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

Device Description

The ACIST Navvus II MicroCatheter is a single-lumen monorail catheter designed to be used with standard 0.014 in (0.36 mm) guidewires in the arterial vasculature. The MicroCatheter is compatible with the ACIST RXi family of system hardware which includes the RXi System and RXi Mini. Features unique to each system are denoted specifically.

The Navvus II MicroCatheter distal shaft is 26 cm in length with a pressure sensor located 5 mm from the distal tip. The elliptical distal shaft is 1.68 x 1.91F (0.020 in x 0.025 in) up to 10 mm from the distal tip; a maximum profile of 2.7F (0.036 in) occurs at the pressure sensor. The distal shaft smoothly tapers over the pressure sensor and down to the tip accepting the guidewire. A radiopaque marker band is located 2.5 mm from the distal tip.

The shaft proximal to the monorail section is 2.4F, allowing use in 5F or larger guide catheters. Two white positioning markers are located at 80 cm and 100 cm from the distal tip. The pressure sensor on the catheter utilizes optical sensing technology. Both the optical pressure signal and information for auto calibration are transmitted from the catheter to the RXi hardware.

The ACIST RXi System is designed to provide hemodynamic information for the diagnosis and treatment of coronary and peripheral artery disease. The system is intended for use in catheterization and related cardiovascular specialty laboratories to compute and display fractional flow reserve (FFR) and resting Pd/Pa.

FFR and resting Pd/Pa supplement the visual data provided by angiography and provides an assessment of the lesion severity.

Measurement of FFR and resting Pd/Pa requires simultaneously monitoring the blood pressures proximal and distal to a lesion. The ACIST RXi System includes a single-use MicroCatheter with a pressure sensor for acquisition of the distal pressure. The proximal pressure is acquired via the guide catheter which is monitored by the ACIST RXi System via an interface to the hospital's hemodynamic monitor.

Pd/Pa is the ratio of distal coronary arterial pressure to aortic pressured at resting conditions. The physician may then use the resting Pd/Pa value, along with knowledge of patient history, medical expertise and clinical judgment to determine if an additional measurement of FFR during hyperemia or therapeutic intervention is indicated.

AI/ML Overview

The acceptance criteria and supporting study details for the ACIST Rapid Exchange (RXi) System and Navvus II MicroCatheter are described below.

1. Table of Acceptance Criteria and Reported Device Performance

The provided document focuses on demonstrating substantial equivalence to a predicate device rather than explicitly stating acceptance criteria for a novel device and then reporting performance against those criteria. Instead, it details design verification testing and relies on clinical post-market analysis and supported literature to establish the clinical utility of the derived Pd/Pa values.

For the Navvus II MicroCatheter, the document states that design verification testing demonstrated that the observed differences in Maximum Tip OD and Distal End of Sensor to Markerband did not affect the performance of the device, suggesting an implicit acceptance criterion of "performance unaffected" relative to the predicate.

For the RXi System, the document states that it is identical to the predicate and that the change is simply to include Pd/Pa in the labeling, implying that its performance is already established by the predicate.

The main clinical performance claim revolves around the Pd/Pa measurement and its correlation with FFR. While not explicitly a "device performance" in terms of physical function, the clinical utility of the device hinges on this.

Feature/Metric	Acceptance Criterion (Implicit)	Reported Device Performance
Navvus II MicroCatheter:
Maximum Tip OD	Performance unaffected by 0.06mm difference from predicate	Design verification testing demonstrated performance was unaffected.
Distal End of Sensor to Markerband	Performance unaffected by 0.10mm difference from predicate	Design verification testing demonstrated performance was unaffected.
Dimensional and Visual Inspections	Met documented acceptance criteria	All test results met documented acceptance criteria.
Static Accuracy	Met documented acceptance criteria	All test results met documented acceptance criteria.
Tortuous Path	Met documented acceptance criteria	All test results met documented acceptance criteria.
Durability	Met documented acceptance criteria	All test results met documented acceptance criteria.
Tensile Strength	Met documented acceptance criteria	All test results met documented acceptance criteria.
RXi System:
Functional Equivalence to Predicate	Identical to predicate, no design changes affecting performance	Device is identical to the predicate (K132474); no design changes since original clearance.
Clinical Utility (Derived Pd/Pa):
Optimal Pd/Pa cutpoint for ≤0.80 FFR	Consistent with established clinical evidence and meta-analyses	ACIST-FFR Pd/Pa Post-hoc Sub-Group Analysis identified an optimal cutpoint of 0.91, which is within the range of 0.91 to 0.93 reported in 12/14 studies of Maini et al. meta-analysis.

