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Thirty-second atrial fib threshold may drive overdiagnosis
BOSTON – The standard definition of an episode of atrial fibrillation is a fibrillation event that lasts at least 30 seconds, but a new analysis of monitoring data collected from 615 patients showed that this threshold can label many patients as having atrial fibrillation despite an extremely low disease burden.
A more clinically relevant definition of atrial fibrillation (AF) might be a patient with at least one episode that persists for at least 3.8 hours, because this threshold identified people with a median AF burden of just under 10%, Jonathan S. Steinberg, MD, said while presenting a poster at the annual scientific sessions of the Heart Rhythm Society.
The 30-second threshold for defining an AF episode dates from the early days of atrial ablation treatment, when researchers tracked ablated patients for signs of AF recurrence. But this definition that clinicians devised for a very select subgroup of AF patients subsequently “metastasized” to define AF in all settings, he noted. As one recent example, the 2017 consensus document on screening for AF in asymptomatic people defined asymptomatic patients as having AF if they had at least one 30-second event picked up on an ECG recording (EP Europace. 2017 Oct 1;19[10]:1589-623).
“How we define AF is very important as we look for it in asymptomatic people,” Dr. Steinberg said in an interview.
A better definition of AF might depend on total AF burden, which is the percentage of time the patient’s atrium spends fibrillating. But it’s impossible to directly measure AF burden over a reasonably representative period of time without having an implanted device. If AF is monitored with an external device, the sampling time will be relatively brief, and so the AF assessment needs to rely on a surrogate for AF burden: the longest duration of any measured AF episode.
“No prior AF database has been analyzed like we have,” to correlate AF burden with the duration of the longest AF episode, Dr. Steinberg said.
He and his associates used data collected by Medtronic from 1,040 patients enrolled in a company registry during 2005-2016 with an implanted dual-chamber pacemaker able to detect atrial arrhythmias. The researchers focused on the 615 patients who had AF detected during at least 30 days of monitoring. These 615 patients averaged 72 years of age, 54% were men, and 599 had at least one AF episode of at least 30 seconds duration. Each patient had an average 3.7-year accumulated archive of atrial rhythm data.
The analysis showed a close association between the longest AF episode detected and overall AF burden. Among patients with a longest episode of 30-119 seconds, the median burden was 0.1%. Among patients with a maximum duration of anywhere from 30 seconds to 3.7 hours, the median burden was 0.2%. But among people with a longest episode of 3.8 hours to 5.4 hours, the median burden was 1.2%. In those with a longest episode of at least 24 hours, the median burden was 25%. Finally, in those who had a longest AF episode that lasted at least 3.8 hours, the median AF burden was 9.5%.
Dr. Steinberg acknowledged that a very important additional step needed in this analysis is examining the correlations among AF burden, longest AF episode, and stroke incidence, something he and his associates are now doing. He expressed hope that these data will spur the cardiac electrophysiology community to rethink its AF definition.
The study was funded by Medtronic. Dr. Steinberg has been a consultant and/or has received research funding from Medtronic, AliveCor, Allergen, Atricure, Biosense Webster, G Medical, and National Cardiac. Several of his coauthors were Medtronic employees.
SOURCE: Steinberg J et al. Heart Rhythm Society scientific sessions, B-P001-062.
BOSTON – The standard definition of an episode of atrial fibrillation is a fibrillation event that lasts at least 30 seconds, but a new analysis of monitoring data collected from 615 patients showed that this threshold can label many patients as having atrial fibrillation despite an extremely low disease burden.
A more clinically relevant definition of atrial fibrillation (AF) might be a patient with at least one episode that persists for at least 3.8 hours, because this threshold identified people with a median AF burden of just under 10%, Jonathan S. Steinberg, MD, said while presenting a poster at the annual scientific sessions of the Heart Rhythm Society.
The 30-second threshold for defining an AF episode dates from the early days of atrial ablation treatment, when researchers tracked ablated patients for signs of AF recurrence. But this definition that clinicians devised for a very select subgroup of AF patients subsequently “metastasized” to define AF in all settings, he noted. As one recent example, the 2017 consensus document on screening for AF in asymptomatic people defined asymptomatic patients as having AF if they had at least one 30-second event picked up on an ECG recording (EP Europace. 2017 Oct 1;19[10]:1589-623).
“How we define AF is very important as we look for it in asymptomatic people,” Dr. Steinberg said in an interview.
A better definition of AF might depend on total AF burden, which is the percentage of time the patient’s atrium spends fibrillating. But it’s impossible to directly measure AF burden over a reasonably representative period of time without having an implanted device. If AF is monitored with an external device, the sampling time will be relatively brief, and so the AF assessment needs to rely on a surrogate for AF burden: the longest duration of any measured AF episode.
“No prior AF database has been analyzed like we have,” to correlate AF burden with the duration of the longest AF episode, Dr. Steinberg said.
He and his associates used data collected by Medtronic from 1,040 patients enrolled in a company registry during 2005-2016 with an implanted dual-chamber pacemaker able to detect atrial arrhythmias. The researchers focused on the 615 patients who had AF detected during at least 30 days of monitoring. These 615 patients averaged 72 years of age, 54% were men, and 599 had at least one AF episode of at least 30 seconds duration. Each patient had an average 3.7-year accumulated archive of atrial rhythm data.
