Difference between revisions of "Pacemaker"
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Revision as of 15:24, 2 June 2009
|Author(s)||J.S.S.G. de Jong|
|Moderator||J.S.S.G. de jong|
|some notes about authorship|
- 1 Pacemaker Coding
- 2 Commonly Used Pacemakers
- 3 Pacemaker Indications
- 3.1 ICD Indications
- 3.2 Atrial-sensed ventricular-paced rhythm
- 3.3 AV dual-paced rhythm
- 3.4 Pacemaker Malfunction
- 3.4.1 Failure of appropriate capture, atrial
- 3.4.2 Failure of appropriate capture, ventricular
- 3.4.3 Failure of appropriate inhibition, atrial
- 3.4.4 Failure of appropriate inhibition, ventricular
- 3.4.5 Failure of appropriate pacemaker firing
- 3.4.6 Retrograde atrial activation
- 3.4.7 Pacemaker mediated tachycardia
- 4 External Links
- 5 References
Pacemakers can be categorized according to the NASPE coding system, that usually consists of 3-5 letters.
|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 pacemakers threshold
- VVI: the ventricles are paced, when the intrinsic ventricular rhythm falls below the pacemakers threshold
- VDD: the pacemaker senses the atrial en ventriculair events, but can only pace the ventricle. This type of pacemaker is used in patients with a reliable sinus node, but suffering from the results of an AV-block.
- 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-P): leads in both ventricles are present to synchronize 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 ventricle, they include echocardiography, narrowest QRS finding 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 seperate category and usually not put in the pacemaker category, 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 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.
- Biventricular ICDs (CRT-D): an ICD with biventricular pacing option.
A full list of pacemaker indications can be read in the ESC guidelines on cardiac pacing . 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.
Atrial-sensed ventricular-paced rhythm
AV dual-paced rhythm
to be filled in ...
Failure of appropriate capture, atrial
Failure of appropriate capture, ventricular
Failure of appropriate inhibition, atrial
Failure of appropriate inhibition, ventricular
Failure of appropriate pacemaker firing
Retrograde atrial activation
Pacemaker mediated tachycardia