light drinkers, as previously thought, no harmful effects were detected either.
The researchers are in the process of expanding the study to include more patients and perform further analyses.
Independently of whether alcohol has any effect on the coronary arteries, moderate alcohol consumption has been associated with a number of potential side effects, including negative long-term effects on the brain and heart.
Coauthors include Balint Szilveszter, MD; Zsofia D. Drobni, MD; Marton Kolossvary, MD; Andrea Bartykowszki, MD; Mihaly Karolyi, MD, PhD; Adam Jermendy, MD; Alexisz Panajotu, MD; Zsolt Bagyura, MD; and Pal Maurovich-Horvat, MD, PhD, MPH.
Short-Term Sleep Deprivation Affects Heart Function
Too little sleep takes a toll on your heart, according to a new study presented at the annual meeting of the RSNA.
People who work in fire and emergency medical services, medical residencies, and other high-stress jobs are often called upon to work 24-hour shifts with little opportunity for sleep. While it is known that extreme fatigue can affect many physical, cognitive, and emotional processes, this is the first study to examine how working a 24-hour shift specifically affects cardiac function.
"For the first time, we have shown that short-term sleep deprivation in the context of 24-hour shifts can lead to a significant increase in cardiac contractility, blood pressure, and heart rate," said study author Daniel Kuetting, MD, from the department of diagnostic and interventional radiology at the University of Bonn in Germany.
For the study, Kuetting and colleagues recruited 20 healthy radiologists (19 men and one woman), with a mean age of 31.6 years. Each of the study participants underwent cardiovascular MR (CMR) imaging with strain analysis before and after a 24-hour shift with an average of three hours of sleep.
"Cardiac function in the context of sleep deprivation has not previously been investigated with CMR strain analysis, the most sensitive parameter of cardiac contractility," Kuetting said.
The researchers also collected blood and urine samples from the participants and measured blood pressure and heart rate.
Following short-term sleep deprivation, the participants showed significant increases in mean peak systolic strain (pre = -21.9; post = -23.4), systolic (112.8; 118.5) and diastolic (62.9; 69.2) blood pressure, and heart rate (63; 68.9). In addition, the participants had significant increases in levels of thyroid-stimulating hormone, thyroid hormones FT3 and FT4, and cortisol, a hormone released by the body in response to stress.
Although the researchers were able to perform follow-up examinations on one-half of the participants after regular sleep, Kuetting noted that further study in a larger cohort is needed to determine possible long-term effects of sleep loss.
"The study was designed to investigate real-life work-related sleep deprivation," Kuetting said. "While the participants were not permitted to consume caffeine or food and beverages containing theobromine, such as chocolate, nuts, or tea, we did not take into account factors like individual stress level or environmental stimuli."
As people continue to work longer hours or work at more than one job to make ends meet, it is critical to investigate the detrimental effects of too much work and not enough sleep. Kuetting believes the results of this pilot study are transferable to other professions in which long periods of uninterrupted labor are common.
"These findings may help us better understand how workload and shift duration affect public health," he said.
Aerobics Preserve Brain Volume, Improve Cognitive Function
Using a new MRI technique, researchers found that adults with mild cognitive impairment (MCI) who exercised four times a week over a six-month period experienced an increase in brain volume in specific, or local, areas of the brain, but adults who participated in aerobic exercise experienced greater gains than those who just stretched.
"Even over a short period of time, we saw aerobic exercise lead to a remarkable change in the brain," said the study's lead investigator, Laura D. Baker, PhD, from Wake Forest School of Medicine (WFSM) in Winston-Salem, North Carolina.
The study included 35 adults with MCI participating in a randomized, controlled trial of exercise intervention. Individuals with MCI are at risk of developing Alzheimer's disease (AD), the most common form of dementia, which affects more than 5 million Americans.
The participants were divided into two groups: 16 (average age 63 years) engaged in aerobic activity, including treadmill, stationary bike, or elliptical training, four times per week for six months and a control group of 19 adults (average age 67 years) participated in stretching exercises with the same frequency. High-resolution brain MR images were acquired from all participants before and after the six-month activity period. The MRI results were compared using conventional and biomechanical metrics to measure the change in both brain volume and shape.
"We used high-resolution MR images to measure anatomical changes within areas of the brain to obtain both volumetric data and directional information," said study coinvestigator Jeongchul Kim, PhD, from WFSM.
The analysis revealed that for both the aerobic and stretching groups, brain volume increased in most gray matter regions, including the temporal lobe, which supports short-term memory.
