Short Episodes of Tachycardia, AFib Have Little to No Effect on Stroke Risk

Short episodes of atrial tachycardia (AT) and/or atrial fibrillation (AF) in patients with implanted cardiac devices are not associated with increased risk of stroke and other clinical events, although they were more likely to escalate to longer episodes that did show a slightly significant risk, according to study results reported in Circulation.

The researchers, all members of the RATE (Registry of Atrial Tachycardia and Atrial Fibrillation Episodes) Registry investigators, enrolled a total of 5379 patients from 225 sites from 2006 to 2012 who had either implantable cardiac defibrillators (ICDs) or pacemakers, with follow up every 6 months for 2 years.  Within that cohort, 3141 patients with pacemakers were, on average, 7 years older than the 2238 who had ICDs.

During the study period, there were 2232 hospital admissions. Of those, 342 patients accounted for 478 hospitalizations for clinical events that were defined as symptomatic atrial arrhythmias (n=94), heart failure (n=265), or stroke/transient ischemic attacks (TIAs) (n=47). A total of 837 clinical events were reported in the cohort, including 359 deaths, which was lower than the 949 clinical events that had been statistically predicted.

Approximately 130,000 electrograms (EGMs) taken during the study were used to evaluate the rates of both long and short episodes of AT/AF. A random sample of 600 adjudicated (300 pacemaker and 300 ICD) patients was also used as a control.

Episodes were reported more frequently among patients with ICDs and pacemakers (40% and 37%, respectively) in the cohort than among controls (30% and 31%, respectively), and the correlation grew stronger with longer AT/AF episodes, which were experienced by 29% with ICDs and 32% with pacemakers compared with 20% and 22% of controls, respectively.

Long episodes of AT/AF (defined as those which extended beyond the duration of a single EGM recording) were more likely to be associated with clinical events than short episodes (defined as both starting and ending during a single EGM).

During the 2-year follow-up period, nearly 55% of pacemaker patients and 47% of ICD patients who had brief AT/AF episodes went on to have at least 1 longer episode, which the investigators determined was of “borderline” statistical significance. Progression to longer AT/AF episodes was similar among the short duration group compared to a group who had no AT/AF episodes.

Short AT/AF episodes only were observed in 9% (n=26) of patients with pacemakers and 16% (n = 47) of patients with ICMs, without any progression to longer episodes. Three patients with short episodes only had strokes/TIAs and were given anticoagulants.

Clinical Implications

Anticoagulation therapy is commonly prescribed for patients who are believed to be at higher than normal risk of stroke or other cardiovascular event. The findings of the RATE study suggest that such therapy is not likely to show benefits in stroke reduction for patients with implantable cardiac devices who have only brief episodes of AT or AF. The authors recommend that brief episodes of AT/AF alone should not drive automatic use of anticoagulant therapy, but progression to longer episodes is greater cause for concern.

Disclosures: Drs Swiryn, Benditt, DiMarco, Lloyd-Jones, Orlov, Slawsky, and Waldo report a paid consulting relationship with St. Jude Medical. Mr Karst, Dr Qu, and Ms Turkel are employees of St. Jude Medical. Dr Benditt reports an equity relationshop with St. Jude Medical, a consulting and equity relationship with Medtronic, and grant support from the Dr Earl E Bakken Family in support of Heart-Brain research. Dr DiMarco reports a consulting relationship with Medtronic. Dr Orlov reports consulting and a research grant with Philips Healthcare, and Dr Waldo reports consulting and speaker relationships with Daiichi Sankyo, Janssen, Pfizer, and Bristol-Myers Squibb.

Reference

Swiryn S, Orlov MV, Benditt DG, for the RATE Registry Investigators. Circulation. 2016;134:1130–1140. doi:10.1161/CIRCULATIONAHA.115.020252.