This page separates information contained in the ClinicalTrials.gov record from statistical interpretation. The ClinicalTrials.gov record indicates that results are posted and that both registered primary endpoints have results posted, but it does not provide numerical estimates, confidence intervals, p-values, or formal statistical analyses for those endpoints.
1. Trial at a Glance
HEAT-PPCI was a completed, randomized, parallel-group, unmasked phase 4 trial evaluating unfractionated heparin and bivalirudin in acute ST elevation myocardial infarction. The ClinicalTrials.gov record reports 1829 enrolled participants and two registered primary endpoints assessed at 28 days.
| Feature | HEAT-PPCI |
|---|---|
| Trial name | HEAT-PPCI |
| Brief title | How Effective Are Antithrombotic Therapies in Primary Percutaneous Coronary Intervention |
| Condition | Acute ST Elevation Myocardial Infarction |
| Phase | Phase 4 |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None |
| Primary purpose | Treatment |
| Enrollment | 1829 |
| Arms | 2 |
| Status | Completed |
| Start | 2012-02 |
| Primary completion | 2013-12 |
| Lead sponsor | Liverpool Heart and Chest Hospital NHS Foundation Trust |
2. Clinical Question
The central clinical question can be stated directly from the trial structure: in patients with acute ST elevation myocardial infarction undergoing the trial's primary percutaneous coronary intervention setting, how do the randomized antithrombotic strategies of unfractionated heparin and bivalirudin compare with respect to the registered 28-day primary endpoints?
Population
Patients enrolled in the HEAT-PPCI trial with the condition recorded as acute ST elevation myocardial infarction.
Intervention
Unfractionated heparin.
Comparator
Bivalirudin.
Primary question
How do the randomized antithrombotic strategies compare on 28-day major adverse cardiac events and type 3–5 bleeding according to the BARC definition?
3. Trial Design
Unfractionated heparin
- Intervention type: drug
- Randomized treatment arm
- Primary endpoints assessed at 28 days
Bivalirudin
- Intervention type: drug
- Randomized treatment arm
- Primary endpoints assessed at 28 days
4. Endpoints
The registry lists 2 primary endpoints. Both have a time frame of 28 days and both are recorded in the ClinicalTrials.gov record as having results posted.
| Primary endpoint | Time frame | Results posted | Endpoint classification |
|---|---|---|---|
| Major Adverse Cardiac Events (MACE) in Terms of the Incidence of All Cause Mortality, Cerebrovascular Accident, Re-infarction and Additional Unplanned Target Lesion Revascularization | 28 days | Yes | Other / unclear |
| Type 3-5 Bleeding According to BARC (Bleeding Academic Research Consortium)Definition | 28 days | Yes | Other / unclear |
Understanding the two primary endpoints
The first endpoint is a composite clinical outcome. It incorporates all-cause mortality, cerebrovascular accident, re-infarction, and additional unplanned target lesion revascularization. A participant can therefore contribute to the composite through different component events, which makes the overall MACE result a combination of clinically distinct outcomes.
The second endpoint concerns type 3–5 bleeding according to the BARC definition. Unlike a composite that combines several different clinical event categories, this endpoint is organized around a specified bleeding classification.
Composite endpoint
A MACE result answers whether participants experienced at least one qualifying component of the composite, but the composite rate does not by itself show which component contributed most to the result.
Bleeding endpoint
The BARC type 3–5 endpoint uses a prespecified severity framework. Its interpretation depends on the definition and ascertainment of qualifying bleeding events.
5. Results Availability and Reporting Boundary
The ClinicalTrials.gov record states that results are posted, that 9 outcome measures are posted, and that results are posted for both registered primary endpoints. However, the ClinicalTrials.gov record contains no formal statistical analyses and provide no numerical treatment-group event counts, effect estimates, confidence intervals, or p-values.
The ClinicalTrials.gov record therefore establish that results exist in the registry record, but they do not provide enough numerical information here to reproduce a formal comparison between unfractionated heparin and bivalirudin.
