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

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Arrhythmia

ARRHYTHMIA
Edited by Yingmin Chen

* Definition of Arrhythmia:
The Origin, Rate, Rhythm, Conduct velocity and sequence of heart activation are abnormally.

Anatomy of the conducting system
Pathogenesis and Inducement of Arrhythmia
* Some physical condition
* Pathological heart disease
* Other system disease
* Electrolyte disturbance and acid-base imbalance
* Physical and chemical factors or toxicosis


Mechanism of Arrhythmia
* Abnormal heart pulse formation
* Sinus pulse
* Ectopic pulse
* Triggered activity
* Abnormal heart pulse conduction
* Reentry
* Conduct block

Classification of Arrhythmia
* Abnormal heart pulse formation
* Sinus arrhythmia
* Atrial arrhythmia
* Atrioventricular junctional arrhythmia
* Ventricular arrhythmia
* Abnormal heart pulse conduction
* Sinus-atrial block
* Intra-atrial block
* Atrio-ventricular block
* Intra-ventricular block
* Abnormal heart pulse formation and conduction

Diagnosis of Arrhythmia
* Medical history
* Physical examination
* Laboratory test

Therapy Principal
* Pathogenesis therapy
* Stop the arrhythmia immediately if the hemodynamic was unstable
* Individual therapy

Anti-arrhythmia Agents
* Anti-tachycardia agents
* Anti-bradycardia agents
Anti-tachycardia agents
* Modified Vaugham Williams classification
* I class: Natrium channel blocker
* II class: ß-receptor blocker
* III class: Potassium channel blocker
* IV class: Calcium channel blocker
* Others: Adenosine, Digital

Anti-bradycardia agents
* ß-adrenic receptor activator
* M-cholinergic receptor blocker
* Non-specific activator

Clinical usage
Anti-tachycardia agents:
* Ia class: Less use in clinic
* Guinidine
* Procainamide
* Disopyramide: Side effect: like M-cholinergic receptor blocker

Anti-tachycardia agents:
* Ib class: Perfect to ventricular tachyarrhythmia
1. Lidocaine
2. Mexiletine
Anti-tachycardia agents:
* Ic class: Can be used in ventricular and/or supra-ventricular tachycardia and extrasystole.

1. Moricizine
2. Propafenone

Anti-tachycardia agents:
* II class: ß-receptor blocker
* Propranolol: Non-selective
* Metoprolol: Selective ß1-receptor blocker, Perfect to hypertension and coronary artery disease patients associated with tachyarrhythmia.
* III class: Potassium channel blocker, extend-spectrum anti-arrhythmia agent.
* Amioarone: Perfect to coronary artery disease and heart failure patients
* Sotalol: Has ß-blocker effect
* Bretylium
* IV class: be used in supraventricular tachycardia
* Verapamil
* Diltiazem
* Others:
Adenosine: be used in supraventricular tachycardia

Anti-bradycardia agents
* Isoprenaline
* Epinephrine
* Atropine
* Aminophylline
Proarrhythmia effect of antiarrhythmia agents
* Ia, Ic class: Prolong QT interval, will cause VT or VF in coronary artery disease and heart failure patients
* III class: Like Ia, Ic class agents
* II, IV class: Bradycardia

Non-drug therapy
* Cardioversion: For tachycardia especially hemodynamic unstable patient
* Radiofrequency catheter ablation (RFCA): For those tachycardia patients (SVT, VT, AF, AFL)
* Artificial cardiac pacing: For bradycardia, heart failure and malignant ventricular arrhythmia patients.

