What is the initial approach to a patient presenting with symptomatic tachycardia?

Initial Workup of Symptomatic Tachycardia

The initial approach to symptomatic tachycardia begins with immediate assessment of hemodynamic stability—if the patient shows acute altered mental status, ischemic chest pain, acute heart failure, hypotension, or shock, proceed directly to synchronized cardioversion without delay for diagnostic workup 1, 2.

Immediate Stabilization and Assessment

First Steps (Do Not Delay)

• Attach cardiac monitor, obtain vital signs, establish IV access, and assess oxygen saturation 3, 2
• Provide supplemental oxygen if hypoxemia or respiratory distress is present (tachypnea, retractions, paradoxical breathing), as hypoxemia commonly drives tachycardia 3, 2
• Identify and treat reversible causes while initiating rhythm management 2

Critical Decision Point: Rate Threshold

• Heart rate ≥150 bpm indicates a primary arrhythmia requiring immediate workup regardless of symptoms 3
• Heart rate <150 bpm typically represents physiologic stress (fever, dehydration, pain, anxiety) unless ventricular dysfunction is present 3, 2
• Lower the threshold for workup (<150 bpm) if known ventricular dysfunction exists, as these patients decompensate more readily 3

Stability-Based Algorithm

For UNSTABLE Patients (Altered Mental Status, Chest Pain, Heart Failure, Hypotension, Shock)

Perform immediate synchronized cardioversion 1, 2

• Sedate if conscious and time permits 2
• For witnessed, monitored unstable VT, consider precordial thump only if defibrillator not immediately available 1, 2
• Do not delay cardioversion to obtain 12-lead ECG 1, 2
• Presume wide-complex tachycardia is ventricular tachycardia and cardiovert immediately 2

For STABLE Patients

Obtain 12-lead ECG to characterize the rhythm 1, 2

Step 1: Determine Regularity

• Assess if rhythm is regular or irregular 2
• Irregular palpitations suggest premature beats, atrial fibrillation, or multifocal atrial tachycardia 1
• Regular paroxysmal palpitations with abrupt onset/termination suggest AVRT or AVNRT 1

Step 2: Assess QRS Width

For Narrow-Complex Regular Tachycardia:

• Administer adenosine 6 mg rapid IV push, followed by 12 mg if needed 1, 2
• In select unstable cases, adenosine trial before cardioversion is reasonable 1
• Avoid adenosine if pre-excitation (Wolff-Parkinson-White) with atrial fibrillation/flutter is present, as this can accelerate ventricular response and cause degeneration to ventricular fibrillation 2

For Wide-Complex Tachycardia:

• Presume ventricular tachycardia until proven otherwise 2, 4
• For regular monomorphic wide-complex tachycardia of uncertain origin, IV adenosine is relatively safe for diagnosis and treatment 1, 2
• Never give adenosine for irregular or polymorphic wide-complex tachycardia—it may cause degeneration to ventricular fibrillation 1, 2
• Consider amiodarone 150 mg IV over 10 minutes for confirmed VT 2
• Alternative antiarrhythmics: procainamide or sotalol, but avoid sotalol if QT prolonged 1, 2
• Verapamil is absolutely contraindicated for wide-complex tachycardia unless proven supraventricular origin 1

Special Diagnostic Considerations

Baseline ECG Findings

• If pre-excitation present on resting ECG with history of paroxysmal regular palpitations, presume AVRT and refer to electrophysiology without needing to capture the arrhythmia 1
• Pre-excitation with irregular paroxysmal palpitations suggests atrial fibrillation, requiring urgent EP evaluation due to sudden death risk 1

Post-Resolution Workup

• Even after spontaneous termination, suspected ventricular tachycardia requires urgent cardiology consultation and echocardiography 3
• Recurrent supraventricular tachycardia episodes warrant Holter monitor or event recorder 3

Critical Pitfalls to Avoid

• Never delay cardioversion in unstable patients while obtaining 12-lead ECG 2
• Never use AV nodal blocking agents (adenosine, beta-blockers, calcium channel blockers) in pre-excited atrial fibrillation—this accelerates ventricular response 2
• Never give adenosine for irregular or polymorphic wide-complex tachycardia 2
• Never normalize heart rate in compensatory tachycardia where cardiac output depends on the rapid rate 2
• Never combine multiple AV nodal blocking agents with overlapping half-lives—this causes profound bradycardia 2
• Do not treat sinus tachycardia with antiarrhythmics; treat the underlying cause 2

Referral Indications

• Wide-complex tachycardia of unknown origin 1
• Clear history of paroxysmal regular palpitations 1
• Drug-resistant or drug-intolerant narrow-complex tachycardia 1
• Patients desiring freedom from long-term drug therapy 1
• Any suspected ventricular tachycardia, even if self-terminated 3