Different Waveforms, Different Waveforms, Different ResultsDifferent Results

Understanding the Differences Between Biphasic Technologies

Defibrillation WaveformsDefibrillation Waveforms

• Waveforms describe the electrical pulseCurrent DeliveryTime Direction of Current Flow

• Three in use todayMonophasic Damped Sine Wave (MDS)Biphasic Truncated Exponential (BTE)Rectilinear Biphasic (RBW)

Damped Sine WaveDamped Sine Wave

Unchanged for 30 YearsUnchanged for 30 Years• Requires high energy

and current.• Not highly effective

for patients with high transthoracic impedance.

Biphasic Truncated ExponentialBiphasic Truncated Exponential

The First Generation:The First Generation:• Adapted from low

impedance ICD applications.

• Impedance causes waveform to change shape.

Rectilinear Biphasic WaveformRectilinear Biphasic Waveform

Designed Specifically Designed Specifically for External Use:for External Use:• Constant CurrentConstant Current

eliminates high peaks

• Fixed DurationFixed Duration stabilizes waveform in face of varying impedance levels.

The Road Map for TodayThe Road Map for Today

• Scientific DataExperimental Studies

Human Trials

• A Functional ComparisonCurrent Delivery

Impedance Handling

• The AHA Position

The Biphasic AdvantageThe Biphasic Advantage

Experimental Studies Have Shown:Experimental Studies Have Shown:• Performance varies with shape• Lower defibrillation thresholds• Less post-shock dysfunction

Performance Varies with ShapePerformance Varies with Shape

)

Dixon et al. Circulation 1987;117:358-364.

Def

ibri

llati

on

Th

resh

old

(Vo

lts)

10M 2.5-7.53.5-6.5 5-5 6.5-3.57.5-2.50

50

100

150

200

250

300

(Canine) epicardial electrodes

Waveform Shape (msec)

Lower Defibrillation ThresholdLower Defibrillation Threshold

Canine heart3 minutes untreated followed by 2 minutes

femoral compression

0

20

40

60

80

100

120

10 sec 5 minFibrillation time

DF

T (

J)M B

54±19

38±10 41±5

80±30

M B

Walcott et al. Circulation 1998; 98:2210-2215.

Key Findings

1 Monophasic DFT increased by 40% (p <0.05)

2 Biphasic DFT remained constant

Reduced Dysfunction - 7 min VFReduced Dysfunction - 7 min VF

Mean arterial pressure higher (p<0.05)

Biphasic defibrillation produces less dysfunction

Ejection fraction higher (p<0.01)

Tang et al. Journal of American College of Cardiology, 1999;34:815-822.

Studied in pigs

Humans Data Is PlentifulHumans Data Is Plentiful

Clinical Trials Show:Clinical Trials Show:• Efficacious for both VF & AF• Biphasic advantage “grows” with

extended-duration VF • Less energy required

Published Data is on Low EnergyPublished Data is on Low Energy

0 200 400 600 800 1000

High-EnergyBiphasic

Low-EnergyBiphasic

912 Patients 1,2,3,4,5

0 Patients

Randomized Patients in Peer-Reviewed JournalsRandomized Patients in Peer-Reviewed Journals

1 Brady et al. Circulation 1996;94:2507-2514.2 Mittal et al. Journal of American College of Cardiology, 1999; 34:1595-1601.3 Mittal et al. Circulation 2000;101:1282-1287.4 Schneider et al. Circulation 2000;102:1780-1787.5 Higgens et al. Prehospital Emergency Care 2000;4:305-313.

200J

> 200J

Agilent VF Trial - BTE WaveformAgilent VF Trial - BTE Waveform

Bardy et al. Circulation 1996;94:2507.

86% 86%

60%

80%

100%

130J BTE 200J MDS

n = 316p = ns

First-ShockEfficacy

Medtronic VF Trial - BTE WaveformMedtronic VF Trial - BTE Waveform

83%

90%

60%

80%

100%

130J BTE 200J MDS

n = 115p = ns

Higgins, et al. Prehospital Emergency Care. 2000;4:305-313.

