Lecture 9 (Pacemakers) Flashcards
Symptoms that may require a pacemaker
syncope or presyncope, dizziness, light-headness, fatigue, mental confusion, palpitations (sick-sinus rhythm) excercise intolerance
Non-Invasive Testing
12 lead EKG, ambulatory monitor, exercise testing, autonomic testing (tilt table for neurocardiogenic syncope)
Holter Monitor
worn for 1-2 weeks
Event Recorder
worn for 1 month
Implantable Loop Recorder
outpatient surgery worn for longer durations
Invasive Testing
Electrophysiology testing and Implantable loop recorder
Electrophysiology study can find:
spot of an unusual heart rhythm
Class 1 Pacemaker indication
beneficial, useful, effective, acceptable and necessary
Class2 Pacemaker indication
evidence/opinion in favor for use; usefullness and efficacy have been proven
Class 3 Pacemaker Indication
Not useful or effective; may be harmful; DO NOT PUT PACEMAKERS IN THESE PATIENTS!
Pacemaker Considerations
1-association of SYMPTOMS with an arrhythmia
2-LOCATION of conduction abnormality likelihood of progression
3-Risk of arrhythmia (bifascicular block)
Pacemaker Considerations-Symptoms
Correlate SYMPTOMS with rhythm esp important for bradycardia (use ambulatory monitor or careful hx or log book)
Bradycardia Symptoms
most common symptoms we see: dizziness, light-headedness, syncope, fatigue, poor exercise tolerance
Pacemaker considerations-Location
Disease within AV Node
Significant PR prolongation, mobitz type 1 (wenckebach) normal QRS
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
Most common indication for pacemaker implantation
Sinus node dysfunction (#1), AV block
Sinus node dysfunction definition
periods of bradycardia, tachycardia, prolonged pauses or alternating bradycardia and tachycardia
Sinus Node Dysfunction pacemaker indication Class 1
1st-correlate symptoms w/ bradycardia; class 1: HR less than 40 (symptomatic), symptomatic chronotropic incompetence (with exercise);
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
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
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
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
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
contains battery that provides the energy for sending impulses to the heart
pulse generator
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
MI
what percentages of acute MI has SCA as initial presentation
20-25%
average survival rate of Sudden cardiac arrest
8%
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
