bradycardia

definition

  • HR < 60

causes

  • problems with
    • SA node
    • AV node or purkinje
    • extrinsic: vagal tones

SA node dysfunction

sinus bradycardia

  • normal: trained athletes, sleep
  • pathological:
    • right coronary ischemia
    • age related myocardial fibrosis
    • intracranial hypertension
    • postop scarring
    • infiltrative disease: sarcoidosis
    • sleep apnea: nocturnal bradycardia
    • electrolytes
    • hypothyroidism
    • medications
      • BB
      • donepezil, neostigmine, pyridostigmine
      • digoxin

Other types of sinus node dysfunction

  • sinus arrest, junctional escape rhythm
  • sinus with pauses
  • tachy brady syndrome: SVT/af/aflutter, sinus node shut down from fibrosis/rate control blockade/suppression. At time of conversion, goes into long pauses
  • sinoatrial exit block: failure of impulse to exit SA
  • secondary sinoatrial exit block:
    • failure of p wave to form
    • p to p shortening, followed by drop beat
  • Sx
    • usually asymptomatic, syncope, fatigue, lightheadedness, dyspnea
  • Treatment
    • symptomatic patient: pacemaker
    • atrial based pacing support
    • most patient get RV lead for backup
    • high vagal tone: very dramatic bradycardia with normal HR between episodes
      • sinus slowing before bradycardia
      • nausea, vomiting, diaphoretic
    • SA node dysfunction: lower HR at baseline

AV nodal block

1st degree

  • PR > 200 ms
  • no treatment

3rd degree

  • AV dissociation in HIS purkinje
  • sx determined by rate of escape
  • pause dependent VT: torsades de pointe => syncope

2nd degree

  • AV node itself
  • causes:
    • lupus
    • lyme
    • iatrogenic: AV ablation, pacemaker placement
  • Mobitz 1: progressively longer PR, then dropped beat, regularly irregular
    • before/after drop beat, changes in PR the greatest
    • canon A waves, progressively softer 1st heart sound
  • Mobitz 2: HIS purkingje
    • fixed PR
    • dropped beat
    • wide QRS
  • 2:1 weckeback: Mobitz 1 has narrow QRS. Mobitz 2 has wide QRS
  • walk the patient: increase sympathetic tone. Type 1 gets better on atropine. Type 2 does not change
  • Type 2: prophylactic pacing

treatment

Inpatient

  • symptomatic: give atropine first
  • dopamine gtt second line
  • epinephrine gtt 3rd line
  • transcutaneous pacing or temporary pacing wire (preferred) placement if unstable or asystole

Outpatient

  • pacemaker indications
    • symptomatic bradycardia with no reversible cause
    • permanent afib with symptomatic bradycardia
    • alternating BBB
    • 3rd degree block, Mobitz 2, high degree AV block (>1 nonconducted P)
  • treat if EF < 40%
  • biV pacemaker because RV pacing alone = worse EF
  • Pace RV: wide QRS, LBBB
  • if RBBB develops followed by pacing: biV pacemaker
  • < 30%: ICD CRT biV pacing
  • CXR: pacemaker = skinny. atrial = ventricular
  • icd: coil at RV insertion
  • Biv: 3rd lead, RV anterior, LV posterior