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The ACIST RXi System is indicated for obtaining intravascular pressurements for use in the diagnosis and treatment of coronary and peripheral artery disease. The ACIST Navvus II MicroCatheter is intended for use with the ACIST RXi System.

The current RXi system obtains intravascular pressure measurements for use in the diagnosis and treatment of coronary and peripheral artery disease. The RXi measures intravascular pressure in a hyperemic state following administration of adenosine as fractional flow reserve (FFR). The proposed software update for the RXi system adds a diastolic pressure ratio (dPR), which measures intravascular pressure in a non-hyperemic (resting) state. Both current and proposed ACIST RXi Systems are used in conjunction with the Navvus Catheter.

The proposed RXi System console containing embedded software that provides the main user interface. The system is used with the Navvus catheter which contains a pressure sensor for acquisition of pressure distal (Pd) to a lesion. The proximal aortic pressure (Pa) is acquired via an interface to a third-party hemodynamic system. The system is intended for use in catheterization and related cardiovascular specialty laboratories to compute and display fractional flow reserve (FFR) using hyperemic agents and/or nonhyperemic indices of diastolic pressure ratio (dPR) and PdPa for physiological assessment of ischemic stenotic lesions.

Measurement of FFR requires simultaneously monitoring the blood pressures proximal and distal to a lesion while inducing hyperemia. dPR is a measure of the diastolic portion of the hemodynamic waveform and can be used by the physician to perform a physiologic assessment without inducing hyperemia in the patient.

The provided text describes the ACIST RXi System and Navvus II MicroCatheter, with a focus on a software update to include a diastolic pressure ratio (dPR) modality. The information primarily relates to the substantial equivalence determination for this medical device, rather than a clinical study evaluating an AI device's performance against human readers. Therefore, many of the requested points, particularly those pertaining to AI device performance evaluation criteria (e.g., sample size for test set, number of experts, adjudication method, MRMC study, training set details), are not present in the provided document.

However, I can extract information related to the device's performance and the study that demonstrated its substantial equivalence.

Here's a summary of the available information based on the provided text, addressing your points where possible and noting where information is not available:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria for the dPR functionality were primarily based on demonstrating agreement with an FDA-cleared reference device (Volcano iFR Modality) when compared to FFR measurements.

2. Sample Size Used for the Test Set and Data Provenance

• Sample Size: The document mentions "a dataset collected in a prospective clinical study." The exact number of patients or waveforms in this dataset is not specified.
• Data Provenance: The dataset was collected in the "prospective CONTRAST clinical study," suggesting real-world clinical data. The country of origin is not specified.
• Retrospective or Prospective: The study is explicitly stated as prospective.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts

This information is not applicable/not available as the study did not involve human experts establishing ground truth for an AI device. The ground truth was established by another medical device (FFR measurements).

4. Adjudication Method for the Test Set

This information is not applicable/not available as the study did not involve human experts requiring adjudication.

5. If a Multi Reader Multi Case (MRMC) Comparative Effectiveness Study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance

An MRMC study was not done. This study demonstrates the performance of a new device modality (dPR calculation) against an existing device/modality (iFR) and a reference standard (FFR), not an AI algorithm assisting human readers.

6. If a Standalone (i.e. algorithm only without human-in-the-loop performance) was done

Yes, the diagnostic performance evaluation was essentially a standalone assessment of the dPR algorithm's output compared to iFR and FFR. It states: "Resting and hyperemic pressure readings from each recorded waveform were measured using the ACIST RXi System and Navvus Catheter, and in parallel, the Philips Verrata PLUS wire and Philips (Volcano) CORE Mobile system." This describes an evaluation of the device's output (dPR) against other device outputs (iFR, FFR).

7. The Type of Ground Truth Used

The ground truth used for demonstrating substantial equivalence was Fractional Flow Reserve (FFR) measurements using a cutpoint of 0.80.

8. The Sample Size for the Training Set

This information is not applicable/not available. The dPR algorithm is a new calculation modality added to existing software, not a deep learning AI model that requires a separate training set. The calculations are based on known physiological principles.

9. How the Ground Truth for the Training Set Was Established

This information is not applicable/not available for the same reason as point 8. The dPR calculation is based on established hemodynamic principles, not learned from a labeled training set.

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