Sunday, 22 February 2015

ECG of the Week - 16th February 2015 - Interpretation

This week's ECG case comes with three ECG's. They are from an 85 yr old female who presented with a 12 hour history of feeling generally unwell. Her past medical history includes congestive cardiac failure (EF 35%), chronic renal impairment and paroxysmal atrial fibrillation. Medications included a calcium-channel blocker and a beta-blocker.
On arrival her blood pressure was 125/65 and she had a GCS of 15.
These ECG were each performed at ~30 minutes intervals.
Check out the comments on our original post here.

I'm going to abridge our usual format for this week's interpretation to focus on the key features of the three ECG's.

ECG 1
Click to enlarge
Rate:
  • 30
Rhythm:
  • Regular
  • No p waves visible
Axis:
  • Normal
Intervals:
  • QRS - Normal (80-100ms)
Additional:

  • Flat T waves all leads
  • Baseline artifact

Interpretation:

  • Significant bradycardia with absence of P waves. 
  • DDx: 
    • AF with complete heart block & junctional escape
    • SA Exit Block with junctional escape
    • Sinus Node Dysfunction

What happened next ?

As Vince has mentioned in the comments we were worried about drug toxicity and potassium as potential reversible causes. An urgent VBG showed a potassium of ~6 mmol/L. The patient was on relatively low doses of both beta & calcium channel blockers with no recent change in dose and her renal function was at the patient's normal baseline.
Following discussion with cardiology re: urgent vs semi-elective pacing the patient was commenced on an isoprenaline infusion. The ECG below was performed following 20-30 mins of isoprenaline therapy.

ECG 2
Click to enlarge
I think this is the most interesting of the patient's ECGs.

Rate:
  • 60
Rhythm:
  • Regularly irregular
    • Recurring pattern of long R-R followed by short R-R
    • Complexes following short R-R (#3,6,9) have differing morphology from others, best appreciated in precordial leads
  • No p waves visible
Axis:
  • Normal
Intervals:
  • Complexes #1,2,4,5,7,8,10
    • QRS - Normal (80-100ms)
  • Complexes #3,6,9
    • QRS - Prolonged (120ms) when measured in leads aVF, V1-5
Additional:
  • Baseline artifact in precordial leads
Interpretation:

When I looked at this ECG quickly I thought it was just AF but on examination I think it's still the junctional escape with no organised atrial activity as seen in ECG 1 with the additional of another pacemaker focus / bigeminy likely secondary to the isoprenaline. These additional complexes where mechanical effective and the patient felt symptomatically better. 
Anyone else got any thoughts on this ECG ?

ECG 3
Click to enlarge
The patient now decided to fix herself :-)

Rate:
  • ~96 bpm
Rhythm:
  • Regular
  • Sinus rhythm
Axis:
  • Normal
Intervals:
  • QRS - Normal (80-100ms)
  • QT - 340 ms QTc - 430ms (Bazette's)
Additional:
  • Broad notched P in lead II
  • Baseline artifact - we changed the dots, leads, and the machine !

Interpretation:

  • Patient is back in sinus rhythm
What happened next ?

The following day she had an elective dual chamber pacemaker insertion.

References / Further Reading

Life in the Fast Lane

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