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Arrhythmias and Devices
Module 1
1
Objectives
• Recognize typical rhythms and rhythm disorders
2
Arrhythmias and Devices
Overview
• The Conduction System
– Normal Conduction
– Automaticity & Action Potential
– Causes of Rhythm Disorders
• Rhythm Disorders
– Categories
• Disorders of Impulse Formation
• Disorders of Impulse Conduction
– Mechanisms
• Arrhythmia Recognition and Classification
– Bradycardias
– Tachycardias
3
Cardiac Conduction
Sinus Node
Sinus Node
(SA Node)
• The Heart’s ‘Natural Pacemaker’
– Rate of 60-100 bpm at rest
4
Cardiac Conduction
AV Node
Atrioventricular
Node (AV Node)
• Receives impulses from SA node
• Delivers impulses to the His-Purkinje
System
• Delivers rates between 40-60 bpm if
SA node fails to deliver impulses
5
Cardiac Conduction
HIS Bundle
Bundle of His
• Begins conduction to the
ventricles
• AV Junctional Tissue:
– Rates between 40-60 bpm
6
Cardiac Conduction
Purkinje Fibers
Purkinje Network
Bundle Branches and Purkinje
Fibers
• Moves the impulse through the
ventricles for contraction
• Provides ‘Escape Rhythm’:
– Rates between 20-40 bpm
7
Normal Sinus Rhythm
8
Impulse Formation in SA Node
9
Atrial Depolarization
10
Delay at AV Node
11
Conduction through Bundle Branches
12
Conduction through Purkinje Fibers
13
Ventricular Depolarization
14
Plateau Phase of Repolarization
15
Final Rapid (Phase 3) Repolarization
16
Normal ECG Activation
This pattern of depolarization results in efficient mechanical contraction
– which is the purpose – to pump blood.
17
Reading ECG Squares
Intervals and Timing
Horizontal axis – time:
• Each small square = 40 ms
• Each block = 200 ms (5 ea. 40
ms squares)
Converting this to a rate in
bpm:
• 1 min = 60,000 ms, so:
• 60,000/ms = bpm
– 60,000/600ms = 100 bpm
Pacemakers and ICDs
calculate intervals (ms), not
in rates (bpm)
18
ECGs Annotation
Normal Ranges in Milliseconds:
• PR Interval 120 – 200 ms
• QRS Complex 60 – 100 ms
• QT Interval 360 – 440 ms
19
Status Check
This ECG shows a QRS duration
of about 100 ms – a normal
duration.
If this represents efficient
ventricular contraction…
…then what effect could a QRS
duration of 200 ms have on
mechanical efficiency and cardiac
output?
Click for Answer
Inefficient contraction
20
Status Check
Match the term on the left with the description on the right
Click for Answer
• P-R Interval
• AV Node
• Purkinje Network
• Bundle Branches
Escape rate is 40-60 bpm
Connect His bundle to
Purkinje network
Normally 120-200 ms
Depolarizes the Ventricles
21
We’ve Seen How the Normal Pattern of
Conduction Occurs But:
• What triggers the depolarization – what causes that first
cell to depolarize?
• If a cell depolarizes, why does it result in depolarization in
other cells?
22
Automaticity
Cardiac Cells are unique
because they
spontaneously depolarize
• Upper (SA Node)
– 60-80 bpm
• Middle (AV Junction)
– 40-60 bpm
• Lower (Purkinje Network)
– 20-40 bpm
23
Automaticity
Once a pacemaker cell initiates an impulse, its neighboring
cells follow suit – like dominos.
