1.42
Code 1.42 — intermittent (paroxysmal) supraventricular tachycardia (Novacode rhythm class 1, equivalent to Minnesota Code 8-4-2). The recording shows short runs of fast supraventricular rhythm that start and stop suddenly, interrupted by normal sinus rhythm. Paroxysmal SVT is common, often occurs in otherwise healthy young people, and in most cases can be cured.
What happens during an episode
Most paroxysmal SVTs are re-entrant: an electrical impulse circulates in a loop formed by two pathways — within the AV node (AVNRT) or via an accessory pathway (AVRT). A premature beat can start the circuit; another premature beat or vagal stimulation can stop it. That is why episodes begin and end abruptly, unlike sinus tachycardia, which speeds up and slows down gradually.
Triggers and symptoms
- Triggers: bending, sudden movements, caffeine, alcohol, lack of sleep, stress, premature beats
- Symptoms: sudden pounding heartbeat, pulsation in the neck, dizziness, breathlessness, chest tightness
- Between episodes the ECG may be completely normal — Holter monitoring, event recorders or smartwatch ECGs help to capture episodes
- A short PR interval with delta wave on the resting ECG suggests WPW syndrome and an accessory pathway
Management
During an episode
- Vagal manoeuvres: modified Valsalva (strain while lying, then raise the legs), cold water on the face
- If ineffective — emergency care; adenosine terminates most episodes
Long term
- Rare, well-tolerated episodes: observation, trigger avoidance
- Frequent or poorly tolerated episodes: medicines or catheter ablation, which cures most cases
if an episode causes chest pain, fainting or severe breathlessness, or lasts longer than 15–20 minutes despite vagal manoeuvres.
References
- Page RL, Joglar JA, Caldwell MA, et al. 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia. Circulation. 2016;133(14):e506–e574. doi:10.1161/CIR.0000000000000311
- Prineas RJ, Crow RS, Zhang ZM. The Minnesota Code Manual of Electrocardiographic Findings. 2nd ed. London: Springer; 2010. doi:10.1007/978-1-84882-778-3
This article is for general information and does not replace a consultation with a doctor. ECG findings must be interpreted by a physician together with symptoms and other tests.
Published on 14 May 2019