What is the dose of diltiazem for supraventricular tachycardia (SVT)?

Diltiazem Dosing for Supraventricular Tachycardia (SVT)

For acute treatment of SVT, intravenous diltiazem should be administered at 0.25 mg/kg IV bolus over 2 minutes, with the option to increase to a maintenance infusion at 5-10 mg/h, up to 15 mg/h if needed. 1

Acute Management of SVT

First-line approaches:

• Vagal maneuvers should be attempted first for acute treatment of regular SVT 1, 2
• Adenosine is the first-line medication (6-12 mg IV bolus) with success rates of approximately 95% for terminating AVNRT 2

When to use diltiazem:

• Intravenous diltiazem is highly effective as second-line therapy for acute termination of SVT in hemodynamically stable patients 1
• Diltiazem has shown termination rates of 84-100% at doses of 0.15-0.45 mg/kg 3
• Diltiazem is particularly effective for AVNRT with 100% conversion rate at 0.25 mg/kg dosing 3, 4

Diltiazem administration protocol:

• Initial dose: 0.25 mg/kg IV bolus administered over 2 minutes 1
• Maintenance dose: Infusion at 5-10 mg/h, up to 15 mg/h if needed 1
• Time to conversion typically occurs within 2 minutes after completion of infusion 4
• If first bolus is ineffective, a second bolus may be administered after 5 minutes 5

Alternative agents when diltiazem fails:

• Synchronized cardioversion is recommended for hemodynamically stable patients when pharmacological therapy is ineffective 1
• Verapamil (5-10 mg IV bolus over 2 minutes) can be used as an alternative calcium channel blocker 1
• Beta blockers (esmolol, metoprolol, propranolol) are reasonable alternatives but may be less effective than diltiazem 1, 5

Ongoing Management of SVT

Oral diltiazem for long-term management:

• Oral diltiazem is recommended for ongoing management in patients with SVT who are not candidates for catheter ablation 1, 2
• Typical dosing is 90 mg every 8 hours (270 mg daily) 6
• Clinical response to IV diltiazem predicts subsequent response to oral therapy 6

Important Precautions and Contraindications

Avoid diltiazem in:

• Patients with AV block greater than first degree or SA node dysfunction (in absence of pacemaker) 1
• Patients with Wolff-Parkinson-White syndrome with atrial fibrillation/flutter 1, 2
• Patients with hypotension or decompensated systolic heart failure 1, 2
• Patients with cardiogenic shock 1

Potential adverse effects:

• Hypotension (most common side effect, occurs in approximately 11% of patients) 3
• Worsening heart failure in patients with pre-existing ventricular dysfunction 1
• Bradycardia 1
• Abnormal liver function (rare) 1

Drug interactions:

• Use with caution when combined with other drugs that have SA and/or AV nodal-blocking properties 1
• Diltiazem is a substrate of CYP3A4 and a moderate CYP3A4 inhibitor 1
• Use with caution in patients with hepatic or renal dysfunction 1

Clinical Pearls

• Diltiazem works by prolonging refractoriness and slowing conduction through the AV node 4
• Diltiazem is more effective than esmolol for terminating SVT (100% vs 25% efficacy in comparative studies) 5
• For patients with SVT involving accessory pathways, diltiazem has shown 81% efficacy 4