1. Definition Incidence Sudden Cardiac Death Death occurs within minutes
Cardiac in nature
Unwitnessed death
Incidence
375,000 people suffer Sudden Cardiac Death per year
Approximately 43 people every hour
75,000 (20%) survive

2. Sudden Cardiac Arrest

3. Magnitude of SCA in the U.S.
167,366
Stroke3
450,000
SCA claims more lives each year than these other diseases combined
SCA4
Lung Cancer2
157,400
#1 Killer in the U.S.
Breast Cancer2
40,600
AIDS1
42,156
1 U.S. Census Bureau, Statistical Abstract of the United States: 2001.
2 American Cancer Society, Inc., Surveillance Research, Cancer Facts and Figures 2001.
Heart and Stroke Statistical Update, American Heart Association.
4 Zheng Z. Circulation. 2001;104:

4. Sudden Cardiac Arrest is one of the Leading Causes of Death in the U.S.5 , 1 2 3 S C A S t r o k e L u n g C a c e r
Approximately 300,000 Americans die from Sudden Cardiac Arrest every year. Data from 1996 shows that other major causes of death affected fewer people:
SCA ~300,000
Stroke ,500
Lung Cancer ,000
Breast Cancer ,100
AIDS ,000
Fire ,000 B r e a s t C n c A I D S
Source: Statistical Abstract of the U.S. 1998, Hoover’s Business Press, 118th Edition

5. Causes Sudden Cardiac Death 80-90% are tachyarrhythmias
Only 10-20% are due to an acute myocardial infarction or to bradyarrhythmias

6. Underlying Arrhythmia of Sudden Cardiac ArrestVT
62%
Primary VF 8%
Torsades
de Pointes
13%
Bradycardia
17%
The majority (83%) of arrhythmias leading to SCA are tachyarrhythmias.
Adapted from Bayés de Luna A. Am Heart J ;117:

7. Coronary Heart Disease
An estimated 13 million people had CHD in the U.S. in
Sudden death was the first manifestation of coronary heart disease in 50% of men and 63% of women. 1
CHD accounts for at least 80% of sudden cardiac deaths in Western cultures.3
Etiology of Sudden Cardiac Death2,3
80% Coronary Heart Disease
15% Cardiomyopathy
5% Other*
* ion-channel abnormalities, valvular or congenital heart disease, other causes
1 American Heart Association. Heart Disease and Stroke Statistics—2003 Update. Dallas, Tex.: American Heart Association; 2002.
2 Adapted from Heikki et al. N Engl J Med, Vol. 345, No. 20, 2001.
3 Myerberg RJ. Heart Disease, A Textbook of Cardiovascular Medicine. 6th ed. P. 895.

8. SCD
CAD Risk Factors

9. “Reduced left ventricular ejection fraction (LVEF) remains the single most important risk factor for overall mortality and sudden cardiac death.”1

10. SCD Rates in Post-MI Patients with LV Dysfunction
TRACE: Kober L, et al. N Engl J Med 1995; 333:
CAPRICORN: The CAPRICORN Investigators. Lancet 2001; 357:
EMIAT: Julian DG, et al. Lancet 1997; 349:
MADIT: Moss AJ. N Engl J Med. 1996;335:
MUSTT: 1) Buxton AE. N Engl J Med. 1999;341: ) Buxton AE, et al. Journal of Interventional Cardiac Electrophysiology 9, , ) Buxton AE, et al. N Engl J Med 2000; 342:
MADIT II: 1) Moss AJ. N Engl J Med. 2002;346:877-83, 2) Arrhythmic mortality data from: Moss AJ. Presented at ACC Latebreaking Clinical Trials, March 2002.
Total Mortality ~20-30%; SCD accounts for ~50% of the total deaths.
References in slide notes. * MADIT-II mortality values at 20 months.

