Pacemaker: Difference between revisions

Latest revision as of 17:32, 24 June 2010

Author(s)	J.S.S.G. de Jong
Moderator	J.S.S.G. de jong
Supervisor
some notes about authorship

A pacemaker is indicated when electrical impulse conduction or formation is dangerously disturbed. The 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.

In the first example, the atria are being paced, but not the ventricles, resulting in an atrial paced rhythm. Accordingly the ventricular complex is delayed until the atrial signal has passed through the AV node. In the second image the ventricles are paced directly, resulting in a ventricular paced rhythm. As ventricular pacing occurs exclusively in the right ventricle the ECG shows a left bundle branch block pattern. An exception to this rule is left ventricular pacing in patients with congenital anomalies and patients with surgically placed epicardial pacemakers. Another exception is septal or RVOT placement of the pacing lead, which results in a less widened to normal QRS complex.

A (used) DDDr pacemaker

Chest x-ray of a patient with a pacemaker

Ventricular paced rhythm shows ventricular pacemaker spikes

DDD paced rhythm

Atrial sensed, ventricular paced rhythm (tracking). Note the LBBB morphology with left axis deviation indicating the pacing lead in the right ventricular apex.

Atrial paced rhythm

Pacemaker Coding

Pacemakers can be categorized according to the NASPE coding system, that usually consists of 3-5 letters.

**The revised NASPE/BPEG generic code for antibradycardia pacing**[1]
I	II	III	IV	V
Chamber(s) paced	Chamber(s) sensed	Response to sensing	Rate modulation	Multisite pacing
O = None	O = None	O = None	O = None	O = None
A = Atrium	A = Atrium	T = Triggered	R = Rate modulation	A = Atrium
V = Ventricle	V = Ventricle	I = Inhibited		V = Ventricle
D = Dual (A+V)	D = Dual (A+V)	D = Dual (T+I)		D = Dual (A+V)

Commonly Used Pacemakers

The most often used codes are:

AAI: The atria are paced, when the intrinsic atrial rhythm falls below the pacemaker's threshold.
VVI: The ventricles are paced, when the intrinsic ventricular rhythm falls below the pacemaker's threshold.
VDD: The pacemaker senses atrial and ventricular events, but can only pace the ventricle. This type of pacemaker is used in patients with a reliable sinus node, but with an AV-block.
DDD: The pacemaker records both atrial and ventricular rates and can pace either chamber when needed.
DDDR: As above, but the pacemaker has a sensor that records a demand for higher cardiac output and can adjust the heart rate accordingly.
Biventricular pacemakers (CRT-P): Leads in both ventricles are present for synchronized contraction. The lead pacing the left ventricle is usually positioned in the coronary sinus. This cardiac resynchronization therapy can improve symptoms and survival in some heart failure patients. Several optimizing methods are being evaluated to find the most effective pacing delay between left and right ventricles. They include echocardiography, finding the narrowest QRS, and invasive hemodynamic measurements with pressure and flow wires.
ICD (Internal Cardioversion Device): This device can detect and treat Ventricular Tachycardia and Ventricular Fibrillation. ICDs are a separate category and usually not considered pacemakers although they do have a pacing function. Usually the first treatment is anti-tachy pacing (pacing at a rate +- 10% above the ventricular rate in ventricular tachycardia, which can convert the rhythm to sinus rhythm). If this is not effective, a defibrillator shock is delivered, usually with 16-36 Joules of energy. ICDs can save lives in patients who have a high risk of ventricular arrhythmias. All ICDs have optional pacemaker activity to treat bradycardias. New biventricular ICDs have 3 leads: an atrial lead, a left ventricular lead and a right ventricular lead.
Biventricular ICDs (CRT-D): an ICD with biventricular pacing option.

Pacemaker Indications

A full list of pacemaker indications can be read in the ESC guidelines on cardiac pacing [2]. A selection of class I indications is: chronic symptomatic third- or second degree (Mobitz I or II) atrioventricular block, syncope with sinus node disease, alternating bundle branch block, and persisting AV block after surgery.

