Ventricular tachycardia including torsades de pointes and polymorphic ventricular tachycardia


 * Associate Editor-In-Chief:

Ventricular Tachycardia

 * Ventricular tachycardia originates from a ventricular focus
 * Lasts more than 30 seconds
 * Broad QRS complexes: rate of >90 beats/minute

Paroxysmal Ventricular Tachycardia

 * 1) Rapid succession of three or more ectopic beats.
 * 2) Sustained if it lasts longer than 30 seconds.
 * 3) Called incessant if the tachycardia is recurrent and the episodes are interrupted by only a few sinus beats.

EKG Findings

 * 1) Abnormal and wide QRS complexes with secondary ST segment and T wave changes.
 * 2) * Usual QRS duration is > 0.12 seconds, may be shorter if the ectopic focus is located in the ventricular septum.
 * 3) * The secondary ST segment and T wave changes are in a direction that is opposite the major deflection of the QRS.
 * 4) * A ventricular rate between 140 and 200 BPM.
 * 5) * When the rate is >200 and has a sine wave appearance, it is called ventricular flutter.
 * 6) * When the rate is <110 BPM it is called non-paroxysmal VT.
 * 7) A regular or slightly irregular (up to 0.03 seconds) rhythm.
 * 8) Abrupt onset and termination.
 * 9) AV dissociation.
 * 10) * Atrial rate slower than ventricular rate.
 * 11) * No relationship between atrial activity and ventricular activity.
 * 12) * There can be VA conduction.
 * The RP interval is >0.11 seconds.
 * Occurs in about 50% of cases.
 * Uncommon when the ventricular rate is rapid (only 1/7 when the rate was>200).
 * 1) Capture beats.
 * 2) * Occurs when a supraventricular impulse is conducted and captures the ventricle.
 * 3) * They are rare.
 * 4) Fusion beats.
 * 5) * Rare in VT at a rapid rate.

Background

 * 1) The peaks of the QRS complexes appear to twist around the isoelectric axis.
 * 2) Polymorphic VT is distinguished from Torsades by the absence of QT prolongation in polymorphic VT.

EKG Findings

 * 1) Paroxysms of VT with irregular RR intervals.
 * 2) A ventricular rate between 200 and 250 beats per minute.
 * 3) Two or more cycles of QRS complexes with alternating polarity.
 * 4) Changing amplitude of the QRS complexes in each cycle in a sinusoidal fashion.
 * 5) Prolongation of the QT interval.
 * 6) Is often initiated by a PVC with a long coupling interval, R on T phenomenon.
 * 7) There are usually 5 to 20 complexes in each cycle.

Clinical Correlation

 * 1) Drugs: quinidine, PCA, norpace, amiodarone, phenothiazines, Tricyclic antidepressants, pentamidine.
 * 2) * with quinidine majority of the cases occur within one week of initiation, and with therapeutic levels
 * 3) Electrolyte imbalances: Hypokalemia, hypomagnesemia, hypocalcemia
 * 4) CAD
 * 5) MVP
 * 6) Variant angina
 * 7) Myocarditis
 * 8) Subarachnoid hemorrhage
 * 9) Congenital QT prolongation
 * 10) Liquid protein diets
 * 11) Hypothyroidism
 * 12) * because of bradycardia and a prolonged QT syndrome
 * 13) Organophosphate poisoning