This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for RETRIEVE-AMI Study (NCT05307965), a randomized na study. The primary outcome is Thrombus Volume (mm^3).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT05307965 |
| Phase | NA |
| Condition | Myocardial Infarction, Thrombus, Coronary Artery Disease |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 81 |
| Arms in the primary outcome | 3 |
| Lead sponsor | Oxford University Hospitals NHS Trust |
| Results posted | Yes |
2. Clinical Question
Population
Participants with acute myocardial infarction undergoing percutaneous coronary intervention (PCI). The trial concerns thrombus in coronary arteries and measures thrombus burden during the procedure.
Intervention
PCI with stent-retriever thrombectomy. The registry describes use of the SolitaireTM X Revascularisation Device in this arm.
Comparator
Two randomized comparison groups: standalone PCI and PCI with thrombus aspiration. The registry describes aspiration as manual thrombectomy catheter treatment alongside PCI.
Primary question
How does measured thrombus volume during PCI, before stent implantation, compare among the three treatment groups? The stated hypothesis is that physical interaction with and capture of the clot by a retriever may reduce clot burden more effectively than the current approaches.
The clinical rationale in the registry is that disrupting a clot during stenting may send clot material into smaller vessels supplying the heart muscle. The trial therefore evaluates a procedural measure of thrombus burden, rather than a long-term clinical outcome as its primary endpoint. Secondary measures include aspects of coronary flow, vessel appearance after stenting, and microcirculatory function.
The record describes a randomized controlled trial with three parallel groups and an enrollment of 81. It does not report the allocation ratio or identify which participants or study personnel were masked. The primary question is therefore best read as a comparison of the recorded thrombus-volume distributions among the assigned procedural strategies, not as a direct estimate of long-term recovery or wellbeing.
3. Trial Design
RETRIEVE-AMI (NCT05307965) is recorded as a randomized, single-masked, parallel-group trial. Its status is completed, with enrollment of 81. The registry lists the phase as NA. The sponsor is Oxford University Hospitals NHS Trust. The listed start date is 2022-05-06 and the primary completion date is 2024-10-24.
The three groups were standalone PCI, PCI with thrombus aspiration, and PCI with retriever thrombectomy. The standalone PCI description says that devices and techniques were guided by clinical decision-making at the patient and institutional level, in accordance with departmental guidelines. The aspiration group is described as standard care with a manual thrombectomy catheter and PCI. The retriever group underwent retriever thrombectomy with the SolitaireTM X Revascularisation Device.
Random allocation is useful because it aims to make treatment groups comparable at the start of a trial, on average. It does not ensure that every group has identical characteristics, particularly in a study with relatively small groups. The registry does not report the method used to generate the allocation sequence, concealment procedures, the intended allocation ratio, or which role was masked. “Single” masking is recorded, but the identity of the masked group is not reported in the registry record.
The primary endpoint was assessed with Optical Coherence Tomography (OCT) during PCI before stent implantation, typically 30 min from the start of the procedure. Primary outcome measurements are reported for 27 participants in standalone PCI, 26 in PCI with thrombus aspiration, and 27 in PCI with retriever thrombectomy. One patient’s OCT run was not analysable because slow flow prevented adequate blood clearance for a reliable measurement. The record does not describe the analysis population in further detail or report a primary between-group analysis.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
At Randomisation
| Stage | Standalone Percutaneous Coronary Intervention | Percutaneous Coronary Intervention and Thrombus Aspiration | Percutaneous Coronary Intervention and Retriever Thrombectomy |
|---|---|---|---|
| STARTED | 27 | 27 | 27 |
| COMPLETED | 27 | 26 | 27 |
| NOT COMPLETED | 0 | 1 | 0 |
Flow Following Randomisation
| Stage | Standalone Percutaneous Coronary Intervention | Percutaneous Coronary Intervention and Thrombus Aspiration | Percutaneous Coronary Intervention and Retriever Thrombectomy |
|---|---|---|---|
| STARTED | 28 | 27 | 26 |
| COMPLETED | 28 | 26 | 26 |
| NOT COMPLETED | 0 | 1 | 0 |
Analysis population for the primary outcome, as defined in the registry: The OCT run for one patient was not analysable due to slow flow precluding good blood clearance for a reliable measurement.
