Putting Out the Fire

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Putting Out the Fire
Shadwan Alsafwah, MD The University
of Tennessee at Memphis Staff
Support Dr. Richard Davis
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Introduction

• Over the past three decades, the adoption of
  highly effective new pharmacological and
  mechanical reperfusion treatments has improved
  survival for patients who experience acute MI
• Unfortunately, reperfusion, although it relieves
  or reduces ischemia and necrosis, is followed by
  morphological and functional changes that
  ultimately result in tissue damage known as
  reperfusion injury
• Myocardium that is viable at the end of the
  ischemic period may therefore lose viability
  during reperfusion

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• Conversely, the extent of myocardial necrosis
  correlates with the severity and duration of
  myocardial ischemia
• The net effects of reperfusion are usually
  beneficial, but strategies or interventions that
  could prevent its negative counterparts would
  optimize myocardial salvage and improve
  functional recovery

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Reperfusion Injury

• Reperfusion injury, occurring with restoration of
  blood flow to ischemic tissue, is associated with
  myocardial cell death and apoptosis,
  microvascular injury, myocardial stunning, and
  arrhythmiasall of which can result in mortality
  and morbidity, including heart failure
• Reperfusion injury can occur after percutaneous
  coronary intervention (PCI) or thrombolysis for
  acute myocardial infarction (MI) as well as after
  coronary blood flow is halted for 30 min or
  longer during coronary artery bypass graft (CABG)
  surgery

Kloner RA, et al. Circulation 104
(2001)29819
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Reperfusion Injury During CABG

• In the controlled ischemia/reperfusion setting of
  coronary revascularization bypass graft surgery,
  where the myocardium must be made ischemic, an
  estimated 3 to 20 of patients experience MI
  associated with reperfusion after bypass grafting
  
• Up till very recently, no effective pretreatment
  to prevent or lessen the loss of viable
  myocardium has been effective

Mangano, DT. West J Med 161 (1994), 879
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Approaches to Prevent from Reperfusion Injury

• Numerous studies evaluating the use of
  pharmacologic and mechanical therapies to
  mitigate reperfusion injury have proven
  unsuccessful not only in CABG surgery but in PCI
  as well
• These approaches have focused on oxygen free
  radicals, neutrophil accumulation and activation,
  intracellular Ca2 overload via sodium-hydrogen
  exchange (NHE) inhibition, complement activation,
  hypothermia, hyperbaric oxygenation, and distal
  embolic protection devices

Stone GW, et al. JAMA 293 (2005), pp.
106372
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• In each of these approaches, specific mechanisms
  of reperfusion injury were targeted
• Their disappointing results might reflect the
  inherent limitations of therapies that target
  specific mechanisms or cell types involved in the
  pathophysiology of reperfusion injury, perhaps
  because they fail to address the full spectrum of
  its complexity

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The Cellular Mechanisms of
Ischemia-reperfusion Injury
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During Ischemia

• Cessation of oxygen supply in ischaemia leads to
  a loss of ATP production and an increase of
  reactive oxygen species (ROS) in the mitochondria
  
• Reduced activity of the ATP consuming Na-K-pump
  leads to Na accumulation in the myocyte and the
  resting membrane potential is lowered
• With the development of acidosis, the
  Na-H-exchanger (NHX) further increases
  intracellular Na
• Under these conditions the Na-Ca2-exchanger
  (NCX) operates in the reverse mode, letting Ca2
  into the cell
• Ca2 also enters through the sarcolemmal L-type
  voltage-gated Ca2-channel (L) as the resting
  membrane potential is low
• The increased Ca2 is taken up into the
  sarcoplasmic reticulum (SR) by the SR Ca2-pump
  SERCA2 (P) and released from there via two types
  of release channels (RYR) and the (IP3R),
  leading to contraction

Zaugg M, et al. BJA 93 (2004), 21-33
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During the First Minutes of Reperfusion

• Reoxygenation during reperfusion restores ATP
  production with a further boost of ROS
• Reactivation of the Na-K-pump by ATP slowly
  restores the sodium gradient leading to normal
  cation fluxes with the NCX eventually extruding
  the excess of cytosolic Ca2
• During the early reperfusion phase when the
  intracellular Ca2 level is still high,
  myocardial contracture (supercontraction of
  myocytes) may develop
• When contracture affects the entire heart as it
  may occur after global ischaemia, it has been
  termed the stone heart phenomenon