24
Action Potential of a Cardiac Cell
5 Phases
Phase 0
– Rapid or upstroke depolarization with
an influx of sodium ions into the cell
Phase 1
– Early rapid repolarization with
transient onward movement of
potassium ions
Phase 2
– Plateau Phase: Continued Influx of
Sodium and slow Influx of Calcium
Phase 3
– Repolarization: Potassium outflow
Phase 4
– Resting Phase
25
Action Potential of a Cardiac Cell
5 Phases
Phase 0
– Rapid or upstroke depolarization with
an influx of sodium ions into the cell
Phase 1
– Early rapid repolarization with
transient onward movement of
potassium ions
Phase 2
– Plateau Phase: Continued Influx of
Sodium and slow Influx of Calcium
Phase 3
– Repolarization: Potassium outflow
Phase 4
– Resting Phase
26
Action Potential of a Cardiac Cell
5 Phases
Phase 0
– Rapid or upstroke depolarization with
an influx of sodium ions into the cell
Phase 1
– Early rapid repolarization with
transient onward movement of
potassium ions
Phase 2
– Plateau Phase: Continued Influx of
Sodium and slow Influx of Calcium
Phase 3
– Repolarization: Potassium outflow
Phase 4
– Resting Phase
27
Action Potential of a Cardiac Cell
5 Phases
Phase 0
– Rapid or upstroke depolarization with
an influx of sodium ions into the cell
Phase 1
– Early rapid repolarization with
transient onward movement of
potassium ions
Phase 2
– Plateau Phase: Continued Influx of
Sodium and slow Influx of Calcium
Phase 3
– Repolarization: Potassium outflow
Phase 4
– Resting Phase
28
Action Potential of a Cardiac Cell
5 Phases
Phase 0
– Rapid or upstroke depolarization with
an influx of sodium ions into the cell
Phase 1
– Early rapid repolarization with
transient onward movement of
potassium ions
Phase 2
– Plateau Phase: Continued Influx of
Sodium and slow Influx of Calcium
Phase 3
– Repolarization: Potassium outflow
Phase 4
– Resting Phase
29
Action Potential of a Cardiac Cell
5 Phases
Phase 0
– Rapid or upstroke depolarization with
an influx of sodium ions into the cell
Phase 1
– Early rapid repolarization with
transient onward movement of
potassium ions
Phase 2
– Plateau Phase: Continued Influx of
Sodium and slow Influx of Calcium
Phase 3
– Repolarization: Potassium outflow
Phase 4
– Resting Phase
30
Action Potential of a Cardiac Cell
Refractory Periods
• ERP - Effective Refractory Period
– AKA: Absolute Refractory Period
– Phases 0, 1, 2, and early Phase 3
– A depolarization cannot be initiated
by an impulse of any strength
• RRP - Relative Refractory Period
– Late Phase 2 and early Phase 3
– A strong impulse can cause
depolarization, possibly with
aberrancy
– “R on T” phenomena
31
Causes of Rhythm Disorders
Congenital
• Present at birth due to genetics, or
conditions during the peri-natal
environment
Cardiac and other diseases
• Myocardial Infarction, high blood
pressure, cardiomyopathy, valvular
heart disease
Acquired
• Medications (even anti-arrhythmic
Rx), diet pills, cold remedies, illegal
drugs, caffeine and/or alcohol abuse,
tobacco use...