Sinus Arrhythmia

Sinus tachycardia
* Sinus rate > 100 beats/min (100-180)
* Causes:
* Some physical condition: exercise, anxiety, exciting, alcohol, coffee
* Some disease: fever, hyperthyroidism, anemia, myocarditis
* Some drugs: Atropine, Isoprenaline
* Needn’t therapy
Sinus Bradycardia
* Sinus rate < 60 beats/min
* Normal variant in many normal and older people
* Causes: Trained athletes, during sleep, drugs (ß-blocker) , Hypothyriodism, CAD or SSS
* Symptoms:
* Most patients have no symptoms.
* Severe bradycardia may cause dizziness, fatigue, palpitation, even syncope.
* Needn’t specific therapy, If the patient has severe symptoms, planted an pacemaker may be needed.
Sinus Arrest or Sinus Standstill
* Sinus arrest or standstill is recognized by a pause in the sinus rhythm.
* Causes: myocardial ischemia, hypoxia, hyperkalemia, higher intracranial pressure, sinus node degeneration and some drugs (digitalis, ß-blocks).
* Symptoms: dizziness, amaurosis, syncope
* Therapy is same to SSS
Sinoatrial exit block (SAB)
* SAB: Sinus pulse was blocked so it couldn’t active the atrium.
* Causes: CAD, Myopathy, Myocarditis, digitalis toxicity, et al.
* Symptoms: dizziness, fatigue, syncope
* Therapy is same to SSS

Sinoatrial exit block (SAB)
* Divided into three types: Type I, II, III
* Only type II SAB can be recognized by EKG.

Sick Sinus Syndrome (SSS)
* SSS: The function of sinus node was degenerated. SSS encompasses both disordered SA node automaticity and SA conduction.
* Causes: CAD, SAN degeneration, myopathy, connective tissue disease, metabolic disease, tumor, trauma and congenital disease.
* With marked sinus bradycardia, sinus arrest, sinus exit block or junctional escape rhythms
* Bradycardia-tachycardia syndrome

Sick Sinus Syndrome (SSS)
* EKG Recognition:
* Sinus bradycardia, ≤40 bpm;
* Sinus arrest > 3s
* Type II SAB
* Nonsinus tachyarrhythmia ( SVT, AF or Af).
* SNRT > 1530ms, SNRTc > 525ms
* Instinct heart rate < 80bmp

Sick Sinus Syndrome (SSS)
* Therapy:
* Treat the etiology
* Treat with drugs: anti-bradycardia agents, the effect of drug therapy is not good.
* Artificial cardiac pacing.

Atrial arrhythmia
Premature contractions
* The term “premature contractions” are used to describe non sinus beats.
* Common arrhythmia
* The morbidity rate is 3-5%
Atrial premature contractions (APCs)
* APCs arising from somewhere in either the left or the right atrium.
* Causes: rheumatic heart disease, CAD, hypertension, hyperthyroidism, hypokalemia
* Symptoms: many patients have no symptom, some have palpitation, chest incomfortable.
* Therapy: Needn’t therapy in the patients without heart disease. Can be treated with ß-blocker, propafenone, moricizine or verapamil.

Atrial tachycardia
* Classify by automatic atrial tachycardia (AAT); intra-atrial reentrant atrial tachycardia (IART); chaotic atrial tachycardia (CAT).
* Etiology: atrial enlargement, MI; chronic obstructive pulmonary disease; drinking; metabolic disturbance; digitalis toxicity; electrolytic disturbance.........

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Cardiac Arrhythmias

Cardiac Arrhythmias
By:Elise Georgi Morris, M.D.

Objectives
* Identify common arrhythmias encountered by the family physician
* Discuss arrhythmia etiologies
* Discuss initial primary care work-up and treatment
* Practice questions

Normal Sinus Rhythm
Implies normal sequence of conduction, originating in the sinus node and proceeding to the ventricles via the AV node and His-Purkinje system.
EKG Characteristics: Regular narrow-complex rhythm

Sinus Bradycardia
* HR< 60 bpm; every QRS narrow, preceded by p wave
* Can be normal in well-conditioned athletes
* HR can be<30 bpm in children, young adults during sleep, with up to 2 sec pauses

Sinus bradycardia--etiologies
* Normal aging
* 15-25% Acute MI, esp. affecting inferior wall
* Hypothyroidism, infiltrative diseases
(sarcoid, amyloid)
* Hypothermia, hypokalemia
* SLE, collagen vasc diseases
* Situational: micturation, coughing
* Drugs: beta-blockers, digitalis, calcium channel blockers, amiodarone, cimetidine, lithium