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

The document references a clinical post-market analysis: "ACIST-FFR Pd/Pa Post-hoc Sub-Group Analysis" and "Maini et al. meta-analysis."

ACIST-FFR Pd/Pa Post-hoc Sub-Group Analysis: This analysis leveraged data from the original ACIST-FFR clinical study. The original study aimed to assess catheterization and standard techniques for Fractional Flow Reserve Measurement.
- Sample Size for Test Set: Not explicitly stated for this sub-group post-hoc analysis. The original analysis was published in Circ Cardiovasc Interv. 2017 Dec; 10 (12). e005905, but the specific number of cases/patients used in this sub-group analysis for determining the optimal Pd/Pa cutpoint is not provided in the submitted document.
- Data Provenance: Not explicitly stated (e.g., country of origin, retrospective/prospective). However, the nature of a "post-hoc sub-group analysis" of a clinical study implies the data was collected prospectively for the original ACIST-FFR study and then retrospectively analyzed for this specific purpose.
Maini et al. Meta-analysis:
- Sample Size for Test Set: Reported on 14 studies. The total number of individual patients or cases across these 14 studies is not specified in the FDA submission, but the meta-analysis itself aggregates data from multiple studies.
- Data Provenance: The meta-analysis aggregated "published resting Pd/Pa diagnostic accuracy studies." This implies diverse geographical origins and likely a mix of prospective and retrospective original study designs.

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

ACIST-FFR Pd/Pa Post-hoc Sub-Group Analysis: The ground truth for this analysis used an FFR cutoff value of ≤0.80 to define stenosis. This FFR measurement itself would be obtained by a clinician (e.g., interventional cardiologist) using the Navvus MicroCatheter. The determination of the FFR value and the interpretation of whether it indicates stenosis (≤0.80) is based on widely accepted clinical consensus and guidelines in interventional cardiology. The document does not specify the number of individual experts or their specific qualifications for establishing this ground truth within the study, but it relies on established FFR thresholds.
Maini et al. Meta-analysis: This meta-analysis compared Pd/Pa to FFR. Therefore, FFR measurements from the 14 included studies served as the ground truth. Again, the number and qualifications of experts involved in the original FFR measurements or their interpretation across these diverse studies are not specified in this document, but FFR measurement and interpretation are standard practices by interventional cardiologists.

4. Adjudication Method for the Test Set

Not explicitly stated. Given that the ground truth for the clinical utility claims is FFR (a quantitative physiological measurement with an established cutoff), a formal adjudication process beyond standard clinical measurement and interpretation protocols is unlikely to have been detailed in this context. The "optimal cutpoint" derived was likely statistical (Receiver Operating Characteristic - ROC curve analysis).

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

No, a multi-reader multi-case (MRMC) comparative effectiveness study comparing human readers with AI assistance vs. without AI assistance was not done. The submission focuses on validating the device's ability to measure pressure and derive Pd/Pa, which subsequently aids clinicians in decision-making, rather than comparing AI-assisted vs. unassisted human interpretation of complex images or data.