32
Causes of Rhythm Disorders
Secondary to other conditions
• Hyper-Thyroid
• Neurocardiogenic Syncope
- Hypersensitive Carotid Sinus Syndrome (CSS)
- Vasovagal Syncope (VS)
33
Rhythm Disorders
2 Categories
Impulse Formation
• Abnormal Automaticity
Disorders of
• Triggered Activity
Impulse Conduction
34
Rhythm Disorders
2 Categories
Impulse Formation
• Abnormal Automaticity
Bradycardia: Abnormally slow rates usually due to
disease
Tachycardia: Excessively rapid rates due to ANS
• Triggered Activity
35
Rhythm Disorders
2 Categories
Impulse Formation
• Abnormal Automaticity
• Triggered Activity
Depolarization occurring in Phase 3 or 4 of the action
potential can trigger arrhythmias
36
Mechanisms of Rhythm Disorders
Triggered Activity
Early Afterdepolarization
• Potential Causes:
- Low potassium blood levels
- Slow heart rate
- Drug toxicity (ex. Quinidine causing
Torsades de Pointes type of VT)
Late Afterdepolarization
• Potential Causes:
- Premature beats
- Increased calcium blood levels
- Increased adrenaline levels
- Digitalis toxicity
37
Rhythm Disorders
Two Categories
Impulse Formation
• Abnormal Automaticity
• Triggered Activity
Impulse Conduction
• Slow or Blocked Conduction
• Reentry
38
Mechanisms of Rhythm Disorders
Slowed or Blocked Conduction
• Impulse generated normally
• Impulse slowed or blocked as it makes its way through the conduction system
39
Rhythm Disorders
Two Categories
Impulse Formation
• Abnormal Automaticity
• Triggered Activity
Impulse Conduction
• Slow or Blocked Conduction
• Reentry
40
Mechanisms of Rhythm Disorders
Reentry Model
Conduction paths are
“mirrored”
Pathway A:
• Slow conduction but
short (fast) refractory
Pathway B:
• Fast conduction but
long (slow) refractory
period
41
Mechanisms of Rhythm Disorders
Reentry Model
A premature event occurs, which is conducted down
the slow pathway. During this “antegrade” conduction,
the fast or “retrograde” pathway is still refractory.
refractory
By the time the slow antegrade conduction is complete, the
fast pathway is no longer refractory, allowing retrograde
conduction to occur.
This “circus” mechanism is maintained as long as the
relationship between fast and slow conduction, and
fast/slow refractoriness persists.
42
Mechanisms of Rhythm Disorders
Reentry Model
These are sometimes referred to as “circus tachycardias.”
This mechanism explains one common arrhythmia seen
in the EP lab: AV node re-entrant tachycardia.
A-V Intervals ms
V-V Intervals ms
Note the almost simultaneous depolarization of the atria
and ventricles.
43
Terminating Reentry
• Spontaneous termination
– Another premature beat that disturbs the underlying
conduction/refractoriness relationships
• Pace the heart at a rate above the tachycardia rate
– Abruptly stop pacing
– This is how implantable cardioverter-defibrillators can stop VT
without a shock (ATP)
44
Bradycardia Classifications
Impulse Formation
Disorders of
Impulse Conduction
45
Bradycardia Classifications
• Sinus Arrest
Impulse Formation
• Sinus Bradycardia
• Brady/Tachy Syndrome
Impulse Conduction
46
Sinus Arrest
• Failure of sinus node discharge
• Absence of atrial depolarization
• Periods of ventricular asystole
• May be episodic as in vaso-vagal syncope, or carotid sinus
hypersensitivity
– May require a pacemaker
47
Sinus Bradycardia
• Sinus Node depolarizes very slowly
• If the patient is symptomatic and the rhythm is persistent
and irreversible, may require a pacemaker
48
Brady/Tachy Syndrome
• Intermittent episodes of slow and fast rates from the SA node
or atria
• Brady < 60 bpm
• Tachy > 100 bpm
• AKA: Sinus Node Disease
– Patient may also have periods of AF and chronotropic incompetence
– 75-80% of pacemakers implanted for this diagnosis
49
Bradycardia Classifications
• Sinus Arrest
Impulse Formation
• Sinus Bradycardia
• Brady/Tachy Syndrome
Impulse Conduction
• Exit Block
• 1st Degree AV Block
• 2nd Degree AV Block