11. Treatments to Reduce SCD
Improving Pump Function
ACE inhibitor
Beta-blocker
Prevention of Arrhythmias
Amiodarone
Terminating Arrhythmias
ICDs
AEDs
Prevent Ventricular Remodeling and Collagen Formation
Aldosterone receptor blockade
Correcting Ischemia
Revascularization
Beta-blocker
Preventing Plaque Rupture
Statin
ACE inhibitor
Aspirin
Stabilizing Autonomic Balance
Zipes DP. Circulation. 1998;98:
Pitt B. N Engl J Med. 2003;348:

12. Ann Noninvasive Electrocardiol. 1999;4:83-91
MADIT II ( ) Multicenter Automatic Defibrillator Implantation Trial II
Objective - To evaluate the role of ICD vs. medical therapy in a group of patients with left ventricular dysfunction and MI
Inclusion - Post MI patients with EF < 30%. No prior assessment of VT in the EP lab. Requirement for freq. PVC’s was dropped six months in to the study (only 23 pts enrolled).
Exclusion - Approved indication for an ICD; Undergone coronary revascularization within 3-months; An MI within the past 1-month
Objective-
Same as slide
Inclusion -
The only inclusion criteria were an EF≤30%and a prior MI. The MI must have occurred more than one month prior to randomization, otherwise there was no restriction as to how old the event was.
Exclusion -
Patients -
The base-line characteristics and the prevalence of cardiac medications at the time of the last follow-up were similar in the two groups. Both groups had similar age and gender distribution.
Results -
Over a 4-yr period with an average follow-up of 20-months, the ICD group resulted in a 5.6% absolute and 31% relative risk reduction in mortality. The study also observed an increased incidence of new or worsened heart failure in the ICD-treated patients compared with those in the conventional treatment arm. Differences in mortality didn’t become beneficial for roughly 9-months after implant between the two groups.
Endpoints -
Death from any cause
Reference-
The New England Journal of Medicine Vol. 346, p , March 2002
Journal of Cardiovascular Electrophysiology Vol. 9, p.878+, August 1998

13. MADIT II Multicenter Automatic Defibrillator Implantation Trial II
Patients - 1,232 randomized in a 3:2 ratio to receive an ICD (752) or conventional medical therapy (490)
Results - Over a 4-yr period with an average follow-up of 20-months, the ICD group resulted in a 5.6% absolute and 31% relative risk reduction in mortality over conventional group % vs. 19.8% respectively
Study terminated early due to this favorable result
Objective-
Same as slide
Inclusion -
The only inclusion criteria were an EF≤30%and a prior MI. The MI must have occurred more than one month prior to randomization, otherwise there was no restriction as to how old the event was.
Exclusion -
Patients -
The base-line characteristics and the prevalence of cardiac medications at the time of the last follow-up were similar in the two groups. Both groups had similar age and gender distribution.
Results -
Over a 4-yr period with an average follow-up of 20-months, the ICD group resulted in a 5.6% absolute and 31% relative risk reduction in mortality. The study also observed an increased incidence of new or worsened heart failure in the ICD-treated patients compared with those in the conventional treatment arm. Differences in mortality didn’t become beneficial for roughly 9-months after implant between the two groups.
Endpoints -
Death from any cause
Reference-
The New England Journal of Medicine Vol. 346, p , March 2002
Journal of Cardiovascular Electrophysiology Vol. 9, p.878+, August 1998

14. MADIT II Multicenter Automatic Defibrillator Implantation Trial II
Probability of Survival
Moss, A. et. al. N Engl J Med 2002;877-83

15. Reductions in Mortality with ICDs Compared to Antiarrhythmic Drugs
60%
MUSTT5
5 years 0%
10%
20%
30%
40%
50%
60%
% Mortality Reduction
54%
MADIT4
2 years
37%
CASH2
2 years
31%
AVID1
3 years
20%
CIDS3
3 years
Reductions in mortality with ICDs vs. drugs:
VT/VF Patients
1 AVID: 31% at 3 years and 39% at 1 year (ICD versus empiric amiodarone or sotalol)
2 CASH: 37% at 2 years (ICD versus amiodarone, metoprolol or propafenone)
3 CIDS: 20% at 3 years (ICD versus amiodarone)
Post-MI Patients
4 MADIT: 54% at 2 years (ICDs versus conventional treatment – mostly amiodarone)
5 MUSTT: 60% at 5 years (ICDs versus conventional treatment – sotalol or amiodarone)
3 Connolly S. ACC98 News Online. April, Press release.
4 Moss AJ. N Engl J Med. 1996;335:
5 Buxton AE. N Engl J Med. 1999;341:
1 The AVID Investigators. N Engl J Med. 1997;337:
2 Kuck K. ACC98 News Online. April, Press release.

