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 AVAI: Atrial Ventricular Arrythmia Incidence (NCT00832975), a registered phase not stated study. The primary outcome is Slow Ventricular Tachycardia Episodes Devices Detected (Between 120-150 Bpm and > 30sec) Atrial Fibrillation (AF) Episodes Devices Detected (> 30 Sec).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00832975 |
| Phase | Phase not stated |
| Condition | Ventricular Tachycardia, Atrial Fibrillation |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 157 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Abbott Medical Devices |
| Results posted | Yes |
2. Clinical Question
Population
The study concerns patients implanted with an implantable cardiac device (ICD), with the brief summary describing the population as patients implanted with a St. Jude Medical ICD. The primary-outcome population is recorded as 157 patients analyzed. Of these, 118 completed 2 years of follow-up and 39 were terminated before completing it. Details such as age, sex, clinical history, and eligibility criteria are not reported in the registry record.
Intervention
This is an observational study, not a treatment comparison. The registry record describes a St Jude Medical ICD/CRT-D group and says the study collected data regarding patients with an implanted device. It does not describe an assigned intervention, treatment schedule, or protocol-driven change in care. Allocation is not stated.
Comparator
No control or comparator group is described. The device group is not a comparison arm against another device or an untreated group. Consequently, the record does not set out a randomized contrast or a like-for-like comparison between groups.
Primary question
The primary outcome counts episodes detected by the device: slow ventricular tachycardia episodes between 120-150 bpm lasting more than 30 seconds, and atrial fibrillation episodes lasting more than 30 seconds. The stated timeframe is 24 months. The registry record therefore asks about device-detected episode occurrence in the observed patient population, rather than a difference between assigned treatments. It does not report the episode counts or a statistical estimate addressing this question.
3. Trial Design
AVAI is an observational study sponsored by Abbott Medical Devices. Its registry title concerns the incidence of slow ventricular tachycardia and atrial fibrillation documented by intracardiac electrogram in patients implanted with an ICD. The brief summary describes the purpose as collecting data regarding the population of patients implanted with a St. Jude Medical ICD. The record gives a study start of 2008-12, primary completion of 2013-02, and status of COMPLETED.
The record reports enrollment of 157 and identifies one device group, titled St Jude Medical ICD/CRT-D. It does not identify a randomized allocation or a control group. Allocation is not stated, and the registry explicitly cautions that the arms are not a like-for-like control comparison. As a result, the design should be read as observational description, not as a randomized evaluation of device effects.
The primary outcome is a count of device-detected episodes, with a stated timeframe of 24 months. The description defines slow ventricular tachycardia as device-detected tachycardia between 120-150 bpm lasting more than 30 seconds; atrial fibrillation episodes are counted only when duration exceeds 30 seconds. The population note says 157 patients were analyzed, 118 completed 2 years of follow-up, and 39 were terminated before completing it.
A secondary outcome concerns cardiovascular mortality and hospitalization rate due to cardiovascular reasons or heart failure. The registry record lists two outcome measures overall, but it does not report a detailed analysis plan, endpoint definitions beyond the primary-outcome description, or results for the secondary outcome. Specific procedures for follow-up, data collection, and handling incomplete observations are not reported in the registry record.
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.
Overall Study
| Stage | St Jude Medical ICD/CRT-D |
|---|---|
| STARTED | 157 |
| COMPLETED | 118 |
| NOT COMPLETED | 39 |
Reasons for not completing this period:
| Reason | St Jude Medical ICD/CRT-D |
|---|---|
| Lost to Follow-up | 7 |
| Protocol Violation | 6 |
| Death | 5 |
| Physician Decision | 4 |
| Withdrawal by Subject | 3 |
| Other reasons | 14 |
Analysis population for the primary outcome, as defined in the registry: 157 patients were analyzed: 118 completed 2 years of Follow Up (FU) and 39 patients were terminated before completing it
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.
