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Dr A Röschl's picture

VT or SVT? Here, Both!

Complex ECGs like this one have to be approached systematically. Firstly, we can see a normal sinus rhythm. A is the first beat of a wide complex tachycardia. This must be a ventricular tachycardia. Although there is a P-wave before the first beat of the tachycardia, it is not premature. Therefore, there is no SVT with aberrant conduction. The first beat of the tachycardia looks different from the subsequent beats because there is a fusion beat present. The VT conducts 1:1 back to the atria (a small negative P-wave can be seen at the end of the QRS complex in V1).

Dr A Röschl's picture

Ventricular Tachycardia After Inferior Myocardial Infarction

76-year-old man, with a history of inferior wall myocardial infarction. He experiences recurrent episodes of brief palpitations, often lasting only 5-15 seconds. In this ECG, at the beginning, the last part of a wide-complex tachycardia is visible. After 2 sinus beats, another wide-complex tachycardia begins (with the same QRS configuration).

Dawn's picture

Wide Complex Tachycardia

The Patient:   The details of this patient’s complaints and presentation are lost, but we know he was a 66-year-old man who was being treated in the Emergency Department. His rhythm went from sinus tachycardia with non-respiratory sinus arrhythmia to multi-focal atrial tachycardia (MAT) to wide-complex tachycardia. The WCT lasted a few minutes and spontaneously converted to an irregular sinus rhythm.

Wide-complex tachycardia:  Ventricular tachycardia or aberrantly-conducted supraventricular tachycardia?  When confronted with a wide-complex tachycardia, it can be very difficult to determine whether the rhythm is ventricular or supraventricular with aberrant conduction, such as bundle branch block. The patient’s history and presentation may offer clues.  It is very important, if the patient’s hemodynamic status is at all compromised (they are “symptomatic”), the WCT should be treated as VENTRICULAR TACHYCARDIA until proven otherwise.  

There have been many lists made of the ECG features that favor a diagnosis of ventricular tachycardia. Here are two such lists:  Life In The Fast Lane, and National Institute of Health.

The ECG:  This ECG shows a regular, fast, wide-QRS rhythm.  The rate is 233 bpm.  It had a sudden onset and sudden offset (not shown on this ECG), and the rhythm lasted about 3-5 minutes. The patient felt the change in rate, but did not become hypotensive or unstable.  Some features that relate directly to the most commonly-referenced VT vs. SVT charts are:

Dawn's picture

ECG Basics: Ventricular Tachycardia

V tach is identified by:  wide QRS complexes (>.12 seconds), rate faster than 100 bpm.  In MONOMORPHIC V tach, all QRS complexes look alike.  There are other mechanisms of wide-complex tachycardia, but they can be difficult to differentiate from a single rhythm strip.  All WCT should be treated as V tach until proven otherwise.

Dawn's picture

Ventricular Tachycardia In A Patient With Myopathy

These two ECGs are from a 77-year-old woman who was complaining of palpitations and mild shortness of breath.  She stated a history of atrial fibrillation.  She was alert, with a systolic BP over 120.  At the hospital, she was found to have cardiomyopathy, resulting in global hypokinesis. She also had significant coronary artery narrowing in her left main, left anterior descending, and circumflex, which were treated with coronary artery bypass graft surgery.

The first ECG was taken on arrival of the EMS crew at the patient’s home.  It shows ventricular tachycardia, rate 226 bpm, All WCTs should be considered to be ventricular tachycardia until proven otherwise.  While WCT can sometimes be difficult to definitively diagnose in the field, this ECG has many features which favor the diagnosis of VT, including:

·         An extremely wide QRS (I measure .24 sec., the machine measures .368 sec.).

·         An extreme left axis deviation (aVF is all negative).

·         Absence of either RBBB or LBBB pattern, with a  completely negative QRS in V6.  This all negative V6 places the liklihood of the rhythm being VT to about 100%.

Dawn's picture

ECG Basics: Torsades Cardioverted

These two strips are from one patient who was electrically cardioverted twice in a few minutes.  The original reason for the cardioversion was Torsades de Pointes, a type of polymorphic ventricular tachycardia associated with a long QT interval.  For more information about TDP, go to this LINK.  It is a bit difficult to comment on the patient's post-cardioversion rhythm, because so little of it is shown.  It appears to be sinus, with a wide QRS.  The QT interval appears slightly prolonged at .44 sec, but it is not known what the QT interval is corrected to a rate of 60/min.  TDP is often seen with QT intervals greater than 600 ms (.6 seconds).  Also THESE STRIPS ARE NOT SIMULTANEOUS, they were taken two minutes apart.  In the first one, the P waves and T waves look so much alike, they could all be P waves.  They do not "march out".  It is necessary to get a long strip, preferably in multiple leads, and a 12-Lead ECG, to properly evaluate the rhythm post-cardioversion. 

