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.

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 – 3 rd 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 – Minish, Travis. Pacemaker Emergencies. – The Implantable Pacemaker, a short historical overview. – Healthy Hearts – Medtronic – Shelton State University – 20Dysrrhythmias-Sinus,%20Atrial,%20Junctional,%20Vent%20.pdf 20Dysrrhythmias-Sinus,%20Atrial,%20Junctional,%20Vent%20.pdf Google Images –