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Pacemaker. Cardiology for Dr. Pelaez By Sai Kumar Reddy American International Medical University, St.Lucia. Pacemaker.
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Pacemaker Cardiology for Dr. Pelaez By Sai Kumar Reddy American International Medical University, St.Lucia
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.
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
I 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