Ventricular tachycardia: Difference between revisions

Torsades de pointes (TdP) is a ventricular tachycardia associated with a prolonged QTc interval on the resting ECG. The ECG during TdP is characterized by twisting of the peaks of the QRS complexes around the isoelectric line during the arrhythmia (changing axis). Torsade de pointes is typically initiated by a short-long-short interval. A ventricle extrasystole (first beat: short) is followed by a compensatory pause. The following beat (second beat: long) has a longer QT interval. If the next beat follows shortly thereafter (third beat: short), there is a good chance that this third beat falls within the QT interval, resulting in the R on T phenomenon and subsequent Torsades de pointes.  

See the chapter on [[LQTS]] for a list of medication and genes that can cause QT prolongation and TdP.

Electrocardioversion is the first treatment for an unconcious patient with incessant TdP.  

'''Additional treatments are:'''

*Withdrawal of any offending drugs and correction of electrolyte abnormalities (potassium repletion up to 4.5 to 5 mmol/liter, the goal should be to make the patient slightly hyperkalemic).  

*Intravenous magnesium sulfate can be helpful to cardiovert TdP in the acute phase in patients with few TdP episodes. If recurrence occurs a continues infusion may be beneficial.

*Beta blockers combined with cardiac pacing as acute therapy for patients with TdP and sinus bradycardia. This prevents extrasystoles and thereby short-long-short sequences.

*Isoproterenol as temporary treatment in patients with recurrent pause-dependent TdP who do not have congenital long QT syndrome.