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.

Continuing our series from the patient with acute AWMI, donated by Jenda Enis Štros, a new dysrhythmia has appeared.  The patient was taken to the cath lab, and a thrombus was removed from the stent.   We now see a wide-complex tachycardia.  The morphology (shape and configuration) of the QRS has changed considerably from the previous ECGs, so we know this is idioventricular in origin.  There are many other clues, but  some major ones are:  the QRS is very wide, there is no associated P wave, all the precordial leads except V1 are negative (precordial concordance), V6 is negative, and the axis is away from II, III, and aVF and toward aVR (aVR is upright).  

Because the rate is about 125/min., this could be called ventricular tachycardia (V Tach) or accelerated idioventricular rhythm (AIVR).  The important fact here is that this rhythm was transitory and the patient remained stable.  Reperfusion dysrhythmias are not uncommon, and the patient is treated as indicated by the clinical condition. 

Here are links to all six ECGs in this series:

http://www.ecgguru.com/ecg/teaching-series-1113-ecg-1-6-acute-anterior-wall-mi

http://www.ecgguru.com/ecg/teaching-series-1113-ecg-2-6-acute-anterior-wall-mi

http://www.ecgguru.com/ecg/teaching-series-1113-ecg-3-6-acute-anterior-wall-mi

http://www.ecgguru.com/ecg/teaching-series-1113-ecg-4-6-acute-anterior-wall-mi

http://www.ecgguru.com/ecg/teaching-series-1113-ecg-5-6-acute-anterior-wall-mi 

http://www.ecgguru.com/ecg/teaching-series-1113-ecg-6-6-acute-anterior-wall-mi

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 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.