ECG Blog #471 — Two for One?

The ECG in Figure-1 was obtained from a man in his 60s — who presented with an acute, febrile pulmonary illness. He has been short of breath — but not having chest pain.

QUESTION:

• How would you interpret the ECG in Figure-1?

Figure-1: The initial ECG in today's case — obtained from a man in his 60s with dyspnea, but no chest pain. (To improve visualization — I've digitized the original ECG using PMcardio).

MY Thoughts on the ECG in Figure-1:

Interpretation of the ECG in Figure-1 is made more challenging by overlap of QRS complexes in multiple leads. That said — there appear to be 2 princpal elements to this rhythm: 

• i) The run of wide beats that begins this ECG (Seen for beats #1-thru-8 — and then for two 3-beat salvos that are seen later in the tracing); and, 
• ii) The lack of sinus P waves for the 2 short periods of narrower beats (ie, for beats #9-11; and 15-17).

PEARL: This is not an easy tracing to interpret. That said — When faced with a complex arrhythmia to interpret, in which there are a number of challenging elements — I find it helpful to: 

• i) Look for an underlying rhythm.
• ii) Begin with those elements that are easier to interpret.

I highlight these points in Figure-2:

• Instead of sinus P waves — Don't the regularly-occurring RED lines in Figure-2 suggest the "sawtooth" pattern of AFlutter (Atrial Flutter) as the underlying rhythm? 
• The rate of these RED lines is approximately 1 large box in duration — or close to 300/minute (which is perfectly consistent with the atrial rate of untreated AFlutter).
• The R-R interval for these 6 supraventricular beats (ie, Narrow QRS complexes #9,10,11 and #15,16,17) — is close to 2 large boxes in duration, which is perfectly consistent to AFlutter with 2:1 AV conduction as the underlying rhythm.

This leaves us to contemplate the etiology of the wide beats:

• As noted earlier — ECG #1 begins with a run of 8 wide beats (beats #1-thru-8 in Figure-2) — with two additional 3-beat runs (beats #9-11 and 15-17). Determining whether these wide beats represent ventricular beats vs supraventricular beats with aberrant conduction is the more difficult part of this tracing.

Figure-2: I've labeled flutter waves — here best seen in lead III.

Assessing the Wide Beats:

Overall — the wide beats appear to be fairly (but not completely) regular. This slight irregularity is best appreciated by looking at the R-R interval in lead II of Figure-3 between beats #12-13 vs between beats #13-14.

• The overall rate of the wide beats is a bit over 150/minute (ie, the R-R interval is less than 2 large boxes in duration).
• In contrast — I thought the narrow beats during AFlutter manifested a more consistently regular rate (as is common with 2:1 AFlutter).
• There are 2 post-ectopic pauses in Figure-3 (highlighted by the double YELLOW arrows). Post-ectopic pauses are a common feature following a run of VT (Ventricular Tachycardia).
• Doesn't the QRS complex of beat #9 in several leads (especially in leads II,III,aVF) look intermediate in morphology between the wide beats that precede it and narrow beats #10,11 that come after it? I therefore thought beat #9 was a fusion beat ("F" in Figure-3) — which if correct, would provide support that the wide beats in today's rhythm were ventricular.
• Finally — QRS morphology of the wide beats in Figure-3 strongly suggests a ventricular etiology because: i) Transition in the chest leads occurs much earlier than expected for Left Bundle Branch Block conduction (ie, the R wave is already all positive by lead V4 — whereas transition usually does not occur with LBBB until at least lead V5, if not V6); ii) LBBB conduction typically manifests a wider monophasic R wave in lead I than in leads II and III — and — LBBB conduction does not produce an all negative QRS in lead aVL (as we see here); — and, iii) The frontal plane axis of the wide beats in Figure-3 is vertical (ie, most positive in leads II,III,aVF compared to lead I ) — which results in a QRS morphology consistent with RVOT VT (Right Ventricular Outflow Track VT) — namely, LBBB-like morphology in the chest leads with an inferior frontal plane axis.

========================================

• NOTE: See ECG Blog #204 (for more on "typical" QRS morphology with LBBB & RBBB, including an ECG Video) — and ECG Blog #323 (for more on the appearance of idiopathic VT, including RVOT VT which is the most common form).

Figure-3: I've labeled post-ectopic pauses and a probable fusion beat.

BOTTOM Line: It's impossible to be 100% certain as to the etiology of the wide beats in today's tracing. That said:

• The underlying rhythm appears to be AFlutter with 2:1 AV conduction.
• The ECG features described above make it most likely that the runs of wide beats in today's rhythm represent NSVT (Non-Sustained Ventricular Tachycardia). We don't know how long the 1st run is (since the tracing begins with VT). After a brief pause — we then see two 3-beat salvos.
• Without more information — it's hard to know what optimal treatment should be. Both AFlutter and PVCs (including NSVT) are commonly seen with hypoxemia — and often resolve once the pulmonary problem and oxygen status are stabilized. Cardioversion is not indicated — since the runs of VT are not sustained. More information is needed.
• Final Thought: I generally look for a single explanation to most of the arrhythmias I encounter. That said — today's case provides an insightful example of ECG features that suggest the occurrence of both an underlying supraventricular rhythm ( = AFlutter) — and, a superimposed ventricular rhythm (ie, repetitive PVCs with a run of NSVT).

==================================

Acknowledgment: My appreciation for the anonymous donation of today's case and this tracing.

================================== 

==============================

Additional Relevant ECG Blog Posts to Today’s Case:

• ECG Blog #185 — Reviews my System for Rhythm Interpretation — with use of the Ps, Qs & 3R Approach.
• 
  
• ECG Blog #287 — Review of AFlutter ...
• 
  
• ECG Blog #220 — Review of the approach to the regular WCT ( = Wide-Complex Tachycardia).
• ECG Blog #196 — Another Case with a regular WCT.
• ECG Blog #263 and Blog #283 — Blog #361 — Blog #384 — Blog #460 — and Blog #468 — More WCT Rhythms ...
• 
  
• ECG Blog #197 — Reviews the concept of Idiopathic VT, of which Fascicular VT is one of the 2 most common types. 
• 
  
• ECG Blog #204 — Reviews the ECG diagnosis of the Bundle Branch Blocks (RBBB/LBBB/IVCD). 
• ECG Blog #203 — Reviews ECG diagnosis of Axis and the Hemiblocks. For review of QRS morphology with the Bifascicular Blocks (RBBB/LAHB; RBBB/LPHB) — See the Video Pearl in this blog post.
• 
  
• ECG Blog #211 — WHY does Aberrant Conduction occur?
• ECG Blog #301 — Reviews a WCT that is SupraVentricular! (with LOTS on Aberrant Conduction).
• ECG Blog #445 and Blog #361 — Another regular WCT rhythm ...
• 
  
• ECG Blog #323 — Review of Fascicular VT.
• ECG Blog #38 and Blog #85 — Review of Fascicular VT.
• ECG Blog #278 — Another case of a regular WCT rhythm in a younger adult.
• ECG Blog #35 — Review of RVOT VT. 
• ECG Blog #42 — Criteria to distinguish VT vs Aberration.