16. Incremental Cost-Effectiveness Results ($LYS)*
Highly Cost Effective
Cost Effective
Borderline Cost Effective
Expensive
Unattractive $0
$20
$40
$60
$80
$100
$120
$140
$160
$180
$200
$LYS (X 1000)
Anticoag.
$174,100
Mitral Stenosis
NSR, Female
Age 351
PTCA
$91,500
Chronic CAD
Mild Angina
1 VD LAD1
Peritoneal
$57,300
Dialysis3
Each of the therapies shown are compared to conventional therapy.
Several studies have been done to estimate the cost-effectiveness of ICD versus antiarrhythmic drug therapy. Results include:
$ per life year saved Source
$7,400 Kupperman. Circulation. 1990
$14,200 Kupersmith. American Heart Journal. 1995
$16,500 Larsen. Journal American College of Cardiology. 1992
$16,900 Muslin. NASPE Meeting. 1997
$27,000 Owens. Annals of Internal Medicine. 1997
Costs per life year saved for other health care investments:
$11,100 Treatment of severe hypertension in men aged 40 years
$32,900 Estrogen therapy for postmenopausal symptoms in women without a prior hysterectomy
$53, School tuberculin testing program (data from Kupperman. Circulation. 1990)
Cardiac
$44,300
Transplant
CHF
Candidate1
Captopril
$28,400
Post MI
EF < .401
ICD
$27,000
Therapy2
CABG
Chronic CAD
Mild Angina
3 VD1
$18,200
*Versus Conventional Therapy
1 Kupersmith. Progress in Cardiovascular Disease Owens. Annals of Internal Medicine Kupperman. Circulation. 1990

17. 375,000 people suffer Sudden Death each year Only 20% survive
GOAL OF ICD THERAPY
375,000 people suffer Sudden Death each year
Only 20% survive
In 1985, the only indication for AICD implantation was survival of 2 sudden death episodes
Today, we are attempting to identify those patients who are at high risk and treat them prior to SCD

18. EF Clinic Program Patient Screening Pathway (The Ohio Heart & Vascular Center)
Determine EF
Does patient have
history of cardiac
arrest, VF, or
symptomatic VT?
Non-Ischemic
Consult EP for
possible CRT-D
Optimize therapies or
consult HF specialist
EF ≤ 35%
Ischemic
PATIENT
40 days post MI
with EF ≤ 30%
NYHA Class I CHF
EF > 35% OR
3 months post
revascularization
possible ICD
3 months
post diagnosis
1. Consider referral
to HF Specialist or HF Program.
2. Repeat diagnostics
with change of symptoms.
Class III or IV CHF
and QRS > 120 ms
Is patient on
optimal medical
therapy?
YES NO
Note: Pathway only begins after optimal medical therapy & coronary evaluation / intervention as appropriate
NYHA Class
II or III CHF
This is a general protocol to assist in the management of patients. This protocol is not designed to replace clinical judgment or individual patient needs.
To the Speaker:
Used with permission from The Ohio Heart & Vascular Center.