Atrial-sensed ventricular-paced rhythm

AV dual-paced rhythm

AV-sequencial paced rhythm

Pacemaker Malfunction

Failure of appropriate capture, atrial

Failure of atrial capture in a patient with atrial standstill, no P waves are seen after the atrial stimuli

Loss of atrial capture

Failure of appropriate capture, ventricular

Failure of ventricular capture

Failure of Appropriate Inhibition, Atrial

Failure of appropiate inhibition results from atrial malsensing.

Atrial malsensing. Atrial spikes are present right after spontaneous atrial activity.

Failure of Appropriate Inhibition, Ventricular

Failure of Appropriate Ventricular Inhibition, ventricular undersensing

Failure of Appropriate Pacemaker Firing

Failure of appropiate ventricular firing due to ventricular oversensing

Atrial malsensing

Retrograde Atrial Activation

Pacemaker Mediated Tachycardia

Pacemaker Mediated Tachycardia, successfully terminated by withholding a ventricular pace, followed by an atrial pace

Pacemaker mediated tachycardia

Termination of pacemaker mediated tachycardia

External Links

Heart Rhytm Society

References

All Medline abstracts: PubMed | HubMed

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+{{clr}}
+{{Box|
+A pacemaker is indicated when electrical impulse conduction or formation is dangerously disturbed. The '''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.
+In the first example, the atria are being paced, but not the ventricles, resulting in an '''atrial paced rhythm'''. Accordingly the ventricular complex is delayed until the atrial signal has passed through the AV node. In the second image the ventricles are paced directly, resulting in a '''ventricular paced rhythm'''. As ventricular pacing occurs exclusively in the right ventricle the ECG shows a left bundle branch block pattern. An exception to this rule is left ventricular pacing in patients with congenital anomalies and patients with surgically placed epicardial pacemakers. Another exception is septal or RVOT placement of the pacing lead, which results in a less widened to normal QRS complex.
+}}
+{{clr}}
+{|align="right"
+|
 [[Image:picture_pacemaker.jpg|thumb|A (used) DDDr pacemaker]]
-[[Image:paced.gif|thumb| Atrial paced rhythm shows atrial pacemaker spikes. The first venricular beat on this image is paced as well.]]
+[[Image:chest_xray_pacemaker.jpg |thumb| Chest x-ray of a patient with a pacemaker]]
 [[Image:paced2.gif|thumb| Ventricular paced rhythm shows ventricular pacemaker spikes]]
-[[Image:Pacemaker2.jpg |thumb| VVI pacemaker rhythm]]
+[[Image:ddd_paced_12lead.jpg |thumb| DDD paced rhythm]]
+[[Image:Pacemaker2.jpg |thumb| Atrial sensed, ventricular paced rhythm (tracking). Note the LBBB morphology with left axis deviation indicating the pacing lead in the right ventricular apex.]]
+[[Image:DVA0838.jpg|thumb|Atrial paced rhythm]]
+|}
+==Pacemaker Coding==
+Pacemakers can be categorized according to the NASPE coding system, that usually consists of 3-5 letters.
+{| class="wikitable" width="80%"
+|+ '''The revised NASPE/BPEG generic code for antibradycardia pacing'''<cite>Bernstein</cite>
+! I || II || III || IV || V
+|-
+| Chamber(s) paced  || Chamber(s) sensed || Response to sensing || Rate modulation || Multisite pacing
+|-
+| O = None || O = None || O = None || O = None || O = None
+|-
+| A = Atrium || A = Atrium || T = Triggered || R = Rate modulation || A = Atrium
+|-
+| V = Ventricle || V = Ventricle || I = Inhibited || || V = Ventricle
+|-
+| D = Dual (A+V) || D = Dual (A+V) || D = Dual (T+I) || || D = Dual (A+V)
+|-
+|}
-A pacemaker is indicated when the electrical impulse conduction or formation is dangerously disturbed. The paced '''pacemaker rhythm''' can easily be recognized on the ECG as it shows '''pacemaker spikes''': vertical signals that represent the electrical activity of the pacemaker.
+==Commonly Used Pacemakers==
+The most often used codes are:
+* '''AAI''': The atria are paced, when the intrinsic atrial rhythm falls below the pacemaker's threshold.
