Next steps for PSVT with tachycardia unresponsive to diltiazem?

Management of PSVT with Heart Rate of 250 Unresponsive to Initial Diltiazem

For PSVT with heart rate of 250 bpm that is unresponsive to initial diltiazem 2.5 mg, immediate synchronized cardioversion is recommended as the next step in management.

Immediate Management Options

1. Increase Diltiazem Dose

• The initial dose of diltiazem (2.5 mg) was insufficient, as guidelines recommend starting with 15-20 mg (0.25 mg/kg) IV over 2 minutes 1
• If the first dose is ineffective, a second higher dose of 20-25 mg (0.35 mg/kg) should be administered after 15 minutes 1
• Studies have shown that when the first bolus of diltiazem is ineffective, a second bolus given after 5 minutes usually succeeds 2

2. Try Adenosine

• Adenosine is the first-line pharmacological agent for stable PSVT with a recommended dose of 6 mg rapid IV push followed by saline flush 1
• If ineffective, a 12 mg dose can be administered 1-2 minutes later 1
• Adenosine has been shown to be more rapid and have fewer severe side effects than calcium channel blockers in terminating PSVT 1, 3

3. Synchronized Cardioversion

• For patients with extremely rapid heart rates (250 bpm) who are unresponsive to initial pharmacological therapy, synchronized cardioversion is the most appropriate next step 1
• Initial energy for narrow-complex SVT: 50-100 J with biphasic waveform, increasing in stepwise fashion if unsuccessful 1
• Cardioversion is highly effective (success rates of 80-98%) in terminating SVT including AVRT and AVNRT 1

Algorithm for Management

1. Assess hemodynamic stability

   • If unstable (hypotension, altered mental status, signs of shock, severe chest pain): immediate synchronized cardioversion 1
   • If stable: proceed with pharmacological management

2. Pharmacological options (if patient remains stable):

   • Increase diltiazem dose: Give additional 20-25 mg (0.35 mg/kg) IV over 2 minutes 1
   • Try adenosine: 6 mg rapid IV push followed by saline flush; if ineffective, give 12 mg 1
   • Consider beta-blockers: Esmolol, metoprolol, or atenolol can be used, though they are less effective than diltiazem for PSVT termination 1, 2

3. If pharmacological management fails: Proceed to synchronized cardioversion with appropriate sedation 1

Important Considerations and Pitfalls

• Avoid combining AV nodal blocking agents with longer half-lives (e.g., diltiazem and beta-blockers) as this can cause profound bradycardia 1
• Caution with pre-excited atrial fibrillation/flutter: Do not use AV nodal blocking agents (including diltiazem) in patients with suspected Wolff-Parkinson-White syndrome as this may accelerate ventricular response 1
• Diltiazem contraindications: Avoid in patients with heart failure, impaired ventricular function, or wide-complex tachycardias of uncertain origin 1
• Adenosine contraindications: Should not be given to patients with asthma 1
• Ensure proper diltiazem dosing: The initial dose of 2.5 mg was significantly lower than the recommended dose (15-20 mg), which likely explains the lack of response 1

After Successful Conversion

• Monitor for recurrence of PSVT 1
• Consider longer-term management options:
  • Oral AV nodal blocking agents (beta-blockers, diltiazem, verapamil) 1
  • Catheter ablation for recurrent symptomatic episodes 4
  • "Pill-in-the-pocket" approach for infrequent, well-tolerated episodes 1