Practice Update: Cardiology

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Significance of
Subclinical Atrial
Fibrillation in Older
Patients
Circulation
Take-home message
• This study followed 256 patients aged 74±6 years with
implanted subcutaneous electrocardiographic monitors
for 16.3±3.8 months to evaluate subclinical atrial fibrillation
(SCAF). SCAF ≥5 minutes was detected in 90 patients. Older
age, higher blood pressure, and larger left atrial dimension
were baseline predictors of SCAF. There was no difference
in SCAF occurrence between patients with or without a
history of TIA, stroke, or systemic embolism.
• These findings demonstrate the frequent detection of SCAF
in older patients; however, the clinical significance is not
clear at this time.
Abstract
BACKGROUND Long-term continuous electrocardiographic monitoring
shows a substantial prevalence of asymptomatic, subclinical atrial fibril-
lation (SCAF) in patients with pacemakers and patients with cryptogenic
stroke. It is unknown if SCAF is also common in other patients without
these conditions.
METHODS We implanted sub-cutaneous electrocardiographic monitors (St.
Jude CONFIRM-AF) in patients ≥ 65 years attending cardiovascular or
neurology outpatient clinics if they had no history of atrial fibrillation (AF)
but did have any of: CHA2DS2-VASc score of ≥ 2, sleep apnea, or body
mass index > 30. Eligibility also required either left atrial enlargement (≥
4.4 cm or volume ≥ 58 mL) or increased serum NT-ProBNP (≥290 pg/mL).
Patients were monitored for SCAF lasting ≥ 5 minutes.
RESULTS 256 patients were followed for 16.3±3.8 months. Baseline age was
74±6 years, mean CHA2DS2-VASc score was 4.1±1.4, left atrial diameter
averaged 4.7±0.8 cm, and 48% had a prior
stroke, transient ischemic attack or systemic
embolism. SCAF ≥ 5 minutes was detected
in 90 patients (detection rate 34.4% per year;
95% confidence interval [CI], 27.7-42.3%).
Baseline predictors of SCAF were increased
age (HR per decade: 1.55; 1.11-2.15), left atrial
dimension (HR per centimeter diameter: 1.43;
1.09-1.86), blood pressure (HR per 10 mmHg
0.87; 0.78-0.98), but not prior stroke. The rate
of occurrence of SCAF in those with a history
of prior stroke, systemic embolism or TIA was
39.4% per year versus 30.3% per year with-
out (p=0.32). The cumulative SCAF detection
rate was higher (51.9% per year) in those with
left atrial volume above the median value
of 73.5 mL.
CONCLUSIONS SCAF is frequently detected
by continuous electrocardiographic monitor-
ing in older patients without prior history of
AF who are attending outpatient cardiology
and neurology clinics. Its clinical significance
is unclear.
Subclinical atrial fibrillation in older patients.
Circulation 2017 Aug 04;[EPub Ahead of
Print], JS Healey, M Alings, AC Ha, et al.
COMMENT
By T. Jared Bunch MD
Atrial fibrillation (AF) continues to increase in incidence
worldwide as populations age and people live longer with
coexistent cardiovascular diseases.1 Tominimize AF-related
comorbidities, early recognition andmanagement of the arrhythmia
is advocated. AF diagnosis has been in a constant state of evolu-
tion as technologies have advanced to allow long-termmonitoring
through multiple types of cardiac implantable electronic devices
(CIED) andwearable devices. CIEDdetection of AF can significantly
precede clinical symptoms and diagnosis of the arrhythmia. Such
detection opportunities provide enthusiasm that very early treat-
ment of the arrhythmia may alter risks of stroke, heart failure, and
death, and perhaps alter that natural history of AF.
AF management is based upon the identification of coexisting
risk factors for adverse outcomes such as aging, diabetes, heart
failure, stroke, vascular disease, etc. These same risk factors
that predict AF outcomes also strongly predict its incidence. In a
study of 100,000 patients without AF followed on average for 9
years, with each additional risk factor the odds of AF increased
significantly from 3.05, 12.9, 22.8, 34.0, and 48.0, respectively.2
In another study of patients with a cryptogenic stroke, AF was
detected with a CIED in 12.4% at 1 year.3 As AF risk factors are
strongly associated with AF incidence, higher-risk patients may
benefit from implantation of a implantable loop recorder (ILR) to
prompt very early AF diagnosis.
Healey and colleagues, on behalf of the ASSERT II trial inves-
tigators, 4 in a study of 256 elderly patients (≥65 years) sought
to determine the incidence of subclinical AF in higher-risk
patients using ILRs. Higher risk was determined if the patient
had a CHA2DS2-VASc score of ≥2 or left atrial enlargement
with obstructive sleep apnea or a body mass index >30, or
an elevated NT-ProBNP ≥290 pg/mL. In this study, 48% of the
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PRACTICEUPDATE CARDIOLOGY