ECG of the Week - 14th April 2014 - Interpretation

This ECG is from a 67yr old male. He had no cardiac history and presented following a minor fall whilst intoxicated.
Someone will likely ask why the ECG was performed, I don't know. I suspect it is one of the 'because we can' ECGs that we all see on a daily basis.
You can see the comments on our original post here.

Click to enlarge

Click to enlarge
Numbered Rhythm Strip
 

Rate:

• Mean ventricular rate ~115 bpm

Rhythm:

• Sinus
• Complexes 3-4, 6-15, 17-18
• Premature atrial complex
• Complexes 2, 5, 16, 19
• Occur earlier than expect
• Notching in terminal portion of T wave prior to complex 2 suggests atrial in origin
• Similar is seen with complexes 5,6,16,19

Axis:

• LAD
• Complexes 1-16
• Unable to comment on axis of complexes 17-19

Intervals:

• Complexes 1-16
• QRS - Prolonged (~130ms)
• QT - 320ms
• Complexes 17-19
• QRS - Normal (100ms)
• QT - 360ms
• Sinus Complexes 3-4, 6-15, 17-18
• PR - Normal (120ms)

Segments:

• Complexes 1-16
• Appropriate discordant ST segment in keeping with LBBB morphology

 Additional:

• LBBB Morphology complexes 1-16
• T waves prominent V1-3, II, III, aVF
• Complexes 2,5 16 subtle different morphology to sinus conducted LBBB QRS complexes 
• Post-extrasystolic pause following PACs
• Cycle lengths
• Sinus LBBB morphology ~510ms
• Sinus narrow complex morphology ~520ms

Interpretation:

• Intermittent bundle branch block
• Frequent PACs

Intermittent Bundle Branch Block

Intermittent bundle branch blocks can occur and are often associated with changes in cycle length, either rapid heart rates (tachycardia / acceleration dependent) or slower heart rates (bradycardia / deceleration dependent). Other causes of intermittent bundle branch block include ischaemia, and changes in autonomic tone.
Whilst intermittent bundle is often considered benign it may result in functional impairment as describe in the case study by Tanaka et al (link below).
You can read a bit more about intermittent bundle branch block in our further reading section below.

References / Further Reading

Life in the Fast Lane

• Left Bundle Branch Block
• Pain free and in VT.. ? Case study
• Premature atrial complex

Articles

• Fisher JD, Aronson RS. Rate-dependent bundle branch block: Occurrence, causes and clinical correlations. J Am Coll Cardiol. 1990;16(1):240-243. Full text here.
• Tanaka H, Hiraishi M, Miyoshi T, Tsuji T, Kaneko A, Ryo K, Yamawaki K, Fukuda Y, Norisada K, Tatsumi K, Matsumoto K, Kawai H, Hirata K. Exercise-induced left bundle branch block and subsequent mechanical left ventricular dyssynchrony -resolved with pharmacological therapy. Cardiovascular Ultrasound 2011, 9:4 . Full text here.

Textbook

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