A Very Wide Complex Tachycardia. What is the Rhythm? Use Lewis Leads!!

A patient with a history of severely reduced left ventricular function, renal insufficiency and atrial fibrillation presented with slight dyspnea, without chest pain or syncope.

He had this initial ECG:

There is a very wide, regular, QRS at 250 ms.  There are no P-waves apparent.   There are few isolated conditions which result in this.
What is one?

Here is the patient's previous ECG: 

There is a wide complex with a Left Bundle Branch Block morphology.  There are no P-waves here either, so it appears to be a junctional rhythm.  (The Differential Diagnosis would also include accelerated idioventricular rhythm originating in the right ventricle).  The QRS here also very wide, but not as wide as on the first ECG above.  Notice that the initial r-wave is wider than normal for LBBB.  

Also note that there is notching in the QRS (a "fragmented" QRS), which contributes to the wider-than-normal LBBB [this is Cabrera's sign (a notch on the ascending limb of the S-wave in V3-V5), a fairly reliable sign of previous MI, similar to a Q-wave].  Notice there is also a notch on the descending limb of the S-wave in all inferior leads II, III, aVF.  There is some T-wave Peaking, suggesting hyperkalemia.  

Overall impression of old ECG: Junctional rhythm and peaked T-waves and wide QRS.  This should make you think of hyperkalemia at the time of the old ECG (unfortunately, I don't know if that is the case).

Overall impression of QRS of new ECG: Even worse hyperkalemia superimposed on the conditions present on the old ECG above.  Indeed, the even wider QRS is due to a K of 7.8 mEq/L.  

How about the rhythm on that first ECG?

The patient was diagnosed with Ventricular Tachycardia and given both amiodarone and lidocaine.  I presume the hyperkalemia was treated as well, but do not have that information.  The rate slowed and became irregular, and the QRS narrowed significantly, but the rhythm still could not be discerned (it was still a wide complex).   This ECG is unavailable.

A consulting physician suspected that the underlying rhythm was atrial flutter, and so applied Lewis Leads.

1. Place the Right Arm electrode on the patient’s manubrium.
2. Place the Left Arm electrode on the 5th intercostal space, right sternal border.
3. Place the Left Leg electrode on the right lower costal margin.
4. Monitor Lead I.

Here is the resulting ECG (limb leads only): 

Perhaps it is better seen here:

Now slow flutter waves (with variable block) are apparent.  They are slow at least partly due to the amiodarone.  Note the axis is different than in the first ECG.  One might be tempted to say "Ahaa!  This different axis is proof that the first ECG was indeed VT!"  But, remember, the Lewis Leads change the axis.  All axis difference is due to lead placement.

The patient was put on hemofiltration to lower the K.  

Diagnosis:

1. Rhythm: Atrial Flutter with 2:1 block, only diagnosed with Lewis leads

2. QRS: Combination of LBBB, old MI and hyperkalemia, all leading to very wide QRS.

LBBB alone seldom has a QRS longer than 200 ms.  See this case of LBBB and hyperK.  

See this case for RBBB and very wide QRS due to hyperK.

Here is an even better case of use of the Lewis Leads