31-01-2013, 11:02 AM
Electronic Pacemaker
Electronic Pacemaker.ppt (Size: 1.8 MB / Downloads: 94)
All heart cells, muscle and conducting tissue, are capable of generating electrical impulses that can trigger the heart to beat.
The SAN - "heart's pacemaker"
SAN - 60-70 beats /minute.
Increases its' rate due to stimuli like exercise, fever…
AVN - 40-60 beats/minute.
The Bundle of HIS 30-40 beats/minute.
Ventricular muscle cells 20-30 beats/minute.
The AVN and remaining parts of the conducting system are less capable of increasing heart rate due to stimuli previously mentioned than the SAN.
Pacemaker implantation
Minimally invasive surgery-local anesthesia-area under collar bone-45 minutes
Small incision -3 inches long- a “pocket” is fashioned in the tissue overlying the muscle.
The leads are inserted through a vein near the site of the pocket, and advanced into the heart using fluoroscopy (x-rays) for guidance.
The leads are then attached to the generator, the generator is placed in the pocket, and the incision is closed.
Pacemakers can be programmed with a handheld device that communicates with the pacemaker through the skin.
When do we need a pacemaker
A very slow heart rate leading to symptoms of fatigue, weakness and dizziness.
Heart rates below 35-40 beats a minute for a prolonged period usually cause problems due to not enough blood flow to vital organs.
A diagnosis found with an electrocardiogram that indicates a potential for sudden drastic drops in the heart rate.
Injury to the heart muscle that may occur after a heart attack that interferes with your heart’s ability to control the heart rate.
To prevent the heart rate from dropping too low when you are taking certain medications to treat a very fast heart rate.
Battery and its lifetime
Because the pacemaker is battery-operated and surgically implanted, battery lifetime is one of the most important considerations.
Lithium iodide cells which can last as long as 15 years is used now a days.
The lifetime of battery is determined
The stimulus requirements,
The current caused by the pacemaker circuitry.
Asynchronous pacemaker
The asynchronous pacemaker produces a pulse at a preset rate, for example 70 bpm, and delivers pulses to the heart regardless of the heart’s natural beating tendency and independent of the QRS complex.
This pacemaker does not increase the heart rate in response to the body demand for more blood during exertion.
P-wave synchronous pacemaker
The SA node depolarization responds to body demands through the vagus nerve and hormones transported in the blood.
In a P-wave synchronous pacemaker, the SA node triggers the pacer, which in turn drives the ventricle.
It is used when the AV node is blocked because of disease.