A 79-Year-Old Woman With a Pacemaker and High Atrial Rates

Jeff S. Healey, MD, MSc, FRCPC; Jonathan P. Piccini, MD, MHS, FACC; Christian T. Ruff, MD, MPH


March 22, 2019

Editorial Collaboration

Medscape &

Clinical stroke risk factors (eg, hypertension, diabetes) are not the only determinants of stroke risk in patients with subclinical atrial fibrillation. Fairly consistent findings suggest that increased duration or burden of subclinical atrial fibrillation also predicts an increased risk for stroke. In the TRENDS study, patients with atrial high-rate events were divided into two groups on the basis of their maximum total daily burden of atrial high-rate events in the prior 30 days.[5] In patients whose burden exceeded 5.5 hours, a borderline significant, 2.2-fold increase in the risk for thromboembolic events was noted. Those with a lesser burden had no measurable increase in the risk for thromboembolism.

A subsequent analysis from the ASSERT trial examined patient outcomes according to their longest individual episode of subclinical atrial fibrillation, using a time-dependent survival analysis technique.[13] This analysis concluded that if patients developed episodes of subclinical atrial fibrillation lasting more than 24 continuous hours, their risk for stroke increased approximately 5-fold, reaching an annual risk of nearly 5% per year. This risk is similar in magnitude to clinical atrial fibrillation and is why the authors suggested that it might be reasonable to treat individuals with these longer episodes in a similar fashion to patients with clinically detected atrial fibrillation.[7,13] However, whether individuals with shorter episodes of subclinical atrial fibrillation should receive oral anticoagulation, or even if they are at increased risk for stroke, remains unclear. Over 2.5 years, only about 15% of such patients develop clinically detected atrial fibrillation or episodes longer than 24 hours; thus, watchful waiting may be a reasonable strategy for most patients.[6,11] The use of remote monitoring of a patient's pacemaker or implanted defibrillator can permit prompt recognition of longer episodes when they develop; however, this has not been shown to reduce stroke risk.[14]

Two large clinical trials are investigating whether patients with shorter episodes of subclinical atrial fibrillation (in one trial, between 6 minutes and 24 hours) benefit from treatment with an oral anticoagulant compared with a strategy of waiting and only treating if longer-lasting episodes or clinical atrial fibrillation develops.[7,8] Determining the optimal treatment strategy for this large group of patients with pacemakers and defibrillators is not only important for their clinical management but has much broader implications in this era marked by the proliferation of long-term noninvasive monitoring for atrial fibrillation, which includes devices marketed directly to patients.[15,16] Increasingly, physicians must determine how to manage patients with short-lasting episodes of subclinical atrial fibrillation detected incidentally during the investigation of other complaints (eg, syncope), or detected by patients themselves after purchasing devices capable of detecting atrial fibrillation.


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