Pacemakers & Implantable Cardio-Defibrillators

Question 1

When to use a pacemaker

Answer 1

• use for bradycardia with symptoms:
  
  • dizziness, lightheadedness, syncope, fatigue, AMS, poor exercise tolerance
• Sinus node dysfunction:
  
  • characterized by periods of bradycardia, tachycardia, prolonged pauses or alternating bradycardia & tachycardia
    
    • HR < 40 bpm-symptomatic
    • Symptomatic chronotropic incompetence (i.e. with exercise)
• AV block:
  
  • complete AV block (3rd degree)
  • Advanced 2nd degree AV block (2:1, 3:1 etc)
  • Symptomatic mobitz type I/II
• Neurogenic syncope
• Post-Mi conduction abnormalities: different criteria
  
  • 3rd degree block
  • persistent 2nd degree block in bundle of HIS
    *

Question 2

4 functions of pacemakers

Answer 2

• simple cardiac depolarization
• sense intrinsic cardiac function
• respond to increased metabolic demand by providing rate responsive pacing
• provide diagnostic information stored by the pacemaker

Question 3

VVI

Answer 3

single chamber pacing (ventricle = V) I = inhibition

paces ventricle if no impulse sensed at a certain point related to rate

paces at rate unless native is sensed

Question 4

AAI

Answer 4

single chamber pacing (atrium = A) I = inhibition

paces atrium if no impulse sensed at a certain point related to rate

paces at rate unless native is sensed

Question 5

DDD

Answer 5

paces atrium at set rate, paces ventricle at set rate – both can be inhibited if senses atrium or ventricle at adequate rate

Question 6

Rate Responsive Pacemakers

Answer 6

provide patients with the ability to vary heart rate when the sinus node cannot provide the appropriate rate

• Indications:
  
  • patients who are chronotropically incompetent (heart cannot reach appropriate levels during exercise or to meet other metabolic demands)
  • patients in chronic atrial fibrillation with slow ventricular response

Question 7

Failure to Capture

Answer 7

When the pacemaker fires, but the heart does not respond → need to turn up the voltage

Question 8

Failure to Pace

Answer 8

When the pacemaker does not fire

can occur when electrical stimulation is near the pacemaker→ inhibits the pacing (such as electrocautery)

Question 9

What demonstrates that a pacemaker is MRI safe?

Answer 9

Question 10

Sudden Cardiac Arrest vs MI

Answer 10

• sudden cardiac arrest: caused by heart electrical system problem
• MI: occurs when one or more of the arteries that supply blood to the heart muscle becomes blocked

Question 11

Holter Monitor

Answer 11

24-48 hours: continuous monitoring, not real time

Question 12

Event Monitor

Answer 12

up to 14 days

self trigger when arrhythmia noted– records for 1 minute

Question 13

Patch Monitor

Answer 13

ordered. & read by cardiologists

14 days only, smaller monitor, pre-paid envelope to return, not real time.

Question 14

Ambulatory BP monitor

Answer 14

• indications:
  
  • elevated BP noted; pt isnt on medications
  • after medication initiation - before add-on therapy
  • persistenly elevated BP despite treatment with 2+ agents
• Function:
  
  • 24 hour wear time
  • BPs q 30 minutes, q 60 min at night
  • average SBP, DBP, daily BP

Question 15

Abnormal Troponin-T, when it peaks and when it returns to normal

Answer 15

• >0.19 ng/mL
• peaks at 12-18 hours
• returns to normal in 5-10 days

Question 16

Abnormal BNP

Answer 16

>100 pg/mL