Transcript ATRIOVENTRICULAR BLOCKS AND CARDIAC PACEMAKERS

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
 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
 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 DYSFUNCTION
 ETIOLOGY
 Unclear
 Fibrosis (most common)
 Structural heart disease
 Medications
 Electrolyte imbalances (HypoK, HypoCa)
 Endocrine (HypoTSH, HypoT)
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 DYSFUNCTION
 SINOATRIAL EXIT BLOCK
 Conduction delay between sinus node and atrium
 Three types
SINUS NODE DYSFUNCTION
 SINOATRIAL EXIT BLOCK
 First Degree
 Conduction delay between sinus node and atria
 Cannot be identified on ECG
 ?Clinical significance
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 DYSFUNCTION
 SINOATRIAL EXIT BLOCK
 Type II – Pause duration that is a multiple of the P-P interval
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 DYSFUNCTION
 TACHY-BRADY SYNDROME
 Bradycardia alternating with brief episodes of SVT
 Usually Afib
 ???Cause
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 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 BLOCK
 FIRST DEGREE AV BLOCK
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 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 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 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 BLOCK
 ECG PRACTICE
ECG 1
SSS (Tachy-Brady)
ECG 2
Type II Second Degree AV Block
ECG 3
Sinus Arrest
ECG 4
3rd Degree AV Block
ECG 5
Type II Second Degree SA Node
Exit Block
ECG 6
First Degree AV Block
ECG 7
Type 1 Second Degree AV Block
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 BLOCK
 INITIAL ASSESSMENT
 Investigations
 Stabilize first!
 ECG
 Bloodwork
 Electrolytes
 Dig level
 Troponin
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 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
 INDICATIONS
 Temporary
 Any symptomatic AV block
 Asymptomatic, but associated with Torsade
 Permanent
 ACC/AHA/HRS 2008 Guidelines:
 Divided into Class Based Recommendations
CARDIAC PACING
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 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 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
Some Things Just Won’t Work
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 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 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 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 PACING
CARDIAC PACING
CARDIAC PACING
 TEMPORARY PACING
 Goal: Restore effective myocardial contraction to increase
adequate cardiac output
 Transcutaneous vs. transvenous pacing modalities
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 PACING
 TRANSCUTANEOUS PACING
 Technique

Apply pads front/back or left/right





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


Front/back preferred
Manifested by wide QRS relating to palpable carotid pulse
If unconscious, start at 200 mA and decrease to lowest current
CARDIAC PACING
 TRANSVENOUS PACING
 Placement of electrode into R Ventricle
 Pacer is VVI mode
 Allows for asynchronous vs synchronous
CARDIAC PACING
 TRANSVENOUS PACING
 Equipment
 Introducer Kit
 Introducer sheath
 Pacing catheter
 External pacing generator
 Cardiac monitor
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 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 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 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 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