Evolution of Pacemakers and Defibrillators: A Comprehensive Guide

1. Pacemakers and Implanted Defibrillators Mike Harlan

2. History • Pacemakers • It is believed that Dr. Albert Hyman was inventor of first pacemaker • First fully functional wearable pacemaker developed in 1957 • First implanted pacemaker 1960 • ICD’s • First implantable ICD developed by Michel Mirowski, first used in a human in 1980 • FDA approved use of ICD’s in 1985

3. Artificial Pacemakers • An internal artificial pacemaker is a small battery-operated device that helps the heart beat in a regular rhythm • An electrode is placed next to the heart wall, and small electrical charges travel through the wire to the heart (usually the right side), causing it to contract. • Most modern pacemakers have a sensing device that turns the pacemaker off when the natural heartbeat is above a certain level

4. Types of Pacemakers • Fixed-rate – fires continuously at a preset rate • Demand – contain a sensing device, fire only when heart rate drops below a set rate • Dual-chambered – stimulates the atria first and then the ventricle

5. Pacemaker Indications • Absolute Indications • Sick sinus rhythm • Symptomatic sinus bradycardia • Tachy-brady syndrome • Atrial Fibrillation with slow ventricular response • Third Degree Heart Block • Chronotropic incompetence • Prolonged QT syndrome

6. Relative Indications Cardiomyopathy Severe refractory neurocardiogenic syncope Paroxysmal atrial fibrillation Results of a recent study showed that pt’s with pacemakers had a one-year recurrence rate of syncope of 19%, compared to 60% of pt’s in the control group

7. Pacemaker Complications • Infection • Thrombophlebitis • Blood clot causes inflammation in vein • Pacemaker Syndrome • Phenomenon where a pt. feels worse after pacemaker placement and presents with progressive worsening of symptoms of CHF • Failure to output • Failure to capture • Failure to sense correctly

8. Internal Cardiac Defibrillators • ICD’s have wires connecting to one or more heart chambers. The wires monitor heart rhythm and deliver shocks to the heart when abnormal rhythm is sensed. • Single chamber ICD’s – wires connect to one or both ventricles • Dual-chamber ICD’s – wires connect to both an atrium and a ventricle • Wires of an ICD connect to small metal box that contains a battery, pulse generator, and computer • ICD’s are indicated for pt’s with hx of life-threatening ventricular tachyarrhythmias or VF • A recent study showed that pt’s that received an ICD had a 31% reduction in mortality rate.

9. ICD complications • Most common problem is that they shock when not needed. This can damage the heart or trigger an irregular heartbeat • Swelling, bruising, or infection after surgery

10. Treatment of pt’s with pacemakers or ICD’s • The presence of a pacemaker or ICD does not alter the emergency treatment of patients • Defibrillation, cardioversion, and pacing can be performed on pt’s with pacemakers or ICD’s • Try to place pads a safe distance (10cm) from a pacemaker or ICD if possible, but don’t delay treatment • A magnet can be placed over the pulse generator to reset the pacemaker to a predetermined rate. This is indicated if a pt. has a runaway pacemaker

11. References • Bledsoe B, Porter R, Cherry R. Essentials of Paramedic Care. Second Edition. Prentice Hall; 2007 • http://emedicine.medscape.com/article/780825-print • http://www.nhlbi.nih.gov/health/dci/Diseases/icd.html • http://emedicine.medscape.com/article/162245-overview • Gregoratos G, Indications and Recommendations for Pacemaker Therapy. American Family Physician, 2005