Continuous EKG identifies asymptomatic subclinical atrial fibrillation (lasting for ≥ 5 minutes) in 35% of individuals older than 65 with any of the following backgrounds: sleep apnea, obesity, CHA2DS2-VASc score of ≥ 2, left atrial enlargement and elevated BNP.
More research is needed to understand the clinical significance of such asymptomatic episodes: Would they lead to more serious paroxysmal, persistent or permanent atrial fibrillation? If so, how often? Would the device be cost effective? Should it be utilized in specific patients, or good for mass screening?
I personally anticipate a wide application of the implantable continuous EKG in the future.
Background: Long-term continuous EKG monitoring shows a substantial prevalence of asymptomatic, subclinical atrial fibrillation (scAfib) in patients with pacemakers and patients with cryptogenic stroke. It is unknown if scAfib is also common in other patients without these conditions.
Methods: We implanted sub-cutaneous EKG monitors (St. Jude CONFIRM-AF) in patients ≥ 65 years attending cardiovascular or neurology outpatient clinics if they had no history of atrial fibrillation (Afib) but did have any of:
- CHA2DS2-VASc score of ≥ 2,
- Sleep apnea,
- Body mass index (BMI) > 30,
- Left atrial enlargement (≥ 4.4 cm or volume ≥ 58 mL),
- Increased serum NT-ProBNP (≥290 pg/mL).
Patients were monitored for scAfib lasting ≥ 5 minutes.
Results: 256 patients were followed for 16.3 months. Baseline age was 74 years, mean CHA2DS2-VASc score was 4.1, left atrial diameter averaged 4.7 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; p<0.05). Baseline predictors of scAfib were:
- Increased age (HR per decade: 1.55; p<0.05),
- Left atrial dimension (HR per centimeter diameter: 1.43; p<0.05),
- Blood pressure (HR per 10 mmHg 0.87; p<0.05),
- 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 without (p=0.32).
- The cumulative scAfib detection rate was higher (51.9% per year) in those with left atrial volume above the median value of 73.5 mL.
Subclinical atrial fibrillation is frequently detected by continuous EKG monitoring in older patients without prior history of Afib who are attending outpatient cardiology and neurology clinics. Its clinical significance is unclear.