6. Planned Analysis
For an endpoint such as the registered 28-day MACE composite, the natural primary analysis would generally compare the proportion of participants experiencing at least one qualifying component during the prespecified 28-day period. A treatment effect could be expressed using a risk ratio, risk difference, odds ratio, or another prespecified binary-outcome measure, depending on the statistical analysis plan.
For the 28-day type 3–5 bleeding endpoint, the same general framework applies if the endpoint is recorded as whether each participant experienced a qualifying bleeding event during the 28-day period. The analysis would compare the incidence of qualifying events between the randomized treatment groups.
| Endpoint | Typical statistical framework | Key quantity to report |
|---|---|---|
| 28-day MACE composite | Binary comparison of participants with at least one qualifying component | Between-group effect estimate with confidence interval and hypothesis-test result |
| 28-day BARC type 3–5 bleeding | Binary comparison of participants meeting the specified bleeding definition | Between-group effect estimate with confidence interval and hypothesis-test result |
For a binary endpoint, a simple risk difference can be written as
where each p represents the proportion of randomized participants experiencing the specified endpoint during the 28-day assessment period.
A risk ratio would instead compare the two event probabilities directly:
A value below 1 would indicate a lower observed event probability in the numerator group, while a value above 1 would indicate a higher observed event probability. The direction must always be read together with the treatment-group ordering.
7. Statistical Methodology
Randomization
Randomization is the central statistical feature of HEAT-PPCI. With 1829 participants enrolled and two randomized arms, the design creates a framework in which baseline characteristics are expected to be balanced in expectation across treatment groups. This balance is probabilistic rather than guaranteed for every individual characteristic.
The most important consequence is that a between-group difference observed after randomization can be interpreted in the context of the assigned treatment without requiring the analyst to assume that clinicians selected treatment independently of prognosis.
Parallel-group comparison
A parallel design means that participants are assigned to one of the two treatment strategies and are then followed within that assigned group. The analysis therefore compares outcomes between independent randomized groups rather than using each participant as their own control.
The precise numerical form of that comparison depends on the endpoint and the prespecified statistical analysis. For HEAT-PPCI, the ClinicalTrials.gov record identifies two 28-day primary endpoints but does not provide the formal effect measure used for them.
Composite endpoint analysis
The MACE endpoint combines four event categories: all-cause mortality, cerebrovascular accident, re-infarction, and additional unplanned target lesion revascularization. For a binary 28-day composite, a participant would generally be classified as having experienced the composite if at least one qualifying component occurred during the specified time frame.
This creates an important interpretive distinction. A statistically different composite rate does not automatically imply that every component changes in the same direction or by the same magnitude. Component-specific event counts are needed to understand the clinical composition of the overall result.
Binary event analysis
When a clinical endpoint is defined by whether an event occurs within a fixed follow-up window, the primary analysis can often be framed as a comparison of event proportions. This is different from a time-to-event analysis, where the exact event time and censoring mechanism are explicitly modeled.
The registry-reported HEAT-PPCI data specify a 28-day time frame but do not identify the statistical analysis used for the posted results. Consequently, a particular test or effect measure is not attributed to the registry.
Confidence intervals
A confidence interval around a treatment effect quantifies statistical uncertainty associated with the estimated effect under the chosen statistical framework. It is not a range containing the individual treatment effects experienced by patients.
For example, if a risk difference were reported, its confidence interval would describe uncertainty around the estimated difference in event probabilities. If a risk ratio were reported, its interval would instead describe uncertainty around the relative event probability.
P-values
A p-value addresses compatibility between the observed data and a specified null hypothesis under the statistical model and testing procedure. It does not measure the size or clinical importance of an effect.
For that reason, a complete presentation of the HEAT-PPCI primary endpoints would ideally include the event counts or proportions in both groups, the treatment-effect estimate, its confidence interval, and the corresponding hypothesis-test result rather than relying on a p-value alone.
