From the Research
AMS episodes on Abbott pacemakers refer to Atrial Mode Switch events, which are a protective feature designed to prevent tracking of rapid atrial rates during atrial tachyarrhythmias like atrial fibrillation. When the pacemaker detects an atrial rate exceeding a programmed threshold (typically 170-180 bpm), it automatically switches from a tracking mode (like DDD) to a non-tracking mode (like DDI or DDIR) to prevent rapid ventricular pacing. This protects the patient from experiencing symptoms of rapid heart rate that would occur if the ventricle followed every atrial beat during an atrial arrhythmia. The pacemaker records these episodes, allowing clinicians to identify previously undetected atrial arrhythmias. The device returns to normal tracking mode once the atrial arrhythmia terminates. When reviewing device diagnostics, physicians should evaluate the frequency, duration, and burden of AMS episodes as they may indicate the need for anticoagulation therapy or antiarrhythmic medications, especially if the patient has risk factors for stroke. The sensitivity and specificity of AMS detection can be adjusted in device programming to optimize arrhythmia detection while minimizing inappropriate mode switches, as seen in a study published in the Journal of Electrocardiology 1. Key considerations for AMS episodes include:
- Evaluation of frequency, duration, and burden of AMS episodes
- Adjustment of device programming to optimize arrhythmia detection and minimize inappropriate mode switches
- Consideration of anticoagulation therapy or antiarrhythmic medications for patients with risk factors for stroke, as discussed in a study published in the American Journal of Cardiovascular Drugs 2. In a study published in Europace, it was found that the total duration of AF is correctly represented by the total duration of AMS and can be considered a reliable measure of total AF duration 3. However, the number of mode switches does not reflect the number of episodes of AF/AT, and increased memory capacity allowing the storing of all EGMs triggered by the initiation of AF/AT would be the ideal setting with which to optimize the diagnostic performance of pacemakers. A more recent study published in Pacing and Clinical Electrophysiology discussed a case of clinical worsening due to inappropriate automatic mode switch during biventricular pacing, highlighting the importance of proper device programming and troubleshooting 4. Overall, AMS episodes on Abbott pacemakers are an important diagnostic tool for identifying atrial arrhythmias and guiding treatment decisions.