Bradycardia
sinus node disease
rate of slow leak decreases
cell may not be able to keep diastolic gradient - if cell can't close, it can't open.
AV node disease
AV delay (first degree heart block)
- not really block
- 1:1 AV conduction, but delay
intermittent AV node block (2nd degree heart block)
- Mobitz I (Wenkebach) - PR prolongation, then block
- usually involves AV node pathology
- Mobitz II: intermittent block, without prolongation
- usually infranodal; serious risk of downward spiral
- 2:1 block: marked PR prolongation, ie 2nd degree block
complete heart block (3rd degree)
infranodal block
- degeneration
- myocardial infarction
- HF with ventricular dilation
rarely causes significant PR prolongation, but frequently shows bundle branch block
rarely...
QRS prolongation
no PR prolongation before block
junctoinal escape
Treatments
withdraw the offending drugs
implant a pacemaker