Lecture 9 (Pacemakers) Flashcards by Danica Yarnell

Symptoms that may require a pacemaker

syncope or presyncope, dizziness, light-headness, fatigue, mental confusion, palpitations (sick-sinus rhythm) excercise intolerance

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Non-Invasive Testing

12 lead EKG, ambulatory monitor, exercise testing, autonomic testing (tilt table for neurocardiogenic syncope)

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Holter Monitor

worn for 1-2 weeks

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Event Recorder

worn for 1 month

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Implantable Loop Recorder

outpatient surgery worn for longer durations

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Invasive Testing

Electrophysiology testing and Implantable loop recorder

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Electrophysiology study can find:

spot of an unusual heart rhythm

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Class 1 Pacemaker indication

beneficial, useful, effective, acceptable and necessary

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Class2 Pacemaker indication

evidence/opinion in favor for use; usefullness and efficacy have been proven

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Class 3 Pacemaker Indication

Not useful or effective; may be harmful; DO NOT PUT PACEMAKERS IN THESE PATIENTS!

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Pacemaker Considerations

1-association of SYMPTOMS with an arrhythmia
2-LOCATION of conduction abnormality likelihood of progression
3-Risk of arrhythmia (bifascicular block)

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Pacemaker Considerations-Symptoms

Correlate SYMPTOMS with rhythm esp important for bradycardia (use ambulatory monitor or careful hx or log book)

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Bradycardia Symptoms

most common symptoms we see: dizziness, light-headedness, syncope, fatigue, poor exercise tolerance

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Pacemaker considerations-Location

Disease within AV Node

Significant PR prolongation, mobitz type 1 (wenckebach) normal QRS

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Pacemaker considerations-Location

Disease below AV Node

-potentially more unstable; normal or minimally prolonger PR Interval, mobits type 2-secondary AV block, QRS abnormal-bundle branch/fascicular blocks

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Most common indication for pacemaker implantation

Sinus node dysfunction (#1), AV block

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Sinus node dysfunction definition

periods of bradycardia, tachycardia, prolonged pauses or alternating bradycardia and tachycardia

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Sinus Node Dysfunction pacemaker indication Class 1

1st-correlate symptoms w/ bradycardia; class 1: HR less than 40 (symptomatic), symptomatic chronotropic incompetence (with exercise);

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Acquired AV Block pacemaker indication class 1

severe conduction regardless of symptoms: complete AV block (3rd degree), advanced 2nd degree AV Block, Symptomatic mobitz type 1/2, mobitz type 2 with wide QRS or chronic bifascicular block, exercise induced 2nd or 3rd degree block

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Sinus Node Dysfunction pacemaker indication Class 2

class 2 (may need it)-sinus brady w/o clear correlation with symptoms, sinus node dysfunction in pt with unexplained syncope

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Acquired AV Block pacemaker indication class 2

consider pacemaker-asymptomatic mobitz type 2 block, 1st degree block with symptoms, bifascicular block with syncope possibly related

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Other pacemaker indications

neurogenic syncope, post-MI conduction abnormalities, long QT syndrome(more commonly ICD w pacer), hypertrophic cardiomyopathy(affects LVOTO), CHF(CRT/BiV Pacer), s/p cardiac transplant (denervation/bradycardia), bradycardia induced ventricular (suppress), anti-tachycardia pacemakers

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Post MI Conduction abnormalities class 1 criteria for pacemaker

3rd degree block, persistent 2nd degree block in HIS bundle, transient infranodal AV block with BBB

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contains battery that provides the energy for sending impulses to the heart

pulse generator

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houses the circuitry that controls pacemaker options

pulse generator

Complete circuit of pacemaker

pacemaker components combine with body tissue to form complete circuit; pulse generator, leads or wires, cathode, anode, body tissue

delivers electrical impulses from pulse generator to the heart and senses cardiac depolarization

leads (insulated wires)

Passive fixation

the tines become lodged in the trabeculae (fibrous meshwork) of the heart

Active fixation

the helix (or screw) extends into the endocardial tissue which allows for lead positioning anywhere in the hearts chamber

leads applied directly to the heart

Myocardial and Epicardial leads

Fixation mechanisms for myocardial and epicardial leads

epicardial-stab in, myocardial-screw in, or suture on

During pacing the impulse (how does it start and travel)

begins in the pulse generator and flows through the lead and the cathode(-) stimulates the heart and returns to the anode (+)

