Atrial fibrillation represents one of the most common cardiac conditions in geriatric patients and it increases the risk of stroke by a factor of five in non-rheumatic atrial fibrillation and by a factor of 17 in rheumatic atrial fibrillation.1 Detection of subclinical atrial fibrillation may be important for the prevention and treatment of thromboembolic complications with anticoagulation.2
Subclinical or ‘silent’ atrial fibrillation is the occurrence and detection of subclinical asymptomatic episodes of paroxysmal atrial fibrillation.3 Research interest has grown in the clinical relevance of atrial fibrillation at an early stage.
It is defined as atrial high-rate episodes (>6 minutes and <24-hours) with lack of correlated symptoms in patients with cardiac implantable electronic devices, detected with continuous ECG monitoring (intracardiac) and without prior diagnosis (ECG or Holter monitoring) of atrial fibrillation.4
With the integration of cardiac devices therapy in the management of heart failure and various cardiac arrhythmias, the incidence of subclinical atrial fibrillation is on the rise. The TRENDS trial established that the incidence of newly detected subclinical atrial fibrillation is 30% in patients using cardiac devices.5
Many of the patients with newly detected subclinical atrial fibrillation are elderly.6 So far, all the major studies looking into the thromboembolic risk have shown an increased stroke rate associated with device-detected subclinical atrial fibrillation.
The minimum duration of subclinical atrial fibrillation that increases the thromboembolic risk is still unclear, ranging from five minutes in some studies to 24 hours.
The TRENDS trial showed that thromboembolic risk increases with episodes lasting for 5.5 hours or more,7 while other trials like the ASSERT study showed the risk to be increased with episodes as brief as six minutes.8
Many patients presenting to cardiology clinics with subclinical atrial fibrillation are elderly with multiple comorbidities and issues with ongoing polypharmacy. This does not make the commencement of anticoagulation a straightforward decision. A lack of awareness of the current evidence in regards to the thromboembolic risk posed by these episodes among some physicians also makes the decision-making process quite slow.
Although the minimum duration of subclinical atrial fibrillation that increases the risk of cryptogenic strokes is still not clear, most studies showed the cut-off duration to range from five minutes to 24 hours.
The lack of temporal relationship of subclinical atrial fibrillation to cryptogenic stroke was examined in three major studies; TRENDS,9 ASSERT10 and IMPACT AF.11 All raised a very important question of whether subclinical atrial fibrillation in itself is a thromboembolic risk or whether it is merely a marker of increased risk in cases of atrial dilatation and/or fibrosis. Again the pathophysiology of cryptogenic strokes in cases of subclinical atrial fibrillation is not clear.
Many of the elderly patients presenting with this condition are struggling with dementia, which can make their compliance to anticoagulants less reliable.
In addition, advanced chronic kidney disease grade can limit the anticoagulant pharmaceutical agents we can use, in addition to increasing the bleeding risk because of platelet dysfunction in some cases.
In 2017, the European Heart Rhythm society (EHRS) published its consensus on device-detected subclinical atrial tachyarrhythmias and their management by reviewing all the research trials since the early 2000s and building up a friendly system of graded guidelines. The consensus is invaluable to our current medical management of these patients considering the lack of official national or international guidelines on this issue.
We strongly recommend that any physician involved in the management of arrhythmias in the elderly should read the consensus as it highlights a lot of important technical diagnostic and therapeutic aspects beyond the scope of this article.4
Should we start anticoagulation in this patient?
Based on the EHRS consensus, we have developed a simplified flow chart for local use to guide our thought process while considering anticoagulation for patients presenting with subclinical atrial fibrillation (Figure 1).
Please note that the decision of whether to start anticoagulation in any patient is still an individualised decision especially among the geriatric population.
By definition, subclinical atrial fibrillation patients should not be presenting with symptoms correlating with the episodes detected by the device, but the presence or lack of symptoms should have no effect on the decision for anticoagulation as clearly documented in the EHRS consensus 4,14,15,16
The bleeding risk, which is a major concern, should be assessed thoroughly on each clinic review by taking a thorough medical history, performing the required comprehensive physical examination, and investigating any reversible causes.
Bleeding risk assessment using the HAS-BLED score is important, as it can guide the frequency of follow ups and clinic reviews (more regular reviews for patients with score >/= 3). Although a high score should not be a reason to withhold anticoagulation therapy in cases with high risk of developing a thromboembolic stroke.