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
| Characteristic | Unit | Standalone Percutaneous Coronary Intervention | Percutaneous Coronary Intervention and Thrombus Aspiration | Percutaneous Coronary Intervention and Retriever Thrombectomy | Total |
|---|---|---|---|---|---|
| Participants analysed | 27 | 27 | 27 | 81 | |
| Age, Continuous | years | 67 (SD 12) | 63 (SD 12) | 63 (SD 13) | 64 (SD 12) |
| Sex: Female, Male: Female | Participants | 3 | 5 | 4 | 12 |
| Sex: Female, Male: Male | Participants | 24 | 22 | 23 | 69 |
| Race and Ethnicity Not Collected | Participants | — | — | — | 0 |
| Region of Enrollment: United Kingdom | participants | 27 | 27 | 27 | 81 |
6. Primary Endpoint
The registry lists the primary outcome as Thrombus Volume (mm^3), measured over During PCI prior to stent implantation (typically 30 min from start of procedure).
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | mm^3 |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is thrombus volume, measured in mm^3 with OCT during PCI before stent implantation. The registry places the measurement at typically 30 min from the start of the procedure. OCT provides an image-based assessment of the coronary artery and its contents; in this trial, the endpoint represents a procedural measurement of the clot burden at that point in treatment.
Thrombus volume is used because the trial’s stated aim is to compare approaches to removing or managing clot during PCI. A direct measurement of clot burden is closely aligned with that aim. It is not, by itself, a measure of later heart function, symptoms, survival, or quality of life. A difference in this procedural measurement would not automatically establish a difference in those later outcomes.
The registry reports the median and inter-quartile range for each group. The median describes the middle of the observed measurements, while the inter-quartile range describes the spread of the central portion of those measurements. These summaries are appropriate ways to describe a distribution when a single average may not capture its shape. The reported ranges are not confidence intervals for the group medians. The record does not give a primary confidence interval, a primary hypothesis test, or a prespecified threshold for a clinically meaningful difference in thrombus volume.
One OCT run was not analysable because slow flow precluded good blood clearance for a reliable measurement. That is a specific measurement limitation recorded for the primary endpoint. Further details about missing-data handling or whether the unavailable measurement was included in any analysis are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The recorded median thrombus volume was 9.8 mm^3 in the standalone PCI group, with an inter-quartile range of 4.5 to 18.1. In the PCI with thrombus aspiration group, the median was 4.8 mm^3, with an inter-quartile range of 1.8 to 8.4. In the PCI with retriever thrombectomy group, the median was 7.7 mm^3, with an inter-quartile range of 2.3 to 18.6. These are descriptive summaries of the observed measurements.
The group summaries do not establish that one approach produced a reliably different thrombus volume from another. The inter-quartile ranges overlap, and the registry record does not report an inferential analysis of the primary endpoint. It gives no primary effect estimate comparing groups, confidence interval for a contrast, or hypothesis-test result. Without those analyses, the precision of any between-group difference cannot be assessed from the primary outcome summaries alone. The medians also do not show the full distribution of measurements within each group.
The group sizes for the primary measurement are small, and one OCT run was not analysable because of slow flow and inadequate blood clearance. A small amount of missing or difficult-to-measure data can matter when group sizes are modest, particularly if measurement availability is related to procedural conditions. The registry record does not report whether the unavailable measurement was related to treatment assignment or how missing primary data were handled.
The secondary results are also limited in how strongly they can support a conclusion. The posted binary comparisons are unadjusted, and the record does not describe a plan for accounting for multiple outcomes or comparisons. A nominal p-value below a conventional threshold on one secondary measure does not, on its own, provide strong confirmatory evidence when multiple measures are being examined. The secondary outcomes may help describe patterns in the recorded procedural findings, but they do not replace a reported primary analysis.
Overall, the registry provides group-level primary endpoint summaries and some secondary outcome counts. It does not report the statistical analysis needed to quantify uncertainty in the primary between-group contrasts. These results describe what was recorded in this trial; they should not be read as proof of benefit, lack of benefit, or a difference in long-term clinical outcomes.
9. Statistical Methods Explained
What the primary summaries represent. The primary endpoint is reported as a median with an inter-quartile range. A median is the central value when observations are ordered. The inter-quartile range describes the middle half of the observed values and gives information about their spread. It is not a confidence interval and should not be interpreted as a range that quantifies uncertainty in the estimated median. The registry does not report a confidence interval or test for the primary comparisons, so the precision of differences among the group medians is not quantified in the record.
