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HEART BLOCKS AND CARDIAC PACEMAKERS. Arun Abbi Jason Mitchell Jan 21, 2010. OUTLINE. SINUS NODE DYSFUNCTION ATRIOVENTRICULAR BLOCKS INTRODUCTION TO CARDIAC PACEMAKERS INSERTION OF TRANSVENOUS CARDIAC PACEMAKER. HEART BLOCK. RELEVENT ANATOMY

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heart blocks and cardiac pacemakers
HEART BLOCKS AND CARDIAC PACEMAKERS

Arun Abbi

Jason Mitchell

Jan 21, 2010

outline
OUTLINE
  • SINUS NODE DYSFUNCTION
  • ATRIOVENTRICULAR BLOCKS
  • INTRODUCTION TO CARDIAC PACEMAKERS
  • INSERTION OF TRANSVENOUS CARDIAC PACEMAKER
heart block
HEART BLOCK
  • RELEVENT ANATOMY
    • Conduction: SA > Atrium > AV Node > His > Purkinje Network
    • AV node highly innervated
      • Responsive to sympathetic and vagal stimuli
      • RCA blood supply
    • His bundle less responsive
      • Dual blood supply
sinus node dysfunction
SINUS NODE DYSFUNCTION
  • Abnormal sinus impulse formation and propagation
  • AKA Sick Sinus Syndrome
    • Umbrella term for:
      • Sinus bradycardia
      • Sinus arrest
      • Sinoatrial exit block
      • Tachy-brady syndrome
sinus node dysfunction1
SINUS NODE DYSFUNCTION
  • ETIOLOGY
    • Unclear
    • Fibrosis (most common)
    • Structural heart disease
    • Medications
    • Electrolyte imbalances (HypoK, HypoCa)
    • Endocrine (HypoTSH, HypoT)
sinus node dysfunction2
SINUS NODE DYSFUNCTION
  • SINUS ARREST
    • Absent sinus P waves > 2 – 3 seconds
      • Result of absent sinus impulse formation
    • Duration of pause is not a function of the P-P interval
sinus node dysfunction3
SINUS NODE DYSFUNCTION
  • SINOATRIAL EXIT BLOCK
    • Conduction delay between sinus node and atrium
    • Three types
sinus node dysfunction4
SINUS NODE DYSFUNCTION
  • SINOATRIAL EXIT BLOCK
    • First Degree
      • Conduction delay between sinus node and atria
        • Cannot be identified on ECG
        • ?Clinical significance
sinus node dysfunction5
SINUS NODE DYSFUNCTION
  • SINOATRIAL EXIT BLOCK
    • Second Degree
      • Intermittant conduction block
        • Type I (Wenkebach) – Progressive shortening of P-P intervals