• 3rd Degree AV Block
• Bi/Trifascicular Block
50
Exit Block
• Transient block of impulses from the SA node
– Sinus Wenckebach is possible, but rare
• Pacing is rare unless symptomatic, irreversible, and
persistent
51
First-Degree AV Block
• PR interval > 200 ms
• Delayed conduction through the AV Node
- Example shows PR Interval = 320 ms
- Not an indication for pacing
- Some consider this a normal variant (not an arrhythmia)
52
Second-Degree AV Block – Mobitz I
• Progressive prolongation of the PR interval until there is
failure to conduct and a ventricular beat is dropped
• AKA: Wenckebach block
– Usually not an indication for pacing
53
Second-Degree AV Block – Mobitz II
• Regularly dropped ventricular beats
– 2:1 block (2 P-waves for every 1 QRS complex)
– Atrial rate = 75 bpm, Ventricular rate = 42 bpm
• A “high grade” block, usually an indication for pacing
– May progress to third-degree, or Complete Heart block (CHB)
54
Third-Degree AV Block
• No impulse conduction from the atria to the ventricles
– Atrial rate = 130 bpm, Ventricular rate = 37 bpm
– Complete A – V disassociation
– Usually a wide QRS as ventricular rate is idioventricular
55
Fascicular Block
Right bundle branch
block and left
posterior hemiblock
Right bundle branch block
and left anterior hemiblock
Complete left bundle
branch block
56
Trifascicular Block
• Complete block in the right bundle branch, and
• Complete or incomplete block in both divisions of the left
bundle branch
• Identified by EP Study
57
Bradycardia Classifications
Summary
• Sinus Arrest
Impulse Formation
• Sinus Bradycardia
• Brady/Tachy Syndrome
Impulse Conduction
• Exit Block
• 1st Degree AV Block
• 2nd Degree AV Block
• 3rd Degree AV Block
• Bi/Trifascicular Block
58
Status Check
Click for Answer
• What is the most likely rhythm disorder that might result in
a patient getting a pacemaker?
– Sinus node disease
• Sinus node disease is otherwise known as?
– Brady-tachy syndrome
• What are some symptoms a patient might complain of?
– Fatigue, shortness of breath, palpitations, inability to perform
activities of daily living, vertigo, syncope, racing heart at rest, slow
pulse rate
59
Status Check
• What are some simple diagnostic tests used to make this
diagnosis?
– 12-lead ECG, GXT, Ambulatory ECG (Holter)
Click for Answer
60
Terms Describing Ventricular Tachycardias
• Paroxysmal (may be used with VT or SVT)
– Ectopic focus, sudden onset, abrupt cessation
• Sustained (usually used with VT)
– Duration of > 30 seconds
– Requires intervention to terminate
• Non-Sustained (usually used with VT)
– At least 6 beats or < 30 seconds
– Spontaneously terminates
• Recurrent (usually used with VT)
– Occurs periodically
– Periods of no tachycardia are longer than periods of tachycardia
61
Terms Describing Ventricular Tachycardias
• Monomorphic
– Single focus
– Complexes are similar with equal intervals
• Polymorphic
– Multiple foci
– Complexes appear different with varied intervals
• Incessant
– Long periods of tachy, short periods of NSR
62
Terms Describing SVT
• SVTs (Supraventricular Tachycardia)—originating from
above the ventricles
– Paroxysmal: Sudden onset and spontaneous cessation
– Persistent: Requires intervention to terminate,
usually >24-48 hour duration
– Permanent or Chronic: Unable to terminate
63
Tachycardia Classifications
Impulse Formation
Disorders of
Impulse Conduction
64
Tachycardia Classifications
• Sinus Tachycardia
• Atrial Tachycardia
Impulse Formation
• Premature Contractions
• Accelerated Junctional Rhythm
• Accelerated Idioventricular
Rhythm (AIVR)
Impulse Conduction
65
Sinus Tachycardia
• Origin: Sinus Node
• Rate: 100-180 bpm
• Mechanism: Abnormal or Hyper Automaticity (for example, exercise)
66
Atrial Tachycardia
•Origin: Atrium - Ectopic Focus
•Rate: >100 bpm
•Mechanism: Abnormal Automaticity
67
Premature Beats
Premature Atrial Contraction (PAC)
• Origin: Atrium (outside the Sinus Node)