Sinus bradycardia--treatment
* No treatment if asymptomatic
* Sxs include chest pain (from coronary hypoperfusion), syncope, dizziness
* Office: Evaluate medicine regimen—stop all drugs that may cause
* Bradycardia associated with MI will often resolve as MI is resolving; will not be the sole sxs of MI
* ER: Atropine if hemodynamic compromise, syncope, chest pain
* Pacing

Sinus tachycardia
* HR > 100 bpm, regular
* Often difficult to distinguish p and t waves

Sinus tachycardia--etiologies
* Fever
* Hyperthyroidism
* Effective volume depletion
* Anxiety
* Pheochromocytoma
* Sepsis
* Anemia
* Exposure to stimulants (nicotine, caffeine) or illicit drugs
* Hypotension and shock
* Pulmonary embolism
* Acute coronary ischemia and myocardial infarction
* Heart failure
* Chronic pulmonary disease
* Hypoxia

Sinus Tachycardia--treatment
* Office: evaluate/treat potential etiology :check TSH, CBC, optimize CHF or COPD regimen, evaluate recent OTC drugs
* Verify it is sinus rhythm
* If no etiology is found and is bothersome to patients, can treat with beta-blocker

Sinus Arrhythmia
* Variations in the cycle lengths between p waves/ QRS complexes
* Will often sound irregular on exam
* Normal p waves, PR interval, normal, narrow QRS

Sinus arrhythmia
* Usually respiratory--Increase in heart rate during inspiration
* Exaggerated in children, young adults and athletes—decreases with age
* Usually asymptomatic, no treatment or referral
* Can be non-respiratory, often in normal or diseased heart, seen in digitalis toxicity
* Referral may be necessary if not clearly respiratory, history of heart disease

Sick Sinus Syndrome
* All result in bradycardia
* Sinus bradycardia (rate of ~43 bpm) with a sinus pause
* Often result of tachy-brady syndrome: where a burst of atrial tachycardia (such as afib) is then followed by a long, symptomatic sinus pause/arrest, with no breakthrough junctional rhythm.

Sick Sinus Syndrome--etiology
* Often due to sinus node fibrosis, SNode arterial atherosclerosis, inflammation (Rheumatic fever, amyloid, sarcoid)
* Occurs in congenital and acquired heart disease and after surgery
* Hypothyroidism, hypothermia
* Drugs: digitalis, lithium, cimetidine, methyldopa, reserpine, clonidine, amiodarone
* Most patients are elderly, may or may not have symptoms

Sick sinus syndrome--treatment
* Address and treat cardiac conditions
* Review med list, TSH
* Pacemaker for most is required

Paroxysmal Supraventricular Tachycardia
* Refers to supraventricular tachycardia other than afib, aflutter and MAT
* Occurs in 35 per 100,000 person-years
* Usually due to reentry—AVNRT or AVRT

PSVT
* Initial eval: Is the patient stable?
* Determine quickly if sinus rhythm
* If not sinus and unstable, cardioversion
* Unstable sinus tachycardia---IV beta-blocker, and treat cause
* Sxs of instability would include: chest pain, decreased consciousness, short of breath, shock, hypotension—unstable sxs require shock
* If stable, determine whether regular rhythm (sinus or PSVT) vs irregular (afib/flutter, MAT)? p waves (MAT vs. AF)?
* If regular, determine whether p waves are present, if can’t see---administer adenosine (6mg, can give 2 doses) or CSM or other vagal maneuvers)

* CSM or adenosine commonly terminate the arrhythmia, esp, AVRT or AVNRT
* Can also use CCB or beta blockers to terminate, if available
* Counsel to avoid triggers, caffeine, Etoh, pseudoephedrine, stress
* No p waves —junctional tachycardia, AVRT or AVNRT, Afib
* AVRT and AVNRT: can have retrograde p waves and short RP interval
* Abnormal p waves morphology: MAT

Atrial Fibrillation
* Irregular rhythm
* Absence of definite p waves
* Narrow QRS
* Can be accompanied by rapid ventricular response

Atrial Fibrillation—causes and associations
* Hypertension
* Hyperthyroidism and subclinical hyperthyroidism
* CHF (10-30%), CAD
* Uncommon presentation of ACS
* Mitral and tricuspid valve disease
* Hypertrophic cardiomyopathy
* COPD
* OSA
* ETOH
* Caffeine
* Digitalis
* Familial
* Congenital (ASD)

Atrial fibrillation--assessment
* H & P—assess heart rate, sxs of SOB, chest pain, edema (signs of failure)
* If unstable, need to cardiovert
* Echocardiogram to evaluate valvular and overall function
* Check TSH
* Assess for RVR
* Assess onset of sxs—in the last 24-48 hours? Sudden onset? Or no sxs?