Zaugg M, et al. BJA 93 (2004), 21-33
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During the Subsequent Hours of Reperfusion

• With the resumption of blood flow, the
  endothelial lining of blood vessels subjected to
  ischemia-reperfusion becomes permeable, thus
  causing interstitial edema
• Endothelial cells in reperfused myocardium assume
  an activated state in which they express adhesion
  proteins, release cytokines, and reduce
  production of NO
• This promotes adherence, activation, and
  accumulation of neutrophils and monocytes in the
  ischemic-reperfused tissue

Piper HM, et al. Ann Thorac Surg 75 (2003), 644-8
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• The release of reactive oxygen species and
  proteolytic enzymes from these activated
  leukocytes can contribute to the damage of
  myocytes and vascular cells
• Vascular plugging by adherent leukocytes and
  aggregated platelets can also promote a slow- or
  no-reflow phenomenon, already favored by tissue
  contracture and increased pressure of
  interstitial edema
• It seems that these additional reperfusion-induced
  noxes contribute to infarct development
  predominantly during the first 2 hours of
  reperfusion, as myocardial necrosis almost
  reaches its final size during this period

Piper HM, et al. Ann Thorac Surg 75 (2003), 644-8
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Adenosine

• Adenosine, an endogenous purine nucleoside, is an
  anti-injury autocoid that targets a broad
  spectrum of the pathophysiology of
  ischemia/reperfusion injury
• It has been shown to improve post-ischemic
  ventricular function and prevent myocardial
  necrosis and apoptosis

Adenosine
Gruber HE, et al. Circulation 80 (1989),
140011
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Adenosine Anti-inflammatory Effects

• Inhibits neutrophil activation, adhesion to
  endothelium, and migration into the myocardium
• Inhibits cytokine release from mononuclear cells
• Inhibits release of oxygen radicals from
  granulocytes
• Inhibits cardiomyocyte apoptosis
• Prevents endothelial damage

Gruber HE, et al. Circulation 80 (1989),
140011
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Gruber HE, et al. Circulation 80 (1989),
140011
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Other Protective Effects

• Adenosine also has an anti-platelet effect that
  may have a role in maintaining infarct artery
  patency
• Increases coronary collateral blood flow during
  ischemia
• In isolated, perfused rat hearts, adenosine given
  at reperfusion increases glucose oxidation and
  inhibits glycolysis, reduces tissue lactate
  levels, and increases ATP levels. These effects
  tend to decrease cellular acidosis and Ca2
  overload and are associated with beneficial
  effects on mechanical function
• Most importantly, adenosine has been shown to be
  a powerful inducer of ischemic preconditioning

Gottlieb RA, et al. J Clin Invest 97 (1996), pp.
23918
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Adenosine Role in Ischemic Preconditioning

• Stimulation of G-protein coupled receptors by
  primary messengers activates phospholipases (PL)
• PL in turn produce two second messengers
  originating from phosphatidylinositol
  bisphosphate (PIP2), namely inositol
  trisphosphate (IP3) and diacylglycerol (DAG)
• DAG activates different protein kinase C (PKC)
  isoforms
• PKC isoforms translocate to their appropriate
  target sites, activating the sarcolemmal and
  mitochondrial ATP-dependent potassium channels
  (K) and initiating distinct gene expression in
  the cell nucleus

Zaugg M, et al. BJA 93 (2004), 21-33
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Beneficial Effects of Intracoronary Adenosine as
an Adjunct to Primary Angioplasty in Acute
Myocardial Infarction
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Methods

• 54 patients with AMI undergoing primary PTCA were
  randomized to either intracoronary adenosine or
  saline (27 patients in each)
• Inclusion criteria
• Patients referred for PTCA within 3 hours
  from the onset of AMI underwent diagnostic
  coronary angiography. If the culprit lesion was
  suitable for PTCA and presented with a TIMI flow
  from 0 to 2, the patient was included in the
  study and randomized