Population: All patients
| Characteristic | Unit | St Jude Medical ICD/CRT-D |
|---|---|---|
| Participants analysed | 157 | |
| Age, Continuous | years | 61.67 (SD 13.39) |
| Sex: Female, Male: Female | Participants | 35 |
| Sex: Female, Male: Male | Participants | 122 |
6. Primary Endpoint
The registry lists the primary outcome as Slow Ventricular Tachycardia Episodes Devices Detected (Between 120-150 Bpm and > 30sec) Atrial Fibrillation (AF) Episodes Devices Detected (> 30 Sec), measured over 24 months.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | Episodes |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is expressed as a number of episodes over 24 months. It includes device-detected slow ventricular tachycardia episodes between 120-150 bpm with duration greater than 30 seconds, and atrial fibrillation episodes with duration greater than 30 seconds. The endpoint is therefore based on detections meeting duration and, for slow ventricular tachycardia, rate criteria. Episodes outside those stated criteria are not part of the defined outcome.
Counting episodes can describe recurrent events in a population more fully than simply recording whether a participant ever had an event. However, a count may reflect both how many participants experience an episode and how frequently episodes recur in those participants. Interpretation therefore depends on the unit of analysis and how repeated episodes within one participant are handled. Those analysis details are not reported in the registry record.
Device detection is the specified means of identifying these episodes, and the official title refers to intracardiac electrogram documentation. The endpoint is useful for describing what the implanted devices detected according to the stated criteria. It should not automatically be interpreted as a count of independently adjudicated clinical events: adjudication procedures and validation details are not reported in the registry record.
The registry record gives the outcome definition and follow-up timeframe but does not report the observed number of episodes, a rate, or an uncertainty interval. Thus, the endpoint’s role is clear, while the magnitude and precision of the observed event burden cannot be evaluated from the reported primary-outcome information.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record describes the population and the intended primary outcome but does not include primary-outcome results. In particular, it does not report the number of qualifying slow ventricular tachycardia episodes or atrial fibrillation episodes. Without those counts, an estimate of episode burden or its statistical precision cannot be summarized. The completed study status does not, by itself, supply an outcome estimate.
The reported denominator for the analyzed population is 157 patients. The record states that 118 completed 2 years of follow-up and 39 were terminated before completing it. Those figures are important context for a 24-month endpoint, since participants with less follow-up may have had less time in which episodes could be detected. The record does not explain the reasons for early termination, the follow-up time accrued by those participants, or whether and how their observations contributed to the endpoint.
Because this is observational and no comparator is described, the record cannot support a randomized between-group treatment-effect interpretation. The study description instead frames the question as collecting device-related population data. Even if episode counts were reported, they would describe the observed cohort under the recorded follow-up and ascertainment procedures; they would not alone establish that the device caused or prevented events.
The endpoint counts recurrent detections. Such data can be unevenly distributed: some participants may contribute no qualifying episodes while others may contribute repeated episodes. This is a general feature of count outcomes, not a reported finding about AVAI. A population total or mean would not fully describe that pattern, and analysis would need to account for the observation period and clustering of repeated events within a participant. The registry record does not report the distribution of counts or the statistical model used.
The record lists zero analyses. It provides no inferential primary-outcome result, confidence interval, or p-value. No estimate of the association between patient characteristics and episodes is reported either. Any numerical sample-size illustrations associated with an observed effect should be distinguished from observed trial findings: the stated assumptions describe planning illustrations, not observed power, and the registry does not report a trial comparison from which a treatment effect can be interpreted.
Safety information is recorded for the St Jude Medical ICD/CRT-D group, including serious and other adverse-event counts and selected serious-event categories. These figures are descriptive. No comparator is available to determine whether the event burden differs from another group, and the registry does not provide event definitions, exposure-adjusted rates, or a death count. Taken together, the record offers design and reporting context, but not enough primary-outcome information for a quantitative account of the episode findings.
9. Statistical Methods Explained
What does a count endpoint represent?
A count endpoint records how many events meet a definition during a specified observation period. In AVAI, the primary measure is a number of device-detected episodes over 24 months. A count differs from a binary outcome, which would classify each participant only as having or not having an event. Counts retain information about repeated qualifying episodes, although their interpretation depends on the rules for identifying, separating, and attributing repeated detections. Those detailed rules are not reported in the registry record.