Pacing lead implanted in the atrium or ventricle, depending on the chamber to be paced and sensed

single chamber system

Two leads -one implanted in both the atrium and the ventricle

dual chamber systems

four functions of most pacemakers

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

Pacing modes 1st letter

chamber paced V-ventricle A-atrium D-dual

Pacing modes 2nd letter

Chamber Sensed: V,A,D

Pacing modes 3rd letter

Repsonse to sense I-inhibited, O-neither, D-both

paces regardless at set rate

VOO

paces at rate unless native is sensed

VVI

paces atrium unless sense native

AAI

paces atrium and ventricle at set rate

DOO

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

DDD

Rate response pacemakers provide patients with

the ability to vary HR when the sinus node cannot provide the appropriate rate

Rate responsive pacing indicated for

pts who are chronotropically incompetent (HR cannot reach appropriate levels during exercise or to meet metabolic demands; pts in chronic a fib w/ slow ventricular response

when the need for oxygenated blood increases the pacemaker ensures that the HR increases to provide additional CO (type of pacing)

rate responsive pacing

Failure to capture undersensing definition

pacemaker does not see the intrinsic beat and therefore does not respond appropriately

assumed pacemaker setting

minimum of 60

Ventricular dysynchrony electrical definition

inter or intraventricular conduction delays typically manifested as LBBB

Ventricular dyssynchrony mechanical definition

abnormal ventricular conduction resulting in mechanical delay and dysynchronous contraction

Pacemaker/ICD complications seen earlier or at implantation

INFECTION, pneumothorax, hemothorax, vascular injury, valve injury, cardiac perf, thromboembolism, arrhythmia, cardiac arrest, lead dislodgement, wound erosion

Pacemaker/ICD chronic complications

INFECTION, TRICUSPID VALVE problem, vascular thrombus, embolism, perforation, lead fracture, lead dislodgement, increased threshold, inappropriate pace/sense, arrhythmia

What leads to infection after pacemaker or ICD

poor wound healing and erosion

What do you always want to compare to an old chest film

lead fracture and/or dislodgement

Electromagnetic Interference cautions with pacemakers

MRI, antitheft systems, metal detectors, cell phones, mp3s, extracorporeal shock wave lithotripsy, power generating equipment, radiofrequency ablation, tens units most are mannageable with precautions

Interference is caused by an electromagnetic energy with a source that is outside the body

electromagnetic interference

waves most frequently associated with pacemaker interference

50-60Hz

electromagnetic fields that may affect pacemakers are

radiofrequency waves

most common place to find sources of electromagnetic interference devices and what are they

hospitals, surgical and therapeutic equipment esp ELECTROCAUTERY

How do pacemakers respond to a magnet

by switching to an asynchronous pacing mode at a programmed AV delay and a fixed magnet rate depending on the manufacturer, device model, and the status of the battery; DDD->DOO, VVI->VOO, AAI->AOO

Acute and emergency pacing options

esophageal pacing (left atrium) and external (zoll-similar to defibrillator)

Leading cause of death in US

sudden cardiac arrest

caused by heart electrical system problem

SCA

occurs when one or more of the arteries that supply blood to the heart muscle becomes blocked and ischemia causes damage to heart tissue

what percentages of acute MI has SCA as initial presentation

20-25%

average survival rate of Sudden cardiac arrest

how to prevent SCA

Refer high risk pts to electrophysiologist

what can improve survival rates from SCA

increased access to automated external defibrillators

Risk factors for SCA

hx of SCA, prior v tach episode, MI, CAD, HF, Hypertrophic cardiomyopathy, long QT syndrome, a combo of these further increase risk

What is an ICD

implantable cardioverter defibrillator-medical device that automatically detects and treats ventricular and sometimes atrial arrhythmias

What do ICDs detect

v fib, v tach, atrial arrhythmias; designed to discriminate between true ventricular arrhythmias and rapidly conducting supraventricular tachyarrhythmias

designed to terminate VF by shocking the heart

defibrillation shock

designed to terminate VT by pacing the patient out of the arrhythmia

antitachycardia pacing

Ventricle therapies provided by dual chamber ICDs

antitachycardia pacing, cardioversion, defibrillation

Ventricle and atrial therapies provided by dual chamber ICDs

bradycardia sensing and pacing

Best person to call

pacemaker reps

what is hard to read if V paced

BBB or ischemia