First-ShockEfficacy

75%

80%

85%

90%

95%

100%

120J RBW 200J MDS

93%

n = 184p = 0.05

Mittal et al. Journal of American College of Cardiology, 1999; 34:1595-1601.

ZOLL VF Trial - RBWZOLL VF Trial - RBW

First-ShockEfficacy

99%

RBW Superior for Difficult PatientsRBW Superior for Difficult Patients

99%

95%

100%

63%

60%

80%

100%

<90 ohms >90 ohms

120J RBW 200J MDS

p = 0.02

DefibrillationEfficacy

Mittal et al. Journal of American College of Cardiology, 1999; 34:1595-1601.

Out-of-Hospital ExperienceOut-of-Hospital Experience

Gliner & White: Resuscitation 1999.

19%

26%

55%

93%

0%7%0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

MONO200-360J

BI3 x 150J

N=210

N=129

Key Findings

1 All biphasic patients defibrillated

2 Significantly more converted to an organized rhythm with biphasic waveform (P<0.0003).

OrganizedAsystoleVF

Last Rhythm Recorded~6.5 (1-17) minutes fibrillation

Out-of-Hospital ExperienceOut-of-Hospital Experience

ORCA Trial (n=115)ORCA Trial (n=115)• Comparison of 200-360J monophasic shocks

with 150J biphasic shocks for out-of-hospital cardiac arrest

• Collapse to first shock = 8.9 minutes

Schneider et al. Circulation. 2000; 102:1780-1787.

Outcome Monophasic Biphasic

1st shock success 36/61 (59%) 52/54 (96%) p<0.0001

3rd shock success 42/61 (69%) 53/54 (98%) p<0.0001

Overall Success 49/58 (84%) 54/54 (100%) p=0.003

Page, et al. Circulation 2000; Supplement 102: II-574 (abstract).

91%86%

0%

20%

40%

60%

80%

100%

200J BTE 360J MDS

n = 209p = ns

Agilent AF Trial - BTE WaveformAgilent AF Trial - BTE Waveform

Car

diov

ersi

on E

ffic

acy

Car

diov

ersi

on E

ffic

acy

0%

20%

40%

60%

80%

100%

MonophasiMonophasicc Rectilinear BiphasicRectilinear Biphasic200 J100 J 300 J 360 J 120 J70 J 150 J 170J

68%

85%91% 94%

21%

44%

68%

79%

p=0.005

p<0.0001

Mittal et al. Circulation 2000; 101:1282-1287.

Randomized MultiCentern=165

ZOLL AF Trial - RBWZOLL AF Trial - RBW

RBW in Clinical PracticeRBW in Clinical Practice

Niebauer MJ, et al. PACE 2000; 23: 605 (abstract).Niebauer, MJ, et al. Circulation. 2000 Supplement 102:II-574 (abstract).

Initial Report:• 100% efficacy for 125

AF patients• 85% converted at 50

joules• 100% efficacy in

subset of patients previously converted with 720J monophasic

In a continuation of the series they reported success in 713 of 714 patients (99.8%).

Overall FindingsOverall Findings

• Biphasic waveforms are effective for both VF and AF.

• Low-energy BTE waveforms produce clinical results equivalent to monophasic technology.

• Low-energy RBW waveforms produce clinical results superior to monophasic technology.

A Functional ComparisonA Functional Comparison

• Response to Impedance

• Current Delivery Characteristics

• Clinical Performance

• AHA View

““. . . the essential . . . the essential requirement for electrical requirement for electrical ventricular defibrillation is ventricular defibrillation is the attainment of a sufficient the attainment of a sufficient current density. . .” current density. . .” 11

1 WA Tacker. Electrical Defibrillation. Boca Raton, Florida, CRC Press, Inc.; 1980 p14.

The Important RelationshipThe Important Relationship

Voltage

ImpedanceCurrent=

Ohm’s Law Tells Us . . .• As the impedance increases, voltage must

increase to deliver the same amount of current.

