What signs of atrial fibrillation (AFib) may be increasing while you take lacosamide?
Atrial fibrillation can cause symptoms that come and go. People often notice them more when their heart rate rises or their rhythm becomes irregular. Common signs include:
- Palpitations (feeling a fluttering, racing, or pounding heartbeat)
- Shortness of breath, especially with activity or when lying flat
- Dizziness, lightheadedness, or feeling faint
- Chest discomfort or pressure
- Unusual fatigue or weakness
- Reduced exercise tolerance
If these symptoms are happening more often after starting or increasing lacosamide, it may reflect rhythm instability that should be checked promptly with your clinician.
Could lacosamide itself trigger AFib or rhythm changes?
Lacosamide can affect heart conduction. It is known to cause rhythm/conduction effects in some people, which can show up as changes in heart rate or rhythm (for example, worsening arrhythmias or abnormal conduction patterns). Because of that, AFib symptoms can feel like they are increasing after starting or changing the dose, particularly in people with existing heart rhythm problems or other cardiac risk factors.
If you are taking lacosamide and also have AFib, your prescriber may need to review your dose and your heart monitoring results (such as an ECG, Holter/event monitor, and electrolyte or medication review).
What symptoms are emergencies?
Get emergency care (or call local emergency services) if you have AFib symptoms plus any of the following:
- Chest pain/pressure lasting more than a few minutes, or with sweating/nausea
- Fainting or severe dizziness
- Severe shortness of breath at rest
- Signs of stroke: face drooping, arm weakness, speech trouble, sudden confusion, sudden vision changes, sudden severe headache
These are time-sensitive regardless of whether lacosamide is related.
When should you contact a doctor urgently (not just “wait and see”)?
Contact your clinician soon or seek urgent evaluation if:
- Palpitations are new, stronger, or happening more frequently
- Your resting heart rate is persistently very fast
- You feel repeated near-fainting, significant dizziness, or worsening breathlessness
- AFib episodes last longer than usual, come with chest discomfort, or don’t improve with your usual plan
What to do right now if you suspect AFib is worsening on lacosamide
- Check your pulse and, if possible, use a home device (smartwatch/ECG monitor) to capture rhythm when symptoms occur.
- Note timing: when you took lacosamide, when symptoms started, and whether you missed doses or changed other medications.
- Do not stop lacosamide suddenly unless a clinician tells you to, because sudden withdrawal can increase seizure risk. Instead, contact your prescriber promptly to adjust or review treatment.
What information your clinician will likely want
Expect questions about:
- Your lacosamide dose and when it was started or increased
- Other heart meds (rate or rhythm control drugs), anticoagulants, and any recent changes
- Your baseline AFib history (paroxysmal vs persistent, typical episode length)
- Recent ECG results and whether any conduction abnormality was noted
Sources
None provided in the question. If you share your lacosamide dose, how long you’ve been on it, your age, and what your AFib symptoms are (plus any recent ECG findings), I can help you interpret what to discuss with your prescriber and what “red flag” thresholds to use.