Atrial Arrhythmias and Thromboembolic Events
In patients without a prior history of atrial fibrillation (AF), is detection of atrial arrhythmias by implanted cardiac resynchronization therapy (CRT) devices associated with thromboembolism (TE)?
This was an observational study conducted at a single center in Denmark. Consecutive patients without a history of AF who underwent implantation of a CRT device for symptomatic systolic heart failure from 2000-2010 were included in the study. The device was interrogated at 1 month, and 6 months after the procedure, and every 6-12 months thereafter. Early atrial high rate episodes (AHREs) were defined as sustained atrial arrhythmias (≥6 minutes) that occurred within the first 6 months after implantation. Patients were followed from implantation to death or September 2013.
A total of 394 patients (71% with CHA2DS2-VASc ≥4) were followed for a median of 4.2 years after the 6-month visit. AHREs were detected in 79 patients (20%) within the first 6 months after implantation. Clinical AF was diagnosed in 79 patients (20%) at a median of 2.4 years after implantation. Patients with AHREs were more likely to develop clinical AF as compared to those without (10%/year vs. 4%/year, hazard ratio 2.4, p = 0.001). A TE event occurred in 11/79 patients (14%) with AHREs as compared with 19/315 patients (6%) without early atrial arrhythmias (p = 0.028). However, this risk could only be demonstrated in patients with AHREs lasting >24 hours. AHREs were detected in 10 patients in the 2 months preceding the TE event, including three patients with AF at the time of the event. AHREs were not associated with all-cause mortality.
Detection of AHREs occurred in about 20% of patients undergoing CRT for heart failure and was associated with development of clinical AF. AHREs >24 hours were associated with TE, but there appeared to be no temporal relationship between atrial arrhythmias and embolism.
This study highlights the impact of atrial arrhythmias detected by cardiac implantable electronic devices (CIEDs) with respect to development of clinical AF and TE. It failed to show a temporal relationship between the occurrence of arrhythmias and TE, consistent with prior studies. It is possible that AF may simply be a marker as opposed to a direct cause of embolism. Causes of TE other than AF include left ventricular thrombus, and aortic/carotid/vertebral atherosclerotic disease. A prior study failed to show improved outcomes among patients with CIEDs in whom anticoagulation was initiated (and discontinued) based on remote detection (and “resolution”) of atrial arrhythmias. It is reasonable to initiate and maintain oral anticoagulation in device patients with AHREs and who are at risk for TE.
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