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Pacemaker: Difference between revisions
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* '''AAI''': The atria are paced, when the intrinsic atrial rhythm falls below the pacemaker's threshold. | * '''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. | * '''VVI''': The ventricles are paced, when the intrinsic ventricular rhythm falls below the pacemaker's threshold. | ||
* '''VDD''': The pacemaker senses | * '''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 | * '''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. | * '''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 | * 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. | * '''[[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. | * Biventricular ICDs ('''CRT-D'''): an ICD with biventricular pacing option. | ||
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===Atrial-sensed ventricular-paced rhythm=== | ===Atrial-sensed ventricular-paced rhythm=== | ||
===AV dual-paced rhythm=== | ===AV dual-paced rhythm=== | ||
[[Image:DVA0968.jpg|thumb|AV-sequencial paced rhythm]] | |||
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==Pacemaker Malfunction== | |||
====Failure of appropriate capture, atrial==== | ====Failure of appropriate capture, atrial==== | ||
[[Image:DVA0856.jpg|thumb|Failure of atrial capture in a patient with atrial standstill, no P waves are seen after the atrial stimuli]] | [[Image:DVA0856.jpg|thumb|Failure of atrial capture in a patient with atrial standstill, no P waves are seen after the atrial stimuli]] | ||
[[File:Atrial_capture_loss.svg|thumb|Loss of atrial capture]] | |||
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====Failure of appropriate capture, ventricular==== | ====Failure of appropriate capture, ventricular==== | ||
[[File:ECG000020.jpg|thumb|Failure of ventricular capture]] | [[File:ECG000020.jpg|thumb|Failure of ventricular capture]] | ||
[[File:Ventricular_noncapture.svg|thumb|Failure of ventricular capture]] | |||
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====Failure of Appropriate Inhibition, Atrial==== | ====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.]] | |||
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====Failure of Appropriate Inhibition, Ventricular==== | ====Failure of Appropriate Inhibition, Ventricular==== | ||
[[File:Ventricular_undersensing.svg|thumb|Failure of Appropriate Ventricular Inhibition, ventricular undersensing]] | |||
====Failure of Appropriate Pacemaker Firing==== | ====Failure of Appropriate Pacemaker Firing==== | ||
[[File:Ventricular_oversensing.svg|thumb|Failure of appropiate ventricular firing due to ventricular oversensing]] | |||
[[File:Atrial_malsensing.svg|thumb|Atrial malsensing]] | |||
====Retrograde Atrial Activation==== | ====Retrograde Atrial Activation==== | ||
====Pacemaker Mediated Tachycardia==== | ====Pacemaker Mediated Tachycardia==== | ||
[[Image:DVA1225.jpg|thumb|Pacemaker Mediated Tachycardia, successfully terminated by withholding a ventricular pace, followed by an atrial pace]] | |||
[[File:Pacemaker_mediated_tachycardia.svg|thumb|Pacemaker mediated tachycardia]] | |||
[[File:Termination_of_pmt.svg|thumb|Termination of pacemaker mediated tachycardia]] | |||
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{{Box| | {{Box| | ||