Randomization and group comparison. Random assignment is intended to reduce systematic differences between groups at baseline. In a randomized trial, comparisons can be interpreted in relation to assigned treatment, subject to the analysis approach, missing data, and trial conduct. The registry identifies randomization and a parallel-group design, but does not report the allocation method, concealment, or analysis population. The primary outcome is summarized separately for each of three groups; it is not presented as a single two-group comparison. The record lists no reported primary analysis.
Risk differences for binary outcomes. Some secondary results compare counts of participants with an outcome using a risk difference. In general, a risk difference is the event proportion in one group minus the event proportion in the other group, expressed on the probability scale. A negative estimate means that the recorded event proportion was lower in the first named treatment group than in the comparator group under the stated comparison direction. This is a descriptive contrast unless an inferential method and assumptions are specified. The confidence interval describes statistical uncertainty in the estimate under the method used; it does not address bias, missingness, or whether the outcome is clinically important.
For example, the posted risk-difference intervals for the underexpansion and malapposition comparisons include zero. The intervals for the TIMI Flow comparisons also include zero. For the MBG < 3 comparisons, the posted interval is -0.541 to -0.051 and the unadjusted p-value is 0.024. The record does not report adjusted analyses for these secondary comparisons. A confidence interval that includes zero indicates that the data and method are compatible with no risk difference, as well as with differences in either direction within the interval. A p-value is not the probability that a treatment has no effect; it measures how unusual the data would be under a specified null model and assumptions.
Unadjusted inference and multiplicity. When several outcomes or comparisons are examined, the chance of observing at least one nominally small p-value can increase. This is the general statistical issue of multiplicity. A prespecified primary endpoint and a clearly stated analysis hierarchy can help readers distinguish confirmatory questions from exploratory ones. The registry identifies 12 outcome measures and seven posted secondary outcomes, but a multiplicity strategy is not reported in the registry record. The posted p-values should therefore be interpreted as unadjusted results, not as evidence that accounts for the full set of outcome questions.
Planning illustrations are not observed power. The sample-size illustrations use the observed effect as a reference and show planning for different fractions of that effect. They assume a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. These are planning illustrations, not the trial’s original sample-size justification and not a calculation of observed power. Sample-size calculations depend on assumptions about the effect to detect and the design. Using an effect estimated from a small trial as the planning target can give an unstable basis for a future study. The protocol’s sample-size justification and any design assumptions beyond those stated for the illustrations are not reported in the registry record.
Over-dispersion and distributional shape. General statistical explanation: for count outcomes, over-dispersion means that variation is greater than a simple model assumes. If present, standard errors from an unsuitable model may be too small, making intervals too narrow and tests too optimistic. The primary endpoint is reported as a median and inter-quartile range, not as a count-model estimate. The registry does not report a model for the primary outcome or diagnostics for distributional assumptions, so no conclusion about over-dispersion can be drawn from the record.
What is unavailable in the record. The registry lists no reported analyses for the outcome comparisons. It does not give a detailed statistical analysis plan, primary contrast, adjustment strategy, missing-data method, or analysis-population definition. The simple unadjusted secondary comparisons help describe the posted counts, but they are not a substitute for a prespecified and fully reported trial analysis.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 12 outcome measures and seven posted secondary outcomes. Examining several outcomes creates a multiplicity issue: even when no real difference exists, a set of separate tests can produce an apparently notable result by chance. A prespecified statistical analysis plan can state which outcome is primary, how secondary outcomes will be interpreted, and whether the significance threshold or analysis will account for multiple comparisons. Such a plan is not reported in the registry record.
The posted secondary p-values are unadjusted. This means they do not account for the other outcome tests in the record. The registry also does not report whether the comparisons were planned before the data were examined, whether there was a hierarchy among secondary outcomes, or whether any analyses were exploratory. Consequently, isolated secondary p-values should not be treated as definitive evidence.
Missingness is specifically noted for the primary OCT measurement: one patient’s run was not analysable because slow flow prevented good blood clearance for a reliable measurement. The record does not explain how that unavailable measurement was handled in the primary analysis or whether the reason was related to treatment assignment. It also does not report a broader missing-data strategy or sensitivity analyses.
The denominators differ across some posted secondary measures. The registry does not explain whether this reflects different available data, outcome-specific eligibility, or another reason. The analysis population is not described in detail, and there is no reported intention-to-treat or per-protocol analysis definition. The record also does not provide an account of participants excluded from each analysis or reasons for exclusion.
