Cardiology 28: Pacemakers Flashcards
Pacemaker
Delivers electric pulses that cause a heart to beat
Increases or regulates a rhythm
Implantable Cardioverter Defibrillator
Delivers electric shocks to terminate fast rhythms
Can deliver anti-tachycardia pacing (ATP) to overdrive a fast rhythm
Also functions as a pacemaker
Pulse Generator
Contains a battery that provides the energy for sending electrical impulses to the heart
Houses the circuitry that controls pacemaker operations
Passive fixation
The tines become lodged in the trabeculae of the heart
Active fixation
The helix (or screw) extends into the endocardial tissue Allows for lead positioning anywhere in the heart’s chamber
The leads are applied directly to the heart by 3 mechanisms
Epicardial stab-in
Myocardial screw-in
Suture-on
Unipolar Pacing System
Contains a Lead with Only One Electrode Within the Hear
The impulse:
- Flows through the tip electrode (cathode)
- Stimulates the heart
- Returns through body fluid and tissue to the IPG (anode)
Bipolar pacing system
Contains a Lead with Two Electrodes Within the Heart.
The Impulse:
1.Flows through the tip electrode located at the end of the lead wire
2.Stimulates the heart
3.Returns to the ring electrode above the lead tip
Class I Indication
Conditions for which there is evidence and/or general agreement that permanent pacemakers should be implanted
Class II Indication
Conditions for which permanent pacemakers are frequently used but there is divergence of opinion with respect to the necessity of their insertion
Class III Indication
Conditions for which there is general agreement that pacemakers are unnecessary
List of Class I indications For SA node dysfunction
- Documented symptomatic sinus bradycardia, including frequent sinus pauses that produce symptoms. May be due to long-term drug therapy of a type and dose for which there is no accepted alternative
- Symptomatic chronotropic incompetence (of the sinus node)
Those include are : 1.Sinus bradycardia (symptomatic !) Syncope, passing out , dizziness. 2.Sinus arrest 3.Sinus pause (SA exit block) Greater than 3 seconds 4.Brady-tachy syndrome 5.Atrial flutter or atrial fibrillation with symptomatic bradycardia 6.Chronotropic incompetence Cant get it to increase with activity
List of Class II indications for SA node dysfunction
1a. Symptomatic patients with sinus node dysfunction and documented rates of < 40 bpm without a clear-cut association between significant symptoms and the bradycardia
AKS syncope, dizziness etc.
1b. In minimally symptomatic patients, chronic heart rate < 30 bpm while awake
Class III Indications for sinus node dysfunction(AKA not indicated)
Asymptomatic sinus node dysfunction or due to unnecessary drug therapy.
3rd degree heart block is a Class I indication for pacemaker in AV Block. what is associated with 3rd degree heart block ?
1.Symptomatic bradycardia (including those from arrhythmias and other medical conditions that require drug therapy)
2.Documented periods of asystole > 3 seconds
Escape rate < 40 bpm in awake, symptom free patients
3.Post AV junction ablation
4.Post-operative AV block not expected to resolve
5.Neuromusclar diseases with AV block
Second degree heart block associated with ________ becomes a class I indication for pacemaker in AV block.