• Mechanism: Abnormal Automaticity
• Characteristics: An abnormal P-wave occurring earlier than expected,
followed by compensatory pause
68
Premature Beats
Premature Junctional Contraction (PJC)
• Origin: AV Node Junction
• Mechanism: Abnormal Automaticity
• Characteristics: A normally conducted complex with an absent P-wave,
followed by a compensatory pause
69
Premature Beats
Premature Ventricular Contraction (PVC)
• Origin: Ventricles
• Mechanism: Abnormal Automaticity
• Characteristics: A broad complex occurring earlier than expected,
followed by a compensatory pause
70
PVC Patterns
Bigeminy
- Every other beat
Trigeminy
- Every third beat
Quadrigeminy
- Every fourth beat
71
Multifocal PVC
• Origin: Varies within the Ventricle
• Mechanism: Abnormal Automaticity
• Characteristics: Each premature beat changes axis; implies a different focus
of origin for each beat
• Note: PVCs by themselves are not a predictor of VT/VF, nor do they imply
the need for a defibrillator
72
Accelerated Junctional Rhythm
• Origin: AV Node or Junctional Tissue
• Mechanism: Abnormal Automaticity
• Characteristics: Occurs when AV nodal cells depolarize at a rate
faster than the sinus node
73
Accelerated Idioventricular Rhythm
• Origin: Ventricle
• Mechanism: Abnormal Automaticity
• Rate: Ventricular rate >sinus rate, but <VT
• Characteristic: May dominate and take over the underlying rhythm
74
Accelerated Idioventricular Rhythm
Sinus Rhythm being taken over by an Idioventricular Rhythm
75
Tachycardia Classifications
Based on disorder
• Sinus Tachycardia
• Atrial Tachycardia
Impulse Formation
• Premature Contractions
• Accelerated Junctional Rhythm
• Accelerated Idioventricular
Rhythm (AIVR)
Impulse Conduction
• Atrial Flutter
• Atrial Fibrillation
• AVRT/AVNRT
• Ventricular Tachycardia
• Ventricular Fibrillation
76
Atrial Flutter
•Origin: Right and Left Atrium
•Mechanism: Reentry, circus tachycardia, may be “clockwise” or
“counter-clockwise”
•Rate: 250 – 400 bpm
•Characteristics: Rapid, regular P-waves, regular R-waves
77
Atrial Fibrillation (AF)
• Origin: Right and/or left atrium, pulmonary veins
• Mechanism: Multiple wavelets of reentry
• Atrial Rate: > 400 bpm
• Characteristics: Random, chaotic rhythm; associated with irregular
ventricular rhythm
78
Atrial Fibrillation (AF)
79
AF Mechanism
• Paroxysmal: Sudden onset and spontaneous cessation
• Persistent: Requires intervention to terminate, usually > 24-48 hour
duration
• Permanent or Chronic: Unable to terminate
• “AF begets AF”
– The more frequent the AF the more frequently it will re-occur and episodes
tend to last longer
80
Other AF Mechanisms
Mutifocal Atrial Tachycardia
• Mechanism: Abnormal Automaticity
(multi-sites)
• Characteristics: Many depolarization
waves; activation occurs asynchronously
Not commonly used terms anymore,
usually just called “AF”
Single Foci
• Mechanism: Abnormal Automaticity (singlefocus, usually in the Posterior Left Atrium)
• Characteristics: Rapid discharge; single
ectopic site
• Parasystole – rare
81
Atrial Flutter vs. Atrial Fibrillation
Summary of Disease Characteristics
Atrial Flutter
Atrial Fibrillation
Atrial Rate
250 to 400 bpm
400 bpm
Ventricular
Rate/Rhythm
Usually regular
Varies with conduction
Pattern
Saw tooth baseline
Grossly irregular
Irregular or almost flat
baseline
“Irregularly irregular”
Underlying Mechanism Reentry via macro reentrant circuit
Typically multiple
wavelet reentry
82
AVRT
AV Re-entrant Tachycardia
• An SVT caused by the existence of an extra pathway from
the atria to the ventricles
– Extra pathway + AV Node = reentry
• Two Types
– Orthodromic
– Antidromic
83
AVRT
Orthodromic
• Mechanism: Reentry
• Rate: 180 - 260 bpm+
• Characteristics: Extra electrical pathway
to ventricles
Accessory Pathway
Conduction to the ventricles via the AV node
(normal conduction) - then from Ventricles to
the Atria via the accessory pathway.
