Essentials for pacemakers and ICD's-2...The new england journal of medicine n engl j med nejm.org 1...

Essentials of Pacemakers and ICD’s

Rajesh Banker, MD, MPH

• Stimulate cardiac depolarization • Sense intrinsic cardiac function • Respond to increased metabolic demand by

providing rate responsive pacing • Provide diagnostic information stored by the

pacemaker

Pacemakers have 4 basic functions:

3

Pacemaker Indications:

• Indications are primarily symptom based: • Symptomatic Sinus Node dysfunction • Symptomatic 2nd or 3rd degree heart block

• More uncommonly, prophylaxis can be considered as well

• Sinus Nodal dysfunction or high grade heart block with very low baseline heart rates (<35)

• Bradycardia dependent ventricular tachyarrhythmia

Implantable pulse generator (IPG)

Lead wire(s)

Components

Courtesy www.medtronicacademy.com

• Contains a battery that provides the energy for sending electrical impulses to the heart

• Houses the circuitry that controls pacemaker operations

Circuitry

Battery

The Pulse Generator:


• Deliver electrical impulses from the pulse generator to the heart

• Sense cardiac depolarization

Lead

Leads Are Insulated Wires That:


• Endocardial or transvenous leads • Myocardial/Epicardial leads

Types of Leads

Transvenous Leads Have Different “Fixation” Mechanisms

• Passive fixation – The tines become

lodged in the trabeculaeof the heart


Transvenous Leads

• Active Fixation – The helix (or screw)

extends into the endocardial tissue

– Allows for lead positioning anywhere in the heart’s chamber


Myocardial and Epicardial Leads

• Leads applied directly to the heart

– Fixation mechanisms include:

�Epicardial stab-in �Myocardial screw-in �Suture-on


• Pulse generator: power source or battery

• Leads or wires • Cathode (negative

electrode) • Anode (positive

electrode) • Body tissue

IPG

Lead

Anode

Cathode

Pacemaker Components Combine with Body Tissue to Form a Complete Circuit


• Begins in the pulse generator

• Flows through the lead and the cathode (–)

• Stimulates the heart • Returns to the anode (+)

During Pacing, the Impulse:

Impulse onset*


• Flows through the tip electrode (cathode)

• Stimulates the heart • Returns through body

fluid and tissue to the IPG (anode)

A Unipolar Pacing System Contains a Lead with Only One Electrode Within the Heart; In This System, the Impulse:

Cathode

Anode

-

+


Anode

• Flows through the tip electrode located at the end of the lead wire

• Stimulates the heart • Returns to the ring

electrode above the lead tip

A Bipolar Pacing System Contains a Lead with Two Electrodes Within the Heart. In This System, the Impulse:

Cathode


Unipolar leads

• Unipolar leads may have a smaller diameter lead body than bipolar leads

• Unipolar leads usually exhibit larger pacing artifacts on the surface ECG


Bipolar leads

• Bipolar leads are less susceptible to oversensing noncardiac signals (myopotentials and EMI)

Coaxial Lead Design


Rate Responsive Pacing

�When the need for oxygenated blood increases, the pacemaker ensures that the heart rate increases to provide additional cardiac output

Adjusting Heart Rate to Activity

Normal Heart Rate

Rate Responsive PacingFixed-Rate Pacing

Daily Activities


A Variety of Rate Response Sensors Exist

• Those most accepted in the market place are: – Activity sensors that detect physical movement and increase the rate

according to the level of activity – Minute ventilation sensors that measure the change in respiration rate and

tidal volume via transthoracic impedance readings


• Activity sensors employ a piezoelectric crystal that detects mechanical signals produced by movement

• The crystal translates the mechanical signals into electrical signals that in turn increase the rate of the pacemaker

Piezoelectric crystal



• Minute ventilation can be measured by measuring the changes in electrical impedance across the chest cavity to calculate changes in lung volume over time

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Position Function

1 Chambers Paced

2 Chambers

Sensed

3 Response to

Sensed Stimulus

4 Rate

Modulation?

O (none) O O O (non-rate responsive)

A (atrium) A T (triggered) R (rate responsive)

V (ventricle) V I (inhibited)

D (both atrium & ventricle)



Pacemaker Codes

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Pacemaker Complications:

Pneumothorax

Pericarditis

Perforation of the atrium or ventricle

Lead Dislodgement

Venous thrombosis

Infection

Problems with PacemakersFailure to Capture

Causes: • Threshold rise (electrolytes, drugs) • Lead dislodgement • Lead fracture • RV infarct

Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005.

Problems with PacemakersFailure to Pace

Causes: • Oversensing • Battery failure • Internal insulation failure • Conductor coil fracture


Problems with PacemakersFailure to Sense

Causes: • Undersensing • Lead Fracture


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What’s next for pacemakers?

