Flashcards in implantable cardiac rhythm management devices: anesthesia implications Deck (51)
what does the pacemaker system consist of ?
-pulse generator: power source or battery
-leads or wires
*pulse generator and leads are the things we need to be able to identify and sometime manipulate
what is the cathode?
negative electrode; refers to a pathway
*"cathode current departs", or leaves device/battery
what is the anode?
*current returns to device/battery
what is opposite of cathode and anode?
cation = positively charged
anion = negatively charger
*cathode and anode are the currents that transmit these
what is a bipolar pacemaker system?
-the body tissue is part of the circuit
what is unipolar pacemaker system?
body tissue contact is essential for grounding
*if contact not made, grounding does not occur so pacing does not occur
describe the pulse generator
-contains a battery that provides energy for sending electrical impulses to the heart
-houses the circuitry that controls pacemaker operations
describe the anatomy of the pacemaker
-connector: top portion; contains the atrial and ventricular connector; where atrial and ventricular wires, leads connect
-hybrid: center; merges connector and battery; "brain" of the pacemaker; holds the resistors, defibrillation protection, output capacitors, clock, and reed switch (most of pacemaker components in the hybrid)
-battery: bottom portion
describe the leads of the pacemaker
-deliver electrical impulses from the pulse generator to the heart
***sense cardiac depolarization
describe the pacing lead components
-connector pin: connects into the top connection portion of the pacemaker
-electrode (tip): prongs around here hold into the wall of the heart muscle
when was the first pacemaker implanted?
when was the first implantable cardioverter-defibrillator (ICD) implanted?
what was significant about pacemakers and defibrillators in the US in 2003?
-325,800 pacemakers implanted
-127,300 defibrillators implanted
what are indications for a pacemaker?
-chronic atrioventricular (AV) heart block
*chronic bifascicular and trifascicular block
**AV heart block after acute MI (damaged tissue, so section doesn't receive signal well)
**Sinus node dysfunction
*hypersensitive carotid sinus and neutrally mediated syndromes (neurogenic syncope)
-children and adolescents with bradycardias
**cardiac transplantation (disconnect b/w host and implant)
**heart failure, a fib
-termination of tachydysrhythmias
where are endocardial leads placed?
inserted intravenously through a major vessel
where are epicardial or myocardial leads placed?
inserted subcostally; embedded either above the cardium or in the myocardium
where are transvenous leads placed?
inserted via a large vein, distal to the heart
describe unipolar pacing
placement of negative electrode in the atrium or ventricle and the positive (ground) electrode distant from the heart (metallic portion of the pulse generator acts as the ground of positive electrode and is placed in Sub Q tissue)
describe bipolar pacing
placement of both the negative and positive electrodes in the cardiac chamber being paced
describe atrioventricular timing
timing that is preset in the pacemaker of a dual chamber pacing b/w atria and ventricles
what activates rate adaptive pacing?
*increase in respiratory rate or minute ventilation (runners)
*increase in body movement
-shortened QT interval
-increased atrial rate
-rise in central venous temperature
-decrease in venous blood pH
-increase in RV stroke volume
-increase in ventricular pump action
*not all pacemakers are rate adaptive; depends upon how active and/or if frequent changes in hemodynamics
describe biventricular pacing
allows both ventricles to contract and allows maximum volume
*used for functional hemodynamic abnormalities with asynchronous ventricular contraction r/t conduction delays and leading to prolonged isovolumetric time, compromised diastolic filling time, and ineffective atrial contraction
describe the NASPE classification of pacing
I) chamber paced: V- ventricle, A- atrium, D- dual, O- none, S*- A or V
II) chamber sensed: V, A, D, O, S*
III) response to sensing: T- triggers pacing, I- inhibits pacing, D- dual (T & I), O- none
IV) programmable functions; rate modulation: P- programmable rate &/or output; M- multiprogrammability of rate, output, sensitivity, etc.; C- communicating functions (telemetry); R-rate modulation; O-none
V) antitachyarrhythmia functions: P- pacing, S- shock, D- dual (P & S), O- none
what are indications for ICDs?
-cardiac arrest d/t V tach or V fib
-drug resistant VT with hemodynamic impact causing syncope
-patients with coronary artery disease and a history of sudden death with documented sustained VT
-prevention for patients with coronary artery disease and nonsustained VT
what are functions of ICDs?
-cardioversion and defibrillation
how does a defibrillator usually work?
-typically detects VT or fibrillation and terminates by overdrive pacing and delivering high energy shock
what are ICD generator, rate-sensing leads?
electrodes to deliver high energy shocks via wire mesh patch electrodes applied directly to the epicardial surface of the heart
where are normal placements of ICDs?
-upper chest or lower abdomen
*defibrillators are bigger so seen more often in abdominal area where there is more sub q fat for placement
*need to know placement to consider bovie pad placement
what questions should be asked during a pre op eval concerning ICDs?
-is there a device?
-why was the device implanted?
-what type of device?
-is the patient dependent on the device?
-what is the device's function?
-when was the last visit to the doctor
-when was the last time you called in to have device checked? how often?
-last time battery was changed?
-any issues with the devices? if so, what?
-vertigo or syncope?