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:

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%.

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 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.

For discussions by Jason Roediger (ECG GURU extroidonairre) on recognizing ventricular tachycardia, go to this LINK, and this LINK.