Cardea SOLO™ ADX S400 Software – Clinical Review (Section 7)

Cardea SOLO™ ADX S400 Software uses RAAPTr™ technology, developed with global cardiologists and scientists, for fast and efficient ECG waveform analysis and arrhythmia detection. The software also includes viewing, editing, and reporting tools that improve clinical efficacy and diagnosis time for patients.

Learn to review ECG trace data, correct errors in demographic or diary data entry, edit the diagnostic summary, and finalize the PDF report with the given tools. After the draft PDF report is presented, Cardea SOLO™ ADX S400 Software will offer a menu of options for interactive review and editing of the summary finding.

Figure 7.1. Report Review Options menu.

ECG Analysis Precautions. Automated ECG analysis algorithms may not detect certain abnormalities, requiring a licensed physician to perform a review of interpretations. Clinical findings must complement computerized interpretations to provide significant results.

Patients with implantable pacemakers or active stimulator devices, including TENS units, deep brain stimulators, muscle activators, and spinal cord stimulators, may cause misclassification of beats and rhythms or render the recorded ECG signal unanalyzable due to interference with pacing and stimulators.

The following sections discuss the functionality of each menu option.

ECG Trace Review

The ECG TraceViewer has been designed to support rapid access to any 10 second strip in the entire recording. Clicking on the Open TraceViewer button, Figure 7.1, presents the TraceViewer, Figure 7.2.

RR View is a display format that shows changing rhythms. Access it by clicking the Date tab and it allows visualization of the onset and termination of atrial fibrillation. By clicking on any point, associated 10-minute ECG traces are shown. The display can be toggled between RR View and Avg HR View by clicking the “RR View” checkbox.

Figure 7.2. RR View showing heart rate for every RR interval.

Additional examples of ECG rhythms are shown in the following figures

Figure 7.3 Example RR plots for premature atrial contractions (PACs), premature ventricular contractions (PVCs), and atrial bigeminy.

The Avg HR View displays heart rate averages and ranges in 10-minute intervals for a selected date. Clicking on a date provides access to its corresponding averages. A red dot indicates a patient event button push. Bars below the panels show the burden of Atrial Fibrillation and Ventricular beats, providing a quick ECG record overview.

Figure 7.4. TraceViewer, Day Averages view.

Clicking the “Close” button on the top right will close the TraceViewer and return to the Report Review Options menu, Figure 7.1.

Clicking at any time point in the day view (RR or Average view) will present the 5-minute ECG record associated with the selection, Figure 7.5.

Figure 7.5. 10-minute TraceViewer.

• On the top right of the screen are the “Forward”, “Back” buttons. Clicking Forward or Back, or clicking the < or > arrow keys on the keyboard, will advance or decrement the time view by 5-minutes.
• Clicking at any point on any of the 5 one minute traces will display a 10 second view of the trace in the window at the bottom of the screen, centered on the click point. Heart rate and time are shown at the left of the 10 second display.
• ECG data in a 10 second window can be exported as comma-separated data for external analysis. Copy with Ctrl-C and paste with Ctrl-V in Excel. Use Data/Text to Columns to separate the data, which includes a True/False flag indicating validity.
• If there is a patient marker within the 10-minute view, its location will be highlighted with a red asterisk (_*) and when opened the 10 second window will automatically be positioned on the preceding segment.
• Segments of the ECG found positive for Atrial Fibrillation will be underscored with a blue line. Ventricular beats are highlighted with a vertical red line. The light dashed vertical blue lines in the 10 second bottom window view are the isoelectric point for each beat (onset of the QRS).
• Cardea SOLO™ ADX S400 Software analyzes the record for muscle and motion artifacts and excludes these noise segments from analysis. Excluded segments are indicated by displaying the trace in light gray.
• Clicking on the date dropdown (top left), or the Previous or Next buttons (top left) will return to the Day view.

Beat annotations (labels) 

NOTE: Beat annotations (labels) conform with ANSI/AAMI EC57:2012, e.g.

