ELECTROPHYSIOLOGY: Ventricular tachycardia: diagnosis of broad QRS complex tachycardia

Abstract

W hen confronted with a tachycardia having a broad QRS complex, it is important to be able to diVerentiate between a supraventricular and a ventricular tachycardia. Medication given for the treatment of a supraventricular tachycardia (SVT) may be harmful to a patient with a ventricular tachycardia (VT).1 2 A reasonable haemodynamic condition during a tachycardia may erroneously lead to the wrong diagnosis of SVT.3 Familiarity with the ECG signs allowing the diagnosis of a VT is therefore essential. But as will be discussed here, the ECG should not only tell you how to distinguish VT from other tachycardias with a broad QRS complex, but also to suspect its aetiology and its site of origin in the ventricle. Both aspects are important in decision making about the prognostic significance of VT and correct treatment. Classification of tachycardias with a broad QRS complexAs shown in fig 1, broad QRS tachycardia can be divided in three groups. x SVT with bundle branch block-Bundle branch block (BBB) may be pre-existing or can occur when the refractory period of one of the bundle branches is reached because of the heart rate of the SVT (so called tachycardia related or phase 3 block). BBB can also occur because of retrograde invasion in one of the bundle branches. 4 These causes of BBB can be found in patients with atrial tachycardia, atrial flutter, atrial fibrillation, atrioventricular (AV) nodal tachycardia, and also during orthodromic circus movement tachycardia (with AV conduction over the AV node and ventriculo-atrial (VA) conduction over an accessory AV pathway).x SVT with AV conduction over an accessory AV pathway-This may occur during atrial tachycardia, atrial flutter, atrial fibrillation, AV nodal tachycardia, and during antidromic circus movement tachycardia (with AV conduction over an accessory AV pathway and VA conduction over the AV node or a second accessory AV pathway). It is also the case in the so called Mahaim tachycardia where AV conduction goes by way of a slowly conducting right sided accessory AV pathway or a nodo-ventricular fibre inserting into the right ventricle.

ACC/AHA/ESC 2006 Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death

“…In the absence of other data, it should be assumed that patients experiencing sustained monomorphic VT are at risk for recurrent VT and should be treated for this arrhythmia in the same manner as are patients without biomarker release accompanying VT. Electrical cardioversion is always indicated for hemodynamically unstable tachycardia. Managing the patient presenting with well-tolerated, wide-QRS tachycardia is facilitated by differentiating between VT, SVT with aberrant conduction, and preexcited tachycardia (354). This can usually be accomplished by consideration of the history and examination of the 12-lead ECG during tachycardia.…”

An accurate electrocardiographic algorithm for differentiation of tremor-induced pseudo-ventricular tachycardia and true ventricular tachycardia

“…These electrocardiographic changes may cause unnecessary panic and increase the use of health care resources [1,4]. We are the first to create an electrocardiographic algorithm for differentiation of tremor-induced pseudo-VT from true VT.…”

Diretrizes

“…Esta arritmia se relaciona a quadros de intoxicação digitálica, doença miocárdica grave por cardiomiopatia avançada e doença sem cardiopatia estrutural, como a taquicardia catecolaminérgica familiar. 19,20,21,22,23,24,25,26 A presença de dissociação AV, com frequência ventricular maior que a atrial, ou a presença de batimentos de fusão e captura são diagnósticos para TV. Existem algoritmos que auxiliam essa diferenciação na ausência desses sinais.…”