What is the initial workup and management for a patient with tachycardia?

Initial Workup of Tachycardia

Immediate Assessment and Stabilization

The first priority is determining whether the tachycardia is causing hemodynamic instability or is secondary to an underlying condition. When heart rate is <150 bpm, symptoms of instability are unlikely to be caused primarily by the tachycardia unless ventricular dysfunction is present 1, 2.

Initial Clinical Evaluation

• Assess for signs of instability: acute altered mental status, ischemic chest discomfort, acute heart failure, hypotension, or shock 1.
• Evaluate oxygenation status: assess work of breathing (tachypnea, intercostal retractions, suprasternal retractions, paradoxical abdominal breathing) and pulse oximetry 1.
• Provide supplemental oxygen if oxygenation is inadequate or increased work of breathing is present 1.
• Establish IV access and continuous cardiac monitoring 1.

Essential Diagnostic Workup

Electrocardiography (Critical First Step)

A 12-lead ECG during tachycardia is the single most important diagnostic test and must be obtained before any treatment that might terminate the rhythm 1, 2.

• Obtain 12-lead ECG during tachycardia to identify the mechanism 1, 2, 3.
• Obtain 12-lead ECG at rest (if not currently in tachycardia) to identify pre-excitation (WPW pattern), prolonged QT interval, Brugada pattern, conduction abnormalities, or baseline rhythm 1, 2.
• Classify the rhythm based on two key variables:
  • QRS width: narrow (<120 ms) vs. wide (≥120 ms) 1, 3
  • Regularity: regular vs. irregular 1

ECG Classification Framework

Narrow-complex tachycardias (QRS <120 ms) 1:

• Sinus tachycardia (most common)
• Atrial fibrillation
• Atrial flutter
• AV nodal reentry (AVNRT)
• Accessory pathway-mediated tachycardia (AVRT)
• Atrial tachycardia
• Multifocal atrial tachycardia (MAT)

Wide-complex tachycardias (QRS ≥120 ms) 1:

• Ventricular tachycardia (most common—assume VT until proven otherwise)
• SVT with aberrancy
• Pre-excited tachycardias (WPW syndrome)
• Ventricular paced rhythms

Critical ECG Features to Identify

For wide-complex tachycardia, look for features diagnostic of ventricular tachycardia 1:

• AV dissociation (ventricular rate faster than atrial rate)—diagnostic of VT
• Fusion complexes—diagnostic of VT
• Concordance of precordial QRS complexes (all positive or all negative)—suggests VT or pre-excitation
• Apply Brugada criteria or Vereckei algorithm if needed

For narrow-complex regular tachycardia, examine P wave characteristics 1:

• Short RP interval (P wave closer to prior QRS): typical AVNRT or orthodromic AVRT
• Long RP interval (P wave closer to subsequent QRS): atypical AVNRT, PJRT, or atrial tachycardia
• Pseudo S waves in inferior leads and pseudo R' in V1: typical AVNRT
• P wave in early ST segment: orthodromic AVRT

Laboratory Evaluation

Essential laboratory tests to identify reversible causes and precipitants 2:

• Serum electrolytes: hypokalemia and hypomagnesemia can precipitate arrhythmias 2
• Thyroid function tests (TSH): exclude hyperthyroidism 2
• Complete blood count: identify anemia as a secondary cause 2

Cardiac Imaging

• Transthoracic echocardiogram is recommended to detect structural heart disease, assess left ventricular function, evaluate chamber sizes, and identify valvular abnormalities 1, 2.

Clinical History Details

Document specific episode characteristics 2:

• Frequency and duration of episodes
• Mode of onset: sudden vs. gradual (sudden onset suggests reentrant mechanism)
• Mode of termination: sudden vs. gradual
• Associated symptoms: palpitations, chest pain, dyspnea, lightheadedness, near-syncope, syncope, fatigue 1, 4, 5
• Triggers: exercise, caffeine, alcohol, stress
• Sensation of neck pulsations (suggests AVNRT) 4

Assess for orthostatic vital signs to evaluate volume depletion or autonomic dysfunction 2.

Ambulatory Monitoring (If Diagnosis Unclear)

If tachycardia is not documented on initial ECG but history is suspicious 1, 2, 3:

• 24-48 hour Holter monitor for frequent episodes
• Event recorder for infrequent episodes (patient-activated)
• Implantable loop recorder for very infrequent episodes

Immediate Cardiology Referral Criteria

Urgent referral to cardiac electrophysiologist is required for 2:

• Pre-excitation (WPW pattern) on baseline ECG with history of palpitations—risk of sudden death if atrial fibrillation develops with rapid accessory pathway conduction
• Wide-complex tachycardia of unknown origin
• Syncope during tachycardia or with exercise—suggests structural heart disease, long QT syndrome, or other high-risk conditions

Management of Sinus Tachycardia

No specific antiarrhythmic treatment is indicated for sinus tachycardia 2. Instead, identify and treat the underlying cause:

• Fever
• Dehydration
• Anemia
• Hyperthyroidism
• Medications (sympathomimetics, anticholinergics)
• Hypoxemia
• Pulmonary embolism
• Sepsis

Common Pitfalls to Avoid

• Never administer verapamil or diltiazem for wide-complex tachycardia until VT is definitively excluded—this can cause hemodynamic collapse in VT or accelerate ventricular rate in pre-excited atrial fibrillation leading to ventricular fibrillation 1.
• Do not assume wide-complex tachycardia is SVT with aberrancy—most wide-complex tachycardias are ventricular in origin and should be treated as VT until proven otherwise 1.
• Do not delay obtaining 12-lead ECG during tachycardia for other interventions—this is the definitive diagnostic tool 1, 2.
• Do not miss pre-excitation on baseline ECG—these patients require urgent electrophysiology referral due to sudden death risk 2.