Tachycardia While Taking Lexapro (Escitalopram)
Your increased heart rate is most likely caused by escitalopram itself, which can induce tachycardia through multiple cardiac mechanisms including QT prolongation, changes in autonomic tone, and direct effects on cardiac ion channels.
Understanding Escitalopram's Cardiac Effects
Escitalopram belongs to the SSRI class of antidepressants, which are well-documented causes of tachycardia. The American College of Cardiology identifies SSRIs as medications that can trigger tachycardia, particularly when combined with other serotonergic drugs 1. The FDA drug label for escitalopram specifically documents tachycardic outliers occurring in 0.2% of patients in controlled trials 2.
Mechanisms of Escitalopram-Induced Tachycardia
Escitalopram causes tachycardia through several distinct pathways:
Direct cardiac electrophysiological effects: Escitalopram inhibits sodium channels (INa) and can shorten atrial action potential duration, both of which promote arrhythmias 3
Autonomic nervous system effects: SSRIs can increase sympathetic tone while also having antimuscarinic effects that remove parasympathetic brake on heart rate 3, 1
QT interval prolongation: The FDA reports that escitalopram 20mg produces a mean QTcF prolongation of 6.6 msec, with supratherapeutic doses (30mg) causing 10.7 msec prolongation 2. This QT prolongation can trigger compensatory tachycardia and increase arrhythmia risk 3
Critical Risk Factors to Assess
You need immediate evaluation if any of these apply:
Age >65 years: Recent research demonstrates that 20% of patients over 65 years reach potentially pro-arrhythmic escitalopram concentrations even on just 10mg daily due to age-dependent reduction in drug clearance 4
Concurrent medications: Combining escitalopram with other QT-prolonging drugs (ondansetron, domperidone, antipsychotics, other antidepressants) significantly increases arrhythmia risk 3, 1
Cardiac history: Pre-existing heart disease, conduction abnormalities, or structural heart disease substantially increase risk 5
Current dose: The FDA warns against doses >20mg daily due to QT prolongation and arrhythmia risk 2
Immediate Actions Required
Obtain an ECG immediately to assess:
- QTc interval: Treatment should be stopped if QTc >500 msec 3
- Heart rate and rhythm: Document whether tachycardia is sinus or another arrhythmia 3
- QRS duration: Widening suggests sodium channel blockade 3
- QRS/QTc ratio: Values <0.23 predict higher risk of ventricular arrhythmias in escitalopram toxicity 6
Check electrolytes immediately, particularly potassium and magnesium, as hypokalemia and hypomagnesemia potentiate drug-induced arrhythmias 3.
Management Algorithm
If Heart Rate <150 bpm and No Symptoms of Instability:
- Obtain baseline ECG and electrolytes 3
- Review all concurrent medications for QT-prolonging agents or other serotonergic drugs 3, 1
- Consider dose reduction if on >10mg daily, especially if age >65 years 4
- Implement therapeutic drug monitoring (TDM): Keep serum escitalopram concentrations <100 nM to reduce arrhythmia risk 4
If Heart Rate ≥150 bpm or Symptoms Present:
The American Heart Association guidelines indicate that heart rates ≥150 bpm are more likely to cause symptoms of instability 3. Assess for:
- Acute altered mental status
- Chest discomfort
- Acute heart failure signs
- Hypotension or shock
- Lightheadedness, dizziness, or syncope 3, 7
If any instability is present, this requires immediate emergency evaluation with continuous cardiac monitoring 3.
Alternative Explanations to Rule Out
While escitalopram is the likely culprit, the American College of Cardiology emphasizes evaluating for secondary causes 7:
- Infection/fever: Check temperature and inflammatory markers 7
- Dehydration: Assess volume status and orthostatic vital signs 3, 7
- Anemia: Obtain complete blood count 7
- Hyperthyroidism: Check TSH, especially as escitalopram can unmask thyroid dysfunction 3, 7
- Anxiety/panic: May coexist with depression but can independently cause tachycardia 7
Critical Drug Interactions
The following combinations with escitalopram dramatically increase tachycardia and arrhythmia risk:
- Other serotonergic drugs (SNRIs, tricyclics, MAOIs, tramadol, triptans): Risk of serotonin syndrome with severe tachycardia and arrhythmias 1
- QT-prolonging medications (antipsychotics, ondansetron, metoclopramide, certain antibiotics): Additive QT prolongation increases torsades de pointes risk 3, 1
- Sinoatrial node inhibitors (digoxin, beta-blockers): Paradoxically, case reports show escitalopram can cause bradycardia when combined with these agents, followed by rebound tachycardia 5
Long-Term Monitoring Recommendations
If continuing escitalopram despite tachycardia:
- Repeat ECG at 7 days after any dose change 3
- 24-hour Holter monitoring if symptoms are intermittent or exercise-related 3
- Therapeutic drug monitoring to maintain serum concentrations <100 nM, especially in patients >65 years 4
- Regular electrolyte monitoring, particularly if on diuretics or other medications affecting potassium/magnesium 3
When to Discontinue Escitalopram
Stop escitalopram immediately if:
- QTc interval >500 msec on ECG 3
- QTc prolongation >60 msec from baseline 2
- Development of ventricular arrhythmias 2, 6
- Persistent symptomatic tachycardia despite dose reduction 5
- Sinus bradycardia alternating with tachycardia (suggests autonomic instability) 8, 5
The cardiovascular effects typically resolve within 48 hours of discontinuation 8, 5.
Common Pitfalls to Avoid
Don't assume tachycardia is "just anxiety" in patients on escitalopram—this is a documented cardiac side effect requiring ECG evaluation 2, 4
Don't ignore "mild" tachycardia in elderly patients—age-related pharmacokinetic changes mean therapeutic doses can reach toxic concentrations 4
Don't combine escitalopram with other QT-prolonging drugs without ECG monitoring and clear clinical justification 3
Don't rely solely on QTc interval—the QRS/QTc ratio may better predict arrhythmia risk in escitalopram toxicity 6