VI) Sensorized cardiac pacemakers Flashcards
Cite three function of the heart
- Supply of organs with oxygen
- Transport of metabolic agents
- Transport of carbon dioxide
What are coronaries ?
Coronaries are arteries that surround the heart on the external surface and that vascularise cardiac muscle for contraction.
What could cause an occlusion of the coronaries ?
Heart attack/infract or necrosis of heart muscle. in the lattest case the tissue would die and this is not counterable. what’s lost is lost.
Describes the structures that are involved in heart contraction.
1The sinoartroal node 2The atrioventricular node 3Atrioventricular bundle 4bundle brancges 5purkinje fibers
We have to excite the sinoatrial node in the right atrium. since the muscle tissue is conducting, the thing passes from the right atrium to the left one. the atrioventricular discharge passes trough the insulation in the purkinje fibers and it twist a lil bit the heart.
The nerves conduct the electric signal faster than muscles (they have the hability to overwrite something). but afterwards the cell is silent (other ward infinite back and forth contraction).
In that way there is a simultaeous contraction of the l/r ventricle and then of the l/r atrias.
Draw the pattern of activity of pacemaker cells and explain why it is like this.
If we look at the actual pacemaker cell we see gradual depolarization till an AP,. then it goes back to resting potential.There is in fact a leakage current till the treshold is reached, then there is a constant autonomous AP. afterwards there is a hyperpolarization and the cell shuts till the leakage curent excites again the cell.
so how if i want to accelerate or decelerate the heart beat ? how it happens physiologically ?
you can change the velocity of the leakage rate (if lower, goes slower, if higher, goes faster).
What is the aim of the electrocardiogram ?
Recording of the electrical heart activity.
How the electrocardiogram works ?
you place an electrode on the right arm and the rther on the left leg. When the wave’s moving toward the left leg you get a positive deflection (corresponding to the wave moving down into the left and right ventricles
10 electrodes : four limb electrodes on each limb and six “precordial” electrodes (V1 to V6)
the right leg is often used as a neutral lead. The precodial electrodes are placed all around the torso and are called chest leads, they are all positive. On the arms, the electrodes are called Augmented vectors (right or left)
The left foot is called the augmented vector foot. Each of augmented vectors detect any positive deflection coming toward them.
The point of having 12 leads in total makes it easier to see exactly how the wave of depolarization moves through the heart.
describe the steps leading to our actual pacemakers.
1958 first portable cardiac pacemaker (Medtronic, USA): transistors, battery, percutaneous leads
2004 : implantable cardiac pacemakers.
Now complex micro electronics.
What is the working principle of pacemakers?
artificialy depolarize heart muscle cells while sensing residual functionality.
Cite the pacemaker components.
Simulator and battery, cables with plugs and electrode.
What is the goal of creating a sensor controlled pacemaker ?
Measure physiological status or disturbance to adapt to physical and mental load.
Cite the three mechanism to control in the heart and explain each.
Chronotropic (frequency, open loop control), inotropic (streght of contraction, closed loop control), dromotropic (conduction, velocity over AV node, closed loop control).
Which input variables can be controled for pacemakers ?
Partial pressures (oxygens, carbon dioxide) saturation of oxygen, tidal volume or stroke volume.
