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.
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%.
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.
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.
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.
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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.
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.
A 66 year old man is complaining of palpitations and chest pain which radiated to his left arm and neck, which lasted 20 minutes, then went away. Paramedics found him in V Tach. His BP was 120/80 and his pulse 120/min. He converted to a narrow-complex rhythm while being given amiodarone, but became nauseated. He returned to V Tach, and his symptoms disappeared. This patient had an implanted defibrillator, which never went off. How do we know this is V Tach?
First, ALWAYS consider any wide-complex tachycardia to be VT unless you have proof that it is not. When symptoms include chest pain, it can be especially dangerous to miss the diagnosis of VT. Remember, some VT can be asymtomatic, even for prolonged periods of time.
ECG signs that this is VT include: QRS is extremely wide (>.14 sec), no P waves associated with the QRS complexes, negative complexes in V4, V5 and V6. In fact, this patient has negative "precordial concordance" - all the chest leads are negative. This is a strong sign of VT. The wide little r wave in V1, greater than .04 sec (one small block) is a strong indicator of VT, as is the delayed nadir of the S waves in V1 through V3 (the slope of the S wave is not steep, indicating a long time to depolarize the ventricles).
For more about V Tach criteria, browse this site and visit the ECG blogs on the Favorites page. It is a favorite topic among ECG experts.
This ECG was presented earlier this week as an example of SVT with LBBB aberrancy, which was ultimately converted with one dose of adenosine in the Emergency Department. It is the most shared and commented on ECG yet to appear on the Guru. The diagnosis given was the one accepted by the medical staff who cared for the patient, who was a man in his 30's who presented to the Emergency Department complaining of a rapid heart rate. He was ambulatory with stable vital signs, in spite of the tachycardia. He reported that he has had several episodes of fast heart rate which responded to either Valsalva maneuvers or, in some cases, medication in the ED. He was told he might benefit from an ablation procedure, but he did not have health insurance and continued to use the ED as his primary source of medical care. When he was admitted to the ED, the tech initially called for help, thinking the monitor showed ventricular tachycardia. The ED physician felt that this represented LBBB aberrancy, possibly rate-dependent, and he treated the patient with adenosine. The rhythm converted to sinus after one dose, and the patient remained stable throughout the process. He was advised to undergo further observation and testing, but he declined due to financial concerns, and the fact that he usually succeeded in relieving his symptoms with "bearing down".
Wide-complex tachycardias can be difficult to assess simply from an ECG. The patient's stability depends more upon general health and cardiac output issues than the origin of the tachycardia. When we presented this ECG, we also presented the diagnosis he had upon discharge from the ED.
Subsequently, ECG Guru Dr. Ken Grauer, a frequent contributer to this site, offered his alternative diagnosis and his explanation of why he believes this to be v tach. Other well-respected ECG experts have also questioned the original diagnosis. Please refer to the comments below for this very helpful explanation. Unfortunately, this patient is lost to followup, as this incident occurred some time ago.
WTCs remain a most fascinating topic, especially for those who enjoy "detective work". We thank Dr. Grauer, Tom Bouthillet, and others for their contributions to the ECG Guru on this topic.
This is an interesting ECG for showing students AV sequential pacing and also ventricular tachycardia. The unusual thing about this ECG is that the V Tach starts at the time the machine begins recording the precordial leads. This particular ECG machine shows a slight "gap" at the lead change, so we don't see the actual start of the V Tach. Both rhythms have wide QRS complexes. The pacemaker is pacing the right ventricle, so you will see a wide QRS with a leftward axis, as the impulse spreads up and leftward toward the left ventricle. The V Tach portion is, of course, limited to the precordial leads, so we cannot plot the frontal plane axis. But, it meets many of the accepted criteria for ventricular tachycardia, including: very wide QRS, negative QRS in Lead V6, absence of RBBB or LBBB pattern. For more on recognizing V Tach in a WCT, go to Ask the Expert at this LINK.
This is also a very good example of how the interpretation by the machine can be wrong. Always read the ECG yourself!
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