What medication should be given to a patient with tachycardia?

Medication Selection for Tachycardia Management

The medication choice for tachycardia depends primarily on the type of tachycardia (narrow vs. wide complex) and the patient's hemodynamic stability, with electrical cardioversion being the first-line treatment for any hemodynamically unstable tachycardia regardless of type. 1

Initial Assessment

• Hemodynamic stability assessment: Look for:

  • Systolic BP ≤90 mmHg
  • Chest pain
  • Heart failure symptoms
  • Heart rate ≥150 beats/min with symptoms

• ECG characteristics:

  • Narrow complex (<0.12 sec) vs. wide complex (≥0.12 sec)
  • Regular vs. irregular rhythm
  • Presence and morphology of P waves

Treatment Algorithm

Hemodynamically Unstable Tachycardia (any type)

• Immediate synchronized cardioversion (100J, 200J, 360J as needed) 2, 1
• Ensure adequate sedation if patient is conscious

Hemodynamically Stable Narrow-Complex Tachycardia

1. First-line approaches:

   • Vagal maneuvers (Valsalva, carotid sinus massage if no carotid bruit) 1
   • IV adenosine (6mg rapid bolus, may repeat with 12mg if ineffective) 2, 1

2. If first-line fails:

   • IV diltiazem or verapamil (calcium channel blockers) 2
     • Diltiazem: 15-20 mg (0.25 mg/kg) IV over 2 minutes; additional 20-25 mg in 15 minutes if needed
     • Verapamil: 2.5-5 mg IV over 2 minutes; may repeat as 5-10 mg every 15-30 minutes
   • IV beta-blockers (atenolol, esmolol, metoprolol, propranolol) 2
     • Metoprolol: 5 mg over 1-2 minutes, repeated as needed every 5 minutes to maximum 15 mg

3. If pharmacological therapy fails:

   • Synchronized cardioversion 2

Hemodynamically Stable Wide-Complex Tachycardia

1. If ventricular tachycardia suspected:

   • IV amiodarone (150 mg over 10 min, followed by infusion) for VT with heart failure or AMI 1
   • IV procainamide (20-50 mg/min until arrhythmia suppressed, hypotension ensues, QRS increases >50%, or max dose 17 mg/kg) for monomorphic VT without heart failure/AMI 2, 1
   • IV lidocaine (1-3 mg/kg) can be considered for VT 3

2. If SVT with aberrancy suspected:

   • Proceed with caution - treat as VT if uncertain
   • Adenosine may be considered but carries risk 4

Atrial Fibrillation Management

• Rate control: Beta-blockers or diltiazem 1
• Rhythm control: Consider ibutilide, dofetilide, flecainide, or amiodarone 1

Important Considerations and Pitfalls

• Never give verapamil or diltiazem for wide-complex tachycardias of uncertain origin as they can cause hemodynamic collapse in VT 1
• Never delay electrical cardioversion in unstable patients 1
• Maintain adequate electrolyte levels during treatment (K+ >4.0 mEq/L, Mg2+ >2.0 mg/dL) 1
• Correct reversible causes (electrolyte abnormalities, ischemia, drug toxicity) 1
• Adenosine can induce ventricular fibrillation in patients with ventricular tachycardia - use with caution in wide-complex tachycardias 4
• Diltiazem may be more effective than adenosine in converting certain types of SVT to normal sinus rhythm (95% vs. 72% success rates) 5

For long-term management after acute treatment, refer the patient for cardiology evaluation to consider ongoing pharmacological therapy or catheter ablation, which has success rates of 80-95% for many types of SVT 1, 6.