Heart Block
1o
Delayed AV conduction.
Prolonged PR interval >0.2s.
Asymptomatic but may indicate underlying heart disease.
No action for ICU or anaesthesia.
2o
Mobitz 1 (Wenckebach)
Progressively lengthening PR interval then missed QRS
Impaired conduction proximal to His
Normal in fit young people
Mobitz 2
Constant PR interval but some Ps not conducted either in a regular (2:1, 3:1, 4:1) or irregular ratio.
Impaired conduction (disease) below His.
Therefore more likely to progress to 3.
Have drugs ready (atropine, isoprenaline).
Consult cardiologist advice.
Usually needs pacing.
3o (complete)
Complete failure of AV conduction.
No correlation of P and QRS.
Ventricular activity maintained by escape rhythm from His if blockage at AV node (narrow QRS) or more distally if blockage distal to AV node (trifascicular block) (wide – slower and less reliable).
Needs pacing.
Bundle Branch Block
RBBB
Normal
RVH / strain
IHD
LBBB
IHD
↑BP
Aortic valve dis
LB divides into anterior and posterior fascicle. Damage at this point does not widen QRS but alters axis
LAHB - LAD
LPHB – RAD
Combination of 1 hemiblock and RBBB is bifascicular block (seen on ECG by RBBB and LAD – if RBBB and RAD cannot tell if RAD from just RBBB or from LPHB).
Short step away from complete so needs pacing.
Trifascicular block as above is either distal complete block or if incomplete is bifascicular block with 1o block too.
LAD
LBBB
LAHB
LVH
Cardiomyopathy, congen dis
RAD
RBBB
RVH
LPHB
Infants