Circulation: ICD ventricular defibrillation testing affects cognitive function

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A standard test of implantable cardioverter-defibrillators (ICDs) is linked to significant thought-processing problems that improve for most patients within a year after the device is inserted, according to a study published in the March 2 issue of Circulation: Arrhythmia and Electrophysiology.

After an ICD is inserted, electrophysiologists 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, according to previous studies. However, the long-term thought-processing, or 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," said Claire N. Hallas, PhD, lead author and assistant professor of psychology at the Sultan Qaboos University's College of Medicine and Health Sciences in Muscat, Oman

Hallas and colleagues performed cognitive exams in 52 U.K. patients prior to ICD implantation, and at six weeks, six months and 12 months post-procedure. The average age of patients was 61 years and 86 percent were male.

Overall, results showed that one-third of patients experienced a cognitive problem at the six-week, six-month and 12-month periods.

Researchers found that 20 percent of the post-cognitive exams showed a 20 percent decrease in impairment from exam scores prior to implantation. Patients showed the greatest loss of impairment in visual recall and attention.

The majority of patients who developed cognitive impairments, however, regained those functions within a year.

Investigators eliminated the influence of age-related cognitive problems by comparing their results to data on healthy, age-matched individuals.

Patients also completed surveys on anxiety, depression and quality of life, which researchers found to be unrelated to mental ability.

"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," Hallas said

She concluded that 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 three months."