6. Standalone (Algorithm Only Without Human-in-the-Loop Performance) Study

Yes, in a sense. The core "performance" of the RXi System (when coupled with the Navvus II MicroCatheter) in calculating Pd/Pa and FFR is a standalone algorithm function based on acquired pressure data. The "optimal cutpoint" of 0.91 for Pd/Pa in relation to FFR (≤0.80) was determined algorithmically (via ROC curve analysis) from a dataset. This demonstrates the performance of the device's computational output (Pd/Pa value) in relation to FFR, independent of real-time human interpretation during the calculation. However, the clinical application of these values always involves a human-in-the-loop (the physician making treatment decisions).

7. Type of Ground Truth Used

The primary ground truth used for the clinical utility claim regarding Pd/Pa was Fractional Flow Reserve (FFR).

For the ACIST-FFR Pd/Pa Post-hoc Sub-Group Analysis, the derived optimal Pd/Pa cutpoint was established using an FFR cutoff value of ≤0.80 measured with the Navvus MicroCatheter to define stenosis. FFR is a physiological measurement, widely accepted as a gold standard for assessing the hemodynamic significance of coronary artery lesions.
The Maini et al. meta-analysis also compared Pd/Pa to FFR as its gold standard.

8. Sample Size for the Training Set

The document does not explicitly mention a "training set" in the context of an AI/ML algorithm being trained.

The "ACIST-FFR Pd/Pa Post-hoc Sub-Group Analysis" used data from the "ACIST-FFR clinical study." The overall sample size of this study is not provided in detail in the current document, only referenced by its publication. It's more akin to a validation set used to derive a cutpoint from existing data rather than an AI training set.
Similarly, the Maini et al. meta-analysis is an aggregation of 14 separate studies, each with its own patient population.

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

As no explicit "training set" for an AI/ML algorithm is described, this question is not directly applicable in the terms of the provided document. However, if interpreting the data used to determine the Pd/Pa cutpoint (from the ACIST-FFR study) as analogous to a "training set" for establishing a diagnostic threshold:

The ground truth for this data was FFR (Fractional Flow Reserve) measurements within those clinical studies. FFR is established by simultaneously measuring pressure distal to a stenosis (Pd) and aortic pressure (Pa) under maximal hyperemia and calculating their ratio (Pd/Pa under hyperemia). A value of ≤0.80 is widely accepted as indicating a hemodynamically significant stenosis. These measurements are performed invasively using specialized catheters (like the Navvus MicroCatheter itself) and guide catheters, interpreted by trained interventional cardiologists based on established physiological principles.

Summary

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September 13, 2019

ACIST Medical Systems, Inc. Sherri Mellingen Principal Regulatory Affairs Specialist 7905 Fuller Road Eden Prairie, Minnesota 55344

Re: K190473

Trade/Device Name: ACIST Rapid Exchange (RXi) System and Navvus II MicroCatheter Regulation Number: 21 CFR 870.2870 Regulation Name: Catheter Tip Pressure Transducer Regulatory Class: Class II Product Code: DXO, OBI Dated: August 13, 2019 Received: August 14, 2019

Dear Sherri Mellingen:

We have reviewed your Section 510(k) premarket notification of intent to market the device referenced above and have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to legally marketed predicate devices marketed in interstate commerce prior to May 28, 1976, the enactment date of the Medical Device Amendments, or to devices that have been reclassified in accordance with the provisions of the Federal Food, Drug, and Cosmetic Act (Act) that do not require approval of a premarket approval application (PMA). You may, therefore, market the device, subject to the general controls provisions of the Act. Although this letter refers to your product as a device, please be aware that some cleared products may instead be combination products. The 510(k) Premarket Notification Database located at https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm identifies combination product submissions. The general controls provisions of the Act include requirements for annual registration, listing of devices, good manufacturing practice, labeling, and prohibitions against misbranding and adulteration. Please note: CDRH does not evaluate information related to contract liability warranties. We remind you, however, that device labeling must be truthful and not misleading.

If your device is classified (see above) into either class II (Special Controls) or class III (PMA), it may be subject to additional controls. Existing major regulations affecting your device can be found in the Code of Federal Regulations, Title 21, Parts 800 to 898. In addition, FDA may publish further announcements concerning your device in the Federal Register.