Marzilli M, et al. Circulation 101 (2000), pp.
21549
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• Exclusion criteria
• -History of bronchospasm
• -Therapy with theophylline derivatives
• -Patients who had received thrombolytics in
  
• ER
• The 2 groups were similar for age, sex, and
  infarct location

Marzilli M, et al. Circulation 101 (2000), pp.
21549
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Clinical and Angiographic Characteristics
Marzilli M, et al. Circulation 101 (2000), pp.
21549
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Treatment Regimen

• The obstruction of the infarct-related artery was
  crossed with a 0.014-in guidewire
• Over-the-wire balloon catheter was positioned at
  the level of the obstruction
• The wire was pulled out, and diluted contrast was
  injected through the central lumen of the
  catheter to confirm positioning of the catheter
  tip and to assess patency of the distal vessel
• The balloon was inflated, and either adenosine (4
  mg in 2 mL saline) or saline (2 mL) was
  hand-injected into the distal vascular bed
• The rate of injection was such as to complete
  treatment in 1 minute

Marzilli M, et al. Circulation 101 (2000), pp.
21549
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• The guidewire was then readvanced into the distal
  vessel, and the balloon was deflated to initiate
  reperfusion of the ischemic territory. The
  dilatation procedure was completed according to
  standard technique
• Stenting of the dilated coronary segment was
  performed only for suboptimal balloon results or
  flow-limiting dissections
• After completion of the dilation procedure,
  patients were observed in the catheterization
  room for 30 minutes. The final angiogram was then
  obtained, and the patient was transferred to ICU
• Technically, the drug was administered distal to
  the coronary obstruction and before the onset of
  reperfusion

Marzilli M, et al. Circulation 101 (2000), pp.
21549
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End Points

• The primary end points of this study were
  feasibility and safety of intracoronary adenosine
  administration in the setting of primary PTCA and
  its effect on coronary blood flow
• As secondary end points, indexes of myocardial
  damage, including left ventricular regional
  function, Q-wave MI, recurrence of angina,
  nonfatal MI, heart failure, and cardiac death
  were evaluated

Marzilli M, et al. Circulation 101 (2000), pp.
21549
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Results Feasibility and Safety

• The injections of adenosine or saline in the
  distal coronary bed were well tolerated and free
  of side effects
• No patients complained of worsening of chest pain
  
• No patients suffered from hemodynamic instability
  
• No bradyarrhythmias or tachyarrhythmias were
  associated with this protocol, including
  adenosine injection into the RCA

Marzilli M, et al. Circulation 101 (2000), pp.
21549
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Results Angiographic Results
Effect of adenosine (ADO) on coronary blood
flow Intracoronary adenosine was associated
with higher incidence of TIMI 3 flow and with a
significant reduction in prevalence of
no-reflow phenomenon
Marzilli M, et al. Circulation 101 (2000), pp.
21549
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Results The Clinical Events

Marzilli M, et al. Circulation 101 (2000), pp.
21549
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Results Clinical Course
Effect of adenosine (ADO) on clinical Course
In adenosine group, a significant reduction of
death, Q-wave MI, and major adverse cardiac
events (MACE) was observed
Marzilli M, et al. Circulation 101 (2000), pp.
21549
29
Results Left Ventricular Function
Percentage of initially abnormal segments showing
worsening (remodeling) or recovery at 1 week
Adenosine (ADO) adjunct to direct PTCA was
associated with early recovery of wall motion
Marzilli M, et al. Circulation 101 (2000), pp.
21549
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A Randomized, Double-Blinded, Placebo-Controlled
Multicenter Trial of Adenosine as an Adjunct to
Reperfusion in the Treatment of Acute Myocardial
Infarction (AMISTAD-II)
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Design

• Double-blinded, placebo-controlled, randomized
  study conducted in 13 countries (390 sites) and
  enrolled 2,118 patients between June 1999 and
  December 2000
• Objectives to determine the effect of
  intravenous adenosine on clinical outcomes and
  infarct size in ST-segment elevation myocardial
  infarction (STEMI) patients undergoing
  reperfusion therapy

Ross AM , et al. J Am Coll Cardiol 45 (2005),
pp. 177580
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Methods

