Pacemaker questions Flashcards
What are typical temporary epicardial pacemaker settings follow cardiac surgery
Rate 90 bpm Atrial output 5mA atrial sensitivity 1.0 mV Ventricular 5mA Ventricular sensitivity 2.0mV Atrioventricular delay (AVD) 150 msec Mode (DDD)
Compared to NSR VVI pacing causes decreased cardiac output. Describe 2 mechanisms that account for this decrease
Loss of atroventricular synchrony (atrial kick)
loss of depolarization via purkinje system resulting discordant ventricular contraction
List 3 diagnoses or groups of patients that are particulary adversely affected by the loss of sinus rhythm
Those with ventricular hypertrophy (aortic stenosis, severe HTN)
Those in congestive heart failure
mitral stenosis
List 5 items which may be tracked and used to modulate the rate in a rate responsive pacemaker
heat carbon dioxide electricity lactic acid intra-cardiac pressure movement
How do rate responsive pacemakers work
Particular item is a product of increased metabolism and will be sensed by a transducer. This results in an electrical signal being sensed by the pacemaker electronic circuit and changes the pacemaker automatic interval and therefore the escape rate. As detectino of the item increases, the pacemaker output rate will icnrease, as the sensed paramter decrease, the pacemaker response will also decrease
Describe 2 ways which you would achieve permanent ventricular pacing in a patient with complete heart block and a previously placed mechanical valve in the tricuspid position
Epicardial pacing (subxyphoid, or anterior thoractomy approach)
Transvenous, transcoronary sinus, coronary vein LV wall pacing
Why not cross the Tricuspid valve
Potential damage to the valve
increasing tricuspid regurgitation
increasing possibility of jamming leaflet of a mechanical prosthesis
implanting an automatic internal defibrillator. What are anatomic boundaries that guide a cephalic vein cut down
Deltoid
pectoralis major
“Delto-pectoral groove”
List 2 advantages of cephalic vein cut down over direct subclavian percutaneous cannullation
less chance of lead trauma (crush injury)
less chance of hemothorax
less chance of pneuo
Less chance of chylothorax
Briefly describe the function of a pacemaker designated by the following 3 letters of the International pacemaker code
1) AOO
2) AAI
3) DVI
4) DDD
5) VOO
AOO: fixed-rate atrial pacer
AAI: (rate inhibited), atrial pacer
DVI: Double chamber pacing but only ventricular sensing
DDD: chamber pacing and double change sensing
VOO: Fixed rate, ventricular pacer
List 3 sensor that can be incorporated into a rate-adpative pacemaker
activity (movement)
minute ventilation
QT interval
What is pacemaker tachycardiac
Initiated when ventricular activity is conducted retrograde to the atria results in a premature atrial depolarization.
Pacemaker sense the retrograde-induced atrial event and paces the ventricle following the programmed AV delay. If the verntricular events is again conducted retrograde to the atraium, the endless loop cycle develops.
Why does PMT occur
Loss of AV synchorny
Can be be causes by over/under sensing or loos of atrial capture./PAV/magnet removal
retrograde conduction is related to status of AV node condution. If sinus node dysfunction and intact AV node then retrograde conduction is possible
What is treatment of PMT
Measure the VA conduction time and program a post ventricular atrial rerfractory period (PVRP) that is equal to the VA condution time plus 50ms
PVRP: is the period after a sensed or paced ventricular event which the atrial sensing circuit is refractory. Any atrial event occuring during the PVRAP will not be sense by the atrial circuit.
What features of the pacemaker must occur in order to have PMT
Dual chamber
atrial sensed
loss of AV snychrony.. (sinus node dysfunction with normal AV node condution)
What is Magnet Mode
Causing sensing to be inhibited
temporary turns pacemaker into asynchronus mode “set rate’ “VOO”
What is DDD
paces atria and ventricle
senses atrial and ventricle
atria triggered and ventricle inhibited
AAT
Paces atria
senses atria
triggers generator to fire if atria sensed
What are actions of ICD
Perform cardioversion/defibrillation
Anti-tachycardia pacing–overdrive pacing in an attempt to terminate ventricular tachycardia.
List absolute indications for PPM
- Sick Sinus syndrome
- Symptomatic sinus bradycardia
- trachy-brady syndrome
- 3rd degree heart block
- AF with slow ventricular response
- Chronotropic incompetence
- Prolonged QT syndrome
What does magnet do for pts with ICD
Disables the tachyarrhythmia and therefore does not allows shocks
Magnet does NOT cause asynchronus pacing it would in a pacemaker
Class I indications for AICD
Following sudden cardiac death due to VF or HD instability with VT after excluding reversible causes
Structural heart disease and spontateous sustained VT
Syncope of unclear origin and inducible VF or VT on EPS
LVEF <35% due to MI, 40 days post MI, NYHA II-III
DCM, LVEF <35%, NYHA II-III
LVEF 30%, prior MI, NYHA class I
NSVT due to prior MI, LVEF <40%, , VF or VT on EPS
What are class IIa indications for AICD
IIa Unexplained syncope, significant LV dysfunction, non-ischemic DCM Sustained VT, normal EF HCM with 1 or more RF for SCD ARVD/C with 1 or more RF for SCD Long QT with syncope and VT while on BB Non-hospitalized pts awaiting transplant Brugada syndrome with syncope
Most common reasons to remove AICD
Infection
Lead fracture
Most common reasons for inappropriate defibrillation/shock
SVT
fractured lead
Where do you see the leads for ICD
leads go into the right atrium and the right ventricle
for for CRT you would see a third lead in that goes retrograde through the CS in the LV
What percentage of pts receiving a CRT do not receive any benefit
about 30%
some actually get worse
List 3 sensors that can be incorporated into a rate-adaptive pacemaker
Activity (movement
Minute ventilation
QT interval
What type of pacemaker and why
79 yo pt with longstanding AF, R from 30 to 100bpm on medical treatment, good ventricular function
VVI/VVI(R)
VDD and DDD are contraindicated due to lack of organized atrial activity and risk of tracking atrial tachyarrhythmias
*pt has lived without atrial quick so will not benefit and if you place dual you run the risk of PMT
What type of pacer and why
8 year old 23 KG with complete heart block
VDD
AV synchrony and rate responsiveness is maintained, single lead minimizes risk of subclavian vein thrombosis
DDD is acceptable but the 2 leads is less ideal in smaller children when the same effect can be had with single lead VDD system
What type of pacer and why
80 year old F, with bradycardia persisting for 1 week following AVR. Pre-op EF at 35%. Rhytm strip shows sinus bradycardia with heart rates of 35bpm with PR interval and occasional 2:1 block
DDD
best due to reduced preoperative EF in a hypertrophied ventricle that would be very preload sensitive
VDD not ideal due to need for occasional atrial pacing
What is the North Americans Society of Pacing and Electrophysiology five-position pacemaker classification system
I: Chamber paced–
O–(none); A (atrium), V (Ventriclle, D (dual A + V); S (single A or V)
II: Chamber sensed
O–None; A (atrium), V (ventricle); D (dual A + v); S (single A or V)
III: response to sensing
O—None; T (triggered) ; I (inhibitied); D (dual)
IV: Programmability
O–None, R (Rate modulation)
V: Multisite pacing
O (none), A (atrium), V (ventricle),D (dual A + V)
