The past, present

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The past, present and future of ACT testing
Michael F. Corsello, MS, MBA
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Man lives with arteriosclerosis, and dies of the
complicating thrombosis.
Dedichen J. Brit Med J 1956111038-1039
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in fact, 68 of us in this room will die because
of a blood clot
cheery Corsello thought of the day !
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71 of us will have damaging heart disease
before the age of 55
MORE cheery Corsello thoughts
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(No Transcript)
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Rapid Thrombosis Treatment Management
7 Home
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Thrombosis Management
cTnI
ACT
PT
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• ACT HISTORY

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Coagulation testing

• Monitoring hemostasis

Bleeding
Clotting
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Coagulation testing
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• ACT HISTORY

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ACT history

• ACT discovered in 1966
• Dr. Paul Hattersley Pathologist
• Designed to identify FVIII deficiency quickly
• Handheld test
• Glass tube, 12 mg BD diatomaceous earth, 37
  degree C waterbath, visual fibrin identification
• Used on some renal dialysis patients on heparin
• Noticed prolongation due to heparin

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ACT history

• Shortly after ACT discovery, CPB was growing
• Brian Bull, MD
• Cardiac anesthesiologist read article on ACT
• Thought would help the largest CPB problem
• Heparin therapy guidance
• Performed many seminal studies
• 480 target time study
• Used 2 point dosing curve and physical oxygenator
  (for clots) evaluation
• Did ENTIRE study with handheld ACT test

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ACT history

• 1972 first commercial ACT instrument being
  developed
• Instrument called Hemochron being built in garage
  in Edison, NJ
• Mimicked test tube components (celite, glass
  tube, warmed to 37 C)
• Used magnetic bar displacement to identify when
  blood went from liquid to solid

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• ACT BACKGROUND

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What is an ACT used for

• Maintain Balance
• Bleeding Thrombosis
• Heparin
• Rapid anticoagulant effect
• Individual sensitivities vary significantly
• Potency differences
• Source Bovine or Porcine
• Lot to Lot variability
• Rapidly Reversible with Protamine

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Surgical impact on coagulation

• Monitoring hemostasis

Bleeding
Clotting
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Traditional Activated Clotting Time

• Whole blood test, performed at patient site
• Monitor anticoagulant heparin given during
• Cath Lab (PTCA)
• CVOR (CABG)
• Renal dialysis
• Results available in minutes
• General assessment of delay in normal clotting

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Traditional Activated Clotting Time

• Relies on physical blood clot to turn off
  instrument
• Affected by hemodilution
• Affected variably by platelet dysfunction
• Affected by fibrinogen
• ACT tests have traditionally had marginal
  reliability due to operator variances

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Heparin mechanism of action

• Indirect
• Binds to Antithrombin III, a thrombin inhibitor
  and natural anticoagulant, and enhances its
  activity 100-fold
• Can be neutralized with protamine sulfate

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Fibrin clot formation the coag cascade
Platelet Biochemistries and/or contact activation
Tissue Biochemistries
Intrinsic Pathway

• Since the thrombin is inhibited, it cannot cleave
  circulating fibrinogen to create fibrin (blood
  clot)

Thrombin
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Heparin

• Heparin is not given to prolong the ACT, but
  rather to hyper-activate the ATIII in
  circulation (of the patient) and slowdown
  thrombin generation

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ACT PRESENT
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Mechanical ACT testing
Initiation of cascade Celite (or kaolin) is
added at start of test
Celite
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Proenzyme A
Active Enzyme A
Active Enzyme B
Proenzyme B
Proenzyme C
Active Enzyme C
Proenzyme D
Active Enzyme D
TimeACT
Thrombin
Prothrombin
Inactive enzyme in plasma
Fibrin
Fibrinogen
Clot Forms
Activated Enzyme
Clot formation is detected as endpoint
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Mechanical detection systems Hemochron
Tube containing Celite or Kaolin

• Hemochron detection method
• Single point clot detection
• Detection distance of 90 degrees
• Clot must be stable enough to travel 90o to shut
  off instrument
• Measures physical change in viscosity

The tube is rotated and the position of the
magnetic bar is monitored when the blood clots
the bar moves with rotating tube.
magnetic bar
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Mechanical detection systems Medtronic
Cuvette containing liquid Kaolin

• Preheats test vesicle
• Optical detection of flag motion
• Flag lifts up and dropped
• Measures flag motion through sample
• Clot mass does not need to be as stable (as
  Hemochron) but still measures blood clot
  formation based on viscosity

flag/plunger
The rate at which the plunger falls through the
blood is monitored as the blood clots it slows.
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Mechanical detection systems Hemochron Jr.
Cuvette containing liquid Kaolin

• Preheats test vesicle
• Optical detection of blood movement
• Moves blood thru a restriction
• Fibrin forms, the blood thickens and occludes
  restriction
• Micro-measurement of blood viscosity changes

The blood is pumped back and forth through a
restriction when the blood clots its motion
changes.
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Mechanical detection systems shortfalls

• Not all patients can form a consistent viscous
  clot
• Dilution, heparin, reduced levels of clotting
  factors, cellular components and fibrinogen
• The endpoint in different methods is triggered by
  different threshold viscosity values one reason
  that mechanical methods do not correlate well to
  one another.
• Various methods/levels of automation
• Some systems suggestive of operator influence of
  test result

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Chemical detection systems i-STAT.

