(169 days)
The Zio QX ECG Monitoring System is intended to capture, analyze and report symptomatic and asymptomatic cardiac events and continuous electrocardiogram (ECG) information for long-term monitoring. While continuously recording patient ECG, both patient-triggered and automatically detected arrhythmia events are transmitted to a monitoring center for reporting. After wear, a final report is generated based on beat-to-beat information from the entire ECG recording. It is indicated for use on patients 18 years or older who may be asymptomatic or who may suffer from transient symptoms such as palpitations, shortness of breath, dizziness, light-headedness, pre-syncope, fatigue, or anxiety. The reports are provided for review by the intended user to render a diagnosis based on clinical judgment and experience. It is not intended for use on critical care patients.
The Zio® QX ECG Monitoring System consists of three key device components: (1) Zio QX Patch Recorder with Bluetooth technology, (2) Zio QX Wireless Gateway with both Bluetooth and cellular technology, and (3) the Zio ECG Utilization Service (ZEUS) System for data analysis and reporting.
The Zio® QX Patch is a non-sterile, single-patient-use ECG monitor that provides a continuous, single-channel recording in addition to asymptomatic and symptomatic data transmission for up to 14 days. The Zio® QX Patch is applied and activated by the patient. Once activated, the Patch records ECG without patient interaction, with the goal of improving patient compliance via simplicity of operation. The Zio® QX Patch, in conjunction with the Wireless Gateway and the ZEUS System, has arrhythmia auto-detection capabilities. Additionally, patients have the option of pressing a convenient trigger button which marks the continuous record and initiates the wireless transfer of a 90-second ECG strip. The wireless transfer of data is enabled by the Zio® QX Gateway, which requires Bluetooth proximity to the Patch and cellular network reception but no patient interaction to transmit to the monitoring center. The patient is encouraged to document symptomatic events in either the provided booklet, mobile medical app (iOS 9+, Android 4.4+) or via a patient website, which will support symptom-rhythm correlation in the Zio QX Report.
At the conclusion of the wear period (up to 14 days), the patient removes the Zio® QX Patch and returns it by mail to an iRhythm data processing center.
Upon receipt of both symptomatic/asymptomatic transmissions (during wear) and downloaded continuous ECG data (post wear) at iRhythm's Clinical Center (iCC), the data is processed through the ZEUS detection algorithm and delivered to the QA Tool module where the results are reviewed and/or adjusted by iRhythm's Certified Cardiographic Technicians (CCTs) for accuracy. iRhythm employed and trained Patch in-take and CCT personnel follow internal procedures for processing and are made aware of performance limitations and anomalies with both the detection algorithms and software workflow tools. All anomalies are visible to and, where appropriate, are manually corrected by iRhythm Technologies CCTs during the QA review and/or Patch Report edits. The CCT generates a final report (Zio QX Report) of the ECG findings contained within the data, thereby providing a complete ECG processing and analysis service.
Upon explicit request from a clinician responsible for the patient's healthcare, longer segments of ECG data from the continuous recording on the Patch can also be wirelessly retrieved during the wear period. Alternatively, such periods are also available for inclusion in the final report, where the entire ECG recording is available for review and selective inclusion based on clinical relevance.
The provided FDA 510(k) summary for the Zio® QX ECG Monitoring System (K163512) describes the device's acceptance criteria and the study conducted to prove it meets them.
Here's an analysis of the provided information:
1. Table of Acceptance Criteria and Reported Device Performance
The document states: "Automated ECG analysis performance was quantified for any claimed analysis metrics. The resulting statistics demonstrate sensitivity and positive predictivity levels which satisfy requirements."
However, the specific quantitative acceptance criteria (e.g., minimum sensitivity of X%, minimum PPV of Y% for specific arrhythmia types) and the actual reported performance metrics (e.g., Sensitivity = A%, PPV = B%) are NOT explicitly provided in the excerpt. The document only makes a general statement that the device satisfies requirements.
Without the actual numbers, a precise table cannot be constructed.
2. Sample Size Used for the Test Set and Data Provenance
The document states: "No clinical testing was performed in support of this premarket notification." and "All necessary performance testing was conducted on the Zio® QX ECG Monitoring System to ensure performance as intended per specifications and to support a determination of substantial equivalence to the predicate devices."
