VI] Sensorized Cardiac Pacemaker

Question 1

What are coronaries and what is their role ?

Answer 1

Coronaries are arteries of the heart. They ensure the blood supply of the heart.

Question 2

To what could lead the coronaries occlusion ?

Answer 2

Heart attack/infarct and necrosis of heart muscle.

Question 3

Who’s the “pacemaker” in the heart.

Answer 3

The sinoartrial node

Question 4

Describe the structure/pathway responsible for heart pulses.

Answer 4

1 - Sinoartrial node 
2 - Internodal pathway 
3 - Atrioventricular node 
4- Artrioventricular bundle (Bundle of HIS)
5- Bundle branches
6- Purkinje fibers

Question 5

What leads to slow spontaneous depolarization of the heart cells ?

Answer 5

Leakage currents.

Question 6

What determines the firing frequency of the heart ?

Answer 6

Slope of depolarization, threshold and maximum

diastolic voltage.

Question 7

What is the aim of an electrocardiogram ?

Answer 7

Recording the ELECTRICAL activity of the heart.

Question 8

Defines the different events of electrical recording of the heart (cf: electrical activity of the heart).

Answer 8

Atrial depolarization - QRS complex - Ventricular depolarization - Ventricular repolarization

Question 9

Describe the heart cycle (filling of ventricles and blabla)

Answer 9

Ventricular filling + Atrial contraction (=Ventricular filling, mid to late diastole)
Isovolumetric relaxation + ventricular filling (=ventricular systole , atria in diastole)
Isovolumetric relaxation and ventricular filling (early diastole)

Question 10

Cite the principle and two functionality of cardiac pacemakers

Answer 10

Artificial depolarization of heart muscle cells

Functionalities : sensing of residual functionality and pacing on demand

Question 11

Site pacemakers components

Answer 11

Stimulator and battery - electrodes - cables with plugs

Question 12

Site 5 types of pacemakers

Answer 12

Chamber paced 
Chamber sensed
Response sensing 
Programmability rate modulation 
Antiarrhythmia function

Question 13

What are the goal of sensors in pacemakers

Answer 13

Adapt to physical and mental load that disturb body state

Question 14

Cite the three types on control mechanism in the heart

Answer 14

Chronotropic
Inotropic
Dromotropic

Question 15

What is the chronotropic control mechanism

Answer 15

The control of the frequency - it is an open loop control

Question 16

What is the inotropic control mechanisms ?

Answer 16

The strength of the contraction - closed loop control

Question 17

What is the dromotropic control mechanisms ?

Answer 17

Conduction velocity over AV node

Closed loop control

Question 18

Which Input variable could be taken into account for sensors ?

Answer 18

Partial pressures of oxygen or carbon dioxide
Saturation of oxygen
Tidal volume
Stroke volume

Question 19

Which parameters could be taken into account for frequency adaptative pacemakers

Answer 19

Activity (vibrations/acceleration sensors)
Breathing volume
Blood temperature

Question 20

What would be the function of frequency pacemakers

Answer 20

Adaptâtes of heart frequency under load if Sinoartrial node does not correctly adapt

Question 21

What other input variables could be important for adaptive pacemakers beyond chronotropic incompetence ?

Answer 21

AV conduction Time (dromotropic control, elegant approach)
QT interval of intracardial ECG
Contractibility of myocard (dp/dt)
(Inotropic control, curvature of optic fiber, acceleration of myocard)

Question 22

What is the limit of chronotropic pacemaker ?

Answer 22

No information about hemodynamics needs
No adaptation to mental load or fever
Artefact suppression needed…

Question 23

Which measurement is crucial for inotropic pacemaker ?

Answer 23

Measurement of myocardial acceleration (dp/dt)

PEA: peak endocardial acceleration