• Uses typical activators to start clotting process
• Chemical detection of thrombin formation
• Derivation of lab chromogenic testing
• Controlled sample addition, mixing, and movement
• Lower CVs

A direct chemical detection of thrombin formation
in the sample
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ACT detection systems surgical performance

• Triggered endpoints are typically more variable
• With a 15 C.V., paired results with differences
  of more than 150 second (swing) at 500 seconds
  will be seen.
• With a 20 C.V., paired results can have
  differences as great as 200 second (swing).

Data from academia and package inserts
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Sadly, there is no standard in ACT testing
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Mechanical detection systems shortfalls
Data from Huffman, et.al. 1998 AmSECT meeting
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ACT Innovation
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ACT Innovations

• The first chemical endpoint ACT detection
  released in 2002
• MINIMAL affect from temperature, fibrinogen, RBC,
  PLT variables
• Increased automation
• Limiting operator influence on test result
• Improvement in real-time QA
• Data management
• Improvement of ACT specificity and lower CVs

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First chemical endpoint ACT detection

• Non-mechanical assessment of ACT
• Chemical detects the re-appearance of thrombin

Thrombin
Prothrombin
Since the thrombin is inhibited, it cannot cleave
circulating fibrinogen to create fibrin (blood
clot)
uninhibited thrombin
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First chemical endpoint ACT detection
Thrombin ( its presence converts our substrate
to release an electrical signal )
Gly-Pip-ArgOH

S-CH2CH2OH
S-CH2CH2OH
e-
S-CH2CH2OH
(MeO-PADA)
S-CH2CH2OH
S-CH2CH2OH
electrode
S-CH2CH2OH
S-CH2CH2OH
S-CH2CH2OH
S-CH2CH2OH
S-CH2CH2OH
MeO-PADA
S-CH2CH2OH
S-CH2CH2OH
S-CH2CH2OH
Amperometric sensor
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First chemical endpoint ACT detection
Initiation of cascade Celite (or kaolin) is
added at start of test
Celite
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Proenzyme A
Active Enzyme A
Active Enzyme B
Proenzyme B
Proenzyme C
Active Enzyme C
Proenzyme D
Active Enzyme D
TimeACT
Thrombin
Prothrombin
Inactive enzyme in plasma
substrate
Electroactive Marker
Activated Enzyme
Detected at sensor
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First chemical endpoint ACT detection
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Improved automation

• Automatic sample metering
• Not all of the sample in the cartridge is used
  for testing

This is done because A metered volume has to be
pushed so that the blood volume that moves over
the reagent is reproducible from cartridge to
cartridge.
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Improved automation
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Improved automation
Coagulation sensor
Mixing Control
Mixing Control
Dried reagent
Position of forward oscillation
Amplitude and period of oscillation is controlled
by maintaining the plunger speed the time for
which the conductivity circuit is open or closed
Open Circuit
Position of reverse oscillation
Closed Circuit
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Improved real-time QA
Open circuit reading in contact with dry chip
Open circuit during mixing
Closed circuit during mixing
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Improved real-time QA
Assure heating using probes
Instrument-controlled Quality Assurance at
every step
Assure using conductivity
Heating
Assure by applying high voltage and measuring
current
Mixing
Verify substrate check mixing
Apply low voltage and measure current
Looking for signal increase
Determine using current levels, slopes and
curvature
Thrombin detection
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ACT Future
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ACT Future

• Evolution of ACT methodologies by decades end
• Drift away from viscous detection to direct
  chemical detection of heparin/thrombin
• Improve anticoagulant specificity
• Less environmental impact
• Dilution
• Temperature
• Operator
• Cellular levels
• Antiplatelet agents

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ACT Future

• Alternative anticoagulants
• Many new direct thrombin inhibitors will be used
  clinically
• Need to be compatible with direct and indirect
  anticoagulants
• Continued improvements in automation
• Remove the human influence
• Consistent performance from operator to operator
  and site to site
• Continued improvements in real-time QA
• Trusted answer or no answer In-line monitors

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ACT Future

• Decreasing need to monitor newer drugs
• Some drugs that are just 5-7 years out can truly
  claim such factor specificity, that they indeed
  do not need to be monitored
• This assumption however relies on normal renal
  function
• ACT may be replaced by bedside Creatinine testing