Produces narrow complex SVT.
84
AVRT
Antidromic
• Mechanism: Reentry
• Rate: 180 - 260 bpm+
• Characteristics: Extra electrical pathway
to ventricles. Wide-complex QRS.
Accessory Pathway
Conduction to ventricles via the accessory
pathway. The impulse is then conducted
retrograde to atrial via the AV node.
Produces a wide-complex SVT.
85
Wolff-Parkinson-White
• Origin: A - V conduction outside the AV node. The Wolff pathway
conducts faster than the AV node
• Mechanism: Reentry
• Rate: 180-260 bpm – can be faster
• Characteristics: Short PR Interval (< 120 ms), wide QRS (> 110 ms),
obvious delta wave
86
AVNRT
AV Node Re-entrant Tachycardia
• Origin: AV Node
• Mechanism: Reentry
• Rate: 150 - 230 bpm, faster in teenagers
• Characteristics: Normal QRS with absent P-waves
87
AVRT vs. AVNRT
• AVRT
• AVNRT
– 180 – 260 bpm
– 150 – 230 bpm
– Narrow QRS if orthodromic
– Narrow QRS
– Wide QRS if antidromic
– Short RP
– Delta wave + in SR
– No delta waves
– PR < 120 msec
– Initiating PR long
– 1:1 Conduction
– P-waves buried in QRS
Treatment:
•
– Conduction 1:1, or 2:1 when
distal block present
Ablation
• Rarely is a pacemaker implanted
– Perhaps if AV node is injured during ablation
88
Tachycardia Classifications
Based on disorder
• Sinus Tachycardia
• Atrial Tachycardia
Impulse Formation
• Premature Contractions
• Accelerated Junctional Rhythm
• Accelerated Idioventricular
Rhythm (AIVR)
Impulse Conduction
• Atrial Flutter
• Atrial Fibrillation
• AVRT/AVNRT
• Ventricular Tachycardia
• Ventricular Fibrillation
89
Monomorphic VT
Classification Based on ECG Morphology
• Origin: Ventricles (Single Focus)
• Mechanism: Reentry initiated by abnormal automaticity or triggered
activity
• Characteristics: Rapid, wide and regular QRS. A-V disassociation
90
Polymorphic VT
• Origin: Ventricles (Wandering Single Focus)
• Mechanism: Reentry with movement in the circuit initiated by abnormal
automaticity or triggered activity
• Characteristics: Wide and irregular QRS Complex that changes in axis
91
Torsades de Pointes
“Twisting of the points”
• Origin: Ventricle
• Mechanism: Reentry (movement in focus)
• Rate: 200 – 250 bpm
• Characteristics: Associated with Long QT interval; QRS changes axis
and morphology with alternating positive/negative
complexes
92
Ventricular Fibrillation (VF)
• Origin: Ventricle
• Mechanism: Multiple wavelets of reentry
• Characteristics: Irregular with no discrete QRS
93
Tachycardia Classifications
Summary
• Sinus Tachycardia
• Atrial Tachycardia
Impulse Formation
• Premature Contractions
• Accelerated Junctional Rhythm
• Accelerated Idioventricular
Rhythm (AIVR)
Impulse Conduction
• Atrial Flutter
• Atrial Fibrillation
• AVRT/AVNRT
• Ventricular Tachycardia
• Ventricular Fibrillation
94
Status Check
Identify the Rhythm
• Ventricular Tachycardia
Click for Answer
• Sinus Bradycardia
• Complete Heart Block
• Atrial Fibrillation
• Ventricular Fibrillation
95
Status Check
Identify the Rhythm
• Ventricular Tachycardia
Click for Answer
• Sinus Bradycardia
• Complete Heart Block
• Atrial Fibrillation
• Ventricular Fibrillation
96
Status Check
Identify the Rhythm
• Ventricular Tachycardia
Click for Answer
• Sinus Bradycardia
• Complete Heart Block
• Atrial Fibrillation
• Ventricular Fibrillation
97
Status Check
Identify the Rhythm
• Ventricular Tachycardia
Click for Answer
• Sinus Bradycardia
• Complete Heart Block
