Devices: Difference between revisions

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{{DevelopmentPhase}}
==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:SchematicImg.jpg|right|thumb|300px|Schematic display of a pacemaker.]]
[[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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===Device measurements===
===Device measurements===
[[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.]]


{| class="wikitable" border="1" cellpadding="1" cellspacing="1" width="10%"  
{| class="wikitable" border="1" cellpadding="1" cellspacing="1" width="200px"  
|-
|-
!Ohm’s law:
!Ohm’s law:
|-
|-
|align="center"|U = I x R
|U = I x R




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''R = Impedance''
''R = Impedance''
|}
|}
[[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.]]


====Stimulation threshold (in mV@ms):====  
====Stimulation threshold (in mV@ms):====  
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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.


{| class="wikitable" border="1" cellpadding="1" cellspacing="1" width="100%"
{| class="wikitable" border="1" cellpadding="1" cellspacing="1" width="400px"
|-
|-
!I
!I
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===Explanations of table:===
===Explanations of table:===
====III:====
====III:====
{| border="0" cellpadding="1" cellspacing="1" width="100%"
|-
|bgcolor="#FAF8CC"|
=====Triggered:=====
=====Triggered:=====
|}
A sensed event triggers a pacemaker output pulse  
A sensed event triggers a pacemaker output pulse  
{| border="0" cellpadding="1" cellspacing="1" width="100%"
|-
|bgcolor="#FAF8CC"|
=====Inhibited:=====
=====Inhibited:=====
|}
Detection of physiological heart activitity will inhibit an electrical pacemaker impulse  
Detection of physiological heart activitity will inhibit an electrical pacemaker impulse  
{| border="0" cellpadding="1" cellspacing="1" width="100%"
|-
|bgcolor="#FAF8CC"|
=====Dual:=====
=====Dual:=====
|}
A pacemaker with dual response to sensing will inhibit a pacemaker output pulse if it senses an intrinsic event in that same chamber, but it will trigger a pacemaker output pulse in the ventricle if it senses an intrinsic event in the atrium (after a programmed atrioventricular interval)
A pacemaker with dual response to sensing will inhibit a pacemaker output pulse if it senses an intrinsic event in that same chamber, but it will trigger a pacemaker output pulse in the ventricle if it senses an intrinsic event in the atrium (after a programmed atrioventricular interval)
====IV:====
====IV:====
{| border="0" cellpadding="1" cellspacing="1" width="100%"
|-
|bgcolor="#FAF8CC"|
=====Rate modulation:=====
=====Rate modulation:=====
|}
In some patients, rate adaptive pacing is programmed “on” to ensure that when patients exercise increases, the pacemaker ensures that the heart rate increases to provide additional cardiac output. There are many ways to sense physiological exercise, including motion sensors and ventilation sensors.
In some patients, rate adaptive pacing is programmed “on” to ensure that when patients exercise increases, the pacemaker ensures that the heart rate increases to provide additional cardiac output. There are many ways to sense physiological exercise, including motion sensors and ventilation sensors.


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===Non-capture:===  
===Non-capture:===  
[[Image:AtrialCap.jpg|right|thumb|300px|Failure of atrial capture in a patient with atrial standstill, no P-waves are seen after the atrial stimuli.]]
The electrical impulse is not followed by the myocardium.
The electrical impulse is not followed by the myocardium.


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==Implantable cardioverter defibrillators (ICD)==
==Implantable cardioverter defibrillators (ICD)==
[[Image:Schematicpic.jpg|right|300px|thumb|Schematic display of an ICD]]
[[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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===Arrhythmia detection zones===
===Arrhythmia detection zones===
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.  
{| class="wikitable" border="1" cellpadding="1" cellspacing="1" width="600px"
|-
!SVT discriminators:
|-
|
#Waveform morphology (broad vs. small complex or comparison of morphology with template of normal QRS wave)
#Onset of arrhytmia (sudden vs. slowly)
#Stability of arrhythmia (regular vs. irregular)
#Relationship between P- and R-waves (atrial lead required)
|}


The arrhythmia detection zone is the category in which a predefined therapy will be given:
The arrhythmia detection zone is the category in which a predefined therapy will be given:
*'''Monitor zone (e.g. 160-180 bpm):''' All events in this zone will be recorded in the ICD and can be seen during follow up visits, however no therapy is given.
*'''Monitor zone (e.g. 160-180 bpm):''' All events in this zone will be recorded in the ICD and can be seen during follow up visits, however no therapy is given.
[[Image:ICD.jpg|right|thumb|300px|ICD strook met intracardiale electrocardiogram (EGM): VF met shock. De rode pijl geeft het moment van de shock aan.]]
*'''Fast VT zone (e.g. 180-240 bpm):''' All events in this zone will be recorded in the ICD and can be seen during follow up visits. Therapy is given or not if the arrhythmia satisfies several criteria, which are programmed as well, such as SVT/VT discriminators.
*'''Fast VT zone (e.g. 180-240 bpm):''' All events in this zone will be recorded in the ICD and can be seen during follow up visits. Therapy is given or not if the arrhythmia satisfies several criteria, which are programmed as well, such as SVT/VT discriminators.
*'''VF zone (e.g. >240 bpm):''' All events in this zone will be recorded in the ICD and can be seen during follow up visits and therapy is given immediately.
*'''VF zone (e.g. >240 bpm):''' All events in this zone will be recorded in the ICD and can be seen during follow up visits and therapy is given immediately.
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===Numbers of intervals to detect / Time to detect===
===Numbers of intervals to detect / Time to detect===
The ICD diagnoses an arrhythmia when a sufficient (and programmable) number of events in an event sequence are binned. This is usually stated in an “X out of Y” pattern, such as 12 out of 16 intervals.
The ICD diagnoses an arrhythmia when a sufficient (and programmable) number of events in an event sequence are binned. This is usually stated in an “X out of Y” pattern, such as 12 out of 16 intervals.
[[Image:ICD.jpg|right|thumb|300px|ICD strook met intracardiale electrocardiogram (EGM): VF met shock. De rode pijl geeft het moment van de shock aan.]]


===Therapy===
===Therapy===
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==Cardiac resynchronisation therapy (CRT)==
==Cardiac resynchronisation therapy (CRT)==
[[Image:Schematic.jpg|right|thumb|Schematic display of an CRT device]]
[[Image:CRT_device.svg|right|thumb|400px|Schematic display of an CRT device]]
[[Image:ChestXray.jpg|right|thumb|300px|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]]


CRT-pacemaker (CRT-P) is a biventricular pacemaker with leads in both ventricles to ensure synchronized contraction. A CRT-defibrillator (CRT-D) is an ICD with biventricular pacing option.
CRT-pacemaker (CRT-P) is a biventricular pacemaker with leads in both ventricles to ensure synchronized contraction. A CRT-defibrillator (CRT-D) is an ICD with biventricular pacing option.
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*Right atrial lead
*Right atrial lead
*Right ventricular lead
*Right ventricular lead
*Left ventricular lead (positioned in the coronary sinus)
*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).