19. Indications for ICD Class I Cardiac Arrest Spontaneous sustained VT
Due to VT or VF
Not due to transient or reversible cause
Spontaneous sustained VT
Structural heart disease must be present
Syncope of undetermined origin with:
Sustained VT that has clinical relevance and/or hemodynamic significance
VF induced during EP study when drug therapy to
sustained VT is not preferred
It must be emphasized that ACC, AHA, and NASPE, when developing guidelines for indications, attached different conditions and levels of evidence to consider before implanting an ICD.
Broadly speaking, ICDs are indicated for ventricular tachycardias and ventricular fibrillation. However, VT in most patients with normal hearts can be treated with drugs or ablation, consequently, the guidelines, as we shall see, are more complex than simply saying VT or VF.
You may also refer to Gregoratos G. et al. ACC/AHA/NASPE 2002 guideline update for implantation of cardiac pacemakers and antiarrhythmia devices: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines Available at

20. Indications for ICD Class I (Non-suppressible by antiarrhythmic drugs)
Nonsustained VT with:
Coronary disease
Prior MI
LV Dysfunction
Inducible VF or sustained VT
(Non-suppressible by antiarrhythmic drugs)
Spontaneous sustained VT
Not amenable to other treatments
#5 is a new recommendation (new in 2002) that is related to #2 on the previous slide. When drug therapy or ablation are not options for the patient with sustained VT and a normal heart, an ICD is indicated.

21. Indications for ICD Class IIa LVEF <30% at: 1 month post MI
3 months post coronary revascularization
Class IIa indication:
#1 is a new recommendation which was a result of the MADIT-II study that showed a 31% reduction in mortality in patients over optimal medical therapy: Beta-blockers, ACE inhibitors, statins, etc., and a 5.6% absolute difference over an average follow-up of 20 months.

22. Indications for ICD Class IIb Cardiac Arrest
Assumed due to VF
EP test precluded by other medical conditions
Symptomatic sustained VT while awaiting cardiac transplant
Conditions with life-threatening risk
Long QT Syndrome
Hypertrophic cardiomyopathy

23. Indications for ICD Class III Syncope of undetermined origin
Without structural heart disease
No inducible VT or VF
Incessant VT or VF
VT or VF with an ablatable or surgically treatable cause
WPW, LVOT VT, ILVT, Fascicular VT
Transient or reversible VT
Due to AMI, electrolyte imbalance, drugs or trauma
#1 was modified to reflect the new Class IIb indication (#7) for patients with structural heart disease and syncope as described in the previous slide. Only patients with no structural heart disease are included in this Class III indication.
The wording of Indication #4 was changed to allow for the exclusion of selected patients, for example, patients with structural heart disease who experience a cardiac arrest in the setting of abnormal electrolytes. Such patients may still be at risk for recurrence of ventricular tachyarrhythmias and may benefit from ICD therapy.

24. Psychiatric illness that may:
Indications for ICD
Class III
Psychiatric illness that may:
Be aggravated by device implantation
Preclude follow-up
Terminal illness
<6 month life expectancy
Reflected are Class III Indications which, as noted earlier, are agreed that device therapy is not necessary in these cases.

25. ICD Evolution Evolution of ICD Technology
This picture reveals the ICD implantation methods that evolved as technology progressed. The large devices of 1980 were implanted in the abdomen with epicardial patch leads tunneled down to the abdomen (shown on the left). Then, as lead technology advanced to allow for venous approach, the leads were tunneled down from the subclavian area to the abdomen (shown in center). Today, the small size of an ICD allows for device implantation in the pectoral area (shown on right) with a transvenous lead system.
Evolution of ICD Technology

26. ICD Evolution THEN… Required major surgery Nonprogrammable
High-energy shock only
Indicated for 2X SCD survivors only
1 ½ year longevity
< 1,000 implants/year
When the first human implants occurred in the early 1980’s, the ICD devices were quite large, required major surgery (thoracotomy with multiple incisions, usually under general anesthesia), long hospital stays, the device did not last very long (average of about 18 months). Therefore, ICDs were reserved only for the highest risk patients: those who survived 2 or more SCD events!