"Compared to the stretching group, the aerobic activity group had greater preservation of total brain volume, increased local gray matter volume, and increased directional stretch of brain tissue," Kim said.
Among participants of the stretching group, the analysis revealed a local contraction, or atrophy, within the white matter connecting fibers. According to Kim, such directional deformation, or shape change, is partially related to volume loss, but not always.
"Directional changes in the brain without local volume changes could be a novel biomarker for neurological disease," he said. "It may be a more sensitive marker for the tiny changes that occur in a specific brain region before volumetric changes are detectable on MRI."
He said both MRI measures are important to the treatment of MCI and AD, which require the careful tracking of changes in the brain while patients engage in interventions including diet and exercise to slow the progression of the disease.
Study participants were tested to determine the effect of exercise intervention on cognitive performance. Participants in the aerobic exercise group showed statistically significant improvement in executive function after six months, whereas the stretching group did not improve.
"Any type of exercise can be beneficial," Kim said. "If possible, aerobic activity may create potential benefits for higher cognitive functioning."
Other coauthors on the study are Suzanne Craft, PhD; Youngkyoo Jung, PhD; and Christopher T. Whitlow, MD, PhD.
Study Finds Cause of Visual Impairment in Astronauts
A visual problem affecting astronauts who serve on lengthy missions in space is related to volume changes in the clear fluid that is found around the brain and spinal cord.
Over the last decade, flight surgeons and scientists at NASA began seeing a pattern of visual impairment in astronauts who flew long-duration space missions. The astronauts had blurry vision, and further testing revealed, among several other structural changes, flattening at the back of their eyeballs and inflammation of the head of their optic nerves. The syndrome, known as visual impairment intracranial pressure (VIIP), was reported in nearly two-thirds of astronauts after long-duration missions aboard the International Space Station (ISS).
"People initially didn't know what to make of it, and by 2010 there was growing concern as it became apparent that some of the astronauts had severe structural changes that were not fully reversible upon return to Earth," said study lead author Noam Alperin, PhD, a professor of radiology and biomedical engineering at the University of Miami Miller School of Medicine in Miami.
Scientists previously believed that the primary source of the problem was a shift of vascular fluid toward the upper body that takes place when astronauts spend time in the microgravity of space. But researchers led by Alperin recently investigated another possible source for the problem: cerebrospinal fluid (CSF), the clear fluid that helps cushion the brain and spinal cord while circulating nutrients and removing waste materials. The CSF system is designed to accommodate significant changes in hydrostatic pressures, such as when a person rises from a lying to sitting or standing position. However, the microgravity of space presents new challenges.
"On Earth, the CSF system is built to accommodate these pressure changes, but in space the system is confused by the lack of the posture-related pressure changes," Alperin said.
To learn more about the role of CSF in spaceflight-induced visual impairment and eye changes, Alperin and colleagues performed high-resolution orbit and brain MRI scans before and shortly after spaceflights for seven long-duration mission ISS astronauts.
They compared results with those from nine short-duration mission space shuttle astronauts. Using advanced quantitative imaging algorithms, the researchers looked for any correlation between changes in CSF volumes and the structures of the visual system.
The results showed that, compared with short-duration astronauts, long-duration astronauts had significantly increased postflight flattening of their eyeballs and increased optic nerve protrusion. Long-duration astronauts also had significantly greater postflight increases in orbital CSF volume, or the CSF around the optic nerves within the bony cavity of the skull that holds the eye, and ventricular CSF volume—volume in the cavities of the brain where CSF is produced. The large postspaceflight ocular changes observed in ISS crew members were associated with greater increases in intraorbital and intracranial CSF volume.
"The research provides, for the first time, quantitative evidence obtained from short- and long-duration astronauts pointing to the primary and direct role of the CSF in the globe deformations seen in astronauts with visual impairment syndrome," Alperin said.
There were no significant postflight changes of gray matter volume or white matter volume in either group of astronauts.
Identifying the origin of the space-induced ocular changes is necessary, Alperin said, for the development of countermeasures to protect the crew from the ill effects of long-duration exposure to microgravity.
"If the ocular structural deformations are not identified early, astronauts could suffer irreversible damage," he noted. "As the eye globe becomes more flattened, the astronauts become hyperopic, or far-sighted."
According to Alperin, NASA is studying a number of possible measures to simulate the conditions that lead to VIIP and testing various countermeasures.
Coauthors on the study are Ahmet M. Bagci, PhD; Sang H. Lee, MS; and Byron L. Lam, MD.