• N = a normal beat or a bundle branch block beat that does not fall into the categories described below
• A = a supraventricular ectopic beat (SVEB / PAC): an atrial or nodal (junctional) premature or escape beat, or an aberrant atrial premature beat
• a = a PAC following the initial PAC beat (e.g. a run of SVT would be represented as Aaaaaaa)
• V = a ventricular ectopic beat (VEB / PVC): a ventricular premature beat, an R-on-T ventricular premature beat, or a ventricular escape beat
• Q = a beat that could not be classified
• Z = a label that marks an event that is interpreted as noise

Cardea SOLO™ ADX S400 uses distinct beat templates to categorize beats into classes, accessed via the “Beats” button. Each class’s beat morphology is constructed using up to 75 beats selected from the slowest heart rate sections of the record. These selected beats are time-aligned at the onset of the QRS, and a median average is used to develop the estimated morphology. For each time point, the middle half of all beat samples sorted smallest to largest are averaged.

The behavior of the beats in the class (e.g. premature with a following pause, and with a long QRS duration) is used to classify the class as Normal or Ventricular.

Figure 7.6. Beat morphology for each identified beat class.

The first line under the waveform displays the total beat count and key phase measurements. The RR ratio shows the average interval durations before and after the beat, divided by the heart rate. A ratio of “0.658:0.921” means the class has a short RR interval before the beat and a close RR interval after the beat. Cardea SOLO™ ADX S400 uses this information to determine if the beat is Normal or Ventricular. The clinician can change the classification using a drop-down box, but once classified as Noise, it cannot be undone.

Setting Beats To Noise

Beats that are marked as Noise can only be restored by re-processing the patient’s Sensor Electronics Module. Refer to Section 6.

Changing Beat Classification.

Changing beat classification (e.g. Normal to Ventricular) will, in general, have a significant impact on the rhythm analysis. This change should only be made following careful review of the trace data and associated beat class characteristics. A beat classification change can be returned to the initial designation in subsequent edits.

Clicking on the beat grid will display a pop-up menu that supports interactive editing of the waveform phases (P-onset, P-offset, etc.) or viewing the selected beats in the class in the context of the rhythm strips.

Figure 7.7. Clicking on the beat morphology displays the pop-up menu for interactively editing the beat phases or show the beat class in the context of the ECG trace.

Selecting Edit Phases will display the Phase Editor.

Figure 7.8. Phase Editor.

The Phase Editor supports editing the P-wave onset (Pon) and offset (Poff), the onset of the QRS (Q), end of S (S) and end of T (T). The radio buttons at the bottom can be used to select the phase to be edited. Or, right-clicking in the vicinity of the phase of interest will also select the phase for editing (blue highlighted vertical line). Current measurements are listed at the top of the window.

Clicking on the “Show Beats” menu item will show the first beat of the selected class in the 10 sec rhythm display, centered at the 5 second position. Next, 25 beats are selected from this class, spread uniformly across the ECG recording. Clicking the F5 key will sequentially advance to the next beat in the beat list. This allows the user to review the individual morphologies representative of beats in the class.

Not all detected beats can be classified and assigned to a beat class (Catalogued). The software attempts to assign unclassified beats into either Normal, Ventricular or Noise. For noisy records there may be unassigned “beats” classified as Ventricular that should be removed.

“Delete Uncatalogued V Beats” removes all unclassified ventricular beats from an ECG record. The button only shows up on the Beats page if such beats exist.

Closing TraceViewer updates analysis and PDF report. Beat Classification changes allow “Update Rhythm” button at top right. Clicking updates rhythm analysis, but not report. May change included rhythm strips.

Lead Options: The M400 Sensor records the ECG using two orthogonal leads. In the below figure, Lead 1 (left to top electrode) and Lead 5 (top to right electrode) are the two recorded traces.

Figure 7.9. Electrode trace configurations.

Using Leads 1 and 5, four additional leads can be created like how Leads I and II are used to make six limb leads for a standard 12-lead ECG. These extra leads can improve visualization and axis determination for certain types of ectopy. The Lead Options button (shown in Figure 7.4) displays the six leads available, based on the current 10 second ECG being viewed (at the bottom of Figure 4.5).

Figure 7.10. Lead selection.

Default selection: lead 2 and lead 5. User can select other leads. TraceView updates trace displays. Checkbox sets selected leads for all rhythm strips in report.