Leadless Pacemakers St. Jude Medical and Medtronic devices have concluded their clinical trials

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Approval expected this year

T h e n e w e ngl a nd j o u r na l o f m e dic i n e

n engl j med nejm.org 1

From the Icahn School of Medicine at Mount Sinai (V.Y.R., S.R.D.) and Weill Cornell Medical Center ( J.E.I.) — both in New York; Libin Cardiovascular Institute of Alberta, Calgary, Canada (D.V.E.); Cleveland Clinic, Cleveland (D.J.C.); Keck Hospital of University of Southern Cali-fornia, Los Angeles (R.D.), and Premier Cardiology, Newport Beach (R.B.) — both in California; Intermountain Medi-cal Center Heart Institute, Salt Lake City, (T.J.B.); Central Baptist Hospital, Lexing-ton, KY (G.F.T.); Mayo Clinic, Rochester, MN (P.A.F.); Tufts University School of Medicine, Boston (N.A.M.E.); Sparrow Clinical Research Institute, Lansing, MI (J.I.); Aurora Medical Group, Milwaukee (I.N.); Naples Community Hospital, Na-ples, FL (K.P.); and Methodist University Hospital, Memphis, TN (J.P.). Address reprint requests to Dr. Reddy at the Icahn School of Medicine at Mount Sinai, 1 Gus-tave L. Levy Pl., Box 1030, New York, New York 10029, or at vivek . reddy@ mountsinai . org.

*A complete list of investigators in the LEADLESS II study is provided in the Supplementary Appendix, available at NEJM.org.

This article was published on August 30, 2015, at NEJM.org.

DOI: 10.1056/NEJMoa1507192Copyright © 2015 Massachusetts Medical Society.

BACKGROUNDCardiac pacemakers are limited by device-related complications, notably infection and problems related to pacemaker leads. We studied a miniaturized, fully self-con-tained leadless pacemaker that is nonsurgically implanted in the right ventricle with the use of a catheter.

METHODSIn this multicenter study, we implanted an active-fixation leadless cardiac pacemaker in patients who required permanent single-chamber ventricular pacing. The primary efficacy end point was both an acceptable pacing threshold (≤2.0 V at 0.4 msec) and an acceptable sensing amplitude (R wave ≥5.0 mV, or a value equal to or greater than the value at implantation) through 6 months. The primary safety end point was free-dom from device-related serious adverse events through 6 months. In this ongoing study, the prespecified analysis of the primary end points was performed on data from the first 300 patients who completed 6 months of follow-up (primary cohort). The rates of the efficacy end point and safety end point were compared with perfor-mance goals (based on historical data) of 85% and 86%, respectively. Additional outcomes were assessed in all 526 patients who were enrolled as of June 2015 (the total cohort).

RESULTSThe leadless pacemaker was successfully implanted in 504 of the 526 patients in the total cohort (95.8%). The intention-to-treat primary efficacy end point was met in 270 of the 300 patients in the primary cohort (90.0%; 95% confidence interval [CI], 86.0 to 93.2, P = 0.007), and the primary safety end point was met in 280 of the 300 patients (93.3%; 95% CI, 89.9 to 95.9; P<0.001). At 6 months, device-related serious adverse events were observed in 6.7% of the patients; events included device dislodgement with percutaneous retrieval (in 1.7%), cardiac perforation (in 1.3%), and pacing-threshold elevation requiring percutaneous retrieval and device replace-ment (in 1.3%).

CONCLUSIONSThe leadless cardiac pacemaker met prespecified pacing and sensing requirements in the large majority of patients. Device-related serious adverse events occurred in ap-proximately 1 in 15 patients. (Funded by St. Jude Medical; LEADLESS II ClinicalTrials .gov number, NCT02030418.)

A BS TR AC T

Percutaneous Implantation of an Entirely Intracardiac Leadless Pacemaker

Vivek Y. Reddy, M.D., Derek V. Exner, M.D., M.P.H., Daniel J. Cantillon, M.D., Rahul Doshi, M.D., T. Jared Bunch, M.D., Gery F. Tomassoni, M.D., Paul A. Friedman, M.D., N.A. Mark Estes III, M.D., John Ip, M.D., Imran Niazi, M.D., Kenneth Plunkitt, M.D., Rajesh Banker, M.D.,

James Porterfield, M.D., James E. Ip, M.D., and Srinivas R. Dukkipati, M.D., for the LEADLESS II Study Investigators*

Original Article

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Implantable Cardioverter Defibrillators

All modern defibrillators have all the functions a pacemaker plus:

The ability to pace terminate or defibrillate ventricular tachyarrhythmias (VT/VF)

System-wise, the only differences are: The RV lead which has 1 or 2 defibrillator coils on it The pulse generator is larger to accommodate a larger capacitor and battery

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ICD Indications:

• Indications are primarily prophylactic (Primary Prevention):

• High risk subgroups: • Low EF • Genetic syndromes

• Less commonly, ICDs are implanted for presumed or actual cardiac arrest

• VT/VF without a reversible cause • Syncope with concerning history or findings at EP

Study (presumed arrest)

How do ICDs work?

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How do ICDs work?

Constant sensing by the RV lead for the presence of a fast rhythm

The threshold for detection is user definable ICDs can discriminate between SVT and Ventricular based tachyarrhythmia (VT/VF)

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How do ICDs work?

Once VT/VF is detected, the device has a choice: Pace termination Defibrillation

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Pace Termination

Pace Termination More commonly known as Anti-tachy pacing (ATP) Painless

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Defibrillation

The ICD will charge its capacitor (3-6 seconds) and then deliver therapy

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What’s new?

Subcutaneous ICD:

Courtesy Boston Scientific

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Questions?

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References

Open source slidesets on: https://www.medtronicacademy.com http://www.cardiachealth.org/heart-information/heart-arrhythmia/icd

http://www.cardiachealth.org/heart-information/heart-arrhythmia/icd

Essentials for pacemakers and ICD's-2...The new england journal of medicine n engl j med nejm.org 1...

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