• Enrollment required age over 18 years,
  reperfusion therapy (fibrinolysis or percutaneous
  intervention) within 6 h of onset of ischemic
  type pain (30 min), and electrocardiographic
  evidence of anterior STEMI
• Electrocardiographic requirements were either 2
  mm of ST-segment elevation in at least two
  contiguous precordial leads or new left bundle
  branch block

Ross AM , et al. J Am Coll Cardiol 45 (2005),
pp. 177580
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Exclusion Criteria
Ross AM , et al. J Am Coll Cardiol 45 (2005),
pp. 177580
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Treatment Regimen

• Patients selected for reperfusion therapy were
  randomly assigned to adenosine, 70 µg/kg/min or
  50 µg/kg/min (utilized to evaluate dose-related
  responses), or to placebo in a 111 scheme
• Study drug infusion (3 h) had to be started
  within 15 min either of the start of fibrinolysis
  or before coronary intervention

Ross AM , et al. J Am Coll Cardiol 45 (2005),
pp. 177580
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End Points

• The primary end point was new congestive heart
  failure (CHF) beginning 24 h after
  randomization, or the first re-hospitalization
  for CHF, or death from any cause within six
  months
• Infarct size was measured in a subset of 243
  patients by technetium-99m sestamibi tomography

Ross AM , et al. J Am Coll Cardiol 45 (2005),
pp. 177580
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Results Infarct Size
Infarct size measured as a percent of the LV by
technetium-99m SPECT in the 243 patients in the
infarct size substudy Only the higher
adenosine dose group showed a significant
reduction in median infarct size relative to
placebo (p 0.023)
Ross AM , et al. J Am Coll Cardiol 45 (2005),
pp. 177580
37
Infarct size measured as a percent of the LV by
technetium-99m SPECT in the 28 patients in the
infarct size substudy who suffered a primary end
point compared with the 215 patients who did not
have an end point The group with a primary end
point had larger infarcts than did those without
(p Ross AM , et al. J Am Coll Cardiol 45 (2005),
pp. 177580
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Results Primary End Points

• There was no difference in the primary end point
  between placebo (17.9) and either the pooled
  adenosine dose groups (16.3) or, separately, the
  50-µg/kg/min dose and 70-µg/kg/min groups (16.5
  vs. 16.1, respectively, p 0.43)
• likely explanation for failure of the trial to
  demonstrate a clinical benefit was that it was
  underpowered
• -The sample size calculation was based on a
  reduction of events in the pooled adenosine group
  by 25 compared with placebo. The reduction
  observed was only 11
• -This result in part reflects the modest
  infarct size reduction in the 50 of patients
  receiving the lower adenosine dose

Ross AM , et al. J Am Coll Cardiol 45 (2005), pp.
177580
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Adverse Events by Treatment Groups
Ross AM , et al. J Am Coll Cardiol 45 (2005),
pp. 177580
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AMISTAD-II Results Conclusion

• A 3-h adenosine infusion at 70 µg/kg/min (but not
  at the lower 50-µg/kg/min dose) reduces infarct
  size in anterior MI patients when given in
  conjunction with reperfusion therapy
• The major limitation of this study was that the
  sample size was too small to confirm that the
  observed adenosine-related reduction in the
  combined clinical end point was statistically
  significant

Ross AM , et al. J Am Coll Cardiol 45 (2005), pp.
177580
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Acadesine

• Acadesine was first isolated from a culture
  medium of sulfonamide inhibited Eschericia coli
  in 1952
• During studies in cultured human lymphoblasts it
  was found that Acadesine could augment adenosine
  release from cells under certain conditions

Acadesine
5-Aminoimidazole-4-carboxamide-1-b-riboside
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• Acadesine represents the prototype of a new class
  of Adenosine regulating agents (ARAs) that
  substantially increase endogenous adenosine, but
  importantly, only in ischemic tissue and only
  under conditions of adenosine triphosphate (ATP)
  catabolism
• The exact mechanism of action for increased
  extracellular adenosine during ATP catabolism in
  the presence of Acadesine remains unknown

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Post-Reperfusion Myocardial Infarction
Long-Term Survival Improvement Using
Adenosine Regulation With Acadesine