Effect of Patient Impedance Effect of Patient Impedance on Biphasic Waveformson Biphasic Waveforms

RectilinearBiphasic

High Impedance

First GenerationBiphasic

Low Impedance

-20

0

10

20

30

40

50

0 4 8 12

-10

-20

0

10

20

30

40

50

0 4 8 12

-10

-20

0

10

20

30

40

50

0 4 8 12

-10

-20

0

10

20

30

40

50

0 4 8 12

-10

The Current ParadoxThe Current Paradox

““Defibrillation depends on the Defibrillation depends on the successful selection of energy to successful selection of energy to generate sufficient current flowgenerate sufficient current flow through the heart (transmyocardial through the heart (transmyocardial current) to achieve defibrillation current) to achieve defibrillation while at the same time while at the same time causing causing minimal injuryminimal injury to the heart.” to the heart.”

American Heart Association. Circulation. 2000:1029(suppl I):I-90-I-94.

Two Components of CurrentTwo Components of Current

Peak Current• Highest current delivered over the

course of shock delivery• Associated with myocardial dysfunction

Average Current• Average delivered over the course of

the shock• Determinant of successful defibrillation

Peak Current by WaveformPeak Current by Waveform

43

35

15

0 10 20 30 40

RBW@ 120J

Amps

BTE@ 130J

Mono@ 200J

50

Current

Time

Monophasic at 200 Joules

Biphasic Truncated Exponentialat 150 Joules

Rectilinear Biphasicat 120 Joules

Average Current at 150 JoulesAverage Current at 150 Joules

5

8

11

14

17

20

75 100 125 150

Resistance (ohms)

Cu

rren

t (a

mp

s)

150J BTE

150J RBW

Source: ZOLL Medical Corporation

Average Current at Max EnergyAverage Current at Max Energy

10

15

20

25

75 100 125 150

Resistance (ohms)

Cu

rren

t (a

mp

s)

360J BTE

200J RBW

Source: ZOLL Medical Corporation

1 Higgens et al. Prehospital Emergency Care 2000;4:305-313.2 Bardy GH, et al. Circulation. 1996; 94: 2507-2514.3 Mittal S., et al. Journal of the American College of Cardiology. 1999; 34: 5.

Next to a Common StandardNext to a Common Standard

Studies Used 200J MDS as the ControlStudies Used 200J MDS as the Control

Efficacy

75%

80%

85%

90%

95%

100%

Medtronic1

130JBTE

200JMDS

Agilent2

130JBTE

200JMDS

ZOLL3

120JRBW

200JMDS

Versus the AHA ThresholdsVersus the AHA Thresholds

The 1997 AHA Statement on Biphasic Waveforms defined thresholds for waveform equivalency and superiority.

Only the clinical performance of theOnly the clinical performance of theRectilinear Biphasic waveformRectilinear Biphasic waveform

exceeds the threshold for superiority.exceeds the threshold for superiority.

American Heart Association. Automatic external defibrillators for public access defibrillation: recommendations for specifying and reporting arrhythmia analysis algorithm performance, incorporating new waveforms, and enhancing safety. Circulation. 1997; 95: 1677-1682.

Guidelines 2000 . . .Guidelines 2000 . . .

• Define biphasic energy levels as 200 joules • Fail to address biphasic shocks in excess of

>200 joules• Protocols are waveform specific• Given Class IIa recommendation to biphasic

shocks 200 joules

SummarySummary

• Biphasic waveforms differShapeResponse to ImpedanceCurrent DeliveryDocumented Clinical Performance

• Biphasic waveforms are effective for external defibrillationEquivalent performance with less energyRectilinear biphasics promise superior performance