• Atrial Fibrillation
• Ventricular Fibrillation
98
Status Check
• Ventricular Tachycardia
Click for Answer
• Sinus Bradycardia
• Complete Heart Block
• Atrial Fibrillation
• Ventricular Fibrillation
99
Upcoming Modules
• The Fundamentals of Cardiac Devices
• Basic Concepts—Electricity and Pacemakers
• Applying Electrical Concepts to Pacemakers
• Pacemaker Basics
• Single and Dual Chamber Pacemaker Timing
• Advanced Pacemaker Operations
• Pacemaker Patient Follow-up
• Pacemaker Troubleshooting
• Pacemaker Automatic Features
100
Disclosure
NOTE:
This presentation is provided for general educational purposes
only and should not be considered the exclusive source for this
type of information. At all times, it is the professional
responsibility of the practitioner to exercise independent clinical
judgment in a particular situation.
101
Brief Statements
Indications
•
Implantable Pulse Generators (IPGs) are indicated for rate adaptive pacing in patients who ay benefit from increased
pacing rates concurrent with increases in activity and increases in activity and/or minute ventilation. Pacemakers are
also indicated for dual chamber and atrial tracking modes in patients who may benefit from maintenance of AV
synchrony. Dual chamber modes are specifically indicated for treatment of conduction disorders that require restoration
of both rate and AV synchrony, which include various degrees of AV block to maintain the atrial contribution to cardiac
output and VVI intolerance (e.g. pacemaker syndrome) in the presence of persistent sinus rhythm.
•
Implantable cardioverter defibrillators (ICDs) are indicated for ventricular antitachycardia pacing and ventricular
defibrillation for automated treatment of life-threatening ventricular arrhythmias.
•
Cardiac Resynchronization Therapy (CRT) ICDs are indicated for ventricular antitachycardia pacing and ventricular
defibrillation for automated treatment of life-threatening ventricular arrhythmias and for the reduction of the symptoms of
moderate to severe heart failure (NYHA Functional Class III or IV) in those patients who remain symptomatic despite
stable, optimal medical therapy and have a left ventricular ejection fraction less than or equal to 35% and a QRS
duration of ≥130 ms.
•
CRT IPGs are indicated for the reduction of the symptoms of moderate to severe heart failure (NYHA Functional Class
III or IV) in those patients who remain symptomatic despite stable, optimal medical therapy, and have a left ventricular
ejection fraction less than or equal to 35% and a QRS duration of ≥130 ms.
Contraindications
•
IPGs and CRT IPGs are contraindicated for dual chamber atrial pacing in patients with chronic refractory atrial
tachyarrhythmias; asynchronous pacing in the presence (or likelihood) of competitive paced and intrinsic rhythms;
unipolar pacing for patients with an implanted cardioverter defibrillator because it may cause unwanted delivery or
inhibition of ICD therapy; and certain IPGs are contraindicated for use with epicardial leads and with abdominal
implantation.
•
ICDs and CRT ICDs are contraindicated in patients whose ventricular tachyarrhythmias may have transient or
reversible causes, patients with incessant VT or VF, and for patients who have a unipolar pacemaker. ICDs are also
contraindicated for patients whose primary disorder is bradyarrhythmia.
