ECG of the Week - 3rd February 2014 - Interpretation

An ECG from the archives this week. Unfortunately no clinical information on this case but at a glance it looks like a nice 'rhythmic riddle'.
Check out the comments from our original post here.

 

 

Click to enlarge

 

 

Numbered Rhythm Strip

Click to enlarge

 

Rate:

• Mean ventricular rate ~72 bpm
• Regular atrial activity ~95 bpm

Rhythm:

• Repeating pattern of atrial / ventricular acitivty
• Pattern of:
• Premature junctional complex (# 3, 6, 9, 12)
• Sinus complex with pr interval ~200ms (# 4, 7, 10)
• Sinus complex with pr interval ~300ms (# 2, 5, 8, 11)
• P wave without QRS complex

Axis:

• Normal / Inferior (+90 deg)

Intervals:

• QRS - Normal (100ms)
• QT - 380ms

Segments:

• Nil ST segment change
• Slight prominence anterior T waves

Additional:

• Group beating
• Progressive R-R shortening prior to dropped QRS

Interpretation:

•  Mobitz 1 / Wenckebach (4:3 Pattern)
• Group beating starts with Premature Junctional Complex

 
Check out our previous case of Wenckebach and the reason behind the PR prolongation and RR shortening seen with Wenckebach below:

• ECG of the Week 1st April 2013
• The Wenckebach Counter-Intuition

 Wenckeback Recap
 
I don't have any clinical information on this case, so I don't know the likely cause or outcome.

Type I second-degree AV block

• Can occur during sleep in healthy people
• It is NOT normal during waking hours
• Can result in significant exercise limitation if occurs during waking hours
• Symptomatic patient may require atropine +/- chemical +/- electrical pacing.

Cardiology referral should be made for patients found to have a Wenckebach conduction for specialist opinion on management, further investigation, and PPM consideration

Multiple causes which include:

• Ischaemia / Infarction
• Drugs - anti-arrhythmic, lithium, alcohols
• Inflammatory - myocarditis, endocarditis, Lyme's disease
• Metabolic
• Infiltrative diseases - amyloid, sarcoid
• Obstructive Sleep Apnoea
• Athletic Heart

Features of Wenckebach

 

The cardinal features of Wenckebach which are:

 

• Progressive PR lengthening resulting in non-conducted P wave
• Progressive R-R interval shortening
• R-R interval length of dropped beat less than twice shortest R-R cycle
• Grouped beating

 
References / Further Reading

 

Life in the Fast Lane

 

• AV Block - Mobtiz I / Wenckebach here

Textbook

• Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.