Torsades de pointes electrocardiogram
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Electrocardiography
EKG is the main diagnostic tool in patients with Torsade de pointes. EKG findings that can be seen are:
- Progressive change in polarity of QRS about the isoelectric line occurs
- Prolonged QT interval (QT ≥ 0.60 s or QTc ≥ 0.45 s)
- Pathological U
- Rotation of the heart's electrical axis by at least 180º
- Preceded by short long and short RR-intervals
- Triggered by an early premature ventricular contraction(R-on-T PVC)
- Paroxysms of 5-20 beats at a rate ≥ 200 bpm
- Patients may revert spontaneously to a nonpolymorphic ventricular tachycardia or ventricular fibrillation
Background
- The peaks of the QRS complexes appear to twist around the isoelectric axis.
- Polymorphic VT is distinguished from Torsades by the absence of QT prolongation in polymorphic VT.
EKG Findings
- Paroxysms of VT with irregular RR intervals.
- A ventricular rate between 200 and 250 beats per minute.
- Two or more cycles of QRS complexes with alternating polarity.
- Changing amplitude of the QRS complexes in each cycle in a sinusoidal fashion.
- Prolongation of the QT interval.
- Is often initiated by a PVC with a long coupling interval, R on T phenomenon.
- There are usually 5 to 20 complexes in each cycle.