102
Brief Statements (continued)
Warnings/Precautions
• Changes in a patient’s disease and/or medications may alter the efficacy of the device’s programmed
parameters. Patients should avoid sources of magnetic and electromagnetic radiation to avoid
possible underdetection, inappropriate sensing and/or therapy delivery, tissue damage, induction of an
arrhythmia, device electrical reset or device damage. Do not place transthoracic defibrillation paddles
directly over the device. Additionally, for CRT ICDs and CRT IPGs, certain programming and device
operations may not provide cardiac resynchronization. Also for CRT IPGs, Elective Replacement
Indicator (ERI) results in the device switching to VVI pacing at 65 ppm. In this mode, patients may
experience loss of cardiac resynchronization therapy and / or loss of AV synchrony. For this reason,
the device should be replaced prior to ERI being set.
Potential complications
• Potential complications include, but are not limited to, rejection phenomena, erosion through the skin,
muscle or nerve stimulation, oversensing, failure to detect and/or terminate arrhythmia episodes, and
surgical complications such as hematoma, infection, inflammation, and thrombosis. An additional
complication for ICDs and CRT ICDs is the acceleration of ventricular tachycardia.
• See the device manual for detailed information regarding the implant procedure, indications,
contraindications, warnings, precautions, and potential complications/adverse events. For further
information, please call Medtronic at 1-800-328-2518 and/or consult Medtronic’s website at
www.medtronic.com.
Caution: Federal law (USA) restricts these devices to sale by or on the order of a physician.
103
Brief Statement: Medtronic Leads
Indications
• Medtronic leads are used as part of a cardiac rhythm disease management system. Leads are
intended for pacing and sensing and/or defibrillation. Defibrillation leads have application for patients
for whom implantable cardioverter defibrillation is indicated
Contraindications
• Medtronic leads are contraindicated for the following:
• ventricular use in patients with tricuspid valvular disease or a tricuspid mechanical heart valve.
• patients for whom a single dose of 1.0 mg of dexamethasone sodium phosphate or dexamethasone
acetate may be contraindicated. (includes all leads which contain these steroids)
• Epicardial leads should not be used on patients with a heavily infracted or fibrotic myocardium.
• The SelectSecure Model 3830 Lead is also contraindicated for the following:
• patients for whom a single dose of 40.µg of beclomethasone dipropionate may be contraindicated.
• patients with obstructed or inadequate vasculature for intravenous catheterization.
104
Brief Statement: Medtronic Leads (continued)
Warnings/Precautions
• People with metal implants such as pacemakers, implantable cardioverter defibrillators (ICDs), and
accompanying leads should not receive diathermy treatment. The interaction between the implant and
diathermy can cause tissue damage, fibrillation, or damage to the device components, which could
result in serious injury, loss of therapy, or the need to reprogram or replace the device.
• For the SelectSecure Model 3830 lead, total patient exposure to beclomethasone 17,21-dipropionate
should be considered when implanting multiple leads. No drug interactions with inhaled
beclomethasone 17,21-dipropionate have been described. Drug interactions of beclomethasone
17,21-dipropionate with the Model 3830 lead have not been studied.
Potential Complications
• Potential complications include, but are not limited to, valve damage, fibrillation and other arrhythmias,
thrombosis, thrombotic and air embolism, cardiac perforation, heart wall rupture, cardiac tamponade,
muscle or nerve stimulation, pericardial rub, infection, myocardial irritability, and pneumothorax. Other
potential complications related to the lead may include lead dislodgement, lead conductor fracture,
insulation failure, threshold elevation or exit block.
• See specific device manual for detailed information regarding the implant procedure, indications,
contraindications, warnings, precautions, and potential complications/adverse events. For further
information, please call Medtronic at 1-800-328-2518 and/or consult Medtronic’s website at
www.medtronic.com.
Caution: Federal law (USA) restricts this device to sale by or on the order of a physician.
105
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