Cardea SOLO™ ADX S400 has a Rhythm Editor that can edit episodes of different heart conditions such as Atrial Fibrillation, Ventricular Tachycardia, 3rd Degree AV Block, 2nd Degree AV Block (Mobitz II), 2nd Degree AV Block (Mobitz I), and Supraventricular Tachycardia. The editor can insert, modify or delete episodes. To access the Rhythm Editor, click on the Edit Rhythm button in the TraceViewer window.

• First, select the rhythm to be edited using the drop-down menu.
• Editing of the selected rhythm can be done by specifying a time interval, defined by the Start and End times. Note: Long AF episodes are divided into sequential episodes, each with a 10-minute duration.
• Or, the entire record can be selected. This can be very helpful in removing false positive findings for Atrial Fibrillation or Ventricular Tachycardia.
• Finally, click Insert or Delete.
• Alternatively, individual existing rhythm episodes can be selected and deleted.
• The Previous and Next buttons will update TraceViewer to the specified Episode.
• If you make an error, the Undo and Redo buttons support restoring previous rhythms.

These functions are discussed in more detail below.

Figure 7.11 Rhythm Editor.

The Rhythm Editor and TraceViewer are linked. TraceViewer gives a trace sample number to the Rhythm Editor. The Rhythm Editor then translates it into a Start Time or End Time, or it selects the closest episode type.

Figure 7.12. Selecting Start and End points for editing Atrial Fibrillation.

To set a time interval in TraceViewer, press Ctrl-S or select Start. Next, click on the display for Start and End times. This feature works in both Day view and 10-minute trace view. Doing so will activate the Insert and Delete buttons and allow keyboard keys to function. By clicking Insert, the range will be marked as 100% Atrial Fibrillation. If you want to remove Atrial Fibrillation within the range, select Delete. It is also possible to make changes to episodes outside of the window. This process is applicable to other rhythms as well.

Pause Episodes are defined by the last beat before the pause and the beat that terminates the pause.

Figure 7.13. Defining a Pause.

Click Start and then click in the RR interval before the beat that defines the start of the pause. Next click End and then click just before the beat that terminates the pause. Finally click Insert to add the pause. Or, if the defined time interval encompasses false positive pauses, click Delete.

Choose an episode and make sure TraceViewer is in 10-minute trace mode. Pick the rhythm type and use the Previous/Next buttons or keyboard arrows to move through episodes. Select an episode by clicking on it or using the Select button. The selected episode will be underlined.

Figure 7.14. Selected Atrial Fibrillation episode. Note the magenta underline, indicating this episode is selected.

Once selected, the episode can be deleted by clicking the Delete button, or the keyboard Delete key.

The Undo and Redo buttons have ten levels of memory storage. This feature resets when changing the rhythm selection. Undoing changes in Atrial Fibrillation is possible only while the Rhythm Editor is focused on it. Once a different rhythm is chosen, memory is cleared.

Noise. Selecting the Noise option enables deleting sections of the record from analysis. Set the “Rhythm” to Noise, select the start and end times, and click Delete. NOTE: Noise deletion cannot be undone. Use of the Noise function will enable the “Update Rhythm” button – discussed above.

New Beat Class: Although unusual, the QRS morphology of a Normal Sinus beat can be very similar to a Ventricular beat. This is especially the case for relatively narrow LV fascicular foci PVCs. The main distinction with narrow PVCs is that the T wave vector is different from the major R or S wave vector; that is the T wave is inverted.

Figure 7.15. Note the very similar QRS morphology between the Normal (left) and the Ventricular (right) beats.

The beat classification may mix PVCs with PACs, leading to misclassification. Premature P waves can go unnoticed, resulting in PACs being classified as PVCs or vice versa. The New Beat Class tool addresses this issue by identifying misclassified beats and creating a new beat class. Use the tool as shown in the example below.

The initial view of the beats in TraceViewer:

Figure 7.16. Example of PVCs classified as PACs.

The New Beat Class tool is accessed via the “Options” button at the bottom left of the TraceViewer screen.

The workflow is as follows:

Create a representation of the QRS for the beat type that needs to be re-classified by selecting the waveform examples.

1. The SOLO software will search the entire record for beats that match the selected waveforms.
2. The TraceViewer screen will update with the newly reclassified beats.
3. The UNDO button will remove the results if they are not acceptable
4. The Finish button will add the new Beat Class to the report and close the tool

Note: For premature beats, the percent early, relative to the running heart rate, is also used in the analysis, providing a robust method for identifying premature beats with the target morphology.