8. Statistical Methods Explained
Why does randomization matter?
Randomization creates the basis for a causal comparison between the two assigned treatment strategies. Because assignment is randomized, differences in outcomes can be interpreted primarily in relation to the treatment assignment rather than simply reflecting why a clinician chose one drug over another.
Why is MACE a composite endpoint?
A composite can capture several clinically important outcomes within one prespecified endpoint. This can increase the number of observed events and provide a broader measure of clinical outcome. The trade-off is that the components may differ substantially in clinical importance and frequency, so the composite result should be examined alongside its individual components when those data are available.
What does a 28-day endpoint mean?
The 28-day time frame defines the period during which the registered primary endpoint is assessed. It is not interchangeable with a lifetime risk or a long-term outcome. A treatment difference at 28 days describes the specified early follow-up window.
Why does an unmasked design matter?
In an unmasked trial, treatment assignment is not concealed from the relevant participants or investigators according to the registry's masking classification. For objective events such as death, the absence of masking may have less direct influence on ascertainment than it could for subjective outcomes. For outcomes involving clinical decisions or procedural interventions, however, knowledge of treatment assignment can be relevant to interpretation.
Why does the choice of effect measure matter?
A risk difference, risk ratio, and odds ratio describe different aspects of the same binary outcome. A risk difference is expressed in absolute probability units; a risk ratio is relative; and an odds ratio compares odds rather than probabilities. The same underlying event data can therefore produce numerically different effect measures without any contradiction.
Why should the MACE components be examined separately?
The MACE composite includes all-cause mortality, cerebrovascular accident, re-infarction, and additional unplanned target lesion revascularization. These events are not interchangeable. A composite result therefore does not tell the reader whether the treatment comparison is being driven primarily by mortality, recurrent infarction, cerebrovascular events, revascularization, or a combination of components.
Why should posted results not be reconstructed from memory?
A trial's statistical interpretation depends on the exact analysis population, event definitions, missing-data rules, treatment exposure, effect measure, and prespecified testing framework. Because those numerical details are not contained in the ClinicalTrials.gov record, reconstructing a result from outside knowledge could silently introduce a different analysis or data cutoff.
9. Analysis Population and Missing Data
The ClinicalTrials.gov record identifies the trial as randomized but do not provide definitions for an intention-to-treat population, per-protocol population, as-treated population, safety population, or other analysis sets. They also do not specify how participants with missing 28-day outcome information were handled.
Randomized population
Randomization establishes the principal comparative framework. The ClinicalTrials.gov record does not specify which analysis population was used for the posted primary results.
Missing outcomes
No missing-data or imputation method is provided in the ClinicalTrials.gov record.
Protocol deviations
The ClinicalTrials.gov record does not identify protocol deviations or explain whether any participants were excluded from a particular analysis.
Exposure-based analysis
No as-treated or exposure-based primary analysis is identified in the ClinicalTrials.gov record.
These details matter because the estimated treatment effect can depend on the analysis population and on how incomplete observations are handled. A complete statistical report would therefore identify the population analyzed for each primary endpoint before interpreting the numerical estimate.
10. Multiplicity and the Two Primary Endpoints
HEAT-PPCI has 2 registered primary endpoints. When a randomized trial has more than one primary endpoint, the statistical analysis plan normally needs to specify how the family of primary hypotheses will be handled.
| Primary endpoint | Multiplicity question | Information reported here |
|---|---|---|
| 28-day MACE | How should evidence for this endpoint be combined with evidence for the bleeding endpoint? | Not specified in the ClinicalTrials.gov record. |
| 28-day BARC type 3–5 bleeding | How should this endpoint contribute to the overall primary inference? | Not specified in the ClinicalTrials.gov record. |
Possible prespecified strategies can include requiring both endpoints to be significant, allocating the type I error between hypotheses, or using another hierarchical or multiplicity-control procedure. The ClinicalTrials.gov record does not identify which approach was used for HEAT-PPCI, so no particular multiplicity framework is attributed to the trial.
