1 / 21

External Pacemakers

External Pacemakers. Rafael Ortega, MD Boston University Medical Center. From the Trenches. 70-year-old woman Returns to OR for expanding neck hematoma Cardiac arrest after intubation Management. OBJECTIVES. Review External Pacemakers (EP) Summarize EP historical evolution

benny
Download Presentation

External Pacemakers

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. External Pacemakers Rafael Ortega, MD Boston University Medical Center

  2. From the Trenches • 70-year-old woman • Returns to OR for expanding neck hematoma • Cardiac arrest after intubation • Management

  3. OBJECTIVES • Review External Pacemakers (EP) • Summarize EP historical evolution • Clarify EP indications • Explain the Philips/Agilent HeartStart Unit

  4. 3 in 1 Biphasic Unit Manual Defibrillator Automatic Defibrillator External Pacemaker

  5. Question What is “Biphasic”?

  6. A Few Words on “Biphasic” • Biphasic energy is delivered in two directions • Require less energy for defibrillation • Less myocardial injury and myocardial dysfunction • 150 J should be used for defibrillating ventricular fibrillation (in adults)

  7. Waveform Comparison • Monophasic • Biphasic

  8. Indications for EP • Temporizing measure in patients with symptomatic bradycardia • Little benefit in pulseless situations • May be useful for overdrive-pacing in certain tachycardias.

  9. Early History • 1791: Galvani electrically stimulates dead frog’s heart • 1872: Duchenne resuscitates child tapping precordium with an electrode • 1932: Hyman designs external pulse generator: "artificial cardiac pacemaker“ • 1952: Zoll uses simultaneous precordial and transesophageal electrodes for pacing

  10. 46 Years later • Hesselvik JF. Ortega RA. Simultaneous transesophageal atrial pacing and transesophageal echocardiography in cardiac surgical patients.Journal of Cardiothoracic & Vascular Anesthesia. 12(3):281-3, 1998 Jun.

  11. Who was Dr. Zoll? • A Boston native • Harvard Medical School • Internship BI Hospital • In 1939 joins a research group at BI • WW-ll on Dwight Harken's surgical team Paul Zoll Professor Emeritus HMS

  12. Transvenous Pacing Effect • Temporary and permanent implantable transvenous pacemakers (late 1950’s) superseded the use of external models. • But, these took time to insert • There was still a need for external pacing

  13. 1981: A New Era • Zoll patents and introduces a transcutaneous external pacemaker • Longer pulse duration and larger electrode surface • Reduced current required for capture and increased comfort for the patient • New model could be applied much more rapidly

  14. Pulse Duration and Current • Early models used short (1-2 msec) impulses resembling the action potential of skeletal muscles • Zoll increased duration to 4 msec with a 3-fold reduction in threshold • Stimulation 20% over threshold stimulates only the ventricles. • External pacing requires 30-100 times greater current than transvenous pacing

  15. Question What is the effect of EP on hemodynamics?

  16. Hemodynamics • EP can simultaneously stimulate all 4 heart chambers (in dogs) • Madsen echo demonstrated that atrial stimulation was retrograde without opening the mitral valve. • Atrial-pacing threshold in humans is much higher than for ventricles • Net result: loss of the “atrial kick” • Cardiac output is reduced

  17. Reducing Discomfort • Not a problem under GA • If awake, place electrodes in the midline chest and just below the left scapula • Considered sedation

  18. Question Can you perform CPR and use EP at the same time?

  19. EP During CPR • CPR can be performed with EP pads in place. • No electrical hazard to the person performing CPR • However, turning the unit off during CPR is advisable.

  20. No Heart Damage • No enzymatic, EKG, or microscopic evidence of myocardial damage has been found after pacing (dogs and humans) for as long as 60 minutes • Low risk of triggering ventricular fibrillation

  21. Tutorial

More Related