• To reclassify beats, choose Options/New Beat Class and click Add.
• Select a 10 sec strip in TraceViewer with beats to reclassify.
• Click on each beat to add it to the display and remove by right-clicking.
• Add up to 5 beats to make the Average Beat and reduce noise.

Note: SOLO cross-correlates the family of selected beats, optimally time aligns them, and then computes the average beat morphology that will be used in the search. The vertical lines are spaced at 100 msec.

Figure 7.17 New Beat Class tool.

Clicking the Find button will initiate a search and update TraceViewer with the new classifications:

Figure 7.18. Updated beat classification.

Click Finish to finalize the update, or click UNDO to discard the changes.

Individual Beat Editing. Individual beats can also be edited. In the 10 second rhythm strip at the bottom of the screen, click on any beat. A pop-up menu will appear.

Figure 7.19. Individual Beat Editing.

Pop-up shows beat classification (V) and beat class (2). Options allow changing classification to Normal, PAC, or Noise and jumping to next beat in same class.

Beats can be assigned as Normal, PAC, or Ventricular. Select the section by clicking and dragging the mouse, then release to see the selection menu. Clicking outside of the pop-up menu clears the selection.

Figure 7.20. Resetting individual beats to Normal, PAC or Ventricular.

NOTE: The Mouse down clicks have different meanings, depending on what the user is doing. When the Rhythm Editor is active (window is open – see below) it will capture the mouse clicks; The user cannot edit beat and run types when the Rhythm Editor is active.

Rhythm Strips: Clicking the Rhythm Strip button at the top of the screen will display the Rhythm Strip WaveCollection Tool that enables rapid Rhythm Strip navigation in TraceViewer, supporting review and editing of select ECG strips in the PDF Report:

Figure 7.21. The Rhythm Strip Tool.

Clicking any of the caret (▷) symbols to the left of the category, or double-clicking the category, will display a list of all the rhythm strips that are included in the report. In addition, for VT, SVT and Pauses, additional rhythm strips are included for physician review.

Items that are grayed-out and in italic font represent nominal findings that were excluded from the report. For example, if the PAC findings were less than a burden of 0.5%, the report would be shortened by excluding the PAC report page.

NOTE: When found, AFib, VT, Pauses, Heart Block, and SVT are always included in the report.

Figure 7.22. Expanded strips for Atrial Fibrillation.

• Clicking a strip changes TraceViewer, displaying it in a 5-minute view. A strip can be excluded by clicking “Exclude Strip”, and re-included by selecting it and clicking “Include”.
• Right-clicking on a strip can toggle it between Include and Exclude. A category can be excluded by clicking Exclude, and all included when a strip in the category is selected.
• Reports show patient events from WaveCollection, with up to 100 button presses if over 30 are made.
• The report selects 30 strips based on interest and excludes sinus rhythm for Atrial Fibrillation or Ventricular Tachycardia. Event numbering has gaps for excluded events.

Add Rhythm Strips: Select the segment of the ECG that you wish to add to the report (i.e. it is displayed in the 10 second window at the bottom of TraceViewer). Next, click the “Add Rhythm Strip” button, Figure 7.15. A window similar to the following is displayed:

Figure 7.23. Add Rhythm Strips.

• Select the category appropriate for the rhythm – the strip will be added to that section of the report; and labeled with the description you enter.
• The Rhythm Type “Notable Strips” supports the user in adding particularly noteworthy rhythm strips to the report. The Notable Strips section of the report follows the Overview section, preceding the rest of the report rhythm strips.
• The strip can also be designated as the example ECG on the front page of the Report. Check the “Use as Title Page” checkbox.
• The first eight seconds of the currently displayed ten second rhythm strip will be saved. Rhythm strip heart rate is determined by the strip RR average. A strip description is required before clicking the Save button.
• Upon closing the TraceViewer window, the software will automatically update the PDF report and add or exclude the rhythm strips, as specified.

Options: The Options button (bottom left in figure 7.5 above) provides access to interactive calipers, the beat viewer and rhythm strip printing.

Calipers

Clicking Options / Calipers (lower left on Figure 7.5) will activate the calipers and display two vertical caliper lines on the 10 second rhythm strip. Clicking on the Options / Caliper Help button will display the Caliper Help:

Figure 7.24. Caliper Help window.