Please be advised that FDA's issuance of a substantial equivalence determination does not mean that FDA has made a determination that your device complies with other requirements of the Act or any Federal statutes and regulations administered by other Federal agencies. You must comply with all the Act's requirements, including, but not limited to: registration and listing (21 CFR Part 807); labeling (21 CFR Part 801); medical device reporting of medical device-related adverse events) (21 CFR 803) for devices or postmarketing safety reporting (21 CFR 4, Subpart B) for combination products (see

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https://www.fda.gov/combination-products/guidance-regulatory-information/postmarketing-safety-reportingcombination-products); good manufacturing practice requirements as set forth in the quality systems (QS) regulation (21 CFR Part 820) for devices or current good manufacturing practices (21 CFR 4, Subpart A) for combination products; and, if applicable, the electronic product radiation control provisions (Sections 531-542 of the Act); 21 CFR 1000-1050.

Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21 CFR Part 807.97). For questions regarding the reporting of adverse events under the MDR regulation (21 CFR Part 803), please go to https://www.fda.gov/medical-device-safety/medical-device-reportingmdr-how-report-medical-device-problems.

For comprehensive regulatory information about medical devices and radiation-emitting products, including information about labeling regulations, please see Device Advice (https://www.fda.gov/medicaldevices/device-advice-comprehensive-regulatory-assistance) and CDRH Learn (https://www.fda.gov/training-and-continuing-education/cdrh-learn). Additionally, you may contact the Division of Industry and Consumer Education (DICE) to ask a question about a specific regulatory topic. See the DICE website (https://www.fda.gov/medical-device-advice-comprehensive-regulatoryassistance/contact-us-division-industry-and-consumer-education-dice) for more information or contact DICE by email (DICE@fda.hhs.gov) or phone (1-800-638-2041 or 301-796-7100).

Sincerely.

Stephen Browning Assistant Director Division of Cardiac Electrophysiology, Diagnostics and Monitoring Devices Office of Cardiovascular Devices Office of Product Evaluation and Quality Center for Devices and Radiological Health

Enclosure

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Indications for Use

510(k) Number (if known) K190473

Device Name

ACIST Rapid Exchange (RXi) System and Navvus II MicroCatheter

Indications for Use (Describe)

X Prescription Use (Part 21 CFR 801 Subpart D)

| Over-The-Counter Use (21 CFR 801 Subpart C)

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Premarket Notification - Traditional 510(k)

RXi System and Navvus II Catheter

510(k) Summary

Date Prepared: 2/26/2019

Submitters Name / Contact Person

510k Submitter Address

ACIST Medical 7905 Fuller Road Eden Prairie, MN 55344 Phone - (952) 995 - 9300

Contact for Official/Routine Correspondence

Sherri Mellingen Senior Regulatory Affairs Specialist 7905 Fuller Road Eden Prairie, MN 55344 Phone - (952) 995 - 9381 Email: sherri.mellingen@acistmedical.com

General Information
Trade Name:	ACIST Rapid Exchange (RXi) System and Navvus II MicroCatheter
Common / Usual Name:	Cardiovascular Pressure Measurement System and Navvus Catheter
Classification:	Class 2 per 21 CFR 870.2870
Product Code:	OBI, DXO
Predicate Device:	ACIST RXi® System and Navvus Catheter

Device Description

Navvus II 1.

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2. RXi System

FFR and resting Pd/Pa supplement the visual data provided by angiography and provides an assessment of the lesion severity.

Intended Use / Indications

The ACIST RXi System is indicated for obtaining intravascular pressure measurements 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.

Comparison of Technological Characteristics

The RXi System is identical to the predicate as there have been no design changes since the device was originally cleared. The PdPa function has always existed on the device as this change is simply to include it in the labeling. The Navvus II differs from the predicate device with regard to the tip OD (0.06mm difference) and the distance from the distal end of the sensor to the marker band (0.10 difference). Design verification testing demonstrated that these two small differences did not affect the performance of the device and that the subject device and the predicate device were substantially equivalent. The Navvus II Catheter is substantially equivalent to the legally marketed predicate device in design, intended use, intended population, principles of use, materials, size and sterility.

