ECG of the Week: ECG of the Week - 9th September 2013

This very unique ECG has kindly been donated by a member of our blog team Dr A Keren, a consultant cardiologist and cardiac electrophysiologist.
This ECG is from a middle aged female with a history of cardiac failure.
Check out the comment's from our original post here.

Click to enlarge

Rate:

Rhythm:

Regular
Paced rhythm

A-V Sequential pacing
All complexes paced

Axis:

Normal (~30 deg)

Intervals:

QRS - Prolonged (160ms)
QT - 460ms

Segments:

ST Depression Leads I, II, aVL, V1-6

Discordant to QRS vector

Additional:

T wave inversion leads I, aVL, V1-6

Discordant to QRS vector

Dominant R wave in V1
High frequency signal

Occurs at every alternate QRS complex
Does not occur at any other points during ECG recording

So what's going on here ?

Let's start with the easiest bit of the ECG.
We've got a paced rhythm with the following features:

A-V sequential pacing
Dominant R wave V1
ST and T wave changes discordant to QRS vector

What does this mean ?

The dominant R wave in lead V1 and a Rsr' pattern in lead V2 signifies left ventricular dominant biventricular pacing, commonly referred to as Cardiac Resynchronisation Therapy (CRT).

In CRT pacing leads are placed in the right ventricle, right atrium, and a coronary sinus branch (preferable posterior / posterolateral location). The purpose of CRT is restore the synchronous beating of right and left ventricle, as dyssynchronous ventricular contraction can impair pump function.

I've found a few freely available articles on CRT which are linked to below:

Barold SS, Herweg B. Usefulness of the 12-lead electrocardiogram in the follow-up of patients with cardiac resynchronization devices. Part I. Cardiol J. 2011;18(5):476-86. PMID: 21947982 Full text here
Barold SS, Herweg B. Usefulness of the 12-lead electrocardiogram in the follow-up of patients with cardiac resynchronization devices. Part II. Cardiol J. 2011;18(6):610-24. PMID: 22113748 Full text here
Burkhardt JD, Wilkoff BL. Interventional electrophysiology and cardiac resynchronization therapy: delivering electrical therapies for heart failure. Circulation. 2007 Apr 24;115(16):2208-20. PMID: 17452619 Full text here.
Leclercq C. Problems and troubleshooting in regular follow-up of patients with cardiac resynchronization therapy. Europace. 2009 Nov;11 Suppl 5:v66-71. PMID: 19861393 Full text here

What about the other signal ?

As noted above the most striking feature of this ECG is the high frequency signal overlying every alternate QRS.

We've had a number of potential suggestions from our blog readers including nerve stimulator sources, TENs source, or pacemaker failure. Hat tip to Adrian Baranchuk who suggested a post cardiac surgical cause for this ECG, and he is correct.

The patient had a Cardiomyoplasty procedure for severe heart failure. Skeletal muscle is wrapped around the heart and connected to a high frequency pacemaker which is also connected to the heart in order to trigger the pacemaker. Skeletal muscle is used to increase ejection fraction but is not the same as cardiac muscle. It is hard to make skeletal muscle have a full contraction just with one pacing spike as we do for pacing the heart. To make skeletal muscle contract you need to give it sustained high frequency contraction which in this patient was programmed for every second beat. If you made it every beat, the skeletal muscle would fatigue and be ineffective.

You can read more about cardiomyoplasty in this nice review article by Bocchi, link below:

Bocchi EA. Cardiomyoplasty for treatment of heart failure. Eur J Heart Fail. 2001 Aug;3(4):403-6. PMID: 11511424 Full text here

Acknowledgement

Special thanks to Dr Arieh Keren for sharing this unique ECG and for his explanation of the ECG findings in this case.

References / Further Reading

Articles

Barold SS, Herweg B. Usefulness of the 12-lead electrocardiogram in the follow-up of patients with cardiac resynchronization devices. Part I. Cardiol J. 2011;18(5):476-86. PMID: 21947982 Full text here
Barold SS, Herweg B. Usefulness of the 12-lead electrocardiogram in the follow-up of patients with cardiac resynchronization devices. Part II. Cardiol J. 2011;18(6):610-24. PMID: 22113748 Full text here
Burkhardt JD, Wilkoff BL. Interventional electrophysiology and cardiac resynchronization therapy: delivering electrical therapies for heart failure. Circulation. 2007 Apr 24;115(16):2208-20. PMID: 17452619 Full text here.
Leclercq C. Problems and troubleshooting in regular follow-up of patients with cardiac resynchronization therapy. Europace. 2009 Nov;11 Suppl 5:v66-71. PMID: 19861393 Full text here
Bocchi EA. Cardiomyoplasty for treatment of heart failure. Eur J Heart Fail. 2001 Aug;3(4):403-6. PMID: 11511424 Full text here