Ventricular Escape Beats and Fusion Beats with Interpretation by Dr Ken Grauer, MD

I sent the following rhythm strips to Dr Ken Grauer and asked him for his help in interpreting the following strips. The strips contain PVCs and some escape beats that I thought could be either an aberrantly conducted atrial escape beats or unusual PVCs as there were P waves before the escape complexes. His comments are included after the strips.

Ventricular escape beats presenting fusion complexes

These are Ventricular escape beats. Some escapes manifest fusion.

STRIP A: 

• Beat #7 is a PVC.
• Beat #8 is a ventricular fusion beat. The QRS is wide - the PR is too short to conduct.

STRIP B

• Beat #1 is ventricular fusion - as is beat #6
• Note that the QRS of beat #1 looks a bit different than that of beat #6. Note also that the PR interval is a bit longer preceding beat #1 - which means there was a little more time for some conduction to occur - which is why this beat isn't quite as wide as ventricular escape beat #6

STRIP C

• More of same. Beats #3 and #6 are PVCs
• The escape beats are from yet another ventricular site.. Beats #4 and #7 are escape - with a sightly longer PR preceding beat #7 - so not quite as wide as beat #4.

NOTE: It is sometimes the "theme" that counts more than interpretation of each event on a series of tracings. While I do believe it is likely there is some fusion for beat #8 of Rhythm A and beat #1 of Rhythm B (because the PR interval preceding these beats is a bit shorter than it is preceding the sinus beats - AND - because these two beats look different than the wider escape beat #6 in Rhythm B) - I am not exactly sure of the complexes they fused with ... So the important thing here is the "THEME" = Sinus rhythm with frequent PVCs that manifest a compensatory pause which is terminated by escape beats with some degree of fusion.

The easiest way I've found to explain "fusion" beats - is that beats with fusion manifest a morphology intermediate between normal sinus beats and the beat from "below" that is occurring almost simultaneously. A picture tells 1,000 words. The rhythm below begins with 3 sinus beats. A run of a WCT (Wide-Complex Tachycardia) begins with beat #5. We KNOW this run of WCT is VT with 100% certainty because: i) QRS morphology during WCT is much different and wider than during sinus rhythm; ii) there is AV dissociation (red arrow); and iii) beat #4 is a FUSION beat! That is - IF beat #3 (the sinus beat) and beat #5 were to "have children" - you'd come up with an offspring that might look like beat #4 (which is upright but not nearly as wide as the beats during the run = the "fusion" between sinus and WCT morphologies). Note that not only do QRS morphologies "fuse" - but also the ST-T wave fuses (the T wave of beat #4 is intermediate in morphology between the T of beat #3 and #5). Seeing fusion PROVES a ventricular etiology - as there is no other way this could happen.

Going back to Rhythms A,B,C - We never quite see an escape beat that is not preceded by a P wave - so I'm not quite sure of what this focus will look like that is clearly of different morphology than the PVCs .... but then again - it is "the theme" that I believe counts most in this tracing.

AV dissociation with fusion complex

For more on fusion (where the above tracing came from) - Please GO TO: https://www.kg-ekgpress.com/acls_comments-_issue_11/#AV%20DISSOCIATION%20-%20FUSION%20-%20CAPTURE

Thank you Dr. Grauer for your assistance and the very helpful information regarding these strips.



Some additional strips showing fusion complexes.

Fusion complex

Notice that the P-P interval is regular.  At about the same time that there is a regular sinus discharge a PVC occurs and produces what looks like a PVC with a P wave.

Fusion complexes

The fusion complexes occur regularly in this trigeminal strip.




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GO TO: http://www.amazon.com/dp/1930553250/ref=rdr_ext_tmb

ECG Pocket Brain 2013 is available at this time but the updated ECG Pocket Brain 2014 is being prepared for publication at this time.

ACLS2013  Practice Code Scenarios is very helpful for those needing to review ACLS algorithms or who just need additional practice.  It contains a lot of practical clinical information that is not available in the standard ACLS text.  

• ECG-2014-Expanded Pocket Brain - http://www.amazon.com/dp/1930553250/ref=rdr_ext_tmb
• ACLS-2013-Pocket Brain - http://www.amazon.com/dp/1930553234/ref=rdr_ext_tmb
• ACLS: Practice Code Scenarios-2013 - http://www.amazon.com/dp/1930553242/ref=rdr_ext_tmb
• ACLS-2013-Arrhythmias Expanded Version - http://www.amazon.com/dp/193055334X/ref=rdr_ext_tmb

Author Page: amazon.com/author/kengrauer

Ken Grauer, MD (KG/EKG Press, Professor Emeritus in Family Medicine)

Web Site: www.kg-ekgpress.com

E-Mail: ekgpress@mac.com

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