Counts are often nonnegative and may be concentrated among a subset of participants. General statistical methods for count data therefore consider whether the spread of the observations is larger than expected under a simple count model. Over-dispersion matters because a model that assumes too little variability can produce uncertainty estimates that are too narrow. This is a general methodological point; the registry record does not report a count model, a distributional assessment, or evidence about over-dispersion for AVAI.
Why does follow-up time matter?
Episode counts depend on the time during which each participant is observed. A participant followed for less time has fewer opportunities for a qualifying episode to be detected. In this study the stated outcome timeframe is 24 months, while the population note says 118 participants completed 2 years of follow-up and 39 were terminated before completing it. To interpret a count comparison or rate, an analysis would need to make clear how different observation durations were handled. The registry record does not report whether the endpoint used raw counts, rates, a time-at-risk offset, or another approach.
Incomplete follow-up also raises a missing-data question. Early termination might be related to an outcome, a health change, withdrawal, or administrative circumstances, but the reasons are not stated. Those possibilities should not be treated as findings about AVAI. General statistical practice is to describe the amount and pattern of missing follow-up and to explain the assumptions used when analyzing incomplete observations. The registry record does not report such an approach.
What can a confidence interval tell a reader?
A confidence interval is a way to express the statistical uncertainty around an estimate. It gives a range of values that are compatible with the data under the method’s assumptions. A narrow interval indicates greater precision than a wide interval, but neither width nor location establishes causation. Confidence intervals also depend on the analysis model, the quality of the measurements, and whether the assumptions are reasonable. AVAI’s registry record does not report a primary-outcome estimate or confidence interval, so no such precision statement can be made about its episode counts.
A p-value, when used, addresses how compatible observed data are with a specified null hypothesis under a statistical model. It does not measure the size or clinical importance of an effect, and it does not tell a reader the probability that the null hypothesis is true. No primary-outcome p-value is reported in the registry record. The record lists zero analyses, so there is no formal inferential result to explain.
How should observational evidence be interpreted?
Observational data are collected without random assignment to competing interventions. They can describe a cohort and document event patterns, but comparisons within observational data may be affected by differences among participants, follow-up, or measurement. In AVAI, no comparator group is described, and allocation is not stated. The record explicitly cautions that the arms are not a like-for-like control comparison. Accordingly, a causal treatment-effect interpretation is not supported by the design information in the registry record.
For a recurrent-event endpoint, general analytic choices include summarizing participant-level counts, estimating an event rate over observed time, or using a model designed to account for repeated episodes within participants. These approaches answer related but not identical questions. An event rate uses time at risk; a participant-level summary describes the distribution of burden across people; a repeated-event model can account for within-person dependence. The registry record does not identify which, if any, approach was used.
Sample-size calculations also require careful interpretation. The registry’s planning assumptions describe an illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. For time-to-event tables, the stated planning quantity is total events; for other outcomes, it is participants per arm. These are planning illustrations, not observed power, and they do not establish that AVAI was designed around a randomized two-arm comparison. The record does not report the trial’s own sample-size justification or a protocol-based calculation. Since no comparator or primary-effect estimate is reported, an illustration should not be read as evidence of a treatment effect.
Finally, statistical analysis depends on a clearly defined population and endpoint. The record identifies 157 analyzed patients and specifies a 24-month episode measure, but it does not describe a formal analysis population, exclusions, missing-data procedures, or the method used to combine or distinguish the two types of episode. Those gaps limit reproducibility and prevent readers from reconstructing an inferential analysis from the registry information.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists two outcome measures: the primary episode-count outcome and a secondary outcome concerning cardiovascular mortality and hospitalization rate due to cardiovascular reasons or heart failure. It does not report a multiplicity procedure, such as a rule for adjusting inference when more than one outcome is tested. Because zero analyses are listed and no primary-outcome p-value or confidence interval is reported, the record does not support an assessment of how multiple statistical tests were handled.
