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→Uni- and bipolar sensing and stimulation
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Sensing and stimulation of the myocardium demands a closed electrical circuit. A pacemaker can sense and stimulate in a unipolar and bipolar fashion: | Sensing and stimulation of the myocardium demands a closed electrical circuit. A pacemaker can sense and stimulate in a unipolar and bipolar fashion: | ||
* Unipolar: Pacemaker circuit between 1 electrode at the distal end of lead and the pacemaker pulse generator (large circuit ± 40-60 cm). | * Unipolar: Pacemaker circuit between 1 electrode at the distal end of lead and the pacemaker pulse generator (large circuit ± 40-60 cm). | ||
** Advantage: large pacemaker spikes (easier interpretation pacemaker ECG) | |||
** Disadvantage: extracardiac stimulation (pectoral muscle), sensing of extracardiac signals (such as ventricular depolarisations in the atrial sensing channel (far field R waves) or non-physiological noise) | |||
* Bipolar: Pacemaker circuit between 2 electrodes at the distal end of the lead (small circuit ± 10-15 mm) | * Bipolar: Pacemaker circuit between 2 electrodes at the distal end of the lead (small circuit ± 10-15 mm) | ||
** Advantage: more reliable sensing | |||
** Disadvantage: small pacemaker spikes (difficult interpretation pacemaker ECG) | |||
===Follow up=== | |||
The first 6-8 weeks after implantation, patients are advised not to over-stretch their arm on the same side as the pacemaker (such as golf, swimming etc.) to allow time for the lead to mature. | |||
Control visits for pacemakers are usually every 6 months. During this visit several electrical parameters are measured: battery status, stimulation thresholds and impedance. | |||
===Complications=== | |||
* Undersensing: An intrinsic depolarization that is present, is not sensed by the pacemaker. This can be due to: | |||
** Inappropriately programmed sensitivity | |||
** Lead dislodgement | |||
** Lead failure, such as lead fracture or insulation failure | |||
** Lead maturation: the amplitude may abruptly decline during the first week after implantion, but these values return to the implantation values after about 6-8 weeks as the lead “matures” | |||
* Oversensing: The pacemakers senses signals on the marker channel that do not correspond to the ECG pattern. This can be physiologic (e.g. ventricular pulse or myopotentials) or non-physiologic (e.g. lead fracture or if the lead is loose from the pacemaker pulse generator or outside interference such as TENS therapy or surgical diathermy). | |||
==ICD== | ==ICD== | ||
*Overzicht trials met link naar pubmed | *Overzicht trials met link naar pubmed | ||