The decision to start anticoagulation should be taken after an extensive discussion with the patients, exploring their expectations, their background knowledge, any issues with compliance, any ongoing investigations for previous bleeding episodes or undiagnosed occult malignancies and finally the implications of being on lifelong anticoagulants.
Novel oral anticoagulants (NOACs) versus vitamin K antagonists?
Anticoagulation with vitamin K antagonists (VKA) in atrial fibrillation has been the mainstay of therapy for decades to prevent stroke and systemic embolism.17,18 However, the need for regular monitoring of INR (International Normalized Ratio) and multiple drug and food interactions of VKA have led to the development of novel oral anticoagulants (NOACs). Most guidelines now recommend the use of NOACs over vitamin K antagonists.
The European Heart Rhythm Society recommends using NOACs or well controlled VKAs with the TTR >70% (time in therapeutic INR range >70%).4
The Canadian Cardiovascular Society recommends the usage of NOACs over VKA, while the American Heart Association (AHA), American College of Cardiology (ACC) and Heart Rhythm Society HRS all state that considering VKA in patients with end-stage CKD (creatinine clearance CrCl <15ml/min or are on hemodialysis) is reasonable.19
In geriatric patients it is very important to consider their baseline kidney function, in addition to exploring whether the facilities to have regular monitoring of their INR are available (nurse home visits, medical services available at the nursing home, close by GP surgeries or walk in centers).
Subclinical atrial fibrillation is a common finding on cardiac device interrogations in elderly patients. Unfortunately, there are still evidence gaps that will hopefully be clarified over the next few years. Getting familiar with the current evidence is a must for correct management of these cases, in addition to a thorough comprehensive medical assessment. Using risk scores is very helpful as a guide in these cases, but management should adopt a more holistic approach while reviewing these patients. This is exceptionally important when the arrhythmia burden is very low.
Dr Ramy Goubran, Cardiology Research Fellow, Liverpool Heart and Chest hospital
Conflict of interest: none declared
5. Ziegler PD, Glotzer TV, Daoud EG, et al. Detection of previously undiagnosed atrial fibrillation in patients with stroke risk factors and usefulness of continuous monitoring in primary stroke prevention. Am J Cardiol 2012; 110: 1309–14
7. Glotzer TV, Daoud EG, Wyse DG, et al. The relationship between daily atrial tachyarrhythmia burden from implantable device diagnostics and stroke risk: the TRENDS study. Circ Arrhythm Electrophysiol 2009; 2: 474–80
9. Daoud EG, Glotzer TV, Wyse DG, et al. TRENDS Investigators, et al. Temporal relationship of atrial tachyarrhythmias, cerebrovascular events, and systemic emboli based on stored device data: a subgroup analysis of TRENDS. Heart Rhythm 2011; 8: 1416–23
11. Martin DT, Bersohn B, Waldo AL, et al. Randomized trial of atrial arrhythmia monitoring to guide anticoagulation in pa- tients with implanted defibrillator and resynchronization devices. Eur Heart J 2015; 36: 1660–68
13.Kolb C, Wille B, Maurer D, et al. Management of far-field R wave sensing for the avoidance of inappropriate mode switch in dual chamber pacemakers: results of the FFS-test study. J Cardiovasc Electrophysiol 2006; 17: 992–97
14. Capucci A, Santini M, Padeletti L, et al. Monitored atrial fibrillation duration predicts arterial embolic events in patients suffering from bradycardia and atrial fibrillation implanted with antitachycardia pacemakers. J Am Coll Cardiol 2005; 46: 1913–20
15. Glotzer TV, Daoud EG, Wyse DG, et al. The relationship between daily atrial tachyarrhythmia burden from implantable device diagnostics and stroke risk: the TRENDS study. Circ Arrhythm Electrophysiol 2009; 2: 474–80
16. Oriani G, Glotzer TV, Santini M, et al. Device-detected atrial fibrillation and risk for stroke: an analysis of > 10,000 patients from the SOS AF project (Stroke preventiOn Strategies based on Atrial Fibrillation information from implanted devices). Eur Heart J 2014; 35: 508–16
18. Roskell NS, Samuel M, Noack H, et al. Major bleeding in patients with atrial fibrillation receiving vitamin K antagonists: a systematic review of randomized and observational studies. Europace. 2013; 15(6): 787–97