Broad Complex Tachycardias is defined as a heart rate greater than beats per minute (bpm). More about Broad Complex Tachycardias.‎Causes · ‎Presentation · ‎Differential diagnosis · ‎Investigations. Broad complex tachycardia—Part II. BMJ ; doi: (Published 30 March ) Cite this as: BMJ ; A. Wide Complex Tachycardia: Definition of Wide and Narrow. Related .. The QRS duration is very broad, approaching ms; the rate is bpm. 2. At first.


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A possible explanation is the change in the broad complex tachycardia of the AV ring during the systolic cycle. During AVNRT, the retrograde P occurs early in systole when the AV ring broad complex tachycardia still positioned backward towards the atria, whereas during VT with retrograde conduction, the retrograde P occurs later in systole when the AV ring has moved towards the apex of the heart which enlarges the atria and minimizes the venous backflow.

Through the same mechanism, the frog sign is absent in orthodromic circus movement tachycardias.

A challenging broad-complex tachycardia

This lead is usually one of the inferior leads considering the lead in which the QRS complex is the most modest, i. QRS variability can indicate AV dissociation.

Obviously, care should be taken to record technically excellent ECGs without disturbances of the baseline. The mechanism of changes in QRS amplitude is not completely clear.

The most probable explanation is that the QRS voltage is determined broad complex tachycardia the variability of ventricular filling and volume. With aberrant conduction or ventricular pre-excitation, any supraventricular tachycardia SVT may present broad complex tachycardia a broad complex tachycardia and mimic VT.

Atrial tachycardia with aberrant conduction: Aberrant conduction usually manifests as either left or right bundle branch block and the bundle branch block may predate the tachycardia.

Broad Complex Tachycardia

When polymorphic VT is encountered broad complex tachycardia the acute setting it is frequently the result of an acute cardiac insult and it rapidly deteriorates into ventricular fibrillation.

Patients with congenital prolonged QT syndromes may present with recurrent episodes of Torsades de pointes. As with other forms of polymorphic VT, Torsades is not usually sustained but it will recur if the underlying cause is not corrected. The cardinal features of polymorphic VT are see Figures 5 and 6: Prolonged QT-interval Figure 6: Polymorphic Ventricular tachycardia Broad complex tachycardia Polymorphic VT that develops in association with an acute coronary syndrome requires immediate DC cardioversion, as it frequently degenerates into ventricular fibrillation.

Those patients with Torsades de pointes who are stable require intravenous magnesium and correction of underlying abnormalities eg. Patients frequently do not have any broad complex tachycardia structural heart disease and the origin of the tachycardia is the posterior fascicle or less commonly the anterior fascicle of the left bundle branch see Figure 1.

As the wave of depolarisation originates in specialised conducting tissue, the resultant QRS complex is of a relatively short duration 0.

A challenging broad-complex tachycardia

It is important broad complex tachycardia note that all the analyses that help broad complex tachycardia clinician distinguish SVT with aberrancy from VT also help to distinguish single wide complex beats i.

Scar tissue, as seen in patient with prior myocardial infarctions or with cardiomyopathy, may further slow intramyocardial conduction, resulting in wider QRS complexes in both situations. The site of VT origin: The timing of engagement of the His-Purkinje network: Flecainide, a class Ic drug, is an example that is notorious for widening the QRS complex at faster heart rates, often resulting in bizarre-looking ECGs that tend to cause diagnostic confusion.

Systematic approach to wide complex tachycardia: The following historical features Table I powerfully influence the final diagnosis.


A WCT that occurs in a patient with a history of prior myocardial infarction can be broad complex tachycardia assumed to be VT unless proven otherwise.

Historical features to help distinguish causes of WCT It should be noted that hemodynamic stability is not always helpful in deciding about the probable etiology of WCT.

Broad complex tachycardia

Many patients with VT, especially younger patients with idiopathic VT or VT that is relatively slow, will not experience syncope; on broad complex tachycardia other hand, some older patients with rapid SVT with or without broad complex tachycardia will experience dizziness or frank syncope, especially with tachycardia onset.

Physical Examination Tips to Guide Management. Absence of these findings is not helpful, since VT can show VA association 1: Of course, such careful evaluation of the patient is only possible when the patient is hemodynamically stable during VT; any hemodynamic instability such as presyncope, syncope, pulmonary edema, angina should prompt urgent or emergent cardioversion.