These reporting gaps do not establish that the trial’s conduct or analysis was inappropriate. They mean that readers cannot assess key protections against selective interpretation, quantify the impact of missing data, or determine precisely which participants contributed to each comparison. For the primary endpoint, the absence of a reported inferential analysis is especially important because the descriptive group summaries do not quantify uncertainty in between-group differences.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Standalone Percutaneous Coronary Intervention | 5 | 27 | 18.5% |
| Percutaneous Coronary Intervention and Thrombus Aspiration | 4 | 27 | 14.8% |
| Percutaneous Coronary Intervention and Retriever Thrombectomy | 1 | 27 | 3.7% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Standalone Percutaneous Coronary Intervention | 2 of 27 |
| Percutaneous Coronary Intervention and Thrombus Aspiration | 1 of 27 |
| Percutaneous Coronary Intervention and Retriever Thrombectomy | 0 of 27 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Standalone Percutaneous Coronary Intervention | 0 of 27 |
| Percutaneous Coronary Intervention and Thrombus Aspiration | 2 of 27 |
| Percutaneous Coronary Intervention and Retriever Thrombectomy | 4 of 27 |
Most frequent serious adverse event terms
| Event term | Organ system | Standalone Percutaneous Coronary Intervention | Percutaneous Coronary Intervention and Thrombus Aspiration | Percutaneous Coronary Intervention and Retriever Thrombectomy |
|---|---|---|---|---|
| Arrhtymia Related Unplanned Admission | Cardiac disorders | 1 of 27 | 3 of 27 | 1 of 27 |
| Death (Prespecified clinical endpoint) | Cardiac disorders | 2 of 27 | 1 of 27 | 0 of 27 |
| Chest discomfort | General disorders | 1 of 27 | 0 of 27 | 0 of 27 |
| Major GI Bleeding | Gastrointestinal disorders | 1 of 27 | 0 of 27 | 0 of 27 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Standalone Percutaneous Coronary Intervention | Percutaneous Coronary Intervention and Thrombus Aspiration | Percutaneous Coronary Intervention and Retriever Thrombectomy |
|---|---|---|---|---|
| Chest discomfort | Cardiac disorders | 0 of 27 | 1 of 27 | 2 of 27 |
| Symptomatic Hypotension | Cardiac disorders | 0 of 27 | 0 of 27 | 2 of 27 |
| Arrhtymia Related Unplanned Admission | Cardiac disorders | 0 of 27 | 1 of 27 | 0 of 27 |
Serious events with the highest arm-level rate: arrhtymia related unplanned admission (11.1%), death (prespecified clinical endpoint) (7.4%), chest discomfort (3.7%), major gi bleeding (3.7%).
The registry records serious adverse events in all three groups. The serious-event counts are 5 among 27 at risk in standalone PCI, 4 among 27 at risk in PCI with thrombus aspiration, and 1 among 27 at risk in PCI with retriever thrombectomy. Deaths are recorded as 2, 1, and 0, respectively. These are observed counts in the trial groups, not estimates of causal effects.
The record also lists other adverse events affecting 0 of 27 participants in standalone PCI, 2 of 27 in PCI with aspiration, and 4 of 27 in PCI with retriever thrombectomy. The registry’s listed serious-event terms include arrhythmia-related unplanned admission at 11.1%, death as a prespecified clinical endpoint at 7.4%, chest discomfort at 3.7%, and major GI bleeding at 3.7%.
These figures should be read descriptively. The groups are small, and the registry does not report uncertainty intervals, a comparative safety analysis, event adjudication details, or the follow-up period for these counts. It also does not provide enough information to determine whether events were judged related to a particular procedure. The counts therefore do not establish that one strategy is safer or more harmful than another.
12. What the Result Does, and Does Not, Mean
The results describe measured thrombus volume during PCI and a set of secondary procedural outcomes in a randomized trial with three treatment groups. The primary outcome summaries show the median and inter-quartile range for each group. They do not include a reported statistical comparison, confidence interval for a contrast, or hypothesis test. The record therefore does not quantify how precisely the group medians differ.
The secondary comparisons provide some information about observed differences in binary outcomes. Those analyses are unadjusted, and the registry does not report a strategy for handling multiple outcomes. Any apparent signal among the secondary measures should be interpreted cautiously, particularly given the modest group sizes and the absence of a reported analysis plan.
These data do not establish that retriever thrombectomy reduces thrombus volume compared with aspiration or standalone PCI. They also do not establish that the approaches are equivalent. Failure to report a primary test is not evidence of no effect, and overlapping descriptive ranges are not a formal test of equivalence. A study designed to assess equivalence or non-inferiority would require an appropriate margin and analysis, neither of which is reported in the registry record.
