What's the next step for a patient with tachycardia (heart rate over 150 bpm) who is hemodynamically stable and hasn't responded to adenosine?

Management of Persistent Tachycardia >150 bpm After Failed Adenosine

For a hemodynamically stable patient with persistent tachycardia >150 bpm after adenosine failure, administer intravenous diltiazem or verapamil as the next pharmacologic step, or proceed directly to synchronized cardioversion if the patient is hemodynamically unstable or if pharmacologic therapy is contraindicated. 1

Immediate Assessment Required

Before proceeding, you must determine:

• Hemodynamic stability: Look for hypotension (SBP <90 mmHg), acute altered mental status, signs of shock, ischemic chest pain, or acute heart failure 1
• QRS width: Narrow (<0.12s) vs wide complex (≥0.12s) 1, 2
• Pre-excitation on baseline ECG: This changes management significantly, as AV nodal blockers can be dangerous in pre-excited atrial fibrillation 1

Management Algorithm Based on Stability

If Hemodynamically UNSTABLE:

Proceed immediately to synchronized cardioversion 1

• Synchronized cardioversion is highly effective, terminating SVT in essentially 100% of unstable patients who failed vagal maneuvers and adenosine 1
• Do not delay for sedation if the patient is extremely unstable 1
• If time permits and IV access is available, provide sedation before cardioversion 1

If Hemodynamically STABLE:

First-line pharmacologic options (Class IIa recommendation):

1. Intravenous diltiazem or verapamil 1

   • Success rate: 64-98% for terminating SVT 1
   • Slow infusion over up to 20 minutes may reduce hypotension risk 1
   • Monitor closely for hypotension or bradycardia 1

2. Intravenous beta blockers 1

   • Reasonable alternative with excellent safety profile 1
   • Less effective than calcium channel blockers (esmolol was less effective than diltiazem in comparative trials) 1

If pharmacologic therapy fails or is contraindicated:

• Synchronized cardioversion remains highly effective even in stable patients 1
• Success rates of 80-98% when adenosine, verapamil, or diltiazem fail 1
• Consider a second bolus or higher dose of the initial agent before proceeding to cardioversion 1

Critical Pitfalls to Avoid

DO NOT use diltiazem or verapamil if:

• Wide-complex tachycardia of uncertain etiology - may be ventricular tachycardia, and calcium channel blockers can cause hemodynamic collapse or ventricular fibrillation 1
• Pre-excited atrial fibrillation - can accelerate ventricular rate and precipitate ventricular fibrillation 1
• Suspected systolic heart failure - can worsen cardiac function 1

Special Consideration for Pre-excited AF:

If you suspect pre-excited AF (irregular wide-complex tachycardia in a patient with known WPW):

• Hemodynamically unstable: Immediate synchronized cardioversion 1
• Hemodynamically stable: Use ibutilide or intravenous procainamide (Class I recommendation) 1
• Never use AV nodal blockers (adenosine, diltiazem, verapamil, beta blockers, digoxin) 1

Why Adenosine May Have Failed

Understanding adenosine failure helps guide next steps:

• Focal atrial tachycardia: Adenosine terminates only 30-50% of cases; calcium channel blockers or beta blockers are more appropriate 1
• Atrial flutter: Adenosine unmasks but rarely terminates; requires different management 1
• Immediate reinitiation: Adenosine may have briefly terminated the arrhythmia but it immediately restarted - consider antiarrhythmic prophylaxis after conversion 1
• Insufficient dose: Consider that the effective dose has a tenfold range among patients 2
• Ventricular tachycardia with structural heart disease: Adenosine has no effect on catecholamine-facilitated reentrant VT 3

Monitoring After Conversion

• Watch for immediate recurrence - occurs in 35% of patients after successful conversion 2
• Atrial or ventricular premature complexes immediately after conversion may trigger recurrent episodes 1
• If recurrence occurs, antiarrhythmic drugs may be needed to prevent acute reinitiation 1