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Simply explain me psvt

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Here is a clear, simple explanation of PSVT:

PSVT - Paroxysmal Supraventricular Tachycardia

What is it?

PSVT is a family of rapid heart rhythms that start and stop suddenly (hence "paroxysmal") and originate above the ventricles (hence "supraventricular"). The heart suddenly races, then just as suddenly snaps back to normal.
  • Harrison's Principles, 22E

The 3 Types (What Causes It?)

About two-thirds of PSVT cases are caused by one of three mechanisms:
TypeShareMechanism
AVNRT (AV Nodal Reentrant Tachycardia)~65%An electrical loop trapped inside the AV node itself
AVRT (AV Reentrant Tachycardia)~30%Uses a secret "accessory pathway" (extra electrical wire) bypassing the AV node - includes WPW syndrome
Atrial Tachycardia~5%Ectopic focus firing rapidly from atrial tissue
Think of it like an electrical short circuit in the heart's wiring. The signal goes around and around in a loop, making the heart beat very fast.

Who Gets It?

  • More common in women
  • Peak onset in late teens and young adults
  • Most patients have no underlying heart disease
  • Incidence is roughly 35 cases per 100,000 person-years
  • Fuster and Hurst's The Heart, 15E

Symptoms

  • Palpitations (sudden racing heart - the most common complaint)
  • Lightheadedness / dizziness
  • Shortness of breath (dyspnea)
  • Chest discomfort
  • Patients can often pinpoint the exact moment it starts and when it stops

ECG Findings

ECG strip showing PSVT - rapid regular narrow QRS complexes
Key ECG features:
  • Narrow QRS complex (< 100 ms) - fast but normal-looking beats
  • Rate: 130-300 bpm (typically 170-180 bpm)
  • No normal P waves - they are either buried inside the QRS (~70% of cases) or appear as a small "retrograde" (inverted) P wave just before or after the QRS
  • Regular rhythm
  • Tintinalli's Emergency Medicine

Treatment

PSVT treatment algorithm
Step 1 - Vagal maneuvers (first, if patient is stable):
  • Valsalva maneuver (bear down hard like you're straining)
  • Carotid sinus massage
  • These work by boosting the vagus nerve, which slows the AV node and breaks the loop
Step 2 - IV Adenosine (if vagal maneuvers fail):
  • Temporarily blocks the AV node, terminating the reentrant circuit
  • Works in the vast majority of cases
  • Side effects: brief chest tightness, flushing, sense of doom (lasts ~10 seconds)
Step 3 - IV Beta-blockers or Calcium channel blockers (verapamil/diltiazem):
  • If adenosine fails or is contraindicated
  • Slower onset, risk of hypotension
If unstable (hypotensive, unconscious):
  • Synchronized DC cardioversion immediately
Long-term / recurrent PSVT:
  • Catheter ablation - burns the reentrant pathway with radiofrequency energy - this is curative with high success rates

Simple Summary

PSVT = Heart suddenly racing at 150-300 bpm due to an electrical loop, usually no structural heart disease. Fix it acutely with Valsalva or adenosine; cure it long-term with catheter ablation.
  • Harrison's Principles of Internal Medicine 22E | Fuster and Hurst's The Heart, 15E | Tintinalli's Emergency Medicine
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