What is the best course of action for a psychiatric adult patient with tachycardia who is currently taking Seroquel (quetiapine) and Abilify (aripiprazole)?

Management of Tachycardia in a Patient on Seroquel and Abilify

The first priority is to determine whether the tachycardia is drug-induced (most likely from quetiapine/Seroquel) versus a primary cardiac arrhythmia, then immediately obtain a 12-lead ECG to assess for QT prolongation and identify the specific rhythm before initiating treatment.

Immediate Assessment and Risk Stratification

Step 1: Obtain 12-Lead ECG and Assess Hemodynamic Stability

• Measure QTc interval immediately – quetiapine is strongly associated with QT prolongation and tachycardia in therapeutic dosing and overdose, while aripiprazole has low risk for QT prolongation 1, 2, 3.
• Check for sinus tachycardia versus arrhythmia – quetiapine overdose causes sinus tachycardia in the majority of cases (8 of 10 patients in one series), not primary arrhythmias 3.
• Assess hemodynamic stability – if the patient has hypotension, altered mental status, chest pain, or signs of shock, this requires immediate synchronized cardioversion regardless of rhythm 4.

Step 2: Identify the Underlying Cause

Drug-induced tachycardia from quetiapine is the most likely etiology given the known cardiac effects of this medication 1, 2, 3. Key considerations:

• Quetiapine causes dose-dependent sinus tachycardia and QTc prolongation – mean QTc of 487 ms has been reported in overdose, though clinical arrhythmias are rare 3.
• Check for recent dose escalation or overdose – quetiapine concentrations correlate directly with tachycardia severity 3.
• Aripiprazole is unlikely to be the culprit – low-quality evidence suggests aripiprazole does not increase QT interval or cause tachycardia 2.
• Rule out other causes: fever, infection, dehydration, anemia, pain, anxiety, hyperthyroidism, hypoxia, or heart failure 5.

Treatment Algorithm Based on Clinical Presentation

If Hemodynamically Unstable (Hypotension, Altered Mental Status, Chest Pain)

Proceed immediately to synchronized cardioversion – do not delay for pharmacologic therapy when the patient shows severe signs of instability 4.

• Sedate if conscious, but do not delay cardioversion if extremely unstable 4.
• Use 120-200 joules for narrow-complex tachycardia, 100 joules for wide-complex tachycardia 4.

If Hemodynamically Stable with Sinus Tachycardia

The primary treatment is addressing the underlying cause (quetiapine toxicity), not rate control agents 5.

First-Line Management:

• Consider dose reduction or discontinuation of quetiapine if clinically appropriate from a psychiatric standpoint.
• Provide supportive care – IV fluids for dehydration, treat pain/anxiety if present 5.
• Monitor continuously with telemetry for 12-18 hours given the risk of QTc prolongation 1.

If Symptomatic Rate Control is Required:

• IV metoprolol 2.5-5 mg over 2 minutes is the first-line agent for symptomatic sinus tachycardia 6, 5.
• Can repeat every 10 minutes up to 3 doses (maximum 15 mg) 6.
• Critical precaution: Beta-blockers can cause hypotension, worsening heart failure, and bradycardia – use cautiously 6.

Second-Line (if beta-blockers contraindicated or ineffective):

• IV diltiazem 0.25 mg/kg (15-20 mg) over 2 minutes 6, 5.
• Do NOT combine IV diltiazem with IV beta-blockers – this potentiates hypotension and bradycardia 5.
• Diltiazem is contraindicated in decompensated heart failure, hypotension, and cardiogenic shock 6.

If Primary Arrhythmia is Identified (Not Sinus Tachycardia)

Follow ACC/AHA guidelines for specific arrhythmia management 6:

• For supraventricular tachycardia (SVT): Adenosine 6 mg IV push, then 12 mg if needed 6.
• For atrial fibrillation/flutter: Rate control with beta-blockers or diltiazem, consider cardioversion if unstable 6.
• For junctional tachycardia: IV beta-blockers are reasonable first-line (Class IIa), followed by IV diltiazem, procainamide, or verapamil 6.

Critical Pitfalls to Avoid

• Do NOT use adenosine for sinus tachycardia – it is ineffective as sinus tachycardia is not a reentrant rhythm 5.
• Do NOT suppress compensatory sinus tachycardia if the patient has an underlying physiologic cause (e.g., sepsis, hypovolemia) – treat the trigger, not the heart rate 5.
• Do NOT combine IV calcium channel blockers with IV beta-blockers – severe bradycardia and heart block can result 5.
• Do NOT ignore QTc prolongation – quetiapine is associated with torsades de pointes risk, especially in overdose 2, 3.
• Do NOT assume aripiprazole is the cause – evidence shows aripiprazole does not prolong QT or cause tachycardia 2.

Ongoing Monitoring and Disposition

• Continue telemetry monitoring for 12-18 hours if quetiapine overdose or significant QTc prolongation is present 1.
• Repeat ECG every 4-6 hours until QTc normalizes (typically within 18 hours for quetiapine) 1.
• Consult psychiatry regarding medication adjustment – consider switching from quetiapine to aripiprazole monotherapy if cardiac toxicity is problematic 2.
• Consult cardiology if arrhythmias develop or QTc exceeds 500 ms 1.