Afib is the most commonly diagnosed rhythm disturbance, and the numbers are only increasing as the global population ages. According to a study in the Journal of Geriatric Cardiology, 6 to 12 million Americans will have Afib by 2050, and 17.9 million Europeans will have it by 2060.
Ambulatory ECG plays an important role in detecting less frequent bouts of Afib that might not be detected on a one-time standard ECG in the office, which can have implications for getting Afib patients started on important medications and monitoring their responses to therapy.
There are several types of ambulatory cardiac monitoring devices that can provide clinicians with information on patients' arrhythmia status over the course of a few days or even years. Extended ECG monitoring can be used to connect symptoms like syncope, dizziness, palpitations, and chest pain to underlying arrhythmias, and it can also help clinicians look for previously undetected rhythm disorders and choose between multiple therapeutic options.
Monitoring the Effects of Antiarrhythmic Drug Therapy
One potential role of extended ECG monitoring is assessing a patient's response to antiarrhythmic drugs, most of which carry the risk of negative effects on heart rate and conduction speed in the AV node, as noted by the International Society for Holter and Noninvasive Electrocardiology (ISHNE) and the Heart Rhythm Society (HRS) in guidance published in Heart Rhythm in 2017.
For that reason, the societies suggested that "outpatient monitoring with ambulatory ECG may be used when starting antiarrhythmic drugs that do not require hospitalization for initiation." They noted that certain drugs, such as flecainide and propafenone, "can transform atrial fibrillation into atrial flutter with 1:1 AV conduction or aggravate preexisting conduction abnormalities causing QRS prolongation or patterns of AV block." In addition, class III antiarrhythmics like sotalol, amiodarone, dofetilide, and dronedarone carry a risk of torsade de pointes, which can be predicted by various ambulatory ECG findings, including:
- Increasing QT intervals (particularly postpause)
- Prominent U waves
- T-wave alternans
- Greater prevalence of ventricular ectopy
The authors stated that ambulatory monitoring "may be reasonable" during dose initiation and titration in the outpatient setting and pointed out that many antiarrhythmics may worsen sinus or AV node dysfunction, noting that "presence of significant bradyarrhythmia and/or correlation with symptoms may be confirmed with prolonged ECG recording."
Clarifying the Need for Anticoagulation
Prolonged ECG monitoring may also be helpful in evaluating patients who have had an ischemic stroke with no apparent cause—a so-called cryptogenic stroke—that could be identified through a thorough assessment involving 12-lead ECG. According to the ISHNE/HRS guidance, nailing down a definitive Afib diagnosis will determine whether oral anticoagulation, rather than aspirin, is warranted.
"Ambulatory ECG recording after cryptogenic stroke has particular utility, although atrial fibrillation detection is sensitive to the patient selection process, the definition of atrial fibrillation, and the duration of monitoring," the authors noted. They also pointed out that the EMBRACE trial, published in the New England Journal of Medicine, showed that 30-day monitoring uncovered more Afib than 24-hour monitoring and increased the prescription of oral anticoagulation in patients with cryptogenic stroke.
In the most recent European Afib guidelines published in the European Heart Journal, there is a strong recommendation to look for Afib in patients with an acute ischemic stroke or TIA using short-term ECG for at least the first 24 hours, "followed by continuous ECG monitoring for at least 72 hours whenever possible."
Extended ECG monitoring is also crucial in assessing the success of catheter ablation for Afib and could identify a need for additional therapies. Afib recurrence early on after ablation "may indicate greater likelihood of need for additional procedures or drugs," according to the authors of the ISHNE/HRS guidance.
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So-called "pill-in-pocket" approaches facilitated by ECG recordings taken in the outpatient setting have been studied for use of antiarrhythmic drugs and oral anticoagulation in Afib patients. The idea is that patients self-administer medication only in response to an episode of Afib rather than taking it chronically as a way to reduce potential side effects and costs.
A study published in Heart Rhythm suggested a pill-in-pocket approach for antiarrhythmic drug therapy could be effective in patients with symptomatic, sustained Afib, though "rates of treatment failure and adverse events are clinically relevant."
More recently, the strategy has been tested for use of oral anticoagulation, with patients only taking the medication for a defined period of time after Afib is detected on a device. The goal is to reduce the upfront stroke risk and limit the risk of bleeding that comes with chronic anticoagulation. Preliminary data from REACT.COM and TACTIC-AF pilot studies suggests that this approach holds promise.