The analysis showed a close association between the longest AF episode detected and overall AF burden. Among patients with a longest episode of 30-119 seconds, the median burden was 0.1%. Among patients with a maximum duration of anywhere from 30 seconds to 3.7 hours, the median burden was 0.2%. But among people with a longest episode of 3.8 hours to 5.4 hours, the median burden was 1.2%. In those with a longest episode of at least 24 hours, the median burden was 25%. Finally, in those who had a longest AF episode that lasted at least 3.8 hours, the median AF burden was 9.5%.
Dr. Steinberg acknowledged that a very important additional step needed in this analysis is examining the correlations among AF burden, longest AF episode, and stroke incidence, something he and his associates are now doing. He expressed hope that these data will spur the cardiac electrophysiology community to rethink its AF definition.
The study was funded by Medtronic. Dr. Steinberg has been a consultant and/or has received research funding from Medtronic, AliveCor, Allergen, Atricure, Biosense Webster, G Medical, and National Cardiac. Several of his coauthors were Medtronic employees.
SOURCE: Steinberg J et al. Heart Rhythm Society scientific sessions, B-P001-062.
BOSTON – The standard definition of an episode of atrial fibrillation is a fibrillation event that lasts at least 30 seconds, but a new analysis of monitoring data collected from 615 patients showed that this threshold can label many patients as having atrial fibrillation despite an extremely low disease burden.
A more clinically relevant definition of atrial fibrillation (AF) might be a patient with at least one episode that persists for at least 3.8 hours, because this threshold identified people with a median AF burden of just under 10%, Jonathan S. Steinberg, MD, said while presenting a poster at the annual scientific sessions of the Heart Rhythm Society.
The 30-second threshold for defining an AF episode dates from the early days of atrial ablation treatment, when researchers tracked ablated patients for signs of AF recurrence. But this definition that clinicians devised for a very select subgroup of AF patients subsequently “metastasized” to define AF in all settings, he noted. As one recent example, the 2017 consensus document on screening for AF in asymptomatic people defined asymptomatic patients as having AF if they had at least one 30-second event picked up on an ECG recording (EP Europace. 2017 Oct 1;19[10]:1589-623).
“How we define AF is very important as we look for it in asymptomatic people,” Dr. Steinberg said in an interview.
A better definition of AF might depend on total AF burden, which is the percentage of time the patient’s atrium spends fibrillating. But it’s impossible to directly measure AF burden over a reasonably representative period of time without having an implanted device. If AF is monitored with an external device, the sampling time will be relatively brief, and so the AF assessment needs to rely on a surrogate for AF burden: the longest duration of any measured AF episode.
“No prior AF database has been analyzed like we have,” to correlate AF burden with the duration of the longest AF episode, Dr. Steinberg said.
He and his associates used data collected by Medtronic from 1,040 patients enrolled in a company registry during 2005-2016 with an implanted dual-chamber pacemaker able to detect atrial arrhythmias. The researchers focused on the 615 patients who had AF detected during at least 30 days of monitoring. These 615 patients averaged 72 years of age, 54% were men, and 599 had at least one AF episode of at least 30 seconds duration. Each patient had an average 3.7-year accumulated archive of atrial rhythm data.
The analysis showed a close association between the longest AF episode detected and overall AF burden. Among patients with a longest episode of 30-119 seconds, the median burden was 0.1%. Among patients with a maximum duration of anywhere from 30 seconds to 3.7 hours, the median burden was 0.2%. But among people with a longest episode of 3.8 hours to 5.4 hours, the median burden was 1.2%. In those with a longest episode of at least 24 hours, the median burden was 25%. Finally, in those who had a longest AF episode that lasted at least 3.8 hours, the median AF burden was 9.5%.
Dr. Steinberg acknowledged that a very important additional step needed in this analysis is examining the correlations among AF burden, longest AF episode, and stroke incidence, something he and his associates are now doing. He expressed hope that these data will spur the cardiac electrophysiology community to rethink its AF definition.
The study was funded by Medtronic. Dr. Steinberg has been a consultant and/or has received research funding from Medtronic, AliveCor, Allergen, Atricure, Biosense Webster, G Medical, and National Cardiac. Several of his coauthors were Medtronic employees.
SOURCE: Steinberg J et al. Heart Rhythm Society scientific sessions, B-P001-062.
REPORTING FROM HEART RHYTHM 2018
Key clinical point:
Major finding: The median atrial fibrillation burden was 0.1% when the longest AF episode was 30-119 seconds.
Study details: Review of data from 615 patients with AF events in a Medtronic registry.
Disclosures: Medtronic funded the study. Dr. Steinberg has been a consultant and/or has received research funding from Medtronic, AliveCor, Allergen, Atricure, Biosense Webster, G Medical, and National Cardiac. Several of his coauthors were Medtronic employees.
Source: Steinberg J et al. Heart Rhythm Society scientific sessions B-P001-062.