– Pause duration less than twice the P interval

– Grouped P waves

sinus node dysfunction6
SINUS NODE DYSFUNCTION
  • SINOATRIAL EXIT BLOCK
    • Type II – Pause duration that is a multiple of the P-P interval
sinus node dysfunction7
SINUS NODE DYSFUNCTION
  • SINOATRIAL EXIT BLOCK
    • Third Degree
      • Complete conduction block from sinus node to atrium
        • Cannot be distinguished from sinus arrest on ECG
        • Typically results in an escape rhythm
sinus node dysfunction8
SINUS NODE DYSFUNCTION
  • TACHY-BRADY SYNDROME
    • Bradycardia alternating with brief episodes of SVT
      • Usually Afib
      • ???Cause
atrioventricular block
ATRIOVENTRICULAR BLOCK
  • ETIOLOGY
    • Congenital
    • Acquired – Extensive DDX
      • Medications
      • Hyperkalemia (>6.3 mEq/L)
      • Hypoxia
      • Increased vagal tone
      • Ischemia/Infarction (~40%)
      • Fibrosis (~50%)
      • Infection/Inflammation
      • Vascular Disease
      • Idiopathic
    • Usually never identified
atrioventricular block1
ATRIOVENTRICULAR BLOCK
  • FIRST DEGREE AV BLOCK
    • Prolongation of PR > 200 ms
    • Location of block
      • AV node, His bundle, His-Purkinje system
      • Correlate with QRS complex
    • Prognosis
      • Framingham: More likely to develop Afib, require permanent pacemaker, and increased all-cause mortality
    • Locate source of block
      • If AV node, generally benign and no further Ix
      • If infranodal, may require His-bundle electrocardiogram
      • No specific intervention required for stable 1st degree block
atrioventricular block2
ATRIOVENTRICULAR BLOCK
  • FIRST DEGREE AV BLOCK
atrioventricular block3
ATRIOVENTRICULAR BLOCK
  • SECOND DEGREE AV BLOCK
    • Type I (Wenckebach/Mobitz I) - Normal
      • Gradual prolongation of the PR interval followed by dropped QRS
      • Atrial impulses reach AV node while it is partially refractory
      • Location usually the AV node
atrioventricular block4
ATRIOVENTRICULAR BLOCK
  • SECOND DEGREE AV BLOCK
    • Type II – Never normal
      • PR interval constant
      • Usually a result of underlying structural disease
      • Location typically His-Purkinje system
    • High Grade Second Degree
      • 2 or more consecutively blocked P waves
atrioventricular block5
ATRIOVENTRICULAR BLOCK
  • SECOND DEGREE BLOCK
    • Different sites of involvement/prognoses
    • Type I: Generally involves AV node and is benign
    • Type II: Almost always infranodal and may progress to 3rd degree (slow unreliable escape)
    • Difficult to distinguish type in 2:1 conduction block
atrioventricular block6
ATRIOVENTRICULAR BLOCK
  • THIRD DEGREE BLOCK
    • Complete AV node failure to conduct
    • Block may be anywhere in conduction system
    • Constant P-P and R-R intervals but no relationship
    • Variable PR intervals, Atrial HR > Ventricular HR
    • May be hemodynamically unstable
    • Slow heart rate may produce Torsade , especially in women
heart block1
HEART BLOCK
  • ECG PRACTICE
heart block2
HEART BLOCK
  • INITIAL ASSESSMENT
    • Hemodynamic Instability
      • Fatigue, Dizziness, NV, Diaphoresis
      • Hypotension
      • Syncope
      • Dyspnea
      • Chest Pain
    • ACLS Guidelines for Symptomatic Bradycardia
    • Medications
      • Β- Blockers
      • Ca2+ Channel Blockers
      • Digitalis
      • Amiodarone
heart block3
HEART BLOCK
  • INITIAL ASSESSMENT
    • Investigations
      • Stabilize first!
      • ECG
      • Bloodwork
        • Electrolytes
        • Dig level
        • Troponin
heart block4
HEART BLOCK
  • MANAGEMENT
    • O2, IV, Monitors
    • Transcutaneous pacing
    • Transvenous pacing
      • > 30 minutes transcutaneous pacing
      • Unable to obtain capture
    • Consider atropine
    • Consider catecholamines (be cautious)
heart block5
HEART BLOCK
  • CARDIOLOGY CONSULTATION
  • Outpatient
    • New, asymptomatic Type I 2nd Degree (while awake)
  • Inpatient
    • Any symptomatic block
    • New, asymptomatic Type II 2nd Degree
    • Asymptomatic 3rd Degree
    • Concomitant MI/Ischemic symptoms
    • High Grade AV Block
cardiac pacing
CARDIAC PACING
  • INDICATIONS
    • Temporary
      • Any symptomatic AV block
      • Asymptomatic, but associated with Torsade
    • Permanent
      • ACC/AHA/HRS 2008 Guidelines:
        • Divided into Class Based Recommendations
cardiac pacing2
CARDIAC PACING
  • INDICATIONS AV Block
    • Class I
      • 2nd and 3rd Degree
        • Bradycardia with symptoms (C)
        • Associated arrhythmias and medications that produce symptomatic bradycardia (C)
        • Asymptomatic, but asystole >3 sec or escape < 40 bpm or wide QRS escape or Afib and bradycardia with systole >5 seconds (C)
        • After ablation of AV node or unresolving post-op block (C)
        • Associated with MD, Kearns-Sayre syndrome, Erb dystrophy (B)
        • Associated with exercise w/o MI (B)
cardiac pacing3
CARDIAC PACING
  • INDICATIONS AV Block
    • Class IIa
      • Asymptomatic persistent 3rd degree with escape > 40 (C)
      • Asymptomatic 2nd degree with intra or infra-Hisian block (B)
      • Symptomatic 1st or 2nd degree block (B)
      • Asymptomatic 2nd degree block with narrow QRS (B)
    • Class IIb
