What drug will return a patient with tachycardia to sinus rhythm?

Management of Tachycardia with HR 180 bpm

Adenosine is the drug of choice to rapidly convert a patient with a heart rate of 180 bpm to sinus rhythm. 1

Mechanism of Action and Efficacy

Adenosine works by temporarily blocking the AV node, interrupting the reentrant circuit that maintains many forms of supraventricular tachycardia (SVT). It has a rapid onset of action (within seconds) and an extremely short half-life (less than 10 seconds), making it ideal for acute conversion of SVT to sinus rhythm.

Decision Algorithm for Tachycardia Management

1. Initial Assessment:

   • For hemodynamically unstable patients: Immediate synchronized cardioversion 1
   • For hemodynamically stable patients with regular tachycardia: Proceed with pharmacologic management

2. First-line Therapy:

   • Vagal maneuvers (Valsalva, carotid sinus massage) 1
   • If unsuccessful, proceed to adenosine

3. Adenosine Administration:

   • Initial dose: 6 mg rapid IV push followed by saline flush
   • If ineffective, give 12 mg IV push (can repeat once if needed)
   • Adenosine is particularly effective for:
     • AV nodal reentrant tachycardia (AVNRT)
     • AV reentrant tachycardia (AVRT)
     • Sinus node reentry tachycardia 1

Why Not Flecainide or Digoxin?

• Flecainide (Option B):

  • Less effective for acute conversion of SVT 1
  • Studies show poor efficacy for acute conversion compared to other options 1
  • Has significant risks in patients with structural heart disease
  • Requires more time to take effect compared to adenosine

• Digoxin (Option C):

  • Ineffective for acute conversion to sinus rhythm 1
  • Only slows ventricular rate without converting to sinus rhythm in most cases
  • Guidelines specifically state: "In patients with AF following cardiac surgery, we cannot at this time recommend using flecainide, digoxin, or calcium channel blockers for the purpose of conversion to sinus rhythm" 1
  • Conversion rates with digoxin are similar to placebo, consistent with the self-limited natural history of some arrhythmias rather than drug efficacy 1

Special Considerations

1. Caution with adenosine:

   • Brief side effects may include flushing, chest discomfort, and transient asystole
   • Contraindicated in patients with severe asthma or advanced AV block
   • Should be used with caution in patients with severe coronary artery disease 1

2. Alternative options if adenosine fails or is contraindicated:

   • IV beta-blockers (e.g., metoprolol)
   • IV calcium channel blockers (e.g., verapamil, diltiazem)
   • IV amiodarone (particularly in patients with heart failure) 1

3. Monitoring during administration:

   • Continuous ECG monitoring is essential
   • Have resuscitation equipment immediately available
   • Be prepared for potential transient asystole

In conclusion, adenosine is the most appropriate choice for rapidly converting a patient with a heart rate of 180 bpm to sinus rhythm due to its rapid onset, high efficacy in SVT, and excellent safety profile when used appropriately.