Ventricular tachycardia diagnosis

Associate Editor-In-Chief:

The diagnosis of ventricular tachycardia is made based on the rhythm seen on either a 12 lead EKG or a telemetry rhythm strip. It may be very difficult to differentiate between ventricular tachycardia and a wide-complex supraventricular tachycardia in some cases. In particular, supraventricular tachycardias with aberrant conduction from pre-existing bundle branch block are commonly misdiagnosed as ventricular tachycardia. Other rarer phenomena include ashman beats and antedromic atrioventricular re-entry tachcyardias.

Various diagnostic criteria have been developed to determine if a wide complex tachycardia is ventricular tachycardia or a more benign rhythm. In addition to these diagnostic criteria, if the individual has a past history of a myocardial infarction, congestive heart failure, or recent angina, the wide complex tachycardia is much more likely to be ventricular tachycardia.

The proper diagnosis is important, as the misdiagnosis of supraventricular tachycardia when ventricular tachycardia is present is associated with worse prognosis. This is particularly true if calcium channel blockers, such as verapamil are used to attempt to terminate a presumed supraventricular tachycardia. It is therefore wisest to assume that all wide complex tachycardia is VT until proven otherwise.

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.

Differential Diagnosis of Underlying Causes of Ventricular Tachycardia

 * Caffeine
 * Cardiomyopathy
 * Cocaine
 * Congenital Heart Disease
 * Congestive heart failure
 * Electrolyte imbalance
 * Hypertrophic cardiomyopathy
 * Hypocalcemia
 * Hypokalemia
 * Hypomagnesia
 * Iatrogenic due to pulmonary artery catheter, right heart catheterization, or electrophysiologic sutdy
 * Methamphetamine
 * STEMI
 * Ventricular aneurysm