27. ICD Evolution …and NOW Transvenous, single incision
Local anesthesia, conscious sedation
Programmable therapy options
Single, dual and triple chamber
Up to 9 years longevity
> 100,000 implants/year
Today’s devices are implanted pectoraly, either subcutaneously or submuscularly, under local anesthesia and conscious sedation in most patients. Today’s ICDs offer many programmable therapy options with single or dual chamber therapy available. There are an estimated 166,800 ICD implants worldwide annually (as published in the Morgan Stanley Report. “Hospital Supplies & Medical Technology”, Sept. 15, Pg 34.)
Battery longevity projection for Medtronic single chamber ICDs:
(with pacing parameters set at VVI, 60 ppm, 3.0V, 0.4 ms, 500, EGM pre-storage off)
Marquis VR: years – 0% pacing, biannual charges; 8.5 years – 15% pacing, quarterly charges; 7.3 years – 100% pacing, quarterly charges
Maximo VR: years – 0% pacing, biannual charges; 9.8 years – 15% pacing, biannual charges; 7.0 years – 100% pacing, quarterly charges
Battery longevity projection for Medtronic dual chamber ICDs:
(with pacing parameters set at DDD, 60 ppm, 3.0V, 0.4 ms, 500, EGM pre-storage off)
Marquis DR: 8.6 years – 0% pacing, biannual charges; 7.1 years – 15% pacing, quarterly charges; 5.5 years – 100% pacing, quarterly charges
Maximo DR: 8.5 years – 0% pacing, biannual charges; 8.0 years – 15% pacing, biannual charges; 5.4 years – 100% pacing, quarterly charges

28. ICD Evolution
This slide shows the rapid rate at which devices shrunk in size over the years.

29. * The ICD System How it Works Animation
The Implantable Cardioverter Defibrillator (ICD) System consists of an implantable tachyarrhythmia control device and implanted leads. This system delivers electrical impulses and high energy discharges to treat arrhythmias. It also provides bradycardia pacing when needed.
The ICD (often referred to as the device) detects a tachyarrhythmia or bradyarrhythmia by sensing electrical signals generated from cardiac depolarizations. The signals are transmitted to the ICD via leads implanted in the heart. The device analyzes the incoming signals and delivers the appropriate therapy.

30. The ICD System How it Works Atrium & Ventricle Ventricle
Bradycardia sensing
Bradycardia pacing
Antitachycardia pacing
Today’s dual chamber devices can detect and treat bradyarrhythmias as well as some atrial arrhythmias, VT and VF. In addition, they can discriminate SVTs and other atrial tachyarrhythmias to reduce the incidence of inappropriate ventricular therapies, including inappropriate shocks.
In addition to bradycardia pacing therapies, some devices offer treatment in the atrium that includes AT/AF prevention and anti-tachycadia pacing (ATP). In addition, they also offer treatment in the ventricle that includes VT prevention, anti-tachycardia pacing (ATP), cardioversion and defibrillation for ventricular tachyarrhythmias (VT/VF).
Before the development of dual chamber ICDs, VT/VF patients with symptomatic sinus bradyarrhythmias would also receive a pacemaker implant. Dual chamber devices were developed for use in patients with VT/VF who also have a bradyarrhythmias or pacing indication.
Ventricle
VT prevention
Antitachycardia pacing
Cardioversion
Defibrillation

31. ICD Device Components (Header) (Used for Telemetry)
Now, let’s take a look at the system within the defibrillator that provides the both low voltage pulses for pacing and high voltage shock needed for defibrillation therapy.

32. What is the function of an ICD?
Question?
What is the function of an ICD?
Sense
Detect
Therapy
Pace
What is the function of an ICD? It is to sense and detect an arrhythmia, therapy it appropriately, and provide pacing therapy when needed.

33. Question? What is Sensing? It’s what the device sees
The process of identifying cardiac
depolarizations from an intracardiac
electrogram
Sensing is the ability of the device to “see” when a natural (intrinsic) depolarization(EGM) is occurring. The question to be asked and answered in this section is: What is sensing with respect to the ICD system? There are many electric signals inside and outside the body, and the pacemaker needs to sense or “see” only the electric signals from the heart. How does it see those signals? In sensing, the principles of an electric circuit still apply, but the power source generating the current is the heart itself.
It’s what the device sees