The primary endpoint is a procedural imaging measure. It does not directly measure long-term heart muscle damage, recovery, wellbeing, or survival. Secondary flow and imaging findings may provide related procedural information, but they cannot by themselves establish those longer-term outcomes. The adverse-event counts are likewise descriptive and do not support causal safety conclusions without comparative analyses and further details.
The most defensible interpretation is that the registry records group-level procedural measurements and selected event counts, while leaving important questions about statistical uncertainty and analysis methods unanswered. The findings may motivate further study, but conclusions about the relative effects of these strategies require a clearly reported primary comparison and suitably detailed analyses.
13. Why This Trial Matters Statistically
This trial raises a useful statistical question about how to evaluate a three-group procedural study when the primary result is reported descriptively. The medians and inter-quartile ranges allow readers to see the central value and spread in each group. However, without a primary contrast and uncertainty interval, they cannot show how compatible the data are with no difference or with effects of differing sizes. This distinction matters: descriptive summaries and inferential comparisons answer related but different questions.
The trial also illustrates the importance of matching analysis to the structure of the question. There are three randomized groups, so interpretation involves more than one possible comparison. A prespecified plan can clarify whether the main interest is retriever thrombectomy versus standalone PCI, retriever thrombectomy versus aspiration, or an overall difference among all groups. The registry record does not identify a primary contrast or analysis hierarchy.
Secondary outcomes and safety counts add context, but multiple unadjusted comparisons can make isolated results seem more conclusive than they are. Explicitly identifying which results are confirmatory and which are exploratory helps prevent overinterpretation. The record’s lack of a reported multiplicity strategy makes that distinction particularly relevant.
Finally, the primary endpoint is a measure taken during the procedure. It is aligned with the proposed mechanism of reducing clot burden, but a procedural measure is not the same as a patient-centered long-term outcome. Statistical interpretation should preserve that distinction. The trial is therefore a useful example of why complete reporting of the primary analysis, missing-data handling, and outcome hierarchy is essential for assessing both the evidence and its limits.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The primary outcome is not accompanied by a reported between-group analysis. Although the group medians and inter-quartile ranges are available, the registry does not provide a primary effect estimate, confidence interval, or test. This prevents a direct assessment of the precision of the main comparison.
One OCT run was not analysable because slow flow prevented adequate blood clearance. This is a specific limitation of the imaging measurement, and the registry does not explain how it was handled analytically. The record also does not report whether the missing measurement was related to the assigned group or provide sensitivity analyses.
The reported primary and secondary group sizes are modest. Such sample sizes can leave substantial uncertainty in comparisons, especially for outcomes that occur in relatively few participants. The registry does not report the trial’s sample-size justification, so it is not possible to assess the intended detectable effect or the assumptions behind the original design.
Key design and analysis details are absent, including the allocation procedure, concealment, identity of the masked group, primary contrast, analysis population, missing-data approach, and multiplicity strategy. The registry records a single-masked design but does not clarify who was masked. These omissions limit assessment of potential bias and the meaning of the reported comparisons.
The trial’s primary endpoint is a procedural measure, and the posted results do not establish effects on long-term clinical outcomes. The safety counts are also descriptive, without reported comparative uncertainty or detailed event follow-up. Some listed secondary measures do not have numerical analyses reported in the registry record. Together, these features mean that the results support a limited description of observed procedural data rather than a complete statistical assessment of comparative effectiveness or safety.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: RETRIEVE-AMI Study — NCT05307965.
- Registry record last updated 2025-09-05; status last verified 2025-09.
- Results first posted 2025-09-05.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
RETRIEVE-AMI (NCT05307965) is a completed randomized, single-masked, parallel-group trial sponsored by Oxford University Hospitals NHS Trust, with enrollment of 81. It compares standalone PCI, PCI with thrombus aspiration, and PCI with retriever thrombectomy in participants with acute myocardial infarction.
The primary endpoint is OCT-assessed thrombus volume during PCI before stent implantation. The registry reports group medians and inter-quartile ranges, but no primary inferential comparison. One OCT run was not analysable because slow flow prevented reliable measurement. Several secondary procedural outcomes and adverse-event counts are also recorded, but the registry does not report a multiplicity strategy or detailed analysis populations. The posted results are therefore best interpreted as descriptive evidence with important uncertainty about comparative effects.