Dawn's picture

ECG Basics: Ventricular Tachycardia

An example of ventricular tachycardia in Lead II.  This patient's rate is about 190/min.  V Tach will have the following criteria:  Rate greater than 100/min, QRS duration greater than .12 sec. (120 ms), and no P wave associated with the QRS.

It can be difficult to distinguish V Tach from other wide-complex tachycardias without a 12-lead ECG, but all wide-complex tachycardias should be treated as V Tach until proven otherwise, as V Tach is a potentially lethal dysrhythmia.  V Tach can cause a severe reduction in cardiac output which can lead to V Fib and death.

Dawn's picture

Wide Complex Tachycardia

This ECG shows a wide-complex tachycardia with a rate of 137/minute.  No patient information is available other than what is on the ECG.  Here, we will comment for the BASIC LEVEL learner, and allow the ECG Gurus out there to add INTERMEDIATE and ADVANCED level comments.

Beginners and emergency workers should ALWAYS be cautioned to treat all wide-complex tachycardias as VENTRICULAR TACHYCARDIA until proven to be something else.  V Tach is a life-threatening dysrhythmia, and there should be no delay in treatment.  That being said, not all WCTs are V Tach.  The most common "mimic" of V Tach is left bundle branch block.  LBBB can appear along with any supraventricular rhythm, including sinus rhythms, atrial tachycardias, atrial fibrillation, and junctional rhythms.  The diagnostic criteria for LBBB are:  wide QRS (.12 seconds or more), supraventricular rhythm, negative QRS in V1 and positive QRS in V6 and Lead I.  This ECG meets the criteria for LBBB, except that the supraventricular rhythm is hard to prove.  On one hand, P waves are not seen - or at least not easily.  On the other hand, the ECG machine has recorded a PR interval and a P wave axis.  What do you think?

Some of the criteria that would favor the diagnosis of V Tach are not present here: precordial concordance (all QRS complexes in V1 through V6 pointing in same direction), V6 with a negative QRS, AV dissociation.  An extreme axis, especially extreme right, would favor V Tach.  This ECG has an abnormal left axis, which is possible in V Tach AND in LBBB.   For a more thorough discussion by ECG Guru Jason Roediger of the criteria for differentiating V Tach from LBBB and other aberrancy, go to this LINK.

In an emergency setting, WTCs are most often V Tach.  However, should the rhythm turn out to be SVT with aberrant conduction, the usual V Tach treatment protocols would do no harm.  For instance, if the patient is deemed to be "unstable", electric cardioversion is recommended for both V Tach and SVT.  If the patient is stable, the emergency drugs usually recommended are generally safe for both rhythms.

Care should be taken to differentiate SINUS tachycardia from SVT or V Tach.  Sinus tachycardia usually has an obvious physiologic cause (hypoxia, hypovolemia, fear, pain, fever, etc.).  Sinus tachycardia also will be variable in rate, slowing as the cause is alleviated, or speeding if the problem causing the tachycardia becomes worse.  It may require  a long period of observation to determine that the rate is gradually slowing or speeding up.  One would hope to find P waves at some point in sinus tachycardia, and a 12-lead ECG is a great help.


Dawn's picture

ECG Basics: Torsades de Pointes

Torsades de pointes, or polymorphic ventricular tachycardia, is a ventricular tachycardia precipitated by and associated with long QT Syndrome.  Long QT Syndrome can be congenital or acquired.  Torsades is life-threatening, and can be made worse by many drugs, including some of the drugs used to treat VT.  The rate is usually 150 - 250 / min. and the appearance is of a wide-complex tachycardia with QRS morphology changes.  In some leads, it will appear as if it is "twisting" around the isoelectric line, giving it the French name, Torsades de pointes, a ballet term meaning twisting of the points.  For a thorough discussion of Torsades, check this LINK.

Dawn's picture

Ventricular Tachycardia

This is a good example of ventricular tachycardia with PRECORDIAL CONCORDANCE.  The QRS complexes in the chest, or precordial, leads all point downward.  When the precordial leads are all  negative or all positive in a wide-complex tachycardia, there is virtually a 100% chance that the WCT is ventricular tachycardia.  This ECG shows many characteristics of VT, including the extreme "backwards" axis:  aVR is positive and II, III, and aVF are negative.  Lead I is almost equiphasic.  Also, the lack of a clear BBB pattern and a negative V6 are strongly suggestive of VT.  REMEMBER:  In the treatment of wide-complex tachycardia, the rhythm should be considered VT unless proven otherwise.  This is especially true in unstable patients, patients over 50 years old, and patients with known heart disease.

INSTRUCTORS' NOTE:  We purposely left the machine interpretation on this week's ECG of the Week.  How many errors did the machine make?  This might be a good teaching point for students of all levels.



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