What is the appropriate management for a patient presenting in clinic with symptomatic tachycardia of 170 bpm and two near‑syncope episodes in the past 48 hours?

Immediate Referral to Emergency Department for Urgent Cardioversion

This patient requires immediate transfer to the emergency department for urgent evaluation and likely synchronized cardioversion, as symptomatic tachycardia at 170 bpm with near-syncope episodes represents hemodynamic instability that cannot be safely managed in an outpatient clinic setting. 1, 2, 3

Why This Patient is Unstable

• Near-syncope episodes are a critical red flag indicating inadequate cerebral perfusion and hemodynamic compromise, even if the patient appears stable at this moment 1, 3
• The American Heart Association defines hemodynamic instability as the presence of acute altered mental status, ischemic chest discomfort, acute heart failure, hypotension, or signs of shock—near-syncope falls squarely into the altered mental status category 3
• At heart rates >150 bpm with symptoms, the threshold for instability is significantly lower, and immediate intervention is warranted rather than attempting stepwise pharmacologic management 3

Immediate Actions in Your Clinic

Before transfer, you should:

• Apply supplemental oxygen and establish IV access while arranging emergency transport 1
• Obtain a 12-lead ECG immediately to document the rhythm and determine if this is narrow-complex or wide-complex tachycardia, which will guide ED management 1, 3
• Do NOT attempt vagal maneuvers or adenosine in the clinic setting for a patient with near-syncope episodes—this patient needs cardioversion capability immediately available 1, 2
• Monitor vital signs continuously during transport 1

What Will Happen in the Emergency Department

If Hemodynamically Unstable (Which This Patient Likely Is):

• Immediate synchronized cardioversion is the treatment of choice, starting at 50-100 J biphasic, with stepwise increases if initial shock fails 1, 3
• This takes priority over any pharmacologic intervention 4, 1, 2

If Patient Stabilizes and is Deemed Stable:

The ED will follow a stepwise algorithm:

1. Vagal maneuvers first (modified Valsalva maneuver has 43% success rate) 2, 3
2. Adenosine 6 mg IV rapid push if vagal maneuvers fail (90-95% effective for SVT) 1, 2, 3
3. AV nodal blocking agents (diltiazem, verapamil, or beta-blockers) if adenosine fails, with diltiazem showing 64-98% conversion rate 3, 5

Critical Diagnostic Considerations

Narrow vs. Wide Complex Matters:

• If wide-complex tachycardia, assume ventricular tachycardia until proven otherwise and treat accordingly, as improper treatment can be lethal 3
• For wide-complex tachycardia, amiodarone or procainamide are preferred over calcium channel blockers 4, 3
• Never give adenosine, verapamil, or diltiazem if pre-excited atrial fibrillation or wide-complex tachycardia of uncertain etiology, as this may precipitate ventricular fibrillation 1, 3

If Narrow-Complex Regular Tachycardia:

• Most likely AVNRT (AV nodal reentrant tachycardia) or AVRT (AV reentrant tachycardia) 4, 2
• Adenosine serves both therapeutic and diagnostic purposes, unmasking underlying atrial activity 2

Post-Conversion Management

After successful rhythm conversion:

• All patients require cardiology/electrophysiology referral for definitive management 1, 2, 3
• Catheter ablation is first-line definitive therapy with success rates of 94.3-98.5% and is potentially curative 2, 3
• If ablation is declined, oral beta-blockers, diltiazem, or verapamil achieve 80-98% success for long-term suppression 2

Common Pitfalls to Avoid

• Do not assume the patient is "stable enough" for outpatient management just because they are currently conscious and talking—near-syncope episodes indicate they are one arrhythmia away from complete syncope or cardiac arrest 1, 3
• Do not attempt cardioversion in a clinic without full resuscitation equipment and ACLS-trained personnel 2
• Do not give calcium channel blockers if there is any possibility of ventricular tachycardia or pre-excitation syndrome (look for delta waves on baseline ECG if available), as this can cause hemodynamic collapse 1, 3, 5
• Do not delay transfer to obtain extensive workup—the 12-lead ECG is sufficient for initial decision-making 1, 3

Why Outpatient Management is Inappropriate Here

• The combination of rate >150 bpm plus near-syncope episodes places this patient at high risk for sudden cardiac death if the arrhythmia recurs 1, 3
• Clinic settings lack the monitoring, cardioversion equipment, and immediate resuscitation capabilities required for safe management 1, 2
• Even if you successfully convert the rhythm with adenosine, the patient requires telemetry monitoring for recurrence 1, 2