11. Safety and the BARC Bleeding Endpoint
The second registered primary endpoint is Type 3-5 Bleeding According to BARC (Bleeding Academic Research Consortium)Definition, assessed at 28 days.
This endpoint is important statistically because bleeding is not simply a secondary laboratory measurement. It is a clinically defined event outcome with a prespecified severity classification. The analysis therefore depends on consistent event adjudication and application of the BARC definition.
| Safety feature | Supplied HEAT-PPCI data |
|---|---|
| Primary safety-related endpoint | Type 3-5 Bleeding According to BARC (Bleeding Academic Research Consortium)Definition |
| Time frame | 28 days |
| Results posted | Yes |
| Numerical event counts reported here | No |
| Statistical analysis reported here | No |
The ClinicalTrials.gov record does not provide serious adverse-event counts by treatment arm or a broader adverse-event table. Those results are therefore not reproduced or inferred on this page.
12. Design Topics Not Specified in the Supplied Data
Several statistical design features are important enough to check explicitly, but the registry-reported HEAT-PPCI record does not provide enough information to attribute a particular method to the trial.
| Design topic | What is established | What is not reported |
|---|---|---|
| Randomization | Allocation is randomized. | Randomization sequence or specific allocation procedure. |
| Stratification | Not reported in the ClinicalTrials.gov record. | Any stratification factors. |
| Non-inferiority margin | Not reported. | Any non-inferiority margin or non-inferiority testing framework. |
| Crossover | Not reported. | Whether participants switched treatment or how such switching was handled. |
| Factorial design | The design model is parallel with 2 arms. | No factorial component is identified. |
| Interim analysis | Not reported. | Any interim look, stopping boundary, or alpha-spending method. |
| Missing-data / imputation | Not reported. | Any imputation or missing-outcome strategy. |
| Bayesian methods | Not reported. | Any prior distribution, posterior analysis, or Bayesian decision rule. |
| Multiplicity | There are 2 registered primary endpoints. | The formal type I error-control strategy. |
13. Understanding the Statistical Comparison
Randomization does not guarantee identical baseline characteristics between the two groups. Its statistical purpose is to make treatment assignment independent of potential outcomes in expectation, allowing observed between-group differences to be interpreted within a randomized framework.
The MACE endpoint combines all-cause mortality, cerebrovascular accident, re-infarction, and additional unplanned target lesion revascularization. An overall MACE comparison therefore summarizes several event types rather than measuring one homogeneous outcome.
If a formal p-value were reported, it would describe evidence against a specified null hypothesis under the relevant testing framework. It would not by itself describe how large or clinically important the treatment difference was.
An effect estimate accompanied by a confidence interval communicates both the estimated direction and the statistical uncertainty around that estimate. A narrow interval and a wide interval can lead to very different conclusions about precision even when the point estimates are similar.
14. Limitations
- Incomplete numerical results in the ClinicalTrials.gov record: the record states that results are posted, but the ClinicalTrials.gov recordset does not contain the numerical primary endpoint results.
- No formal statistical analyses reported: no formal statistical analyses were posted, so no treatment effect estimate, confidence interval, or p-value can be attributed to the ClinicalTrials.gov record.
- Primary endpoint composition: MACE combines multiple clinically different outcomes, so a composite result requires component-level interpretation when those data are available.
- Unmasked design: the registry classifies the study as having no masking, which can be relevant to outcomes involving clinical assessment or treatment decisions.
- Analysis population not specified: the ClinicalTrials.gov record does not identify whether the posted results used intention-to-treat, per-protocol, as-treated, or another analysis population.
- Missing-data handling not specified: no imputation or other missing-outcome procedure is provided in the ClinicalTrials.gov record.
- Multiplicity strategy not specified: there are two registered primary endpoints, but the ClinicalTrials.gov record does not state how type I error was controlled across them.
