DR Joshna Rajbaran
CARDIAC TROPONIN and OUTCOME in ACUTE HEART FAILURE
NEJM 358;20 MAY 15,2008
- To describe the association between elevated cardiac troponin levels and adverse events in hospitalized patients with ACUTE DECOMPENSATED HEART FAILURE
- Because an objective risk-stratification process for the evaluation of acute decompensated heart failure is lacking.
- The value of measuring serum cardiac troponin when a patient presents with acute decompensated heart failure remains uncertain.
Trop T & Trop I are regulatory proteins with a very high specificity for cardiac injury . They are released early ( 2-4 hrs) & can persist for up to 7 days.
Troponin testing is primarily used as a tool in diagnosing myocardial infarctions.
Elevated levels suggest myocardial or some form of cardiac damage.
Insignificant if used in the absence of S&S of cardiac disease!!
THE KEY DIFFERENCES
- LARGE STUDY
- SHORT TERM OUTCOMES
- IN HOSPITALIZED PATIENTS WITH ACUTE DECOMPENSATED HEART FAILURE.
- Registry data:
- ADHERE( Acute Decompensated Heart Failure National Registry)
- Observational registry
- 274 hospitals
- TIME FRAME :October 2001 January 2004
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- Exclusion criteria:
serum creatinine level>2.0mg/dl
- Ischemic heart failure defined as cause if :
hx coronary artery disease OR
hx myocardial infarction
Not as exclusion criteria!!!
- Troponin measurement:
- Trop T & trop I were interchangeable levels considered positive, with cut-off based on expert consensus!!
- Trop T≥0.1µg/l & Trop I ≥1.0µg/l
- Statistical analysis:
- Primary out-come all causes
- Secondary out-come differences in medical mx / procedures / length of stay between +ve & -ve cohorts
- All outcomes were specified before the data were examined
- Statistical analysis ( cont)
- Associations between therapy & mortality
- Controls used in this regard
- Mortality was adjusted for relevant prognostic factors
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- SAS software
- Study designed by all authors
- ADHERE statisticians
- Time period
- Inclusion criteria
- Exclusion criteria
- IHD/Race / Gender
- troponin measurements justified
- Statistical analysis explained
- Tools and teams stated
- Troponin levels & characterists of the patients
105,388 84,872 ( 80.5% )
Hospitalized Trop tested
Cr < 2mg/dl
4240 (6,2%) 63,684
- There were small but significant differences between the two cohorts!!!
- Troponin- positive patients on admission:
- Lower SBP
- Lower EF
- Less likely AF
- Summary of characteristics given +ve vs –ve Trop
- No comparison made for the two proteins as only 2% had both tested!!
REVISION OF TERMINOLOGY
Odds ratio :provides a more useful way of presenting diagnostic data & can be applied to individual patients in a way that specificity & sensitivity cannot . It is a number btw 0 to infinity IF > 1 indicates that the information increases the likelihood of the suspected diagnoses. IF <1 it decreases the likelihood of the suspected diagnoses!!
SPECIFICITY: the proportion of patients WITHOUT the disease who are correctly identified by the test.
SENSITIVITY: the proportion of patients WITH the disease who are correctly identified by the test.
- In-hospital mortality
- Trop Positive (8.0%) > Trop Negative (2.7%) patients.......... (P<0.001)
- Actuarial analysis
- Trop as a continuous variable
- Adjusted odds ratio for death (P<0.001)
- IHF was not a useful discriminator of Troponin status, nor was it predictive of mortality.
- IHF Trop +ve 53% Trop –ve 52%
- Trop +ve mortality 8,4% IHF
- Trop –ve mortality 2,8% IHF
- Treatment , Troponin status & Mortality
- +ve more likely to receive: nitroglycerine , inotropes & vasodilators
- Resource utilization and mortality
- No interaction between treatment & Troponin status with respect to mortality
- Sample size large but justified
- Basic data adequately described
- Variables taken into account
- Missing data accounted for
- Numbers add up
- High risk cohort established
- Statistical significance assessed
Main findings and their value:
Prognostic value / cost
Early assessment of risk/ triage & management
Add to existing risk-stratification data for predicting the short term risk of death among patients with acute decompensated heart failure... Blood urea>15.4mmol/l
SBP < 115mm Hg
More aggressive therapeutic approach justified
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- Suggested guideline!!!
- Measurement of Troponin levels in patients who present with heart failure provides independent prognostic information regarding in hospital death & other clinical outcomes & can be useful for risk stratification of such patients!!!!
- Retrospective analysis
- ADHERE large data set : investigator discretion , diagnosis not objectively ascertained , cause of death not consistently recorded
- Troponin tests
- Introduction of variability/ bias
- Measurement only at admission
- Interaction with other biomarkers
- Under represented adverse outcomes
STRENGTHS & LIMITATIONS WITH SUGGESTIONS OFFERED
I FOUND NO REASON TO QUESTION THE STATISTICAL APPROACH
SUGGESTIONS FOR FUTURE STUDIES
OTHER RELEVANT STUDIES DOCUMENTED
With relevance to SA
- South African statistics :10 473 mortalities per annum d/t Heart Failure vs. US 55,704
- Further evaluation of other biomarkers vs Trop T required
- Cost factors need to be examined
- Ischaemic heart disease is the commonest cause for acute heart failure in America.
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- Finally , EARLY RISK STRATIFICATION may help identify patients who are likely to receive the greatest benefit from intensive therapy.....that in itself highlights it’s relevance to emergency medicine!!!!