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ASSERT: Subclinical atrial tachyarrhythmias associated with increased risk for ischemic stroke, systemic embolism
Healey JS. N Engl J Med. 2012;366:120-129.
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Subclinical atrial tachyarrhythmias were associated with a significantly increased risk for ischemic stroke or systemic embolism in patients who had undergone implantation of a pacemaker or cardiac defibrillator and who had no history of atrial fibrillation, according to results of the ASSERT trial.
“About 15% of strokes are attributable to documented [AF], and 50% to 60% to documented cerebrovascular disease, but in about 25% of patients who have ischemic strokes, no etiologic factor is identified,” the researchers wrote. “Subclinical [AF] is often suspected to be the cause of stroke in these patients. However, the prevalence and prognostic value of subclinical atrial fibrillation has been difficult to assess.”
The Asymptomatic Atrial Fibrillation and Stroke Evaluation Trial (ASSERT) included 2,580 patients aged at least 65 years who had hypertension but no history of AF. The patients recently had a pacemaker or defibrillator implanted. The researchers evaluated the patients for 3 months for subclinical atrial tachyarrhythmias. The patients were then followed for a mean of 2.5 years. The primary outcome was ischemic stroke or systemic embolism.
At 3 months, 261 patients had experienced subclinical atrial tachyarrhythmias that were detected by the implanted devices. Subclinical atrial tachyarrhythmias were associated with an increased risk for clinical AF (P,.001). They also were associated with an increased risk for ischemic stroke or systemic embolism (P=.007).
After the 3 months, 11 of the 261 patients who experienced subclinical atrial tachyarrhythmias had an ischemic stroke or systemic embolism vs. 40 of the 2,319 patients who did not have subclinical atrial tachyarrhythmias. None of the 51 patients who had an ischemic stroke or systemic embolism had clinical AF by 3 months.
“Episodes of subclinical atrial tachyarrhythmias were almost eight times as common as episodes of clinical [AF],” the researchers wrote. “During the course of the study, clinical atrial fibrillation developed in only 15.7% of the patients with subclinical atrial tachyarrhythmias, suggesting that there can be a lag between subclinical events and clinical detection.”
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