The primary outcome combines two kinds of detections: slow ventricular tachycardia episodes and atrial fibrillation episodes. The definitions are stated separately, but the record does not explain whether the results were intended to be reported separately, combined into one total, or analyzed under a hierarchy. Nor does it provide a testing plan for these components. That uncertainty concerns the analysis strategy; it does not imply that a particular method was used.
Follow-up was incomplete for some participants: 118 completed 2 years and 39 were terminated before completing it, out of 157 analyzed. The reasons for termination, the amount of follow-up for each participant, and the treatment of incomplete observations are not reported in the registry record. There is no reported missing-data strategy or sensitivity analysis.
The registry record does not define an intention-to-treat or per-protocol analysis population, nor does it describe exclusions from the analyzed set. It reports 157 patients analyzed, but does not provide further detail about how that population was formed. As a result, readers cannot determine how incomplete follow-up or any other missing information was handled in the primary endpoint analysis.
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 |
|---|---|---|---|
| St Jude Medical ICD/CRT-D | 67 | 157 | 42.7% |
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 |
|---|---|
| St Jude Medical ICD/CRT-D | 20 of 157 |
Most frequent serious adverse event terms
| Event term | Organ system | St Jude Medical ICD/CRT-D |
|---|---|---|
| Serious AE | General disorders | 51 of 157 |
| Serious Device related AE | Cardiac disorders | 13 of 157 |
| Unspected Serious Device related AE | Cardiac disorders | 3 of 157 |
Most frequent non-serious adverse event terms
| Event term | Organ system | St Jude Medical ICD/CRT-D |
|---|---|---|
| AE | General disorders | 16 of 157 |
| Device related AE | General disorders | 4 of 157 |
Serious events with the highest arm-level rate: serious ae (32.5%), serious device related ae (8.3%), unspected serious device related ae (1.9%).
The safety record lists one group, St Jude Medical ICD/CRT-D, with 157 participants at risk for serious adverse events and 67 affected. For other adverse events, it lists 157 at risk and 20 affected. These are group-level counts, not comparisons against a control group. The registry does not report a death count; that value is not reported in the registry record.
The listed serious-event categories include Serious AE at 32.5%, Serious Device related AE at 8.3%, and Unspected Serious Device related AE at 1.9%. They are presented as selected serious-event terms. The record does not explain how these categories relate to one another, whether they overlap, or whether the percentages use the same denominator and follow-up rules as the affected-participant counts. The figures should therefore be read as registry-reported safety descriptors, not added together or treated as mutually exclusive categories.
Counts of affected participants do not convey how many total events occurred, how long participants were observed, or the severity and timing of every event. Definitions and ascertainment procedures are not reported in the registry record. Without a comparator and more detail on observation time, these figures cannot establish whether event frequency differs from another group or attribute events to the device.
12. What the Result Does, and Does Not, Mean
The record establishes that AVAI was an observational study of patients with implanted cardiac devices and that its primary endpoint concerned device-detected slow ventricular tachycardia and atrial fibrillation episodes. It defines the qualifying episode criteria and gives a 24-month timeframe. It also documents 157 analyzed patients, including 118 who completed 2 years of follow-up and 39 who were terminated earlier.
Those details describe the study’s scope and the follow-up context, but they are not a report of the primary outcome. The registry record does not give the episode counts, an estimated rate, or a measure of statistical uncertainty. It therefore cannot show how many qualifying episodes were observed or how precisely the population’s episode burden was estimated.
The record also does not describe a randomized comparison. No control group is specified, allocation is not stated, and the registry warns that arms are not a like-for-like comparison. The findings that can be described from the record are therefore descriptive and should not be framed as evidence that a device caused a change in episode occurrence.
Safety entries provide counts for the recorded device group and percentages for selected serious-event terms. They do not provide a comparative safety estimate, a death count, or enough detail to interpret exposure time and category overlap. These figures are relevant registry information, but they do not independently establish a causal relationship.