symptomatic bradycardia
Class IIA indications for AV Block include:
Asymptomatic CHB with a ventricular rate > 40 bpm
Asymptomatic Type II 2nd degree AV block with narrow QRS complex
Asymptomatic Type I 2nd degree AV block within the His-Purkinje system found incidentally at EP study
First-degree AV block with symptoms suggestive of pacemaker syndrome and documented alleviation of symptoms with temporary AV pacing
Class IIB indications for AV Block include:
First degree AV block > 300 ms in patients with LV dysfunction in whom a shorter AV interval results in hemodynamic improvement
Class III indications for AV Block include
Asymptomatic 1st degree AV block
Asymptomatic Type I 2nd degree AV block at supra-His level
AV block expected to resolve and unlikely to recur (e.g., drug toxicity, Lyme Disease)
Class I indication for patients with Bifascicular and Trifascicular Block include
Intermittent 3rd degree AV block
Type II 2nd degree AV block
Alternating BBB (goes from right to left)
Class II Indication for Bifascicular and Trifascicular Block include
Syncope not proved to be due to AV block when other causes have been exluded, specifically VT
Prolonged HV interval ( >100 ms)
His to ventrical interval
Class III indication for Bifascicular and Trifascicular Block include
Asymptomatic fascicular block without AV block
Asymptomatic fascicular block with 1st degree AV block
Class I indications for Carotid Sinus and Vasovagal abnormality inclues
Recurrent syncope caused by carotid sinus stimulation; minimal carotid sinus pressure induces a period of asystole > 3 seconds in duration (CSS)
Class II indication for Carotid Sinus and Vasovagal abnormality inclues
Recurrent syncope without clear, provocative events (tilt table test) and with a hypersensitive cardioinhibitory response
Neurally mediated syncope with significant bradycardia reproduced by a head-up tilt table testing (VVS)
Class III indication for Carotid Sinus and Vasovagal abnormality inclues
Asymptomatic with a positive response to carotid sinus massage (CSS)
Recurrent syncope, lightheadedness, or dizziness without a cardioinhibitory response (CSS/VVS)
Situational vasovagal syncope in which avoidance behavior is effective
Vague symptoms such as dizziness, light-eadedness, or both, with hyperactive cardioinhibitory response to CS stimulation
Class I indications for AV Block Associated with Myocardial Infarction – Pacemaker Indications
Persistent and symptomatic 2nd or 3rd degree AV block
Persistent Type 2nd degree AV block in the His-Purkinje system with bilateral BBB or 3rd degree AV block within or below the His-Purkinje system
Transient advanced 2nd or 3rd degree infranodal AV block and associated bundle branch block
Class II indications for AV Block Associated with Myocardial Infarction
Persistent 2nd or 3rd degree AV block at the AV node level
Class III indications for AV Block Associated with Myocardial Infarction
Transient AV block in absence of intraventricular conduction defect
Pre-existing 1st degree AV block with bundle branch block
Class I indications for Implabatable Cardioversive Defibrilator
Cardiac Arrest
Due to VT or VF
Not due to transient or reversible cause
Spontaneous sustained VT ( > 30 seconds)
Structural heart disease must be present
Syncope of undetermined origin with:
Sustained VT that has clinical relevance and/or
hemodynamic significance
VF induced during EP study when drug therapy
sustained VT is not preferred
Nonsustained VT with:
Coronary disease
Prior MI
LV Dysfunction
Inducible VF or sustained VT
(Non-suppressible by antiarrhythmic drugs)
Spontaneous sustained VT
Not amenable to other treatments
Class IIa indications for Implabatable Cardioversive Defibrilator
LVEF <30% at:
1 month post MI
3 months post coronary revascularization
Class IIB indications for Implabatable Cardioversive Defibrilator
Cardiac Arrest
Assumed due to VF
EP test precluded by other medical conditions
Symptomatic sustained VT while awaiting cardiac transplant
Conditions with life-threatening risk
Long QT Syndrome
Hypertrophic cardiomyopathy
Nonsustained VT with:
Coronary disease
Prior MI
LV Dysfunction
Inducible VF or sustained VT
Syncope of undetermined origin with:
Ventricular dysfunction
Inducible ventricular arrhythmias
All other causes of syncope excluded
RBBB and ST Segment Elevation with:
Syncope of unexplained origin, or
Family history of SCD
Syncope and:
Structural heart disease
Extensive testing failed to identify causeClass III indications for Implabatable Cardioversive Defibrilator
Syncope of undetermined origin Without structural heart disease No inducible VT or VF Incessant VT or VF Don’t put them in, they will get shocked constantly VT or VF with an ablatable or surgically treatable cause WPW, LVOT VT, ILVT, Fascicular VT Transient or reversible VT Due to AMI, electrolyte imbalance, drugs or trauma Psychiatric illness that may: Be aggravated by device implantation Preclude follow-up Terminal illness <6 month life expectancy CAD and: LV dysfunction and Prolonged QRS, or Inducible VT in those undergoing bypass
What are the two things that pacemakers do ?
