How should tachycardia be treated?

Treatment of Tachycardia

Immediate Assessment: Stable vs. Unstable

The first and most critical decision is determining hemodynamic stability—unstable patients require immediate synchronized cardioversion regardless of tachycardia type, while stable patients can proceed with pharmacologic therapy. 1, 2, 3

Unstable Patients (Immediate Cardioversion)

• Proceed directly to synchronized cardioversion without delay for any pharmacologic attempts if the patient exhibits hypotension, altered mental status, chest pain suggesting ischemia, or acute heart failure 1, 2, 4
• Administer sedation (etomidate 0.2-0.3 mg/kg IV) to conscious patients before cardioversion 2
• Use initial energy of 100J, escalating to 200J then 360J if initial attempts fail 3

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Narrow-Complex Tachycardia (QRS <0.12 seconds)

Acute Management for Stable Patients

For stable narrow-complex tachycardia, begin with vagal maneuvers, followed by IV adenosine as first-line pharmacologic therapy. 1, 3

Step 1: Vagal Maneuvers

• Attempt Valsalva maneuver or carotid massage first (Valsalva is safer, especially in elderly patients) 4, 3, 5
• These may terminate reentrant arrhythmias involving the AV node 3

Step 2: Adenosine (First-Line Drug)

• Adenosine 6 mg rapid IV push followed immediately by saline flush; if unsuccessful, give 12 mg 1, 4, 3
• Success rate of 93% for terminating AV nodal reentrant tachycardias 6
• Extremely short half-life (seconds) makes it safer than alternatives with minimal hemodynamic effects 6
• Common but brief side effects include chest discomfort, dyspnea, and flushing—warn patients these will resolve within seconds 6

Critical Pitfall: Adenosine may precipitate atrial fibrillation in 1-15% of cases and should be avoided in severe asthma 2, 3

Step 3: AV Nodal Blocking Agents (If Adenosine Fails)

• IV metoprolol 5 mg slow bolus (can repeat if tolerated) 3
• IV diltiazem 5-10 mg over 60 seconds 3
• IV verapamil 5-10 mg over 60 seconds 3

Critical Pitfall: Never give calcium channel blockers and beta blockers sequentially—their overlapping effects can cause profound bradycardia, unlike adenosine's short half-life which allows safe follow-up with these agents 1

Specific Tachycardia Types

Inappropriate Sinus Tachycardia (IST)

• First exclude secondary causes: hyperthyroidism, anemia, dehydration, pain, fever, infection, heart failure, exogenous substances (caffeine, albuterol, cocaine, amphetamines) 1
• Treatment is symptom-driven only—prognosis is benign and lowering heart rate may not alleviate symptoms 1
• Beta blockers are first-line therapy, though often ineffective or poorly tolerated due to hypotension 1
• Calcium channel blockers (verapamil, diltiazem) are reasonable alternatives 1
• Ivabradine (If channel blocker) reduces heart rate by 6-8 bpm without other hemodynamic effects, approved for heart failure patients 1
• Radiofrequency ablation has 76-100% acute success but 27-45% symptomatic recurrence and significant complications (pacemaker requirement, phrenic nerve injury)—reserve for refractory cases only 1

Multifocal Atrial Tachycardia (MAT)

• IV metoprolol or verapamil for acute treatment 3
• Oral verapamil, diltiazem, or metoprolol for ongoing management 3
• IV magnesium may help even with normal magnesium levels 3
• Address underlying conditions (pulmonary disease, electrolyte abnormalities) as these are often triggers 3

Critical Pitfall: Cardioversion is ineffective for automatic tachycardias like MAT and focal atrial tachycardia 3

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Wide-Complex Tachycardia (QRS ≥0.12 seconds)

Critical Principle

Assume all wide-complex tachycardia is ventricular tachycardia (VT) until proven otherwise—misdiagnosis and treatment as SVT can be fatal. 1, 2, 4

Stable Wide-Complex Tachycardia

Regular Monomorphic VT

Procainamide is first-line for stable monomorphic VT in patients without severe heart failure or acute MI. 1, 2, 3

• More effective than amiodarone for early termination 2
• Monitor blood pressure closely during infusion, especially if any heart failure present 2

Amiodarone 150 mg IV over 10 minutes is preferred if there is any concern for impaired left ventricular function, severe heart failure, or acute MI. 1, 2, 4, 3

• Better safety profile in structural heart disease than procainamide 2
• Can repeat dosing up to maximum 2.2 g IV per 24 hours 1

Sotalol 1.5 mg/kg IV over 5 minutes is an alternative, but avoid if QT interval is prolonged 1

Diagnostic Consideration: Adenosine

• IV adenosine may be considered for undifferentiated regular stable wide-complex tachycardia—it is relatively safe and can help diagnose the underlying rhythm 1, 2
• If rhythm terminates, this suggests SVT with aberrancy rather than VT 2
• Never give adenosine for unstable, irregular, or polymorphic wide-complex tachycardia 1

Polymorphic VT (Irregular Wide-Complex)

For polymorphic VT with long QT interval (torsades de pointes), IV magnesium is the primary treatment. 1, 4

• Stop all QT-prolonging medications immediately 1
• Correct electrolyte abnormalities (potassium, magnesium, calcium) 1, 4
• Overdrive pacing or IV isoproterenol may be added if accompanied by bradycardia or pauses 1, 4

For polymorphic VT without long QT (usually ischemic), IV amiodarone and beta-blockers may reduce recurrence 1

Critical Pitfalls for Wide-Complex Tachycardia

Calcium channel blockers (verapamil, diltiazem) are absolutely contraindicated for wide-complex tachycardia of unknown origin—they cause hemodynamic collapse if the rhythm is VT. 1, 2, 4, 3

Do not delay cardioversion in unstable patients to obtain additional diagnostic studies or attempt pharmacologic conversion. 2, 4

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Antiarrhythmic Medications: General Considerations

Antiarrhythmic medications (amiodarone, procainamide, sotalol) have higher toxicity and proarrhythmic risk compared to AV nodal blocking agents—reserve for specific indications. 1

Exception: Pre-excited atrial arrhythmias where typical AV nodal blockers are contraindicated 1

Rapidly correct electrolyte abnormalities (potassium, magnesium, calcium) before or during antiarrhythmic therapy—these disorders exacerbate QT prolongation and increase proarrhythmic risk. 4

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Post-Stabilization Management

• All patients with wide-complex tachycardia require ICU/CCU admission and immediate cardiology/electrophysiology consultation 2
• Catheter ablation has 95% success rate and <5% recurrence for SVT, with <1% risk of heart block—it is the preferred treatment for symptomatic patients with recurrent SVT or Wolff-Parkinson-White syndrome 7, 8
• Consider electrophysiology study and possible ablation once stabilized 2, 4
• For chronic management of SVT, oral beta-blockers are first-line, with oral diltiazem or verapamil as reasonable alternatives 3