      • 1st or 2nd degree with MD, Erb dystrophy, peroneal muscular atrophy +/- symptoms (B)
      • AV block in setting of drug toxicity when block expected to recur (B)
cardiac pacing4
CARDIAC PACING
  • INDICATIONS AV Block
    • Class III
      • Not indicated for asymptomatic 1st Degree (B)
      • Not indicated for asymptomatic Mobitz I with block at AV node (C)
      • Not indicated for AV block that is expected to resolve and unlikely to recur (drug toxicity, Lyme disease, transient increased vagal tone) (B)
    • Also not indicated in:
      • PEA Arrest
      • Traumatic cardiac arrest
cardiac pacing5
CARDIAC PACING
  • PACING MODES
    • 5 Position Nomenclature
    • First 3 Positions most common in pacemaker description
    • Position I: Chamber being paced
      • Atrium (A), Ventricle (V), Both (D), None (O)
    • Position II: Chamber being sensed
      • Atrium (A), Ventricle (V), Both (D), None (O)
    • Position III: Pacemaker’s response to sensing
      • Triggers (T), Inhibits (I), Both (D), None (O)
cardiac pacing6
CARDIAC PACING
  • PACING MODES
    • Position IV: Programmability and Rate Control
      • Hierarchical
      • Rate Modulation (R), Communicating (C), Programmable (P), (O)
    • Position V: Antitachydysrrhythmia Function
      • Pacing (P), Shocking (S), Both (D)
cardiac pacing7
CARDIAC PACING
  • PACING MODES
    • Most pacemakers encountered are:
      • AAIR – Useful for sinus node dysfunction with intact AV node
      • VVIR – Useful for chronically ineffective atria (AF, AFlutter)
      • DDD – Most common. Preserves AV synchrony
        • Reduces risk of AF, reduces signs/symptoms HF, improves QOL
        • No significant mortality benefit over single-chamber pacing
cardiac pacing8
CARDIAC PACING
  • ECG MANIFESTATIONS
    • Depends on Pacing Mode
    • Atrial Pacing
      • Small pacemaker spike prior to P wave with normal morphology
    • Ventricular Pacing
      • LBBB-like and prolonged, inverted QRS (V5/6) and LAD
cardiac pacing11
CARDIAC PACING
  • TEMPORARY PACING
    • Goal: Restore effective myocardial contraction to increase adequate cardiac output
    • Transcutaneous vs. transvenous pacing modalities
cardiac pacing12
CARDIAC PACING
  • TRANSCUTANEOUS PACING
    • Temporary stabilization of symptomatic bradycardia
      • Most patients tolerate pacing for < 15 minutes
      • Pain directly related to current and inversely related to pad size
cardiac pacing13
CARDIAC PACING
  • TRANSCUTANEOUS PACING
    • Technique
      • Apply pads front/back or left/right
        • Front/back preferred
      • Sedate
      • Set HR to 60-80
      • Set current to 0 mA
      • Choose mode
        • Synchronous vs. asynchronous
      • Turn pacemaker on
      • Increase current by 10 mA increments until capture obtained
        • Manifested by wide QRS relating to palpable carotid pulse
      • If unconscious, start at 200 mA and decrease to lowest current
cardiac pacing14
CARDIAC PACING
  • TRANSVENOUS PACING
    • Placement of electrode into R Ventricle
    • Pacer is VVI mode
    • Allows for asynchronous vs synchronous
cardiac pacing15
CARDIAC PACING
  • TRANSVENOUS PACING
    • Equipment
      • Introducer Kit
        • Introducer sheath
        • Pacing catheter
      • External pacing generator
      • Cardiac monitor
cardiac pacing16
CARDIAC PACING
  • TRANSVENOUS PACING
    • External Pacing Generator
      • Delivers electrical current (mA)
      • Output Control Dial
        • Regulates current from 0.1 – 20 mA
      • Rate Control Dial
        • Selects pacing rate
      • Sensitivity Control Rate
        • Threshold suppression of pacer based on native R wave
        • Asynchronous pacing when sensitivity control turned down
cardiac pacing17
CARDIAC PACING
  • TRANSVENOUS PACING
    • Transvenous Pacing Catheter
      • 3 types:
        • Flexible, Semifloating, Rigid/Non-floating
          • Risk of cardiac perforation with rigid catheters
        • Two electrodes attached: + and –
    • Introducer Sheath
      • Facilitates central venous access
cardiac pacing18
CARDIAC PACING
  • TRANSVENOUS PACING
    • Technique
      • Seldinger technique for central venous access
        • R IJ or L Subclavian shown to be most successful
      • Secure introducer sheath
      • Introduce pacing electrode
      • Inflate balloon when electrode passed through the 20 cm mark
        • Moot if no pulse
      • Set pacing generator to max current
      • Set rate between 60-80
      • Asynchronous sensitivity
cardiac pacing19
CARDIAC PACING
  • TRANSVENOUS PACING
    • As cath is advanced, monitor will show pacing spikes
    • Pacing spikes followed by wide QRS indicating of RV placement
      • Electrical capture
    • Assess for pulse
      • Mechanical capture
    • Deflate balloon and secure cath in place
    • Set pacing threshold
cardiac pacing20
CARDIAC PACING
  • TRANSVENOUS PACING
    • Complications
        • Inherent to central venous access
          • Arterial puncture, PTX, infection
        • Right heart catheterization
          • Failure to capture, failure to sense, dysrrhythmias
        • Cardiac perforation
        • Lead displacement
        • Electrode coiling