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Table 1: Comparison with Predicate
	Subject Device	Predicate Device	Comparison ofK132474 to SubjectDevice
510(k) #	TBD	K132474
Intended Use /Indications	The ACIST RXi System is indicated for obtaining intravascular pressure measurements for use in the diagnosis and treatment of coronary and peripheral artery disease. The ACIST Navvus MicroCatheter is intended for use with the entire family of ACIST RXi Systems.		Same
Principles of Use	Calculates FFR and Pd/Pa based on simultaneous acquisition of pressure from two transducers:The flexible distal tip of the catheter that contains the optical pressure sensor is advanced over the proximal end of the 0.014 in (0.36 mm) guidewire that is already in place in the distal vasculature. The Navvus catheter is advanced over the wire and positioned with the radiopaque marker in the coronary ostium, 3 mm outside the tip of the guide catheter. Equalization must take place with the Navvus Catheter distal tip just outside the tip of the guide catheter. Pressure is measured less than 3 mm proximal from the marker band visible under fluoroscopy. The guide catheter is flushed with saline solution. Then the Navvus Catheter sensor is advanced past the lesion under study.		Same
Display Features	Navvus distal (Pd) and proximal/aortic (Pa) pressure, Pd/Pa, and FFR		Same
IntendedAnatomicalLocation	Coronary and peripheral vasculature		Same
Configuration	Navvus Catheter is a 0.022" catheter with and integrated pressure sensor that is used in the real-time calculation of FFR and Pd/Pa together with a detachable cable for connection to a diagnostic computer.		Same
Coating	No		Same
Marker Band?	Yes - 2.5mm from distal tip		Same
Maximum TipOD	Tip OD 0.75mm MAX	Tip OD 0.69mm MAX	Differs 0.06mm
Table 1: Comparison with Predicate
	Subject Device	Predicate Device	Comparison of K132474 to Subject Device
Distal End of Sensor to Markerband	2.31+/- 0.25mm	2.41+/- 0.25mm	Differs by 0.10mm
Effective (Working) Length	145 cm to 155 cm		Same
Compatible Guidewire Diameter (max)	0.014"		Same
Single use, sterile?	Yes		Same
Sterilization method	Ethylene Oxide		Same
Intended Population	This product is designed for use in adult patients identified by a physician as suitable candidates for vascular pressure measurement after taking into consideration the patient's anatomy and health status.		Same

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Non-Clinical Bench Testing

The following non-clinical bench testing was completed on the Navvus II MicroCatheter:

Dimensional and Visual Inspections Static Accuracy Tortuous Path

Durability Tensile Strength

Pd/Pa Clinical Post-Market Analysis and Supported Literature

The expected FFR value in a normal vessel without a stenotic lesion or obstruction to blood flow is a value of 1.0. Based on clinical evidence, a threshold or cutpoint value of ≤ 0.80 is commonly considered for treatment with a therapeutic intervention, while a value > 0.80 is commonly considered for deferment. An established, clinically evident Pd/Pa threshold or cutpoint such as this is indeterminate, but guidance for use of PdPa for clinical decision making may be considered by referring to the existing, supportive clinical evidence from multiple diagnostic accuracy studies performed on resting Pd/Pa.

A recent meta-analysis was reported by Maini et al., based on published resting Pd/Pa diagnostic accuracy studies which examined the overall diagnostic accuracy of Pd/Pa compared to FFR. The meta-analysis reported on 14 studies with an optimal cutpoint ranging from 0.875 to 0.96 and resulted in cutpoints from 0.91 to 0.93 in 12 of the 14 studies in the meta-analysis.

