ECG Case 81: Atrial Flutter with 4 : 1 AV Block

ECG Interpretation

  • Atrial flutter, best seen in lead III
  • 4 : 1 block
  • Normal axis
  • Normal QRS complexes
  • Sloping ST segment depression, best seen in leads V5–V6

Atrial flutter with 4:1 AV block

Clinical interpretation

This shows atrial flutter with what appears to be a stable 4 : 1 block. The ST segment depression suggests digoxin effect.

What to do ?

The stable 4 : 1 block has caused a regular heartbeat, so the arrhythmia was not suspected at the time of the clinical examination.

There is nothing in this ECG to indicate the underlying disease, which could be ischaemic, rheumatic or a cardiomyopathy: echocardiography is needed.

The downward-sloping ST segments suggest digoxin treatment. Digoxin will tend to maintain a fairly high degree of block but will not affect the underlying rhythm. Intravenous flecainide may convert the heart to sinus rhythm, but DC cardioversion may be necessary.