Review of “Avoid Study”
Presented by:
Paul T. Frantz, MD
Medical Director, Cardiology
Carilion Clinic, Roanoke Va
27th Annual Regional Cardiac Symposium
September 30, 2016
No disclosures
Background Information
• Laboratory studies on dogs:
• High concentrations of O2 might be of benefit
• Limited human studies:
• High O2 resulted in ↓ CO, ↑ BP & ↑ SVR
• ↑ coronary resistance, ↑ free radicals, microcirculation
• Supplemental O2 in hospital: no benefit
• Russian Study: mixed results
• Hyperbaric O2 during thrombolysis: no benefit
• Cochrane Collaboration: pooled data
suggests harm but under powered
AVOIDStudy
AirVersusOxygenInST‐elevation
MyocarDial Infarction
DrDionStubMBBSPhDFRACP
BakerIDIHeart&DiabetesInstitute,MelbourneAustralia
StPaul’sHospitalVancouver,Canada
Stub, D, et al.Circulation. 2015;131:2143-2150
Trial Design: Is O2 beneficial prior
to reperfusion?
ParamedicsAssessPatient
SymptomsofSTEMI<12hours,O2 Sats≥94%
ST‐elevation≥2contiguousECGleads
IntendedforprimaryPCI
Randomize 1:1
N=218
Oxygen
8L/minuteviafacemask
N=223
NoOxygen
UnlessO2 fallsbelow94%than
minimumtitratedO2viamask
PhysicianconfirmsSTEMI
PrimaryPCI
O2(8L/min)inCathLab
ExclusionCriteria
Oxygensaturation<94%onpulseoximeter
Oxygenadministrationpriortorandomization
Alteredconsciousstate
Plannedtransporttoanon‐participatinghospital
PrimaryPCI
NoO2inCath Lab
unlessO2 fallsbelow94%
CardiacEnzymesfor72hours
CardiacMRIandclinicalfollowup6months
Pre‐Hospital
In‐Hospital
Results
%ofpatientsreceivingoxygen
SpO2inpatientswithSTEMI
100%
OxygenArm
99%
NoOxygenArm
98%
97%
96%
95%
Arrival
Arrival
of
at
paramedics hospital
Arrival
at
cathlab
2hours
4hours
post
post
procedure procedure
Primary Endpoint: Infarct Size
Creatine Kinase, U/L
Areaundercurvep=0.04
Primary Endpoint: Infarct Size
Troponin I, mcg/L
Areaundercurvep=0.12
Endpoints from ‘AVOID’
• Primary: O2 group vs no O2: (favoring no O2)
• Increased MI size by peak CK levels (p=0.01)
• Troponin I – non-significant result
• Trend for ↑ MI size at 6 mo by cardiac MRI (p=0.06)
• Secondary: O2 group vs no O2 (favoring no O2)
• More frequent arrhythmias (5.5% vs 0.9%) (p=0.05)
• More frequent recurrent MI’s (40% vs 31%) (p<0.01)
• Other endpoints: no difference
• Mortality: trend for better survival with O2 (p=0.11)
• 4/218 with O2; 10/223 w/o O2: ?Chance?
PaO2 Results from ‘AVOID’
Problems with ‘AVOID’
• Differences in two groups:
• % Ant MI
• % resolution of ST ▲’s
• O2 administered at 8 L/min
• Biomarkers are a surrogate end point
• Some of no O2 patients received O2 for ↓ O2 sats, O2
in cath lab & O2 in PCU
• ABG’s not measured
• Different mechanisms for arrhythmias vs MI
Conclusions from ‘AVOID’
Supplemental oxygen therapy in patients with STEMI
but without hypoxia appeared to:
• increase myocardial injury
• Increase recurrent myocardial infarction
• Increase major cardiac arrhythmia
• Was associated with larger myocardial infarct size
assessed at six months
Underpowered for primary endpoints but suggestive
SCAAR study in progress with 5000 – results years
away
“Take Home” Conclusions:
• Routine oxygen administration not
associated with reductions in symptoms or
infarct size
• High flow oxygen supplementation may be
accompanied by harm
• Withholding routine oxygen therapy is safe
in normoxic patients with an AMI
On the basis of current evidence:
“Providing oxygen to patients with acute
STEMI en route to primary PCI is indicated
for patients with hypoxemia or overt
pulmonary congestion”
Dr. Karl Kern,
Univ of Arizona
“Supplemental oxygen in stable, normoxic
STEMI patients may not be necessary”