34. Sensing Sensing - what the device “sees”
Electrical Activity - what the device is looking for
Sensing can be simplified by definition as all electrical activity seen by the device. The eyeball that dictates what the device sees is located on the lead and is known as the sensing electrode circuit (bipolar).
Lead – contains the ‘eyeball’ of the device

35. Morphology Comparison
The EGM Signal
Farfield
Morphology Comparison
SINUS RHYTHM VT
EGM Source = Variable

36. Therapy: Marker Channel™ ICD Function Annotations
TP = Anti-Tachycardia Pacing Initiated (ATP)
CE = Charge End
CD = Charge Delivered
These annotations will be seen to indicate therapy initiation and delivery once an arrhythmia has been detected.
The following will be annotated as appropriate:
TP – for anti-tachycardia pacing to therapy VT or FVT,
CE – indicates the programmed energy charge has ended and is ready to be delivered by the ICD, and
CD – indicates that electric shock therapy (either cardioversion or defibrillation) has been delivered
The amount of energy delivered is determined by the programmed setting on the ICD. More on programming therapies later in this section.
* in Medtronic devices

37. Classifies rhythm by detection zone:
Detection Rate
Measured in:
Beat-to-beat intervals (milliseconds), or
Beats-per-minute (BPM)
Classifies rhythm by detection zone:
VT = Ventricular Tachycardia
VF = Ventricular Fibrillation
Detection Rate is the rate at which an interval (or beats) must fall to meet the criteria as being a rapid rhythm in need of therapy. A range of rates defines the “detection zone.” If a beat is sensed within a programmed detection zone, that beat is then marked appropriately and counted for sustainability (discussed next).
Rate classifies the type of tachyarrhythmia defined by the programming of “detection zones” as either being:
VT = Ventricular tachycardia
FVT = Fast ventricular tachycardia (an option in some devices, but not all – we will discuss this further later
in this section), and
VF = Ventricular fibrillation
We will discuss more on detection zones later in this section.
* Note: While the concept of device detection is universal, the type of tachyarrhythmias defined by an ICD may vary between manufactures.
Programmable in ranges of rates
Example: VT = 162 bpm – 188 bpm
VF = 188 bpm and faster

38. Can you name some therapies delivered by an ICD?
Question?
Can you name some therapies delivered by an ICD?
This slide is intended to test the audience as to the types of ICD electric therapy they are familiar with. It will also determine areas of which to concentrate for those therapies not identified as being an option.

39. ICD Therapy ICD Therapies Low Power (Pacing Therapies)
Anti-tachycardia Pacing (ATP
Bradyarrhythmia Pacing
High Power (Shock Therapies)
Cardioversion
Defibrillation
The therapies delivered from an ICD can be categorized as being of Low or High power. Low power refers to pacing therapies delivered, while high power refers to shock therapy.
Low power pacing therapies delivered by an ICD include anti-tachycardia pacing (ATP), and bradyarrhythmias pacing similar to those available in pacemakers. There are different types of ATP therapies available (example: Burst, Ramp) depending on device and manufacturer. The ATP selections available in Medtronic devices are detailed later in this module.
High power shock therapies delivered by an ICD include Cardioversion (CV) and Defibrillation, and require the use of a high voltage delivery coil (lead). Cardioversion and Defibrillation behaviors are detailed later in the module.

40. Tachyarrhythmia Therapy
ICD Therapies
Tachyarrhythmia Therapy
Anti-Tachycardia Pacing (ATP)
Pacing pulses delivered at a rate faster than the rhythm detected
Can successfully terminate re-entrant tachycardias
Low Power
ICDs emit electric energy in an effort to depolarize and put into refractory the cardiac cells involved in maintaining the tachyarrhythmia. There are various ways that energy is delivered, with some being more aggressive and painful than others. The first one we will discuss is Anti-Tachycardia Pacing (ATP).