• Click to move the caliper onset point. Press and hold the left mouse key to move the offset point, and drag left or right. The time interval is displayed at the bottom and updates as the mouse moves.
• Use the arrow keys to move left or right by one RR interval.
• The Beat Viewer on the 10-minute ECG TraceViewer presents an average waveform when the mouse is right-clicked or when selected from the Options button on Figure 7.5. The waveform is made from beats that match the morphology and are within ±15 beats of the clicked beat.
• To pick a beat class, click past the QRS onset and within the RR interval after the beat.

Figure 7.25. Beat Viewer.

• The phases P-onset (Pon), P-offset (Poff), Q onset, end of S and end of T are automatically picked.
• Phases can be edited by first selecting the phase.
• The above blue vertical line, and the activated Pon radio button at the lower left, indicate that the onset of the P-wave is enabled for editing.
• Clicking on the waveform anywhere before the Poff phase will move the Pon marker and update the measurements at the top of the window.
• Right-clicking on a phase marker, or on the appropriate radio button, will enable editing or addition (if not automatically picked) of that phase.
• Clicking on the Beat Viewer window continuously updates the displayed waveform until it is closed.
• All measurements, heart rate, and date/time are appended to an Excel .csv file named “Phase Measurements.csv”. This can be used for QT dynamics studies.
• Use the Beat Viewer to check for P-Waves in ECG segments with AFib. It helps to reduce noise and assess the presence of P-Waves by comparing clear sinus rhythm to suspect areas. It can also view PVC and ventricular tachycardia beats.

Workflow Tip: To work efficiently, start by reviewing the Beat Morphologies and modify their class type as needed. Use the Rhythm Editor (Noise) to delete noisy parts. After removing unwanted sections and finalizing the Beat assignments, click the “Update Rhythm” button to proceed with rhythm strip review and editing.

Closing TraceViewer will trigger an update of the report, reflecting all of the edits.

Print Clicking Options:

• Print Strip (lower left on Figure 7.5) will print 50 or 100 second rhythm strips, centered on the current ten second rhythm strip, to a standard Windows connected printer.
• Selecting Options / Print Page will print the entire 10-minute view.

Figure 7.26. Example of a 100 second rhythm strip highlighting ST abnormalities.

Edit Demographics

The “Edit Demographics” button shown in Figure 7.1 will re-open the Additional Information screen (see Section 6.2.3, Figure 6.5) populated with all the information previously entered. The information on this screen may be edited. Editing this data does not trigger a need to re-process the ECG data stored on the Electronics Module as all needed data are saved to disk during the initial processing step. Clicking the “Done” button, Figure 6.5, will start the report generation process, concluding with the presentation of the updated PDF report.

Edit Dx

Cardea SOLO™ ADX S400 Software automatically creates a summary paragraph or bullets of the Initial Findings. As you review the trace data, you may wish to review and edit the summary findings (see Report Figure 6.9 above), or add concluding remarks, diagnosis or recommendations in the clinician’s Interpretation Window. To edit these fields, click the “Edit Dx” button, Figure 7.1. Cardea SOLO™ ADX S400 Software will present a text editing window, Figure 7.21 below.

NOTE: Access to the Edit Dx functionality is controlled by User settings – See Section 4.2 User Setup. Users without over-reading privileges cannot enter interpretation text or set the report status (Normal, Borderline, or Abnormal).

Figure 7.27. Edit Dx window.

Delete AFib and VT Findings

Initial Findings of Atrial Fibrillation (AFib) or Ventricular Tachycardia (VT) are very significant clinical findings. Although Cardea SOLO™ ADX S400 Software has a very high Sensitivity and Positive Predictive Value for AFib and VT, the ECG data should be carefully examined.

If P waves are seen on these strips (and not Flutter P-waves), a complex atrial rhythm could be falsely diagnosed as AFib. If fibrillation is present on some of the strips and P waves seen on others the AFib burden could be less than reported. In either case, the ECG data should be carefully reviewed in TraceViewer. Complex atrial rhythms can be precursors to AFib.

Some motion artifact noise, particularly as recorded by a single lead, can appear to be VT. The TraceViewer can be very helpful in reviewing the overall rhythms and noise at the time of suspected VT.