- Additional design features not specified: the ClinicalTrials.gov record does not identify stratification, interim monitoring, crossover, Bayesian methods, or a non-inferiority margin.
These limitations do not negate the randomized design. They define the boundary between what can be independently explained from the registry fields and what would require the complete statistical analysis plan, detailed results tables, or another primary source.
15. Why This Trial Matters Statistically
HEAT-PPCI is a useful teaching case because its design concentrates several fundamental clinical-trial concepts into a relatively direct randomized comparison: random allocation, a parallel-group structure, an unmasked design, a composite efficacy endpoint, a defined bleeding endpoint, and a fixed 28-day assessment period.
| Concept | How it appears in HEAT-PPCI |
|---|---|
| Randomization | Participants were randomized to one of two treatment arms. |
| Parallel design | The registry identifies a parallel design model with 2 arms. |
| Unmasked trial | Masking is recorded as none. |
| Binary clinical outcome | The registered 28-day endpoints can naturally be framed around whether a participant experienced a qualifying event. |
| Composite endpoint | MACE combines all-cause mortality, cerebrovascular accident, re-infarction, and additional unplanned target lesion revascularization. |
| Safety endpoint | Type 3–5 bleeding is registered using the BARC definition. |
| Fixed follow-up | Both primary endpoints have a 28-day time frame. |
| Multiple primary endpoints | The trial has 2 registered primary endpoints, making multiplicity an important design consideration. |
16. Statistical Interpretation: What a Complete Result Would Need to Show
A high-quality statistical presentation of HEAT-PPCI's primary outcomes would not stop at stating which treatment group had fewer or more events. For each primary endpoint, the reader would ideally see the event count and denominator for each randomized group, the absolute event probability, an appropriate relative effect measure, its confidence interval, and the hypothesis-test result under the prespecified analysis plan.
Absolute effect
The difference in event probabilities shows how far apart the groups are on an absolute scale.
Relative effect
A risk ratio or odds ratio describes the comparison on a relative scale and can communicate proportional differences.
Precision
The confidence interval shows the statistical uncertainty surrounding the estimated effect.
Hypothesis testing
The p-value, if used, should be interpreted within the prespecified multiplicity and testing framework rather than as a standalone measure of clinical importance.
For the MACE endpoint in particular, a complete report should also show the contribution of all-cause mortality, cerebrovascular accident, re-infarction, and additional unplanned target lesion revascularization. A single composite percentage cannot answer those component-specific questions.
17. Longitudinal Trial History
Enrollment begins
The ClinicalTrials.gov record identifies February 2012 as the trial start.
Primary study period completed
The ClinicalTrials.gov record identifies December 2013 as the primary completion date.
Results posted
The ClinicalTrials.gov record classifies the trial as completed and states that results are posted, including results for both registered primary endpoints.
18. Related Tutorials
Learn more about the methods used in this trial:
19. Related Statistical Calculators
20. Sources
- ClinicalTrials.gov: NCT01519518 — HEAT-PPCI.
- PubMed: Publication indexed under PMID 25002178.
- PubMed: Publication indexed under PMID 24219045.
Continue through Clinical Biostats
Explore the statistical concepts behind randomized clinical trials, treatment-effect estimation, composite endpoints, and confidence intervals.
21. Record Summary
HEAT-PPCI is a completed randomized phase 4, parallel-group trial with 1829 enrolled participants, two treatment arms, no masking, and a primary purpose of treatment. The registered interventions are unfractionated heparin and bivalirudin, and the two registered primary endpoints are 28-day MACE and 28-day type 3–5 bleeding according to the BARC definition.
The most important statistical teaching point is the distinction between what the registry says was measured and what the ClinicalTrials.gov record allows us to quantify. The record states that results are posted for both primary endpoints, but the ClinicalTrials.gov record contains no numerical event counts, effect estimates, confidence intervals, or p-values.