Devices
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Pacemakers
A pacemaker monitors the electrical impulses in the heart. When needed, it sends small electrical impulses to the heart muscle to maintain a normal heart rate.
A pacemaker rhythm can easily be recognized on the ECG. It shows pacemaker spikes: vertical signals that represent the electrical activity of the pacemaker. Usually these spikes are more visible in unipolar than in bipolar pacing (see below).
Patients
In general, pacemaker implantation is indicated in patients with a documented irreversible bradycardia which causes symptoms. Symptoms associated with bradycardia can be lightheadedness, palpitations, dyspnea, angina and syncope. The causal relation between the abnormal heart rhythm and symptoms is crucial for the decision to implant a pacemaker.
Implantation
Pacemaker implantation is performed under local anaesthesia in a sterile operating room or catheterization laboratory. Implantation starts with inserting the pacemaker lead(s), most often into the left or right cephalic vein. Fluoroscopy is used to ensure the appropriate location in the atrium or ventricle. Leads are often positioned in the auricle of the right atrium and/or the right ventricular apex.
| Wet van Ohm: |
|---|
| U = I x R |
| U = Voltage |
| I = Current |
| R = Impedance |
Device measements
- Stimulation threshold (in mV@ms): The stimulation threshold is the minimum stimulus intensity (in mV) and duration (in ms) necessary to capture the heart.
- Sensitivity (in mV): The degree that the pacing system “sees” or senses signals, controlled by the sensitivity setting which is graduated in mV.
- Impedance (in Ω): The total pacing impedance is the sum of all resistance to the flow of the electrical impulses.
- Battery: Device longevity is estimated based on the remaining battery voltage and battery impedance (and past history of percent pacing in case battery status is checked at follow up visits).
If these tests are within limits, the pacemaker leads are properly positioned. Thereafter, the pacemaker pulse generator is implanted subcutaneously or subpectorally under the left or right clavicle.
Programming
Pacemaker codes
Pacemakers can be categorized according to the NASPE coding system that usually consists of 3-5 letters.
ICD
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