To remove false findings for AFib or VT, click the “Delete AFib Findings” or “Delete VT Findings” checkbox and Update to re-create the report without them. A confirmation window will appear, and all original text and interpretations will be replaced.

Edits and added Interpretations should follow deletion of AFib or VT.

Following your edits, close the PDF Report if open, and click Update. The report will be updated and displayed.

NOTE: The Rhythm Editor in TraceViewer can also be used to select the entire record and delete AFib or VT.  

Delete Findings

Deleted AFib or VT findings can only be restored by re-processing the raw data from the Sensor’s Electronics Module. Refer to Section 6.

Record Status and Confirmation

The buttons below the text box, for entering the physician’s Interpretation, also support setting the status of the test (Record Status) (see Figure 7.23). The draft PDF report is initially marked as Unconfirmed. The over reading physician documents their confirmation and assessment of the report findings by selecting Normal, Borderline, or Abnormal. Next, click Save – Cardea SOLO™ ADX S400 will regenerate the PDF report with the finalized Findings, Interpretation, Record Status, physician’s name and date.

Figure 7.28. Finalization of Report.

ST Analysis

The System supports assessing the ECG traces for ST segment changes. The analysis is somewhat CPU intensive and not required on most ECG recordings. It is therefore supported as a post Download and Analysis function. ST abnormalities are defined by the minimum ST segment change, as defined by the user profile (See Report Options, figure 4.4 above). The default settings are +/- 200 µVolts (Elevation / Depression) and 3 minute duration. To be called as an ST anomaly the ECG ST changes must exceed the minimum voltage and minimum duration. The ST measurement is made at the point 60 msec beyond the end of the S-wave (j+60 msec) and is relative to the measurement at the onset of the QRS (isoelectric point).

Clicking the ST Analysis button will launch the search for abnormal ST episodes. As the search proceeds a window is displayed that shows the progress (green bar) and lists episodes found.

Figure 7.29. ST Status Window.

At the conclusion of the search you can update the PDF report by clicking the “Update Report” button. The below shows an example rhythm strip identified by the ST analysis functionality.

Figure 7.30 Example ST Rhythm Strip.

Heart Rate Variability (HRV)

Cardea SOLO™ ADX S400 analysis also includes tools for HRV analysis for both Root Mean Square of the Successive Differences (RMSSD) between normal beat intervals and Standard Deviation of Normal to Normal (SDNN) beat intervals. The selection of which method will be used is set in the User Preferences (See figure 4.4 above). Non normal sinus rhythms (e.g.: Atrial Fibrillation) are excluded.

The ECG record is divided into 10 minute segments and HRV is computed for each. The following plots summarize the findings.

Figure 7.31 RMSSD multi-day summary. The top box represents HRV from midnight to noon, and the bottom plot is for noon to midnight. Each dot reflects a 10 minute interval. For this record, HRV is high during the sleeping period from 10 pm to 7 am, and low during the normal waking hours.

HRV is also a function of heart rate, shown in the associated figure.

Figure 7.32. HRV versus Heart Rate.

Activity Summary

• The Cardea Patient Sensor includes a 3-axis accelerometer that continuously monitors body position, movement and step counts.
• As noted above, it is important for the patient to be in a relaxed upright position for the first three minutes from the time of sensor activation. This allows the sensor to determine the orientation of the sensor on the patient and then derive the patient’s position as upright or supine for each moment of the recording.
• The raw acceleration data can also be converted to an Activity Index following the methods of Bai et. al. (https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0160644).
• The activity index has been grouped into four categories: Sedentary, Mild, Moderate and Vigorous.
• Heart rate ranges and duration of time spent in each category are included in the Report, along with average steps per day and percentage of time spent in a supine position.

Figure 7.33. Activity Summary.

The level of activity is also included on each rhythm strip.

Figure 7.34. Rhythm strip showing the patient’s Activity level.

Open Report (.pdf)

If you have closed the report PDF and need to re-open it, click on the “Open Report (.pdf)” button, shown on Figure 7.1. Cardea SOLO™ ADX S400 Software will re-open the report.

Report Completion

When you have finished your review, and possibly updated the report, click “Done”. Cardea SOLO™ ADX S400 Software will return you to the User Option Menu screen, Figure 6.2, ready to process another patient’s Sensor data.