+* '''VVI''': The ventricles are paced, when the intrinsic ventricular rhythm falls below the pacemaker's threshold.
+* '''VDD''': The pacemaker senses atrial and ventricular events, but can only pace the ventricle. This type of pacemaker is used in patients with a reliable sinus node, but with an AV-block.
+* '''DDD''': The pacemaker records both atrial and ventricular rates and can pace either chamber when needed.
+* '''DDDR''': As above, but the pacemaker has a sensor that records a demand for higher cardiac output and can adjust the heart rate accordingly.
+* Biventricular pacemakers ('''CRT-P'''): Leads in both ventricles are present for synchronized contraction. The lead pacing the left ventricle is usually positioned in the coronary sinus. This cardiac resynchronization therapy can improve symptoms and survival in some heart failure patients. Several optimizing methods are being evaluated to find the most effective pacing delay between left and right ventricles. They include echocardiography, finding the narrowest QRS, and invasive hemodynamic measurements with pressure and flow wires.
+* '''[[ICD]]''' (Internal Cardioversion Device): This device can detect and treat [[Ventricular Tachycardia]] and [[Ventricular Fibrillation]]. ICDs are a separate category and usually not considered pacemakers although they do have a pacing function. Usually the first treatment is anti-tachy pacing (pacing at a rate +- 10% above the ventricular rate in ventricular tachycardia, which can convert the rhythm to sinus rhythm). If this is not effective, a defibrillator shock is delivered, usually with 16-36 Joules of energy. ICDs can save lives in patients who have a high risk of ventricular arrhythmias. All ICDs have optional pacemaker activity to treat bradycardias. New biventricular ICDs have 3 leads: an atrial lead, a left ventricular lead and a right ventricular lead.
+* Biventricular ICDs ('''CRT-D'''): an ICD with biventricular pacing option.
+{{clr}}
+==Pacemaker Indications==
+A full list of pacemaker indications can be read in the ESC guidelines on cardiac pacing <cite>Vardas</cite>. A selection of class I indications is: chronic symptomatic third- or second degree (Mobitz I or II) atrioventricular block, syncope with sinus node disease, alternating bundle branch block, and persisting AV block after surgery.
-In the first example image, the atria are being paced, but not the ventricles, resulting in a '''atrial paced rhythm'''. Accordingly the ventricular beat is delayed until the atrial signal has passed the AV node. In the second image the ventricles are paced directly, resulting in '''ventricular paced rhythm'''. As ventricular pacing occurs exclusively in the right ventricle the ECG shows a left bundle branch pattern. An exception to this rule is left ventricular pacing in patients with congenital anomalies and patients with an epicardial pacemaker that has been placed during surgery.
+===Atrial-sensed ventricular-paced rhythm===
+===AV dual-paced rhythm===
+[[Image:DVA0968.jpg|thumb|AV-sequencial paced rhythm]]
+{{clr}}
-===Pacemaker Coding===
+==Pacemaker Malfunction==
-Pacemakers can be categorized according to the NASPE coding system, that usually consists of 3-5 letters.
-* The first letter represents the chamber where the signal is "sensed": O=none, A=atria, V=ventricle, D=dual (atrial and / or ventricle)
-* The second letter represents the chamber that is being paced: A=atria, V=ventricle, D=dual (atria and / or ventricle)
-* The third letter represents the action that follows the sensed signal: O = none, T = triggered, I = inhibited (i.e. if the heart beats by itself, the pacemaker is silent) and D = dual (T + I).
-* The fourth letter denotes whether the pacemaker has a fixed rate (0 = none) or has rate modulation (R).
-* The fifth letter indicates whether the pacemaker can pace both the atria and right chamber. This letter is seldomly used.
-===Commonly Used Pacemakers===
+====Failure of appropriate capture, atrial====
-The most often used codes are:
