ACLS Management of Tachycardia
Immediately assess for hemodynamic instability—this single determination dictates whether you have seconds (unstable) or minutes (stable) to act and drives all subsequent management decisions. 1
Immediate Actions Upon Encountering Tachycardia
- Attach cardiac monitor, establish IV access, and obtain vital signs while simultaneously evaluating for signs of hemodynamic compromise 1
- Assess oxygenation status by looking for tachypnea, intercostal retractions, suprasternal retractions, and paradoxical abdominal breathing—provide supplemental oxygen if saturation is inadequate or work of breathing is increased 1
- Obtain a 12-lead ECG to define the rhythm, but never delay cardioversion if the patient is unstable 1
The Critical Fork in the Road: Unstable vs. Stable
Unstable Tachycardia (Immediate Synchronized Cardioversion)
Proceed directly to synchronized cardioversion if ANY of these signs are present: 1
- Acute altered mental status
- Ischemic chest discomfort
- Acute heart failure
- Hypotension
- Shock
Cardioversion technique: 1
- Establish IV access before cardioversion if possible
- Administer sedation if the patient is conscious
- Do not delay cardioversion to sedate an extremely unstable patient
- Have defibrillator ready for potential complications
Stable Tachycardia (Time for Rhythm Analysis)
First, rule out sinus tachycardia as a compensatory response by considering underlying causes such as fever, dehydration, anemia, hypotension, or other physiologic stressors 1
Rhythm-Specific Management for Stable Patients
Sinus Tachycardia
Never treat sinus tachycardia with antiarrhythmics or rate-control agents—this is a physiologic response to an underlying condition and treating the rate can precipitate cardiovascular collapse 1, 2
- Direct all therapy toward identifying and treating the underlying cause 1
Narrow-Complex Regular Tachycardia (SVT)
Follow this exact sequence: 1, 3, 4
- Vagal maneuvers first (Valsalva, carotid massage if no bruits)
- Adenosine 6 mg rapid IV push if vagal maneuvers fail
- Adenosine 12 mg rapid IV push if 6 mg ineffective (can repeat once)
- Synchronized cardioversion if pharmacologic therapy fails or is contraindicated
Critical safety point: Always have the defibrillator ready when administering adenosine, as it may precipitate rapid atrial fibrillation in patients with Wolff-Parkinson-White syndrome 1
Wide-Complex Tachycardia
Assume ventricular tachycardia until proven otherwise—this assumption prevents potentially lethal treatment errors 1, 5
Pharmacologic options for stable wide-complex tachycardia: 1
- IV procainamide
- IV amiodarone
- IV lidocaine
The differentiation between VT and SVT with aberrancy is critical because improper therapy may have lethal consequences 5
Critical Pitfalls That Kill Patients
- Never assume narrow-complex tachycardia is benign—always assess hemodynamic stability first, as even SVT can cause cardiovascular collapse 1
- Never give calcium channel blockers or beta-blockers for wide-complex tachycardia unless VT is definitively ruled out, as this can cause cardiovascular collapse in true VT 1
- Never treat compensatory sinus tachycardia with rate-control agents—this removes the body's compensatory mechanism and can precipitate shock 1
- Never delay cardioversion in unstable patients to obtain a 12-lead ECG, establish better IV access, or achieve deeper sedation 1
- Never use adenosine in irregular wide-complex tachycardia (likely atrial fibrillation with aberrancy or pre-excitation), as this may accelerate ventricular response 1
The Underlying Cause Matters
In stable patients, always search for and correct precipitating factors: 2, 6
- Electrolyte abnormalities (hypokalemia, hypomagnesemia)
- Myocardial ischemia
- Drug toxicity or proarrhythmic effects of antiarrhythmics
- Hypoxia
- Acidosis