When should a workup be initiated for tachycardia?

When to Work Up Tachycardia

Initiate immediate workup when heart rate is ≥150 beats per minute or when any patient shows signs of hemodynamic instability (altered mental status, chest pain, heart failure, hypotension, or shock), regardless of heart rate. 1

Heart Rate Threshold for Primary Workup

• Heart rate ≥150 bpm indicates a likely primary arrhythmia requiring immediate evaluation, as this threshold distinguishes true tachyarrhythmias from physiologic responses 1
• Below 150 bpm, tachycardia is typically secondary to underlying physiologic stress (fever, dehydration, pain, anxiety, hypoxemia) unless ventricular dysfunction is present 1
• Lower the threshold for workup (<150 bpm) in patients with known ventricular dysfunction, as these patients are more vulnerable to hemodynamic compromise from tachycardia 1

Immediate Workup Triggers Based on Clinical Instability

Proceed directly to workup and treatment without delay when any of these signs are present 2, 3:

• Acute altered mental status 2, 3, 1
• Ischemic chest discomfort or pain 2, 3, 1
• Acute heart failure 2, 3, 1
• Hypotension or signs of shock 2, 3, 1

In unstable patients, do not delay cardioversion to obtain diagnostic studies—immediate synchronized cardioversion takes priority over 12-lead ECG 3

Initial Workup Components

When tachycardia workup is indicated, perform the following systematically 3, 1:

• Attach cardiac monitor and obtain vital signs 3, 1
• Establish IV access 3, 1
• Assess oxygen saturation and respiratory status (tachypnea, retractions, paradoxical breathing), as hypoxemia is a common reversible cause of tachycardia 1
• Obtain 12-lead ECG to define rhythm characteristics, but only after stabilization in unstable patients 1
• Provide supplemental oxygen if hypoxemia or respiratory distress is present 3

Special Situations Requiring Workup

Self-Terminated Tachycardia

• Any suspected ventricular tachycardia requires urgent cardiology consultation and echocardiography even if self-terminated 3, 1
• Recurrent episodes of supraventricular tachycardia warrant consideration of Holter monitor or event recorder to capture the arrhythmia 1

Pre-Excitation Patterns

• If pre-excitation is present on resting ECG with history of paroxysmal regular palpitations, presume AVRT and refer to electrophysiology without needing to capture the arrhythmia 3
• Pre-excitation with irregular paroxysmal palpitations suggests atrial fibrillation, requiring urgent EP evaluation due to sudden death risk 3

Hypertensive Patients

• In hypertensive patients, assess for occult heart failure symptoms if resting heart rate >80-85 bpm by clinical examination, biomarkers (BNP), or echocardiogram 2
• Search for associated comorbidities such as arrhythmias (atrial fibrillation, atrial flutter), anemia, hyperthyroidism, and sepsis 2
• Consider 30-day event monitoring or implantable cardiac monitor to detect rare arrhythmias 2

Referral Indications

Refer to cardiology or electrophysiology when 3:

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

Critical Pitfalls to Avoid

• Never delay cardioversion in unstable patients while obtaining 12-lead ECG 3
• Never use AV nodal blocking agents in pre-excited atrial fibrillation, as this accelerates ventricular response and can be lethal 3
• Never give adenosine for irregular or polymorphic wide-complex tachycardia, as it may cause degeneration to ventricular fibrillation 2, 3
• Never normalize heart rate in compensatory tachycardia where cardiac output depends on the rapid rate 3
• Never combine multiple AV nodal blocking agents with overlapping half-lives, as this causes profound bradycardia 3

Age-Specific Considerations

Neonates and Infants

• In the first week of life, the upper normal limit (98th percentile) is 166 beats/min; in the first month it is 179 beats/min 2
• After six months, the upper normal limit declines to approximately 160 beats/min 2
• Work up sinus tachycardia in neonates when associated with fever, infection, anemia, pain, dehydration, hyperthyroidism, or myocarditis 2
• If myocarditis is suspected, perform echocardiogram 2