CONDUCTION PROBLEMS (The ECG Made Easy)

First degree block
One P wave per QRS complex.
PR interval greater than 200 ms.
Second degree block
Wenckebach: progressive PR lengthening then
non-conducted P wave, and then repetition of the
cycle.
Mobitz type 2: occasional non-conducted beats.
2:1 (or 3:1) block: two (or three) P waves per QRS
complex, with normal P wave rate.

Third degree (complete) block
No relationship between P waves and QRS complexes.
Usually, wide QRS complexes.
Usual QRS complex rate less than 50/mm.
Sometimes narrow QRS complexes, rate 50—60/min.
Right bundle branch block
QRS complex duration greater than 120 ms.
RSR pattern.
Usually, dominant R wave in lead V1.
Inverted T waves in lead V1, and sometimes in leads
V2-V3.
Deep and wide S waves in lead V6
Left bundle branch block
QRS complex duration greater than 120 ins.
M pattern in lead V6, and sometimes in leads V—V
No septal Q waves.
Inverted T waves in leads 1, VL, V5—V6 and, sometimes, V4.
Bifascicular block
Left anterior hemiblock (i.e. marked left axis with deep S waves in leads II and III).
Right bundle branch block (see above).