Atrial fibrillation--management
* Rhythm vs Rate control—if onset is within last 24-48 hours, may be able to arrange cardioversion—use heparin around procedure
* Need TEE if valvular disease (high risk of thrombus)
* If unable to definitely conclude onset in last 24-48 hours: need 4-6 weeks of anticoagulation prior to cardioversion, and warfarin for 4-12 weeks after

Atrial Fibrillation
* Cardioversion: synchronized (w/QRS) delivery of current to heart; depolarizes tissue in a reentrant circuit; afib involves more cardiac tissue, but cardiovert
* Defibrillation: non-synchronized delivery of current

Atrial fibrillation--management
* Rate control with chronic anticoagulation is recommended for first line approach for majority of patients; overall Afib is a stable rhythm
* Beta-blockers (atenolol and metoprolol) or calcium channel blockers (verapamil or diltiazem) recommended. Digoxin not recommended for rate control
* Anticoagulation: LMWH and then warfarin; can use aspirin for anticoagulation if CI to warfarin, not as effective

Atrial fibrillation--management
* Goal INR of 2.5 (2.0-3.0)
* Rhythm control---second line approach, if unable to control rate or pt with persistent sxs
* Can also consider radiofrequency ablation at pulm veins
* P wave from another atrial focus
* Occurs earlier in cycle
* Different morphology of p wave
* Benign, common cause of perceived irregular rhythm
* Can cause sxs: “skipping” beats, palpitations
* No treatment, reassurance
* With sxs, may advise to stop smoking, decrease caffeine and ETOH
* Can use beta-blockers to reduce frequency

1st Degree AV Block
* PR interval >200ms
* If accompanied by wide QRS, refer to cardiology, high risk of progression to 2nd and 3rd deg block
* Otherwise, benign if asymptomatic

2nd Degree AV Block Mobitz type I (Wenckebach)

* Progressive PR longation, with eventual non-conduction of a p wave
* May be in 2:1 or 3:1
Wenckebach, Mobitz type I
* Usually asymptomatic, but with accompanying bradycardia can cause angina, syncope esp in elderly—will need pacing if sxs
* Also can be caused by drugs that slow conduction (BB, CCB, dig)
* 2-10% long distance runners
* Correct if reversible cause, avoid meds that block conduction

2nd degree block Type II (Mobitz 2)
* Normal PR intervals with sudden failure of a p wave to conduct
* Usually below AV node and accompanied by BBB or fascicular block
* Often causes pre/syncope; exercise worsens sxs
* Generally need pacing, possibly urgently if symptomatic

3rd Degree AV Block

* Complete AV disassociation, HR is a ventricular rate
* Will often cause dizziness, syncope, angina, heart failure
* Can degenerate to Vtach and Vfib
* Will need pacing, urgent referral
* Extremely common throughout the population, both with and without heart disease
* Usually asymptomatic, except rarely dizziness or fatigue in patients that have frequent PVCs and significant LV dysfunction
* No treatment is necessary, risk outweighs benefit
* Reassurance
* Optimize cardiac and pulmonary disease management

Non-sustained Ventricular tachycardia
* Defined as 3 or more consecutive ventricular beats
* Rate of >120 bpm, lasting less than 30 seconds
* May be discovered on Holter, or other exercise testing

Non-sustained ventricular tachycardia
* Need to exclude heart disease with Echo and stress testing
* If normal, there is no increased risk of death
* May need anti-arrhythmia treatment if sxs
* In presence of heart disease, increased risk of sudden death
* Need referral for EPS and/or prolonged Holter monitoring

Ventricular fibrillation
* Defibrillation

Practice Questions—Case studies

References

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