• Journal of the American College of Cardiology, In
  Press, Corrected Proof, Available online 11 May
  2006

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Design

• Multi-institutional (54 centers), prospectively
  designed, randomized, placebo-controlled, and
  double-blinded study that assessed the effects of
  acadesine versus placebo on MI and secondarily on
  the combined outcome of cardiac death, MI, or
  stroke assessed at 4 days after CABG surgery
• Long-term follow-up study was prospectively
  designed to investigate the effects of acadesine
  versus placebo on 2-year, all-cause mortality
  after perioperative MI
• Hypothesized that, assessed against placebo,
  acadesine treatment improved 2-year survival
  among those patients suffering post-reperfusion
  MI

Mangano DT, et al. JACC, in press
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Methods

• 2,698 patients undergoing CABG surgery were
  randomized to receive placebo (n 1,346) or
  acadesine
• (n 1,352) by intravenous infusion (0.1
  mg/kg/min 7 h) starting approximately 15 min
  before induction of anesthesia, and also in
  cardioplegia solution (placebo or acadesine 5
  µg/ml)
• Myocardial infarction was prospectively defined
  as 1) new Q-wave with CK-MB elevation (daily
  electrocardiography 16 serial CK-MB
  measurements) or 2) autopsy evidence

Mangano DT, et al. JACC, in press
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Baseline Characteristics for All Patients,
Patients Suffering MI, and Patients Not Suffering
MI
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Results Post-reperfusion MI

• Myocardial infarction occurred in 100 of the
  2,695 patients enrolled (3.7)
• Although acadesine reduced the incidence of MI
  (placebo, 4.01 54 of 1,345 acadesine, 3.41
  46 of 1,350), the reduction was not
  statistically significant (p 0.24)
• The occurrence of a perioperative MI conferred a
  4.2-fold increased risk in 2-year mortality
• -Among the 2,595 patients not suffering
  infarction, 2-year mortality was 4.28, versus
  18.0 among the 100 patients suffering infarction
  (p
• -The primary mortality effect appeared over
  the first 30 days after infarction

Mangano DT, et al. JACC, in press
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Kaplan-Meier analysis of 2-year survival
according to with or without postoperative
myocardial infarction (MI) among the 2,698 study
patients
Mangano DT, et al. JACC, in press
52

• The impact of acadesine treatment on
  post-infarction survival was significant.
  Acadesine treatment was associated with a
  4.3-fold reduction in 2-year mortality from
  27.78 (15 of 54 placebo) to 6.52 (3 of 46
  acadesine) (p 0.006) with the principal benefit
  occurring over the first 30 days after MI
• The acadesine benefit was similar among diverse
  subsets, including gender, race, age, and disease
  acuity

Mangano DT, et al. JACC, in press
53
(A) Kaplan-Meier analysis of 2-year
survival according to the use or non- use
of acadesine among the 100 study patients
who sustained post- reperfusion MI
(B) Two-year mortality by-MI and
by-treatment
Mangano DT, et al. JACC, in press
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Two-year mortality acadesine versus placebo by
patient characteristic
Mangano DT, et al. JACC, in press
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Results of Multivariable Logistic Regression for
2-Year Mortality Among All Patients
Mangano DT, et al. JACC, in press
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Study Conclusion

• Post-reperfusion MI conferred a four-fold
  increased risk of long-term mortality
• Importantly, acadesine treatment was associated
  with a four-fold reduction in 2-year mortality
  after perioperative post-reperfusion, acute MI
• It is the first study of this size to demonstrate
  an important reduction in mortality associated
  with reperfusion-induced MI in any setting of
  clinical revascularization and the first to show
  a sustained benefit over the long term

Mangano DT, et al. JACC, in press
57
Summary

• Reperfusion injury, occurring with restoration of
  blood flow to ischemic tissue, is associated with
  myocardial cell death and apoptosis result in
  increased mortality and morbidity
• Adenosine and adenosine agonists are myocardial
  protectants. Their mechanisms of action include
  mainly anti-inflammatory effects and ischemic
  preconditioning
• The therapeutic approach of safely increasing
  endogenous adenosine at the site of ischemia
  enables reduction of reperfusion injury and
  post-infarction mortality

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Thank YOU