The ACIST-FFR Pd/Pa Post-hoc Sub-Group Analysis' identified an optimal cutpoint of 0.91. The cutpoint was derived from a post-hoc receiver operating characteristic (ROC) curve analysis using an FFR cutoff value of ≤0.80 measured with the Navvus MicroCatheter to define stenosis. The 0.91 cutpoint is within the range of 0.91 to 0.93 as was reported in 12 of the 14 studies in the Maini et al., meta-analysis.

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RXi System and Navvus II Catheter

Standards

The following is a summary of the standards used in testing for the RXi System and Navvus II MicroCatheter:

Table 3: Standards used in non-clinical bench testing
Test	Industry Standards	FDA Recognition Number, Version and Date
Design Verification	EN ISO 13485:2016, Medical Devices, Quality Management Systems	Not recognized by FDA
Device Performance	EN ISO 13485:2016, Medical Devices, Quality Management Systems	Not recognized by FDA
ISO 10555-1, Sterile and Single Use Intravascular Catheters General Requirements		6-3018/14/2015
Risk Management	EN ISO 14971, Application of Risk Management to Medical Devices	5-406/27/2016
Medical Electrical Equipment	IEC 60601-1-2:2014, Medical Electrical Equipment	19-89/17/2018
Animal Model	FDA 21 CFR: Part 58 Good Laboratory Practice Regulations	N/A
Packaging & Shelf Life	ISO 11607-1:2006/2010, 11607-2:2006 Packaging for Sterilized Medical Devices	14-454, 14-4551/27/2015
Biocompatibility	ISO 10993-1: 2009 Biological Evaluation of Medical Devices	2-2207/26/2016
Sterilization	ISO 11135:2014 Medical Devices - Validation of Routine Control of Ethylene Oxide Sterilization	14-4524/4/2016

Product Codes

The following product codes are similar to the predicate and subject device (product code OBI) as the devices are classified in accordance with regulation 870.1200: DQO, NLI, NUI, OBJ, OES, OFN, OGZ, ORD. The secondary product code, DXO, is regulated in accordance with regulation 870.2870 and has no similar product codes.

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K190473

Results of design verification testing on the Navus II MicroCatheter demonstrate that the device is substantially equivalent to the predicate device. The subject device has been evaluated through bench testing. All test results met documented acceptance criteria and demonstrated the Navvus II MicroCatheter is substantially equivalent to the predicate device. Finally, the ACIST-FFR Pd/Pa Sub-Group Post-Hoc Analysis, in which all pressure tracings were acquired by the ACIST Navvus MicroCatheter, gave additional information on the clinical use of PdPa and provided further information as compared to the cutpoint range presented in the Maini meta-analysis.

1 Thackery, Lisa,, Rorke, Becky., Larson, Janet A., PdPa, Sub-Group, Post-hoc analysis of data from the ACIST-FFR clinical study which assessed catherrogation and standard techniques for Fractional Flow Reserve Measurement. Original data set analysis published in: Circ Cardiovasc Interv. 2017 Dec; 10 (12). e005905

2 Maini R, Moscona J, Sidhu G, et al. Pooled diagnostic accuracy of resting distal to aortic coronary pressure referenced to fractional flow reserve: The importance of resting coronary physiology. Journal of Interventional Cardiology. 2018;31(5):588-598. doi:10.1111/joic.12517.

3 Lighart Jurgen, Masdjedi Kaneshka, Witberg Karen, et al. Validation of Resure Ratio Calculated by a Novel Algorithm and Its Correlation With Distal Coronary Artery Pressure to Aortic Pressure, Instantaneous Wave-Free Ratio, and Fractional Flow Reserve. Circulation: Cardiovascular Interventions. 2018;11(12):e006911. doi:10.1161/CIRCINTERVENTIONS.118.006911.

Regulation Number and Section

§ 870.1200 Diagnostic intravascular catheter.

(a)
Identification. An intravascular diagnostic catheter is a device used to record intracardiac pressures, to sample blood, and to introduce substances into the heart and vessels. Included in this generic device are right-heart catheters, left-heart catheters, and angiographic catheters, among others.(b)
Classification. Class II (performance standards).