This indicates that the primary performance evaluation for the automated ECG analysis was done as part of non-clinical testing. This likely means simulated or pre-recorded ECG datasets were used.
- Test Set Sample Size: Not explicitly provided.
- Data Provenance: The document does not specify the country of origin of the data or whether it was retrospective or prospective. Given "nonclinical testing," it's likely a retrospective analysis of existing datasets or simulated data.
3. Number of Experts Used to Establish Ground Truth and Qualifications
The document describes the role of human experts in the data processing workflow:
- "...the data is processed through the ZEUS detection algorithm and delivered to the QA Tool module where the results are reviewed and/or adjusted by iRhythm's Certified Cardiographic Technicians (CCTs) for accuracy."
- "All anomalies are visible to and, where appropriate, are manually corrected by iRhythm Technologies CCTs during the QA review and/or Patch Report edits."
- "The CCT generates a final report (Zio QX Report) of the ECG findings contained within the data, thereby providing a complete ECG processing and analysis service."
From this, we can infer:
- Number of Experts: Not explicitly stated as a fixed number for establishing a ground truth dataset for the purpose of the regulatory submission's performance study. However, it implies that multiple CCTs are involved in the standard operational workflow for quality assurance and report generation. For the study proving acceptance criteria, the number of experts used to establish the "ground truth" for the test set is not specified.
- Qualifications of Experts: "iRhythm's Certified Cardiographic Technicians (CCTs)" are mentioned. Their specific experience (e.g., 10 years) is not provided. It also doesn't specify if a higher level of expertise (e.g., cardiologists) was involved in establishing the ground truth for the performance claim.
4. Adjudication Method for the Test Set
The document states that CCTs review and adjust the algorithm's results. This implies a human-in-the-loop system where the CCTs serve as a final arbiter. However, for the non-clinical performance testing used for the regulatory submission, the specific adjudication method to build the "ground truth" dataset is not described. General methods like "2+1" or "3+1" are not mentioned. It's possible that a single CCT or a panel of CCTs established the ground truth in the datasets used for testing.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
The document explicitly states: "No clinical testing was performed in support of this premarket notification."
Therefore, a MRMC comparative effectiveness study involving human readers improving with AI vs. without AI assistance was NOT done for this submission. The device is a "monitoring system" with an automated analysis component that produces a report for human review; the study focuses on the algorithm's performance and the general process, not on human-AI collaboration effectiveness.
6. Standalone (Algorithm Only) Performance
Yes, a standalone performance evaluation of the algorithm was conducted. The document states:
- "Automated ECG analysis performance was quantified for any claimed analysis metrics."
- This falls under "Nonclinical testing."
The device description also clarifies the algorithm's role: "...the data is processed through the ZEUS detection algorithm...". This "ZEUS detection algorithm" is the standalone component whose performance was quantified.
7. Type of Ground Truth Used
The document indicates that CCTs review and "adjust" results to ensure "accuracy" and manually "correct" anomalies. This suggests the ground truth for the performance evaluation (or at least the operational ground truth for report generation) is established by expert consensus/adjudication by Certified Cardiographic Technicians (CCTs). It's not explicitly stated whether a higher level of ground truth (e.g., pathology, clinical outcomes, or adjudication by cardiologists) was used for the non-clinical test set.
8. Sample Size for the Training Set
The document does NOT provide any information regarding the training set's sample size. The focus of the 510(k) summary is on the testing that demonstrates substantial equivalence, not on the details of algorithm development (training, validation).
9. How Ground Truth for the Training Set Was Established
The document does NOT provide any information on how the ground truth for the training set was established. This is typical for a 510(k) submission, which focuses on the validation of the final product.
§ 870.1025 Arrhythmia detector and alarm (including ST-segment measurement and alarm).
(a)
Identification. The arrhythmia detector and alarm device monitors an electrocardiogram and is designed to produce a visible or audible signal or alarm when atrial or ventricular arrhythmia, such as premature contraction or ventricular fibrillation, occurs.(b)
Classification. Class II (special controls). The guidance document entitled “Class II Special Controls Guidance Document: Arrhythmia Detector and Alarm” will serve as the special control. See § 870.1 for the availability of this guidance document.