ECG of the Week - 12th August 2013 - Interpretation

I unfortunately have no clinical information on this ECG, but it looks interesting :-)
Check out our original post of this ECG and the excellent comments here.

Click to enlarge

Rate:

• Ventricular rate 42 bpm
• Atrial rate ~230 bpm

Rhythm:

• Irregular ventricular activity
• Regular atrial activity
• Flutter waves

Axis:

• Normal (~75 deg)

Intervals:

• PR - Nil P waves visible
• QRS - Prolonged (120ms)
• QT - 400ms

Segments:

• Minor ST depression V4-6

Additional:

• rSR' Pattern V1-2
• Variable notching of QRS complexes secondary to superimposed flutter waves
• Flutter waves
• Alternating positive / negative morphology in inferior leads
• Flutter waves are narrow and small
• Relatively long isoelectric segment

Interpretation:

• Atrial flutter
• Variable block

Dr Arieh Keren and Dr Shakeeb Razak, electrophysiology specialists and ECG of the Week blog team members, have reviewed this ECG and shared there thoughts below:

Atypical vs typical flutter

• Typical atrial flutter involves the cavotricuspid isthmus (CTI) 
• Atypical flutter involves a different location than the CTI.

Micro vs macro re-entrant circuit

• Given the small flutter waves and isoelectric segment length this is more likely to be micro re-entry flutter.
• Macro re-entry flutter results in the classic saw tooth pattern with atrial activation occuring throughout the flutter cycle length.

Underlying cause in this case

• The alternating positive / negative atrial morphology suggests an uncommon circuit type.
• A possibility is two seperate micro re-entry ciruit close to each other.
• This suggests a more likely cause in this case of:
• Previous cardiac surgery
• Congential cardiac disease
• Major metabolic derrangement
.

Further Reading Recommendations

Dr Razak has suggested some interesting articles which further explore some of the features and questions raised by this ECG.

• Medi C, Kalman JM. Prediction of the atrial flutter circuit location from the surface electrocardiogram. Europace (2008) 10, 786–796. FULL TEXT
• Pedrinazzi C, Durin O, Mascioli G, Curnis A, Raddino R, Inama G, Dei Cas L. Atrial flutter: from ECG to electroanatomical 3D mapping. Heart Int. 2006;2(3-4):161. FULL TEXT

Both papers provide in-depth reviews of atrial flutter classifications, both new & old, and how the ECG and advanced EP techniques can help differentiate them

Causes of Atrial Flutter

There are a wide range of general potential causes for atrial flutter with variable block including:

• Ischaemia
• Sinus node dysfunction
• Drugs
• Digoxin
• Beta-blockers
• Calcium-channel blockers
• Other anti-arrhythmic drugs
• Electrolyte abnormality
• Acid / base disturbance
• Myocarditis
• Cardiomyopathy
• Endocrine
• Hyper- / hypo-thyroid
• Environmental
• Hypothermia

VAQ Corner

A 83 year old patient presents to your Emergency Department complaining of lethargy, nausea, and vomiting. There are on multiple medications but are unable to remember their names.
BP 105/64 RR 17 Temp 37.4 C

Describe and interpret their ECG (100%)

References 

Life in the Fast Lane

• Atrial flutter here

Textbook

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