Prediction of Risk for Patients with Unstable Angina

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Prediction of Risk for Patients with Unstable
Angina

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5 steps of EBM

• Asking answerable clinical questions
• Find out current best evidence
• Critically appraising that evidence for its
  validity, impact, and applicability
• Integrating the critical appraisal with our
  clinical expertise and with our patients unique
  biology, values and circumstances
• Evaluating our effectiveness and efficiency in
  executing steps 1-4 and seeking ways to improve
  them both for next time.

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Introduction

• Coronary Heart disease the leading cause of
  heath for both men and women in USA
• 5,000,000 patients undergoing evaluation in EDs
  with cost of over 6,000,000,000.
• Symptoms are associated with an increased risk of
  sudden death, acute MI, and other
  life-threatening complications
• Stable angina V.S Unstable angina
• High-risk V.S. Low-risk patients

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Introduction

• Identification of patient risk is central to all
  further patient management in unstable angina
• The evidence report focuses on clinical and
  laboratory markers of patient risk
• Chest Pain Units attempt to risk stratify based
  on readily available data
• The evidence report focuses on the assessment of
  the efficacy of the chest pain units.
• Information in this evidence report applies to
  adult men and women

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3 Key Questions

• What are the immediate clinical and ECG
  characteristics that tare independently
  associated with an increased risk of adverse
  outcome in patients with either chest pain that
  raises suspicion of cardiac ischemia or diagnosed
  unstable angina?
• AST(1954), LDH(1955), CK(1960s), CK-MB(1980s),
  Myoglobin(1994), cTnT cTnI(1994)

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3 Key Questions

• What is the prognostic value or negative troponin
  test in patients with proven or suspected
  unstable angina?

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3 Key Questions

• Are chest pain units and ED protocols effective,
  cost-saving, and safe for triaging patients with
  suspected unstable angina or myocardial
  infraction?

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Methodology Q1Data Sources

• MEDLINE form 1966 to 1998
• Keyword
• chest pain, angina pectoris, unstable angina,
  vatiant angina, vasospastic angina, acute
  coronary syndrome.
• Risk, stratification, prognosis, outcome,
  multivariate analysis

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Methodology Q1Study Selection

• Goal identify the factors in the clinical
  evaluation that identified higher risk patients.
• Multivariate analysis
• Studies without providing the quantitative
  results were excluded
• Evaluate clinical and ECG vatiables assessed on
  initial presentation in the ED or within the
  first 24 hours of admission in hospital.
• Studies focus on the importance of ST elevation
  were excluded.
• Statistically significant p value lt 0.05
• Non-English language studies were excluded.

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Methodology Q1Predictor Variables

• Demographic characteristics
• age, sex, race/ethnicity
• Medical history
• prior MI, unstable or stable angina,
  revascularization, congestive heart failure,
  cerebrovascular disease, hypertension, diabetes,
  and smoking history
• Symptom characteristics
• frequency, duration, and pattern of chest pain
• Initial physical examination findings
• blood pressure, heart rate, and pulmonary rales
  or other evidence of congestive heart failure
• Initial ECG findings
• ST-segment depression, transient ST-segment
  elevation, isolated T-wave inversions, other
  findings, or a normal ECG

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Methodology Q1Outcome Measures

• Cardiac death (death duo to cardiac cause)
• Myocardial infarction
• Urgent revascularization
• Other major cardiac complication
• CHF, nonfatal ventricular arrhythmia, high-degree
  heart block, AV dissociation, cardiogenic shock,
  cardiac arrest, emergent intubation, or insertion
  of an IABP
• A confirmed diagnosis of unstable angina (for the
  topic of chest pain)
• Readmission for unstable angina (for the topic of
  diagnised unstable angina)

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Methodology Q1Data Extraction

• Dr. GO
• Dr. Heidenreich a cardiologist

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Methodology Q1Statistical Analysis and
Reporting

• Quantitative pooled analysis or meta-analysis
• Determine summary estimates for significant risk
  factors
• Studies were stratified by type of patients
  evaluated
• Chest pain or diagnosed unstable angina
• Multivariate results were grouped
• Demographic characteristics
• Medical history features
• Symptom characteristics
• Initial physical findings
• ECG features.

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Methodology Q1Statistical Analysis and
Reporting

• Possible independent risk factors
• Found to be statistically significant in a
  multivariate analysis in at least one study.

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Methodology Q2Data Sources

• MEDLINE(1966-98) EMBASE(1974-98)
• Search criteria
• Troponin
• Angina or unstable or myocardial infarction or
  ischemia
• English
• Excluding animal study

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Methodology Q2Study Selection

• Cohort studies for patients with suspected
  ischemia
• Excluding
• Studies only enrolled patients with MI
• Case-controlled studies
• Studies without outcome of MI or death
• Studies enrolled patients with ST-elevation MI
  unless gave separate data on the non-ST-elevation
  MI

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Methodology Q2Data Extraction

• Initial title review by Dr. Heidenreich
• Total 3 reviewers
• 2 reviewers abstracted data for each article on
  standardized electronic data forms
• 1 reviewer compared their results and settled any
  differences.

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Methodology Q2Outcome Measures Subgroup
Comparisons

• The outcome of MI, death, or revascularization.
• Secondary analysis performed for MI occurring at
  least 48 hours.
• All patients with suspected ischemia (recruited
  from ED) V.S. Patients in whom MI had already
  been excluded (recruited from inpatient service).

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Methodology Q2Statistical Analysis

• Meta-analysis to combine outcome data.
• Estimate summary odds ratio for the ourtome of
  death and MI.
• Peto (fixed-effects) and DerSimonian-Laird
  (random-effects) methods
• Test homogeneity of study effect size
• Q statistic
• Complements the odds radio by providing an
  absolute difference in the adverse event rate
• Examine differences between study subgroups of
  trials.
• Analysis of variance

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Methodology Q3Data Source Study Selection

• MEDLINE from 1966 to 1998
• Randomized or controlled clinical trials
• Non-controlled studies gt 1,000 patients with
  suspected ACS.
• Studies assessed chest pain units, accelerated or
  rapid diagnostic protocols, or ED triage protocols

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Methodology Q3Outcome Measures

• Hospital admission rate
• Cost of care
• MI and death
• Other outcomes if comparisons were made between
  control and intervention groups.

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To be continued
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3 Key Questions

• Prognostic Value of the History, Physical
  Examination, and Electrocardiogram
• Prognostic Value of Troponin
• Evaluation of Chest Pain Units and Emergency
  Department Protocols