Supraventricular tachycardia (SVT) is a fast, regular heart rhythm, usually 150 to 250 beats per minute, caused by a short circuit above the ventricles. Most patients are stable and convert with vagal maneuvers or adenosine, while unstable patients need electrical cardioversion right away.
Key symptoms
- Sudden racing heartbeat that starts and stops abruptly
- Palpitations or pounding in the neck
- Lightheadedness, dizziness or near fainting
- Shortness of breath or chest discomfort
- Anxiety and fatigue after the episode
What you find on exam
- Pulse: fast and regular
- Blood pressure and mental status for signs of instability
- Signs of heart failure or poor perfusion
- Visible pulsing in the neck veins
- Triggers: caffeine, stimulants, dehydration
Tests
- 12-lead ECG: narrow, regular QRS, rate often 150 to 250, P waves hidden
- Continuous monitoring and a rhythm strip recorded during conversion
- Electrolytes and thyroid tests in hospital
- Echocardiogram and referral for recurrent episodes
Treatment basics
- Unstable patient: synchronized cardioversion
- Vagal maneuvers first, such as the modified Valsalva (strain, then lie flat with legs raised)
- Adenosine 6 mg rapid IV push with a flush, then 12 mg if needed
- Diltiazem or a beta blocker such as metoprolol if adenosine fails
- Catheter ablation for recurrent SVT
Red flags
- Low blood pressure, chest pain or confusion
- Wide QRS or irregular rhythm (not simple SVT)
- Fainting during the episode
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Sources: NASEMSO National Model EMS Clinical Guidelines; NCCPA PANCE Content Blueprint; NBOME COMLEX-USA clinical presentations. Written by Making Synapses. Making Synapses is not affiliated with these organizations.