In general, a completed study status means the registry lists the study as completed; it does not guarantee that all planned outcomes or analyses are publicly reported. Here, the record lists zero analyses and does not provide a formal primary-outcome result. The appropriate statistical conclusion is thus limited: the study’s question and some design and follow-up details are documented, while the primary episode result and its precision are not reported in the registry record.
13. Why This Trial Matters Statistically
AVAI illustrates a common distinction in clinical research between defining an outcome and reporting its result. The registry defines a device-detected episode-count endpoint and specifies duration criteria, a rate range for slow ventricular tachycardia, and a 24-month timeframe. A clear definition helps readers understand what the endpoint is intended to capture. But without observed counts or an analysis estimate, the endpoint definition alone cannot answer how much event burden was observed.
The study also highlights why follow-up is part of the statistical interpretation. The record distinguishes participants who completed 2 years from those terminated earlier. This matters for a recurrent event count because time under observation affects opportunities for detection. Without details on individual follow-up time and missing-data handling, readers cannot tell how much incomplete follow-up shaped the endpoint analysis.
Another statistical lesson is the importance of design. An observational cohort can provide descriptive information about a population, but the absence of a like-for-like comparator limits causal inference. This is especially important when readers encounter counts or safety entries and might otherwise interpret them as comparative evidence. The registry explicitly states that the arms are not a like-for-like control comparison.
Finally, safety counts and selected percentages are not interchangeable with a full safety analysis. Interpretation depends on definitions, denominators, time at risk, and whether categories overlap. The record’s limited reporting makes those distinctions visible: useful descriptive entries are present, but the detail needed for comparative or causal conclusions is not. AVAI is therefore a useful example of how registry records can document study structure while leaving important outcome and analysis information unavailable.
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.
Several limitations arise from the information recorded for this study. The primary endpoint is defined, but the registry does not report the observed episode counts, a rate, or an uncertainty estimate. The record lists zero analyses. Consequently, readers cannot evaluate the magnitude or precision of the primary outcome or reproduce an inferential result.
The study is observational and does not describe a comparator group. Allocation is not stated, and the registry cautions that the arms are not a like-for-like control comparison. This limits interpretation to description of the recorded cohort and prevents a randomized comparative interpretation.
Follow-up information is incomplete at the population level: 118 participants completed 2 years, while 39 were terminated before completion, among 157 analyzed. Reasons for termination, individual observation time, and the handling of incomplete follow-up are not reported in the registry record. This is particularly relevant to an episode-count endpoint with a 24-month timeframe.
The record does not specify the statistical model, how repeated episodes within a participant were handled, whether the two episode types were analyzed separately, or how the secondary outcome was defined for analysis. It also does not report multiplicity procedures, analysis populations, or a missing-data strategy. These omissions make it difficult to assess robustness or reproduce the analysis.
Safety reporting is also limited. The registry includes affected-participant counts and selected serious-event percentages, but does not provide event totals, detailed definitions, category overlap, exposure-adjusted rates, or a death count. Baseline characteristics and detailed eligibility criteria are not reported in the registry record, limiting assessment of who the cohort represents.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: AVAI: Atrial Ventricular Arrythmia Incidence — NCT00832975.
- Registry record last updated 2019-02-21; status last verified 2019-02.
- Results first posted 2015-03-03.
- 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
AVAI (NCT00832975), sponsored by Abbott Medical Devices, is an observational study with status COMPLETED. The registry lists enrollment of 157, a study start of 2008-12, and primary completion of 2013-02. Its brief summary describes collecting data regarding patients implanted with a St. Jude Medical ICD.
The primary outcome is the number of device-detected slow ventricular tachycardia episodes between 120-150 bpm lasting more than 30 seconds and atrial fibrillation episodes lasting more than 30 seconds, over 24 months. The record says 157 patients were analyzed; 118 completed 2 years of follow-up and 39 were terminated before completing it. A secondary outcome concerns cardiovascular mortality and hospitalization rate due to cardiovascular reasons or heart failure.
The registry records one St Jude Medical ICD/CRT-D safety group and selected serious-event categories. It lists zero analyses and does not report primary episode counts, a statistical estimate, or a confidence interval. Allocation and a like-for-like comparator are not described.