B.28 Pacemaker Flashcards
B.28 Pacemaker
define
A pacemaker is a device that delivers electrical impulses to the heart to maintain an adequate heart rate when the intrinsic cardiac conduction system fails.
B.28 Pacemaker
define Permanent Pacemakers
capable of pacing the heart to maintain an adequate heart rate in bradyarrhythmia
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define Automated implantable cardioverter defibrillators (AICDs)
Capable of delivering shocks to terminate ventricular tachyarrhythmia
Transvenous AICDs are also capable of pacing the heart to maintain an adequate heart rate in bradyarrhythmia
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define Cardiac resynchronization therapy devices (CRTs)
capable of pacing both RV and LV to improve cardiac output in heart failure and pace the heart to maintain an adequate heart rate in bradyarrhythmia
- Cardiac resynchronization therapy pacemaker (CRT-P): biventricular pacemaker only
- Cardiac resynchronization therapy defibrillator (CRT-D): biventricular pacemaker and AICD
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set-up
Pulse generator: a thin metal case containing a power source to produce electrical impulses and a programmable computer
- Size: ∼ 5 cm across
- Battery life is usually 5–10 years depending on use (e.g., pacing rate, shock frequency).
Leads with electrodes for pacing, sensing, and defibrillating
- Proximal end: connected to the pulse generator
- Distal end: anchored to the myocardium
- Single-chamber PPM: usually right ventricle
- Dual-chamber PPM: right ventricle and right atrium
- ICD: right ventricle with or without right atrium
- CRT: right atrium, right ventricle, and coronary sinus
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basic functions of pacemaker
- Electrodes sense the heart’s electrical activity and transmit it to the pulse generator.
- The pulse generator identifies arrhythmias.
- Electrodes transmit electrical impulses from the pulse generator to the myocardium to pace or cardiovert.
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Implantation
- Leads are inserted into the right ventricle and, in some cases, the right atrium, usually transvenously via the cephalic, axillary, or subclavian vein.
- In biventricular pacemakers, the lead to stimulate the left ventricle is inserted into the coronary sinus.
- In most cases, the generator is implanted on the patient’s nondominant side between the pectoral muscle and the muscle fascia.
B.28 Pacemaker
What are the different types of Permanent Pacemakers (PPMs)
Single-chamber pacemaker: one lead, usually in the right ventricle
Dual-chamber pacemaker: two leads, one in the right atrium and one in the right ventricle
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Function of Permanent Pacemakers (PPMs)
- Cardiac rhythm monitoring
- Antibradycardia pacing
Pacing of the heart if the heart rate drops below a preset threshold
Achieved by delivering an electrical impulse to stimulate myocardial contraction - Both of the following requirements must be met for minimum PPM functioning:
Electrical capture: a pacemaker spike with corresponding ventricular depolarization
Mechanical capture: a cardiac contraction and pulse resulting from electrical capture
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Indications for Permanent Pacemakers (PPMs)
Sinus node dysfunction (SND)
- SND with symptomatic bradycardia
- Symptomatic chronotropic incompetence
- Symptomatic bradycardia due to tachycardia-bradycardia syndrome
- Selected patients with sinoatrial exit block and significant symptoms
AV block
- High-risk AV block
- AV block with symptomatic bradycardia
- Permanent Afib with symptomatic bradycardia
- Certain AV blocks resulting from neuromuscular disease or infiltrative cardiomyopathy
Other causes of syncope:
selected patients with carotid sinus syndrome
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What is the 5 letter system for Permanent Pacemakers (PPMs)
1st letter: chamber(s) that are paced, i.e., A = atrium, V = ventricle, D = dual
2nd letter: chamber(s) that are sensed, i.e., A = atrium, V = ventricle, D = dual
3rd letter: device’s response to sensing native beats, i.e., I = inhibited, T = triggered, D = dual
The 4th and 5th letters are less commonly communicated and denote device programmability and any antitachycardia pacing functions, respectively.
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ECG findings with Permanent Pacemakers (PPMs)
Pacemaker spike: a narrow upward deflection usually with an amplitude of < 5 mm
Ventricular depolarizations that indicate electrical capture
- Paced ventricular beats: wide QRS, often with LBBB morphology, followed by T wave
- Ventricular depolarizations triggered by paced atrial beats: may appear normal if the His-Purkinje conduction system is intact
Fusion beats (e.g., fusion of native beat and PPM beat) and capture beats may be preset
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what would you see on ECG with a DDD pacemaker
DDD pacemaker (most common): senses and paces both chambers; can inhibit impulses to either chamber if native atrial or ventricular beats are sense
- Pacemaker spikes can occur before P waves and QRS complexes.
- No intrinsic electrical activity: results in sequential AV pacing with a paced P wave followed by a paced QRS complex
- AV block with intrinsic sinus node activity: a normal P wave followed by a paced QRS complex
- No sinus node activity with normal AV conduction: paced P wave followed by a normal QRS complex
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VVI pacemaker ECG findings
paced QRS complexes and dissociated P waves
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What are common scienerios where pacemakers are used
Complete AV block → DDD or VVI pacemaker
AF with slow ventricular response → VVI
Sick sinus syndrome with intact AV node → AAI or DDD
Post-cardiac surgery bradyarrhythmias → temporary pacing
HFrEF with LBBB → CRT-P or CRT-D
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Complications
lead dislodgement or fracture
Infection (pocket or endocarditis)
Pacemaker syndrome (AV dyssynchrony → fatigue, dizziness)
Electromagnetic interference (MRI, cautery)
Failure to pace / sense / capture
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Cardiac Resynchronization Therapy
Cardiac Resynchronization Therapy (Bi-Ventricular Pacemaker): A three-chamber pacemaker utilized in the treatment of symptomatic chronic heart failure to enhance cardiac function.
Indications:
- Heart failure NYHA class II-IV with EF ≤ 35%
- Dilated cardiomyopathy
- LBBB with QRS duration > 160 ms
May be used in conjunction with an ICD.
