(Ivanhoe Newswire) -- A standard test of the implantable cardioverter
defibrillator (ICD) is linked to significant thought-processing problems which,
for most patients, improve within a year after the device is inserted.
After an ICD is inserted, doctors check its performance by medically causing
repeated episodes of irregular heartbeat. The procedure, known as ventricular
defibrillation testing, temporarily disrupts brain activity by causing a drop in
blood pressure and blood flow to the brain. However, the long-term cognitive
effects of these disturbances were unclear.
"What's surprising is that this minor procedure, which has very short periods of
ventricular defibrillation induction, results in significant decline in multiple
areas of cognitive function," lead author Claire N. Hallas, Ph.D., assistant
professor of psychology at Sultan Qaboos University's College of Medicine and
Health Sciences in Muscat, Oman, was quoted as saying.
Compared with pre-surgery scores on thought processing exams, more than
one-third of study participants had significant cognitive problems at six weeks,
six months and 12 months after ICD surgery. Attention, short-term memory of
visual words and objects, and auditory words were most commonly affected.
Although most patients regained their normal abilities by 12 months after
surgery, onset of cognitive problems varied among patients. A small group, about
10 percent, did not develop difficulties until 12 months after ICD surgery.
"We're interested now in the psychological and surgery-related factors that
could be related to late-onset cognitive decline," Dr. Hallas said. "We need
more research to understand what risk factors are involved in mediating this
Researchers administered a series of cognitive exams to 52 patients in the
United Kingdom several days before ICD surgery and again six weeks and six
months and 12 months afterwards. The exams measured a range of abilities,
including attention, visual and auditory memory, mental speed and flexibility,
and the ability to manipulate objects. Investigators identified a cognitive
problem when 20 percent of post-surgery exam scores showed a 20 percent decline
from pre-surgery scores.
"We tried to determine whether there were other factors, both surgical and
psychological, that could have influenced dysfunction, which proved not to be
the case," Dr. Hallas said. “Doctors need to be aware of screening patients
early on for particular problems and then referring patients for psychological
testing if they have concerns about effects that are more consistent over two or
SOURCE: Circulation: Arrhythmia and Electrophysiology, March 2, 2010