Module 2- Pacemakers Flashcards
Diagram of the heart
Range of Heart Disease
Normal timing of the heart
- A cardiac impulse is transmitted through the heart
- The impulse starts in the SinoAtrial Node or SA node
- Conducts down to the AtrioVentricular or AV node which causes the depolarization of the myocardium via the His Bundle and the Purkinje Fibers
How could the timing of the heart go wrong?
Bradycardia
- Bradycardia results from a block or defect in the conduction system of the heart
- It is most commonly in the SA or AV node
- It causes the heart to beat too slowly. Pt will commonly present with bruising or broken ribs etc.
Ventricular Tachycardia
- Ventricular tachycardia can result in a heartbeat of 160-200 bpm (too fast)
- The ventricles cannot refill before pumping, leading to impaired circulation
- Very dangerous and can be deadly especially if it progresses to VF.
Ventricular fibrillation
- Ventricular Fibrillation (V-Fib) is the most
dangerous cardiac disturbance - The heart beats rapidly and erratically, causing the ventricles to quiver and not pump any blood
Why might someone need a pacemaker?
The three indications for a pacemaker implant are:
1. Bradycardia (slow heartbeat) AF can cause also
2. Tachycardia and risk of ventricular fibrillation
3. Asynchrony of left and right ventricles in congestive heart failure
Pacemakers for bradycardia are the oldest, best established, and
most common (~75%)
Pacemakers that treat ventricular tachycardia are called
Internal Cardioverter Defibrillators (ICD pacemakers)
Timeline showing an overview of the history of cardiac pacing/pacemakers
What makes up a pacemaker?
Regardless of its indication, an
implantable pacemaker is made
up of 4 components:
- A power source (battery)
- The pulse generator (circuitry) diagnostics
- Leads (up to 3)
- Programmer
The nature of the components in a given pacemaker, particularly the power source and pulse generator, vary considerably depending upon the indication for pacing
Battery of a pacemaker
- In 1972, the batteries changed from rechargeable to the use of lithium iodine batteries → this was a major change to
pacemaker potential - Battery and circuitry are in a hermetically sealed titanium casing
- The generator senses the need for a pulse by analyzing input from the leads
(electrodes) - It then issues a 0.05-1 millisecond pulse (~5 millijoules) by discharging a capacitor
Components of a pacemaker: Leads
- Contain an electrode tip that anchors into the heart
- Conducting wire
- Greatest risks implanting and maintaining
- Some electrodes contain a steroid coating to negate inflammation from metal/tissue interactions
External programmer of a pacemaker
- With this external programmer, the physician is able to set parameters of the stimulus
- Communication occurs via radio frequency or bluetooth telemetry with the pacemaker
- The programmer can detect when the battery is low
- Devices revert to a fail-safe in the event of a device interference
What’s the difference between a pacemaker and an internal cardioverter defibrillator?
ICDs are slightly larger than pacemakers and also monitor the heart for abnormal beating, but they can also deliver a shock if a dangerous rhythm is detected.
https://www.youtube.com/watch?v=3il0ii7Svwk
Chest X-ray showing pacemaker and leads
Diagram of a BiVentricular Pacemaker defibrillator
Left bundle branch pacing
Micra: The first leadless pacemaker
- Micra combines battery and electronics of traditional pacemaker
- It is inserted directly into the right ventricle
The Evolution of Cardiac Device Home Monitoring
Implantable Loop Recorders (ILRs)
