Pacemaker for beginners KITA yosuke Iizuka Hospital

Objectives  Review basic pacemaker terminology and function  Discuss diagnosis and management of pacemaker emergencies

Historical Perspective  Electrical cardiac pacing for the management of brady-arrhythmias was first described in 1952  Permanent transvenous pacing devices were first introduced in the early 1960’s

Pacemaker Components  Pulse Generator  Electronic Circuitry  Lead system

Pulse Generator  Lithium-iodine cell is the current standard battery  Advantages:  Long life – 4 to 10 years  Output voltage decreases gradually with time making sudden battery failure unlikely

Electronic Circuitry  Determines the function of the pacemaker itself  Utilizes a standard nomenclature for describing pacemakers

Pacemaker Nomenclature IIIIIIIVV Chamber Paced Chamber Sensed Response to Sensing Rate Modulation, Programmability Anti- tachycardia Features A=Atrium T=TriggeredP=SimpleP=Pacing V=Ventricle I=InhibitedM=Multi- programmable S=Shock D=Dual R=Rate AdaptiveD=Dual O=None C=Communicating O=None

Lead Systems  Endocardial leads which are inserted using a subclavian vein approach  Actively fixed to the endocardium using screws or tines  Unipolar or bipolar leads

Electrocardiogram During Cardiac Pacing  Pacemaker has two main functions:  Sense intrinsic cardiac electrical activity  Electrically stimulate the heart  VVI- senses intrinsic cardiac activity in the ventricle and when a preset interval of time with no ventricular activity occurs it depolarizes the right ventricle causing ventricular contraction

Pacer spike

Electrocardiogram  Dual chamber pacer is more complicated because the pacer has the ability to both sense and pace either the atrium or the ventricle  Possible to have only atrial, only ventricular or both atrial and ventricular pacing  DDD pacer is a common example of this

Atrial Spike Ventricular Spike

AV Pacing Ventricular Pacing

Magnet Placement  The EKG technician should perform a 12 lead cardiogram and then a rhythm strip with a magnet over the pacer  Often a very poorly understood concept by the non-cardiologist  Does not inactivate the pacer as is commonly believed  Activate a lead switch present in the pacemaker which converts the pacer to a asynchronous or fixed-rate pacing mode  Inhibits the sensing function of a pacemaker

Class I Indications For Permanent Pacing  Third degree AV block associated with:  Symptomatic bradycardia  Symptomatic bradycardia secondary to drugs required for dysrhythmia management  Asystole > 3 seconds or escape rate < 40  After catheter ablation of the AV node  Post-op AV block not expected to resolve  Neuromuscular disease with AV block

Indications  Symptomatic bradycardia from second degree AV block  Bifascicular or trifascicular block with intermittent third degree or type II second degree block  Sinus node dysfunction with symptomatic bradycardia  Recurrent syncope caused by carotid sinus stimulation

Indications  Post myocardial infarction with any of:  Persistent second degree AV block with bilateral bundle branch block or third degree AV block  Transient second or third degree AV block and bundle branch block  Symptomatic, persistent second or third degree AV block

Infections  Pacemaker insertion is a surgical procedure:  1% risk for bacteremia  2% risk for wound or pocket infection  Usually occur soon after pacer insertion  Presence of a foreign body complicates management

Infection  Cellulitis or pocket infection:  Tenderness and redness over the pacemaker itself  Avoid performing a needle aspiration – damage the pacer  Bacteremia: Staphylococcus  aureus and Staphylococcus epi 60-70% of the time  Empiric antibiotics should include vancomycin pending culture

Infection  Consult the pacemaker physician  Draw blood cultures  Give appropriate antibiotics  Frequently the pacer and lead system need to be removed

Case 1  67 year old male presents to the emergency room 12 hours after insertion of a pacemaker complaining of left sided chest pain and shortness of breath  PR96, RR 33, BP 125/85, Oxygen saturation 88% RA  CXR as shown

Pneumothorax  Occurs during cannulation of the subclavian vien  Incidence - ?? Cardiologist dependent  Treatment:  Asymptomatic or small – observation  Symptomatic or large – tube thoracostomy  Notify the pacemaker physician

Case 2  72 year old male presents to the emergency room after a fall, tripped over a bath mat, no LOC  Shortened and rotated left leg  Past history – pacemaker, hypertension  Nurse does an routine pre-op CXR and EKG

Septal Perforation  Usually identified at the time of pacer insertion but leads can displace after insertion  Can occur with transvenous pacer insertion  Keys diagnosis are a RBBB pattern on EKG and a pacer lead displaced to the apex of the heart on CXR

Septal Perforation  Management:  Notify the pacer service  Pacer wire has to be removed but not emergently  Small VSD which heals spontaneously

Conclusions  Pacemakers are becoming more common everyday  We need to understand basic pacing terminology and modes to treat patients effectively.  Most pacer malfunctions are due to failure to sense, failure to capture, over-sensing, or in- appropriate rate  Standard ACLS protocols apply to all unstable patients with pacemakers.