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%.
A paramedic crew responded to the office of a local physician. A 61-year-old male presented with a one-week history of chest pain and shortness of breath. He had a previously undiagnosed atrial fibrillation with rapid ventricular response and left bundle branch block, but was alert. Shortly after transport commenced, the patient became unresponsive with Torsades de Pointes, which rapidly degenerated into ventricular fibrillation. The paramedic placed pads and defibrillated within one minute. After two minutes of compressions, the patient had a fairly regular rhythm with return of spontaneous circulation. Transport time was short. On catheterization, the patient was found to have severe coronary artery disease, requiring coronary artery bypass graft surgery (CABG) A balloon pump was inserted in an attempt to strengthen him for surgery.
What is the rhythm? The 12-lead ECG presented here shows atrial fibrillation at a rate of 138 per minute. The rhythm is irregularly-irregular with no P waves. Since the patient had not yet been diagnosed with atrial fib, obviously no therapy had been initiated to control the rate. There is a PVC near the end of the strip.
This ECG is from a man who was experiencing palpitations and light-headedness with near-syncope. On first look, you will see a wide-complex tachycardia (WTC) with a rate around 240 per minute. It is difficult to assess for the presence of P waves because of the rate and the baseline artifact.
The differential diagnosis of WCT includes ventricular tachycardia and supraventricular tachycardia with aberrant conduction, or interventricular conduction delay (IVCD). We should ALWAYS consider VENTRICULAR TACHYCARDIA first. If the patient is an older adult with structural heart disease, WCT almost always proves to be VT.
ABERRANT SVT? In the setting of SVT with wide QRS, the most common aberrancy is right or left bundle branch block. This ECG could be said to have a “RBBB” type pattern in V1, rSR’ and in Lead I and V6 with a wide S wave. However, the other precordial leads do not have a RBBB pattern.
VENTRICULAR TACHYCARDIA? There are some features of this ECG that favor the diagnosis of VENTRICULAR TACHYCARDIA (VT). They include, but are not limited to:
* Regular, wide QRS complexes, about .14 seconds in this ECG, but varies because of difficulty in measuring the beginning and end of the QRS in each lead. The artifact obscures the exact points of beginning and ending. The QRS complexes, especially from V2 leftward, are very “ugly”, and don’t resemble patterns we would expect with bundle branch block.
* Horizontal plane axis extremely abnormal: Leads II, III, and aVF are negative and aVR and aVL are positive. The biphasic Lead I indicates a nearly vertical axis at around – 90 degrees.
* There is “almost” precordial concordance, but V1 is biphasic.
Unfortunately, we do not see capture beats or fusion beats, which would secure the diagnosis of VT. Disassociated P waves would also be a sure sign of VT, but the artifact in this ECG makes it impossible to say whether there are P waves.
This ECG was obtained from a 45-year-old man who was experiencing palpitations and lightheadedness, which he originally attributed to anxiety. There are short, but frequent periods of ventricular tachycardia, which are self-limiting. This is called "NON-SUSTAINED VENTRICULAR TACHYCARDIA". The underlying rhythm is sinus, with a remarkably long PR interval, and at least one episode of failure of the P wave to conduct, making "second-degree AV block, Type II" a possibility. It is difficult to thoroughly evaluate the underlying rhythm because it is not seen very often in this ECG. The rate of the underlying P waves is about 67 bpm. The PR interval is .40 seconds (400 ms). The "normal" QRS complexes are slightly widened, at about .10 sec (100 ms), which is typical of Type II AVB. The ventricular QRS complexes are wide at .16 sec. (160 ms)
To assist you in using this tracing for teaching, we have also supplied a "marked up" version. The P waves, both visible and hidden, are marked with red lines. The PR intervals are shown in the Lead V1 rhythm strip in green. And the QRS complexes are numbered. QRS complexes numbered 2, 3, 6, and 12 are sinus. The P wave AFTER QRS #5 is non-conducted.
To review the differentiation of ventricular tachycardia from supraventricular tachycardia with aberrant conduction, go HERE.
This wide-complex tachycardia is ventricular tachycardia. Along with the wide QRS and the fast rate, features which favor a diagnosis of VT over BBB include: backwards (extreme right) QRS axis, negative QRS in V6, and an apparently monophasic QRS in V1, as opposed to the rSR' pattern of right bundle branch block.
