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)
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)
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.
