LOS ANGELES – When patients receive shocks from implantable cardioverter defibrillators their anxiety level rises, and so does their mortality rate.
Measured anxiety levels significantly correlated with the occurrence of shocks from ICDs, the total number of shocks that patients received, and how recently the shocks occurred, in a prospective study of 704 consecutive ICD recipients from one U.S. center, Dr. Jason George and his associates reported in a poster at the annual scientific sessions of the American Heart Association.
In addition, patients who received three or more shocks had a 15% mortality rate during a median of 2.8 years of follow-up, significantly more than the 6% rate among patients who received fewer than three shocks, based on prospective follow-up of 690 consecutive ICD recipients at the same center, said Dr. George, a physician at the Cleveland Clinic.
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Shocks from an ICD can raise a patient's anxiety level and mortality rate.
The substantial 36% prevalence of mild or greater anxiety found in these ICD patients suggested that "attention to anxiety may help patients who experience any type of shock," and may be especially helpful to patients who received several shocks or recent shocks, the researchers said.
The link found between higher shock number and increased mortality confirms observations previously made in other studies, they added, although unlike prior reports, the current study found this link only for appropriate shocks. The finding raises the question of whether measures designed to suppress shocks might boost patient survival, they said.
The anxiety analysis included patients who received an ICD more than 4 weeks prior to enrollment into the study at the Cleveland Clinic between March 2009 and December 2010. Patient assessment with the Beck Anxiety Inventory (BAI) showed that 36% had a score of at least 8, the threshold for mild anxiety. The average BAI score among the 239 patients (34% of the patients assessed) who had ever received at least one shock was 8.3, while the average score among the other 465 patients was 6.7, showing that nonshocked patients had minimal anxiety. The difference in average scores between these two subgroups was statistically significant, the investigators reported.
Among patients who had received a shock within 4 weeks of BAI scoring, the average score was 11.2, while among patients who had not received a shock within the prior 4 weeks the average BAI score was 7.1, also a significant difference. The analysis also showed that depression was not significantly associated with shocks.
The mortality analysis performed by Dr. George and his associates at the Cleveland Clinic included 690 patients followed prospectively after they received an ICD between March 2009 and December 2010. During follow-up, a total of 8.3% of the patients died. This analysis showed that patients who received only inappropriate shocks, patients who received two or fewer shocks, and those who received no shocks each had about the same mortality rate, about a 6% rate during the median 2.8 years of follow-up. Patients who received only appropriate shocks had about an 11% mortality rate during follow-up, and patients who received both appropriate and inappropriate shocks had the highest mortality rate, about 22%.
Overall, patients who died received an average of 5.4 shocks, while those who did not die received an average of 2.3 shocks. "These findings suggest that shocks may be a secondary marker of mortality rather than a primary cause of mortality," Dr. George and his associates concluded.
Dr. George and his associates said that they had no disclosures.