+[[Image:DVA0856.jpg|thumb|Failure of atrial capture in a patient with atrial standstill, no P waves are seen after the atrial stimuli]]
-* '''AAI''': the atria are paced, when the intrinsic atrial rhythm falls below the pacemakers threshold
+[[File:Atrial_capture_loss.svg|thumb|Loss of atrial capture]]
-* '''VVI''': the ventricles are paced, when the intrinsic ventricular rhythm falls below the pacemakers threshold
+{{clr}}
-* '''DDD''': the pacemaker records both the atrial and ventricular rate and can pace one of each chambers when needed.
-* '''DDDR''': as above, but the pacemaker has a sensor that records a demand for higher cardiac output and can adjust the heart rate accordingly.
-* Biventricular pacemakers ('''CRT-D'''): leads in both ventricles are present to synchronize contraction. This cardiac synchronization therapy can improve symptoms and survival in some heart failure patients.
-* '''[[ICD]]''' (Internal Cardioversion Device): this device can detect and treat [[Ventricular Tachycardia]] and [[Ventricular Fibrillation]]. Usually the first treatment is anti-tachy pacing (pacing at a rate +- 10% above the ventricular rate in ventricular tachycardia, which can convert the rhythm to sinus rhythm). If this is not effective an defibrillator shock is delivered, usually with 16-36 Joules of energy. ICDs can save lives in patients who have a high risk of ventricular arrhythmias. All ICDs have optional pacemaker activity to treat bradycardias. New biventricular ICDs have 3 leads: an atrial lead, a left ventricular lead and a right ventricular lead.
-===Pacemaker Indications===
+====Failure of appropriate capture, ventricular====
-A full list of pacemaker indications can be read in the ESC guidelines on cardiac pacing <cite>Vardas</cite>. A selection of class I indications are: chronic symptomatic third- or second degree (Mobtiz I or II) atrioventricular block. Syncope with sinus node disease. Alternating bundle branch block. Persisting AV block after surgery.
+[[File:ECG000020.jpg|thumb|Failure of ventricular capture]]
+[[File:Ventricular_noncapture.svg|thumb|Failure of ventricular capture]]
+{{clr}}
-===ICD Indications===
+====Failure of Appropriate Inhibition, Atrial====
+Failure of appropiate inhibition results from atrial malsensing.
+[[File:atrial_malsensing.svg|thumb|Atrial malsensing. Atrial spikes are present right after spontaneous atrial activity.]]
+{{clr}}
-===Atrial-sensed ventricular-paced rhythm===
+====Failure of Appropriate Inhibition, Ventricular====
-===AV dual-paced rhythm===
+[[File:Ventricular_undersensing.svg|thumb|Failure of Appropriate Ventricular Inhibition, ventricular undersensing]]
-===Pacemaker Malfunction===
+====Failure of Appropriate Pacemaker Firing====
-to be filled in ...
+[[File:Ventricular_oversensing.svg|thumb|Failure of appropiate ventricular firing due to ventricular oversensing]]
-====Failure of appropriate capture, atrial====
+[[File:Atrial_malsensing.svg|thumb|Atrial malsensing]]
-====Failure of appropriate capture, ventricular====
+====Retrograde Atrial Activation====
-====Failure of appropriate inhibition, atrial====
+====Pacemaker Mediated Tachycardia====
-====Failure of appropriate inhibition, ventricular====
+[[Image:DVA1225.jpg|thumb|Pacemaker Mediated Tachycardia, successfully terminated by withholding a ventricular pace, followed by an atrial pace]]
-====Failure of appropriate pacemaker firing====
+[[File:Pacemaker_mediated_tachycardia.svg|thumb|Pacemaker mediated tachycardia]]
-====Retrograde atrial activation====
+[[File:Termination_of_pmt.svg|thumb|Termination of pacemaker mediated tachycardia]]
-====Pacemaker mediated tachycardia====
+{{clr}}
+{{clr}}
+{{Box|
 ==External Links==
 [http://www.hrsonline.org/swPositionStatementFiles/ps101036428.asp Heart Rhytm Society]
+}}{{clr}}{{Box|
 ==References==
 <biblio>
 #Vardas pmid=17726042
+#Gregoratos pmid=12379588
+#Bernstein pmid=11916002
 </biblio>
-</biblio>
+}}
 {{clr}}
+[[Category:ECG Textbook]]

Pacemaker: Difference between revisions

Latest revision as of 17:32, 24 June 2010

Contents

Pacemaker Coding

Commonly Used Pacemakers