Cardiology for Dr. PelaezBy Sai Kumar Reddy

American International Medical University, St.Lucia

Pacemaker

Pacemaker• A pacemaker is a battery-powered device

about the size of a pocket watch that sends weak electrical impulses to “set a pace” so that the heart is able to maintain a regular heartbeat.

Anatomy & Physiology of Pacemaker

Types of Pacemakers

• Single-chamber pacemakers stimulate one chamber of the heart, either an atrium or more often a ventricle.

• Dual-chamber pacemakers send electrical impulses to both the atrium and the ventricle and pace both chambers. A dual-chamber pacemaker synchronizes the rhythm of the atria and ventricles in a pattern that closely resembles the natural heartbeat.

Indications for Pacemaker

• Absolute indications– Sick sinus syndrome– Symptomatic sinus bradycardia– Tachy-brady syndrome– Afib with slow ventricular response– 3rd degree heart block– Chronotropic incompetence• Inability to increase heart rate to match exercise

– Prolonged QT syndrome

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Relative indications are:– Cardiomyopathy• Dilated• Hypertrophic

– Severe refractory neurocardiogenic syncope– Paroxysmal atrial fibrillation

Pacemaker defects

• EKG abnormalities due to– Failure to output– Failure to capture– Sensing abnormalities– Operative failures

Pacemaker Failure to Output

• Definition– No pacing spike present despite indication to pace

• Etiology– Battery failure, lead fracture, break in lead

insulation, oversensing, poor lead connection.• Atrial output is sensed by ventricular lead

Pacemaker Failure to Capture

• Definition– Pacing spike is not followed by either an atrial or

ventricular complex• Etiology– Lead fracture or dislodgement, break in lead

insulation, elevated pacing threshold, MI at lead tip, drugs, metabolic abnormalities, cardiac perforation, poor lead connection

Pacemaker Sensing Abnormalities

• Oversensing– Senses noncardiac electrical activity and is inhibited

from correctly pacing– Etiology

• Muscular activity (diaphragm or pecs), EMI, cell phone held within 10cm of pulse generator

• Undersensing– Incorrectly misses intrinsic depolarization and paces– Etiology

• Poor lead positioning, lead dislodgement, magnet application, low battery states, MI

Pacemaker Complications

• Pacemaker syndrome– Patient feels worse after pacemaker placement– Presents with progressive worsening of CHF

symptoms– Due to loss of atrioventricular synchrony, pathway

now reversed and ventricular origin of beat

Pacemaker Operative Failures

• Due to pacemaker placement– Pneumothorax– Pericarditis– Perforated atrium or ventricle– Dislodgement of leads– Infection or erosion of pacemaker pocket– Infective endocarditis (rare)– Venous thrombosis

Electromagnetic Interference

• Can interfere with function of pacemaker • Device misinterprets the EMI causing– Rate alteration– Sensing abnormalities– Asynchronous pacing– Noise reversion– Reprogramming

Electromagnetic Interference

• Examples– Metal detectors– Cell phones– High voltage power lines– Some home appliances (microwave)

Caution

• If you have a pacemaker, you are not supposed to have an MRI (magnetic resonance imaging) test.

Advancement of Technology in Medicine

• Newer pacemakers also can monitor your blood temperature, breathing, and other factors and adjust your heart rate to changes in your activity.

Case • CC: Chills, rigors• HPI:– 65 yom c/o fevers, chills, rigors x 1 day. Positive n/v and

anorexia. Pt states he had recent pacemaker insertion 4 days ago for an arrhythmia.

• PMH:– HTN– Arrythmia– Hypercholesterolemia

• PSHx:– As stated above

Case

• Physical exam– Temp 101.2, HR 110, BP 90/55– EKG

– Diagnosis?

Case

• Pocket Infection• Pacemaker insertion is a surgical procedure– 1% risk for bacteremia– 2% risk for pocket infection

• Usually occurs within 7 days of pacemaker insertion

• May have tenderness and redness over pacemaker site

References• Emedicine

– http://www.emedicine.com/emerg/topic805.htm• Minish, Travis. Pacemaker Emergencies.

– http://www.cgi.ualberta.ca/emergency/rounds/files/pacers3.ppt • The Implantable Pacemaker, a short historical overview.

– http://igitur-archive.library.uu.nl/dissertations/2006-0426-200006/c1.pdf • Healthy Hearts

– http://www.healthyhearts.com/pacemaker.htm• Medtronic

– http://www.medtronic.com/patients/heart.html• Shelton State University

– http://www.sheltonstate.edu/userfiles/File/faculty/s%20warren/NUR%20202%20EKG%20Dysrrhythmias-Sinus,%20Atrial,%20Junctional,%20Vent%20.pdf

• Google Images– http://images.google.com

Thank You