Remember, ALL wide-QRS tachycardias should be treated as V Tach until proven otherwise, as it is a life-threatening arrhythmia. Factors which lower cardiac output during V Tach include: Fast rate, wide QRS, and lack of P wave preceding the QRS. The sudden severe lowering of perfusion that usually accompanies V Tach can lead to rapid deterioraton and ventricular fibrillation.
This ECG was donated to the ECG Guru by Brent Dubois, and was originally published on the FaceBook page, Paramedic Tips & Tricks. We published it to this site three years ago, but believe it should be shown again, as it is somewhat rare to catch a good-quality 12-Lead ECG of an implanted cardioverter-defibrillator pacemaer using overdrive pacing to terminate a ventricular tachycardia. Most of our examples have been rhythm strips.
In this strip, we see the patient in ventricular tachycardia (V tach) at a rate of about 190 / minute. The ICD, in response to the fast rate, delivers a short burst of even faster paced beats. The physological rule in the heart is, "the fastest pacemaker controls the heart". Once the pacemaker has terminated the V tach, it paces at a much slower rate. It is pacing the atria, and the conduction system is intact, allowing the impulse to travel normally through the ventricles. If the sinus node is able to "outpace" the slower paced rhythm, the heart will resume a sinus rhythm.
This is called "overdrive pacing" and is done automatically by an ICD that is programmed to do so. Overdrive pacing can also be accomplished by a temporary transvenous pacer or transcutaneous pacemaker.
This ECG was taken from a patient who was complaining of palpitations and tachycardia, but who was hemodynamically stable, with no history of heart disease. It is an example of RIGHT VENTRICULAR OUTFLOW TRACT TACHYCARDIA, a type of idiopathic ventricular tachycardia. The ECG signs of RVOT are: wide QRS complex, left bundle branch block pattern (QRS negative in V1 and positive in Leads I and V6), heart rate over 100 bpm, rightward or inferior axis (LBBB usually has a normal to leftward axis), AV dissociation.
RVOT accounts for about 10% of all ventricular tachycardias, and 70% of idiopathic VT. It is most often found in structurally normal hearts, but it may occur in patients with arrhythmogenic right ventricular dysplasia. For more on RVOT, read Life In the Fast Lane.
RVOT tachycardia sometimes converts with adenosine. The patient in this example converted after being administered amiodarone.
Wide-QRS rhythms can be difficult to diagnose from the ECG alone. This difficulty is compounded when the rate is fast, as it can be hard to determine if P waves are present before the QRSs, or dissociated, or absent.
This ECG and rhythm strip were donated to the ECG Guru by Ryan Cihowiak. We don't have clinical information on the patient, unfortunately. It is a great example, however, of how difficult WCT can be to diagnose.
In the 12-Lead ECG, we see wide QRS complexes that are regular at a rate of 131 / minute. There are no obvious P waves before the QRS complexes, and no obvious distortion of the T waves, which would suggest a "hidden" P wave. Unfortunately, there is significant artifact, which makes searching for P waves difficult. The pattern overall suggests left bundle branch block, with the negative QRS in Lead V1 and positive QRS complexes in Leads I and V6. However, one requirement for the diagnosis of LBBB is a supraventricular rhythm, and P waves are the best indicator of that. An irregularly-irregular rhythm, indicating atrial fib, would also have made LBBB more likely. In typical LBBB, the frontal plane axis is usually left-normal or left. In this ECG, Lead III is taller than Lead I, putting the axis within normal range, but slightly rightward.
The rhythm strip uncovers something else. Possible P waves are seen in some of the ST segments (arrows). Are these dissociated? Do they represent a first-degree AV block? Are they actually artifact? If this is a supraventricular rhythm, there is LBBB. Then, notice beats #7,8,9. If this rhythm is supraventricular (with LBBB), those must be a salvo of V Tach. But, one of the possible P waves occurs in front of beat #7.
Another possibility is Right Ventricular Outflow Tract Tachycardia. RVOT is a type of V Tach that typically has a LBBB pattern, with a slightly rightward axis. If this is the case, beats #7,8,9 are probably "capture" beats or "fusion" beats. Capture and fusion beats "prove" that the underlying tachycardia is ventricular, since, by definition, capture and fusion represent a return to supraventricular control of the rhythm.
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.
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