Tachycardia and hyperkalemia. What will happen after therapy with 1 gram of Ca gluconate and some bicarbonate?

A 20-something type, 1 diabetic presented by EMS with altered mental status.  Blood pressure was 117/80, pulse 161, Resp 45, SpO2 100 on oxygen.

Here is the 12-lead ECG:

Wide complex tachycardia

What do you think?

The providers thought that this wide QRS was purely due to (severe) hyperkalemia.   They treated with 4 ampules (200 mL) of bicarb and 1 gram of calcium gluconate. 

Note: 1 g of calcium gluconate is insufficient. 1 g of calcium chloride has 3x as much calcium and is indeed a good start.

His pulse on the monitor suddenly went down to 140 and another 12-lead ECG was recorded:

Sinus tachycardia at a rate of 143

There are peaked T-waves typical of hyperkalemia

The K returned at 6.9 mEq/L.

What do YOU think happened here?  What is the diagnosis on the top ECG?  Do you think that this was simply hyperkalemia with a wide complex that resolved with bicarb and calcium?

That top ECG with a wide complex tachycardia has all the features of ventricular tachycardia (VT): slow onset of the QRS, absence of P-waves, very wide, absence of any LBBB or RBBB morphology.  It is VT until proven otherwise and electrical cardioversion is indicated.  

When I was told that this was hyperkalemia that resolved with bicarb and calcium, I told them that, no, this is VT induced by hyperkalemia and that it just happened to coincidentally spontaneously convert at the same time as the administration of (inadequate) hyperkalemia  medicines.

How do I know that it is VT?

1. It just looks like VT

2. First part of QRS has slow onset: look at lead II.  

From onset of QRS to nadir of S-wave is a very long 140 ms.  This is possible with HyperK only, but unlikely.  

In V6, from onset of QRS to nadir of S-wave is 160 ms

3. It does not look like simple hyperkalemia, especially at a level of 6.9 mEq/L.  It might possibly have that appearance with such a wide complex if the K was at a much higher level.

4. It would not resolve with only bicarb and 1 g of calcium gluconate (= 1/3 of a gram of calcium chloride). That is minimal therapy for hyperK.

5. The heart rate changed instantly from 168 to 143.  That is typical of conversion from a re-entrant rhythm. 

6. P-waves appear on the followup ECG and they would not go from absent to present with such minimal therapy

Months later, when I was writing this up, I found the prehospital ECG:

This is typical hyperkalemia without VT.  Classic.  Notice the heart rate is approximately 130

This EMS ECG proves that the rhythm of the top ECG is VT.  It is not sinus tachycardia with hyperkalemia, or even sinoventricular rhythm.

What is sinoventricular rhythm?

Here are 4 cases of sinoventricular rhythm.

2 hours later