When to Work Up Tachycardia
Work up tachycardia immediately when the heart rate is ≥150 beats per minute, as this threshold indicates a likely primary arrhythmia rather than a physiologic response, or when any patient presents with signs of hemodynamic instability regardless of rate. 1
Critical Decision Points for Immediate Workup
Heart Rate Threshold
- Heart rates ≥150 bpm typically indicate a true tachyarrhythmia requiring immediate evaluation and workup 1
- Below 150 bpm, tachycardia is more likely secondary to an underlying physiologic stress (fever, dehydration, pain, anxiety) unless ventricular dysfunction is present 1
Signs of Hemodynamic Instability (Immediate Workup Required)
Work up immediately if the patient exhibits any of the following, regardless of heart rate:
- Acute altered mental status 1
- Ischemic chest discomfort or pain 1
- Acute heart failure 1
- Hypotension or signs of shock 1
- Syncope or severe lightheadedness 2
- Severe dyspnea 2, 3
Common pitfall: Hemodynamic stability does NOT rule out ventricular tachycardia—85% of conscious adults with wide-complex tachycardia and stable blood pressure actually have VT, especially with history of myocardial infarction 4
Initial Workup Components
Immediate Assessment
- Evaluate oxygen saturation and signs of respiratory distress (tachypnea, retractions, paradoxical breathing) as hypoxemia commonly causes tachycardia 1
- Attach cardiac monitor and obtain vital signs 1
- Establish IV access 1
- Obtain 12-lead ECG to define rhythm characteristics, but this should not delay cardioversion if the patient is unstable 1
ECG Classification Determines Further Workup
Narrow-complex tachycardia (QRS <0.12 seconds): Most commonly sinus tachycardia, atrial fibrillation, atrial flutter, or AV nodal reentry 1
Wide-complex tachycardia (QRS ≥0.12 seconds): Assume ventricular tachycardia until proven otherwise, as most wide-complex tachycardias are ventricular in origin 1, 4
Identify Reversible Causes
Search for and address:
- Hypoxemia 1
- Fever, dehydration, anemia 1, 2
- Pain, anxiety 2
- Electrolyte abnormalities 5
- Hyperthyroidism 5
- Medication effects or stimulant use 2, 5
Special Populations Requiring Lower Threshold for Workup
Patients with Impaired Ventricular Function
- Work up at heart rates <150 bpm if known ventricular dysfunction exists, as these patients are more likely to develop instability from tachycardia 1
History of Structural Heart Disease
- Any wide-complex tachycardia in patients with prior myocardial infarction requires immediate workup, as VT is the most likely diagnosis (85% of cases) 4
- Atherosclerotic heart disease patients presenting with regular wide-complex tachycardia should be assumed to have VT 4
Self-Terminated Tachycardia
Even after spontaneous resolution, workup is indicated for:
- Any suspected ventricular tachycardia (requires urgent cardiology consultation and echocardiography even if self-terminated) 2
- Recurrent episodes of supraventricular tachycardia (consider Holter monitor or event recorder to capture arrhythmia) 2, 6
- Atrial fibrillation/flutter (assess CHA₂DS₂-VASc score for anticoagulation need) 2
Persistent Symptoms Despite Rate <150 bpm
- Palpitations with neck pulsations, chest pain, lightheadedness, or dyspnea warrant workup even at lower heart rates 6, 3
- Frequent premature atrial contractions are increasingly recognized as associated with developing atrial fibrillation and may require evaluation 5
When Observation May Be Sufficient
- Single episode of sinus tachycardia that resolves after treating underlying cause (fever, dehydration, pain) in structurally normal heart 2
- Single self-terminated SVT episode in patient with structurally normal heart and no significant symptoms 2
Critical caveat: Diagnosis of anxiety or panic disorder is commonly made in error when supraventricular tachycardia is the actual cause—maintain high index of suspicion 6