Pace and Sense
What are the three types of Pacemakers ?
SIngle chamber
Dual Chamber
Biventricular
Describe a single chamber pacemaker system
The pacing lead is implanted in the atrium or ventricle, depending on the chamber to be paced and sensed (Pacing and sensing is in the same chamber)
Describe a dual chamber pacemaker
One pulse generator with two pacing circuits
Circuit 1 for Atrial pacing and sensing
Circuit 2 for Ventricular pacing and sensing
In pacing mode code, the first letter correlates to …
The Chamber being PACED (Ventricle, Atrium, Dual)
In pacing mode code , the second letter correlates to …
The chamber SENSED (Ventricle, Atrium, Dual)
In pacing mode code, the third letter correlates to
The mode of response (Triggered, Inhibited, Dual, None)
In pacing mode code, the fourth letter correlates to…
Program function (Simple, Multi)
In placing mode code, the fifth letter correlates to
Antitachyarryhthmia component (Pacing, Shocking,Dual)
Intrinsic event
Cardiac events which come from the patient
Inhibited
When the pacemaker stimulus is suppressed due to a spontaneous intrinsic event sensed before the end of the sensing (alert) period
Pacing interval
The rate at which the pacemaker will pace if the patient does not have their own rhythm
How do you calculate the pacing interval? Pacing Rate
Intended pacing rate / 60,000 = Interval (ms)
Interval /60,000
Appropriate atrial sensing involves
Sensing of intrinsic P waves (restart the pacing interval)
Appropriate ventricular sensing involves
Sensing intrinsic QRS waves (these restart the pacing interval)
Capture
The depolarization and resultant contraction of the Atria or Ventricles in response to a pacemaker stimulus.
What are the characteristics of atrial capture on EKG?
Inverted P wave, thin QRS complex
What are the characteristics of ventricular capture on EKG ?
Wide QRS complex, elevated ST segment.
Asynchronous Pacing
Pacing without sensing (continous pacing)
Often used in the OR ***
Often turned on in the presence of magnets **
What is the characteristic of Asynchronous Pacing on EKG ?
Non-sensed P waves in-between beats
VOO
Paces ventricle, senses none, no response given
DOO
Paces atria and ventricles, senses neither, No response given
Demand pacing
Pacing with sensing
Pacing pulse is inhibited by intrinsic “P” or “R-waves”
Sensed events reset the pacing interval
ie. Pacing only occurs when a pause occurs….
AAI
Paced: Atria
Sensed: Atria
Response: Inhibited (by P waves)
VVI
Paced: Ventricle
Sensed: Ventricle
Response: Ihibibited (R waves)
Pacing with sensing in the Ventricle which causes inhibition of the pacing stimulus and resets the pacing interval.
OFTEN DONE WHEN SOMEONE IS APT TO ATRIAL FIBRILLATION ! (Don’t give a crap about atria, make sure the ventricle is working correctly
DDD
Paced: Dual
Sensed:Dual
Response: Inhibition in both
Ability to track Atrial activity in the Ventricular channel
Purpose of dual chamber pacing ?
fill in the blanks for the patient.
In other words, if the patient doesn’t have a P-wave then the pacemaker will pace in the atrium
If the patient doesn’t have a R-wave then the pacemaker will pace in the ventricle
Four States of Dual Chamber Pacing
AV: Atrial and Ventricular Pace
AR: Pace in Atrium, sense in ventricle
PV: Atrial sense and Ventricular Pace
PR: Sense in atria and Ventricle
When would dual Atrial and Ventricular Pacing be needed ?
When paced P waves fail to elicit a QRS complex ventricular pacing will lead to depolarization
Complications of Implantation
Vascular Compromise Pneumothorax Hemothorax Cardiac Perforation Cardiac Tamponade Sedation
Post implantation complications
Lead Dislodgement Diaphragmatic Pacing Pectoral Muscle Pacing Brachial Plexus Injury Infection Must take out the whole device. Migration Of Device Pacemaker-mediated Tachcardia EMI
