Brief Atrial Arrhythmias in Device Patients Don't Up Stroke Risk

CHICAGO, IL — Short episodes of atrial tachycardia (AT) or atrial fibrillation (AF) do not put patients with cardiac rhythm control devices at excess risk of adverse clinical events including stroke, according to a RATE Registry analysis^[1].

Based on careful adjudication of more than 37,000 electrograms (EGMs), US investigators found patients with clinical events were no more likely than those without events to have brief episodes of AT/AF: 5.1% vs 7.9% for pacemaker patients (P=0.21) and 11.5% vs 10.4% for implantable cardioverter defibrillator (ICD) patients (P=0.66).

Principal investigator Dr Steven Swiryn (Northwestern University, Chicago, IL) told heartwire from Medscape, "What we can say is if you have a patient in clinic and they only have short episodes of atrial fibrillation as we defined them, that in and of itself should not be justification to anticoagulate a patient. But on the other hand, you need to keep scrutinizing that patient over time because some but not all of those patients will go on to have prolonged episodes in the future."

He noted that society guidelines recommend oral anticoagulation for all patients with paroxysmal AF with risk factors and no contraindications but don't quantify what duration of AF or frequency of AF episodes are required to warrant anticoagulation.

The issue "is especially important because of how common these little episodes are" in the general and device populations, Swiryn said. During the roughly 2-year follow-up, 50% of a random sample of 300 pacemaker and 300 ICD patients had at least one brief AT/AF episode, defined as those in which the onset and offset of AT/AF was captured within a single EGM recording.

As previously reported by heartwire , Swiryn presented results on the increased risk of clinical events with long AT/AF episodes based on 20,153 adjudicated EGMs from the RATE registry at the American Heart Association 2012 Scientific Sessions.

The current analysis, published online October 17, 2016 in Circulation, includes 37,530 adjudicated EGMs from 1736 patients including the random sample of 600 patients, all patients (cases) with a predefined clinical event, and two case controls without a clinical event matched by age, sex, and device type.

During follow-up there were 837 adjudicated clinical events, including emergency-room visits/hospitalizations for HF, atrial or ventricular arrhythmias, stroke or TIA, syncope, and death.

Multivariable analysis of 1565 patients (all cases and their two controls) revealed that the likelihood of any event after only short AT/AF was significantly less than that for patients with no AT/AF after adjustment for age, sex, history of MI, left atrial dimension, and LVEF (hazard ratio 0.86; 95% CI 0.77–0.97; P=0.01).

In contrast, occurrence of long AT/AF, defined as episodes in which onset and/or offset of AT/AF was not present within a single EGM recording, was linked with incident clinical events compared with those with no AT/AF (HR 1.68; 95% CI 1.49–1.88; P<0.001).

Several studies have linked brief episodes of AT/AF or frequent premature atrial complexes (PACs) to stroke, including the Framingham Study and the recently updated Copenhagen Holter Study^[2], in which >30 PACs/h daily or any runs of >20 PACs increased ischemic stroke risk beyond incident AF in middle-aged persons (HR 1.96).

In the present analysis, the likelihood of stroke or TIA if only short AT/AF was observed was not signficantly different from that of patients with no AT/AF (HR 0.87; 95% CI 0.58–1.31; P=0.51), whereas long AT/AF was associated with incident stroke or TIA (HR 1.51; 95% CI 1.03–2.21; P=0.03).

Swiryn said the rigorous adjudication of EGMs by eight experienced teams makes the RATE analysis unique in its ability to make statements about the clinical implications of brief AT/AF episodes. Prior studies have combined patients with AT/AF <5 min with those without AT/AF, used 12-lead ECGs every 2 years as the influential Framingham study did, or relied on device-documented AT/AF, which is often inaccurate.

"I think this is an important small contribution. It allows you to not prescribe an anticoagulant to someone who is not going to benefit or is very unlikely to benefit. . . . It allows you not to overreact," he said.

The RATE Registry was funded by St Jude Medical. Swiryn reports a paid consulting relation with St Jude. Disclosures for the coauthors are listed in the article.

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