41. Anti-Tachycardia Pacing*
Animation
This animation shows the delivery of ATP therapy for VT.
Click image to view animation

42. Anti-Tachycardia Pacing
ATP delivered at a rate faster than tachyarrhythmia.
Wavefronts collide.
Subsequent Pulse: Wavefronts collide closer to re-entry circuit
Re-entry initiated
With the right timing and number of ATP pulses, the tissue in the excitable gap is depolarized, thus blocking the circulating wavefront and terminating the tachycardia. Here’s a breakdown of the process:
The depolarization wavefront leaves the reentry circuit and spreads through other cardiac tissue. The wavefront is sensed as it reaches the implanted lead.
If a pacing pulse is synchronized to the sensed wavefront and delivered at a rate faster than the tachycardia, it stimulates the tissue at the lead tip before the reentry-inititated waveform arrives. The depolarization wavefront initiated by the lead spreads toward the approaching wavefront from the reentry circuit. These wavefronts collide some distance from the lead tip, and the rate of depolarization and repolarization of the tissue between the lead and the colliding wavefronts is reset.
Another pacing pulse is delivered at a rate faster than the tachycardia, the wavefronts collide further from the lead and closer to the reentry circuit.
Still another pacing pulse is delivered at a rate faster than the tachycardia. The wavefronts collide further from the lead and closer to the reentry circuit.
With the right timing and number of ATP pulses, the tissue in the excitable gap is depolarized, thus blocking the circulating wavefront and terminating the tachycardia.
The timing and number of pacing pulses needed to successfully terminate a re-entry tachyarrhythmia varies greatly. Factors such as lead position and patient chemistry play a significant role in its success. Because many ATP varieties are programmable, there is a great possibility that if ATP does not terminate on a particular attempt, re-programming to a more or less aggressive form of ATP will prove successful.
The following slides will detail the ATP functionality and programming option in most Medtronic ICDs.
Subsequent Pulses: Wavefronts collide even closer to re-entry circuit
Arrhythmia terminated

43. Cardioversion Delivers shock on an R-wave
Aborts if synchronization cannot be obtained due to arrhythmia termination
A cardioversion will always be synchronized and delivered on an R-wave. Cardioversion shocks (even higher-energy ones) could trigger VF if they are delivered during a T-wave. Thus, if synchronization does not occur, the cardioversion shock is aborted. This is referred to as non-committed therapy.
*Note: If cardioversion cannot synchronize because the VT has degenerated to VF, VF will be detected and VF therapy will be delivered.

44. Click image to view animation
Defibrillation *
Animation
This animation shows the delivery of defibrillation therapy for VF.
Click image to view animation

45. ICD Therapy VT FVT VF Benefits of Tiered Therapy
The ICD is capable of delivering a variety of electrical therapies. The clinician can use a tiered approach to programming therapies from the least aggressive (for tachyarrhythmias more easily terminated) to the most aggressive (for lethal VF). This approach is called Tiered Therapy.
The least aggressive Antitachycardia Pacing (ATP) therapy is employed to interrupt the reentry circuit
causing VT and FVT. (ATP is a painless therapy.)
Cardioversion Shocks (CV) are considered moderately aggressive to terminate VT and FVT, usually with
lower energy than needed to terminate fibrillation
Defibrillation Shocks used to terminate VF are the most aggressive
Typically, after initial detection, therapy number one is delivered, and then, if it is ineffective and redetection occurs, therapy number two is delivered. This progression continues until episode termination or all programmed therapies are delivered.
If all programmed therapies are ineffective, no additional therapies are delivered until the episode meets the termination criterion. VF

46. Bradyarrhythmia Therapy
Pacing Modes
Most ICDs offer:
Single Chamber Pacing
AAI(R), VVI(R) and VOO
Dual Chamber Pacing
DDD(R), DDI(R), DOO and ODO
Mode Switch
Separate post-shock pacing programming
Ensures capture
Bradycardia pacing parameters are programmed similarly to pacemakers. Most devices offer single chamber pacing in single chamber devices, and single and dual chamber pacing in dual chamber devices. Further, some dual chamber devices also offer the Mode Switch capability to prevent upper rate tracking in patients with intermittent atrial arrhythmias.
Some ICD models allow for programming separate values for amplitude, pulse width, and pace blanking during charging of the capacitors and post-shock pacing to ensure capture.