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==Pacemakers== | ==Pacemakers== | ||
[[Image:Paced2.gif|300px|right|thumb|Ventricular paced rhythm shows ventricular pacemaker spikes.]] | [[Image:Paced2.gif|300px|right|thumb|Ventricular paced rhythm shows ventricular pacemaker spikes.]] | ||
[[Image: | [[Image:Pacemaker_device.svg|right|thumb|300px|Schematic display of a pacemaker.]] | ||
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 monitors the electrical impulses in the heart. When needed, it sends small electrical impulses to the heart muscle to maintain a normal heart rate. | ||
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[[Image:RedTh.jpg|300px|right|thumb|Determination of stimulation threshold, after the red arrow the stimulus intensify and duration is not sufficient anymore to capture the heart.]] | [[Image:RedTh.jpg|300px|right|thumb|Determination of stimulation threshold, after the red arrow the stimulus intensify and duration is not sufficient anymore to capture the heart.]] | ||
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!Ohm’s law: | !Ohm’s law: | ||
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|U = I x R | |||
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Pacemakers can be categorized according to the NASPE coding system that usually consists of 3-5 letters. | Pacemakers can be categorized according to the NASPE coding system that usually consists of 3-5 letters. | ||
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!I | !I | ||
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==Implantable cardioverter defibrillators (ICD)== | ==Implantable cardioverter defibrillators (ICD)== | ||
[[Image: | [[Image:ICD_device.svg|right|300px|thumb|Schematic display of an ICD]] | ||
[[Image:Subcutaneous_ICD.svg|right|300px|thumb|A fully subcutaneous ICD (SQICD) has a can and lead that are placed subcutaneous but outside of the thorax. This type of ICD does not have te option to give anti-tachypacing or continuous pacemaker functionality, but can deliver a shock to cardiovert ventricular fibrillation.]] | |||
An ICD is a device that monitors heart rhythms. If it senses dangerous rhythms, it delivers shocks or anti-tachypacing (ATP) therapy. Many ICDs record the heart's electrical patterns when there is an abnormal heartbeat. | An ICD is a device that monitors heart rhythms. If it senses dangerous rhythms, it delivers shocks or anti-tachypacing (ATP) therapy. Many ICDs record the heart's electrical patterns when there is an abnormal heartbeat. | ||
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Patients do not meet the evidence based ICD implantation criteria if they have (1) a myocardial infarction within 40 days before ICD implantation; (2) newly diagnosed heart failure at the time of ICD implantation without prior therapy; (3) NYHA class IV symptoms of congestive heart failure. | Patients do not meet the evidence based ICD implantation criteria if they have (1) a myocardial infarction within 40 days before ICD implantation; (2) newly diagnosed heart failure at the time of ICD implantation without prior therapy; (3) NYHA class IV symptoms of congestive heart failure. | ||
A seperate chapter deals with a more complete list of [[ICD indications]] | |||
==Implantation== | ==Implantation== | ||
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The ICD diagnoses rhythm disorders by counting intervals on the intracardiac electrogram. This is a rate-based detection scheme that can be adjusted to meet the individual patient’s needs by programming. The ICD counts the current interval as one value and then average of the current interval and the preceding intervals. If these intervals fall into the same category, the event is binned in that category. If both events are tachycardia of fibrillation, but not in the same category, the interval is binned in the higher category. | The ICD diagnoses rhythm disorders by counting intervals on the intracardiac electrogram. This is a rate-based detection scheme that can be adjusted to meet the individual patient’s needs by programming. The ICD counts the current interval as one value and then average of the current interval and the preceding intervals. If these intervals fall into the same category, the event is binned in that category. If both events are tachycardia of fibrillation, but not in the same category, the interval is binned in the higher category. | ||
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!SVT discriminators: | !SVT discriminators: | ||
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==Cardiac resynchronisation therapy (CRT)== | ==Cardiac resynchronisation therapy (CRT)== | ||
[[Image: | [[Image:CRT_device.svg|right|thumb|400px|Schematic display of an CRT device]] | ||
[[Image:ChestXray.jpg|right|thumb|250px|Chest X-ray of a patient with an CRT device (in posteroanterior and lateral view)<br/>The red arrow is the right atrial lead<br/>The blue arrow is the right ventricular lead<br/>The green arrow is the coronary sinus lead]] | [[Image:ChestXray.jpg|right|thumb|250px|Chest X-ray of a patient with an CRT device (in posteroanterior and lateral view)<br/>The red arrow is the right atrial lead<br/>The blue arrow is the right ventricular lead<br/>The green arrow is the coronary sinus lead]] | ||
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*Right atrial lead | *Right atrial lead | ||
*Right ventricular lead | *Right ventricular lead | ||
*Left ventricular lead | *Left ventricular lead. The left ventricular lead is usually positioned in the coronary sinus, alternatively it can be positioned epicardially on the left ventricle (by a surgical procedure) or intracardially in the left ventricle (through a transseptal puncture). | ||
===Programming, follow up and complications=== | ===Programming, follow up and complications=== | ||
Programming should specifically aim at ensuring atrial-synchronous permanent biventricular pacing, by performing AV-interval optimization (echocardiography guided or using invasive haemodynamic measurments) and performing ventricular-ventricle (VV) interval optimization. Further programming, follow up and complications are similar to pacemakers and ICDs (see above). | Programming should specifically aim at ensuring atrial-synchronous permanent biventricular pacing, by performing AV-interval optimization (echocardiography guided or using invasive haemodynamic measurments) and performing ventricular-ventricle (VV) interval optimization. Further programming, follow up and complications are similar to pacemakers and ICDs (see above). | ||