This presentation is about supra-ventricular tachycardia and its mechanism

1. ‫الرحیم‬ ‫الرحمن‬ ‫هللا‬ ‫بسم‬

2. SUPRAVENTRICULAR
TACHYCARDIAS
SVT

3. Supraventricular Tachycardias
• Supraventricular tachycardia refers to an arrhythmia having three or more complexes
at rates exceeding 100 beats/ minute and originating above the ventricle (i.e. either in
the SA node, atria or in the AV junction).
• Supraventricular tachycardia includes the following conditions:
• Sinus tachycardia
• Atrial fibrillation
• Atrial flutter
• Multifocal atrial tachycardia
• Paroxysmal supraventricular tachycardia (PSVT)
• Wolff-Parkinson-White syndrome
• Junctional tachycardia

4. Re-Entry
• The most common mechanism of arrhythmias is re-entry. This is
particularly true for paroxysmal supra ventricular tachycardia (PSVT).
• Re-entry requires presence of two electro physiologically distinct
pathways around an insulated core (e.g. the AV valve annulus).
• In PSVT, re-entry occurs due to presence of an additional electrical
connection between the atrium and ventricle (e.g. the bundle of Kent) or
within the AV node itself (see figure below).
• In re-entrant rhythms, electrical impulse can cycle and recycle
repetitively.

6. ◦ In re-entry, electrical signals generated from an appropriately timed
premature beat find pathway B still under absolute refractory period,
resulting in conduction block in this limb of the circuit. Meanwhile,
conduction down pathway A proceeds unimpeded. Subsequent
recovery of pathway B allows electrical signals to be conducted
backward (or retrograde), resulting in re-activation of pathway A and
propagation of the re-entry circuit.