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Monday, September 29, 2008

Torsade de Pointes

    Torsade de Pointes

    http://www.emedicine.com/emerg/topic596.htm

  1. Torsade de pointes (TDP), often referred to as torsade, is an uncommon variant of ventricular tachycardia (VT). The underlying etiology and management of torsade are, in general, quite different from those of garden-variety VT. The management of torsade with group IA antidysrhythmic drugs can have disastrous consequences. Differentiating between these entities, therefore, is critically important
  2. Torsade is defined as a polymorphous VT in which the morphology of the QRS complexes varies from beat to beat
  3. The ventricular rate can range from 150 beats per minute (bpm) to 250 bpm
  4. There is regular variation of the morphology of the QRS vector from positive to net negative and back again. This was symbolically termed torsade de pointes, or "twisting of the point" about the isoelectric axis
  5. definition also requires that the QT interval be increased markedly (usually to 600 msec or greater ). Cases of polymorphous VT, which are not associated with a prolonged QT interval, are treated as generic VT
  6. The underlying basis for rhythm disturbance is delay in phase III of the action potential. The delay is mediated by the hERG potassium channel.
  7. Women are 2-3 times more likely to develop TDP than men

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