Cardiac Assist Devices

Cardiac Assist Devices
By: Wayne E. Ellis, Ph.D., CRNA

Types
Pacemakers
AICDs
VADs

History
* First pacemaker implanted in 1958
* First ICD implanted in 1980
* Greater than 500,000 patients in the US population have pacemakers
* 115,000 implanted each year

Pacemakers Today
* Single or dual chamber
* Multiple programmable features
* Adaptive rate pacing
* Programmable lead configuration

Internal Cardiac Defibrillators (ICD)
* Transvenous leads
* Multiprogrammable
* Incorporate all capabilities of contemporary pacemakers
* Storage capacity

Temporary Pacing Indications
* Routes = Transvenous, transcutaneous, esophageal
* Unstable bradydysrhythmias
* Atrioventricular heart block
* Unstable tachydysrhythmias
* *Endpoint reached after resolution of the problem or permanent pacemaker implantation

Permanent Pacing Indications
* Chronic AVHB
* Chronic Bifascicular and Trifascicular Block
* AVHB after Acute MI
* Sinus Node Dysfunction
* Hypersensitive Carotid Sinus and Neurally Mediated Syndromes
* Miscellaneous Pacing Indications

Chronic AVHB
* Especially if symptomatic

Pacemaker most commonly indicated for:
* Type 2 2º
o Block occurs within or below the Bundle of His
* 3º Heart Block
o No communication between atria and ventricles

Chronic Bifascicular and Trifascicular Block
* Differentiation between uni, bi, and trifascicular block
* Syncope common in patients with bifascicular block
* Intermittent 3º heart block common

AVHB after Acute MI
* Incidence of high grade AVHB higher
* Indications for pacemaker related to intraventricular conduction defects rather than symptoms
* Prognosis related to extent of heart damage

Sinus Node Dysfunction
* Sinus bradycardia, sinus pause or arrest, or sinoatrial block, chronotropic incompetence
* Often associated with paroxysmal SVTs (bradycardia-tachycardia syndrome)
* May result from drug therapy
* Symptomatic?
* Often the primary indication for a pacemaker

Hypersensitive Carotid Sinus Syndrome
• Syncope or presyncope due to an exaggerated response to carotid sinus stimulation
• Defined as asystole greater than 3 sec due to sinus arrest or AVHB, an abrupt reduction of BP, or both

Neurally Mediated Syncope
* 10-40% of patients with syncope
* Triggering of a neural reflex
* Use of pacemakers is controversial since often bradycardia occurs after hypotension

Miscellaneous
* Hypertrophic Obstructive Cardiomyopathy
* Dilated cardiomyopathy
* Cardiac transplantation
* Termination and prevention of tachydysrhythmias
* Pacing in children and adolescents

Indications for ICDs
* Cardiac arrest due to VT/VF not due to a transient or reversible cause
* Spontaneous sustained VT
* Syncope with hemodynamically significant sustained VT or VF
* NSVT with CAD, previous MI, LV dysfunction and inducible VF or VT not suppressed by a class 1 antidysrhythmic

Device Selection
* Temporary pacing (invasive vs. noninvasive)
* Permanent pacemaker
* ICD

Pacemaker Characteristics
• Adaptive-rate pacemakers
•Single-pass lead Systems
• Programmable lead configuration
• Automatic Mode-Switching
• Unipolar vs. Bipolar electrode configuration

ICD selection
* Antibradycardia pacing
* Antitachycardia pacing
* Synchronized or nonsynchronized shocks for dysrhythmias
* Many of the other options incorporated into pacemakers

Approaches to Insertion
Mechanics
Unipolar Pacemaker
Bipolar Pacemaker
Indications
1. Sick sinus syndrome (Tachy-brady syndrome)
2. Symptomatic bradycardia
3. Atrial fibrillation
4. Hypersensitive carotid sinus syndrome
* Second-degree heart block/Mobitz II


Complete heart block
* Sinus arrest/block
* Tachyarrhythmias
Supraventricular, ventricular
To overdrive the arrhythmia
Atrial Fibrillation
1. Asynchronous/Fixed Rate
2. Synchronous/Demand
3. Single/Dual Chamber
4. Programmable/nonprogrammable
Synchronous/Demand
Examples of Demand Pacemakers
DDI
VVI/VVT
AAI/AAT
Disadvantage: Pacemaker may be fooled by interference and may not fire

Dual Chamber: A-V Sequential
Facilitates a normal sequence between atrial and ventricular contraction
Provides atrial kick + ventricular pacing
Atrial contraction assures more complete ventricular filling than the ventricular demand pacing unit
A-V Sequential
Disadvantage: More difficult to place
More expensive
Contraindication: Atrial fibrillation, SVT
Developed due to inadequacy of “pure atrial pacing”
Single Chamber
Atrial
Ventricular
“Pure Atrial Pacing”
Problems with Atrial Pacing
Electrode difficult to secure in atrium
Tends to float

Ventricular
Programmability
Table of Pacer Codes
Types of Pulse Generators
Examples
Other Information
Undersensing: Failure to sense ... much more in 105 slides

Cardiac Assist Devices.ppt