PONE-D-20-23023

Comparison of heart rate obtained from shorter duration Holter recordings to 24-hour mean heart rate in dogs with atrial fibrillation

PLOS ONE

Dear Dr. Sanders,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

The Authors should respond to all of the Reviewers' comments. One of the major comments of the Reviewers was the potential added benefit of shorter time periods for Holter monitoring over 24 hour monitoring that usually is carried out, due to the fact that animals would still have to undergo the procedures for placing the Holter. Therefore this, especially, would need to be addressed in a revised manuscript. Furthermore, the Reviewers also noted that the statistical analysis of the manuscript should be strengthened.

Please submit your revised manuscript by Sep 21 2020 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

We look forward to receiving your revised manuscript.

Kind regards,

Daniel M. Johnson, PhD

Academic Editor

PLOS ONE

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at

https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and

https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

2. We note that you have stated that you will provide repository information for your data at acceptance. Should your manuscript be accepted for publication, we will hold it until you provide the relevant accession numbers or DOIs necessary to access your data. If you wish to make changes to your Data Availability statement, please describe these changes in your cover letter and we will update your Data Availability statement to reflect the information you provide.

3. PLOS requires an ORCID iD for the corresponding author in Editorial Manager on papers submitted after December 6th, 2016. Please ensure that you have an ORCID iD and that it is validated in Editorial Manager. To do this, go to ‘Update my Information’ (in the upper left-hand corner of the main menu), and click on the Fetch/Validate link next to the ORCID field. This will take you to the ORCID site and allow you to create a new iD or authenticate a pre-existing iD in Editorial Manager. Please see the following video for instructions on linking an ORCID iD to your Editorial Manager account: https://www.youtube.com/watch?v=_xcclfuvtxQ

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: No

Reviewer #2: Yes

Reviewer #3: I Don't Know

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The authors provide a study that examined whether periods substantially shorter than 24hours of Holter monitoring (ambulatory ECG monitoring) could reasonably accurately reflect the 24 hour average heart rate in dogs with atrial fibrillation.

I have several concerns about the analyses.

First, in previous studies of mean heart rate, investigators suggested trimming the Holter recordings to exclude the first 3 hours and final hour of the recording (https://pubmed.ncbi.nlm.nih.gov/19645836/, see figure 2B) as this removes the effect of stress and anxiety experienced by most dogs when applying the Holter and when returning to have the Holter removed. The residual 20 hours more accurately reflect the true “at home” average heart rate. The authors should consider this approach to see how this affects their interpretation of agreement. They would obviously remove the short periods from these peripheral time periods (because these, too, would be affected by anxiety etc).

The statistical analysis section needs expanding. This reviewer cannot determine what analyses were applied for what purposes. For example, what “study variables” did the authors examine by Spearman Rank Correlation?

The accuracy of short periods might be very dependent on specific dogs. Did the authors account for dog in their analysis? In other words agreement might be high for some dogs and low for others. Examining the % agreement by dog might reveal such a “between dog” effect.

A further approach the authors should consider is to randomly select a 5-minute, 30-minute, 1 hour, 2-hour and 3-hour segment from each dog and see how often these randomly selected segments agree within the predefined limits. This would represent the clinical reality of a client obtaining a heart rate at home.

Minor comments:

Line 88-90. The authors state the limitations of Holters (cost, duration, compliance). However, the study examines Holter recordings and does not provide or discuss what alternatives to Holter monitoring exist or that could substitute Holter monitoring (and this reviewer knows of no such alternatives). Therefore, this statement seems rather contrived and without a solution.

Lines 177-180. If the average rates are not different statistically, then one group cannot have a “slightly higher” rate than the other. Also, a P value should be provided for all statistical testing, whether significant or not. Please amend.

Line 177-180. The average HR for dogs with AF that were not being administered any rate control therapy seem considerably lower than previously documented in dogs with secondary AF. Do the authors have any explanation for this rather low rate? (most previous studies suggest rates exceeding 160-190 bpm). The rates for the group under rate control therapy appears to be consistent with previous observations.

Line 185-186. Could the authors provide scatter plots for each of the short duration recordings vs the Holter recordings plotted as average heart rates? Although the P value for their observation is “not significant”, with only 10 dogs in each group, the probability of this being a false negative is quite large.

Line 204-213. The authors suggest that a 5 minute ECG recording (in-clinic) would mostly agree to within 20% of the Holter-determined average HR. However, this is NOT what the authors showed. To demonstrate that specific idea, the authors would need to examine the 5 minute intervals within the 1st hour of Holter application (while the dog was still in the clinic and stressed) with the average at-home HR. How many of the 240 5-minute intervals obtained during the first hour came within 20% of the average at-home heart rate? If the authors suggest that clients could obtain a 5-minute ECG at home on their pets, the authors would have to suggest how such a feat would be possible, and also demonstrate that doing this would not alter the level of anxiety in the dog during at-home acquisition.

Line 215-220. Several of the “health collars” (e.g. PetPace) can record ECGs in dogs, at least in sinus rhythm. Whether they can accurately count heart rates in dogs with atrial fibrillation remains to be determined. If they can, then they provide continuous monitoring, or can record variable periods for as long as desired (limited by battery life). Therefore, such devices (similar to the iWatch etc, used in humans) are available, but in limited supply.

Reviewer #2: General comments – this manuscript describes a retrospective analysis of subsets of ECG data recorded during a 24 hour Holter recording. While providing interesting preliminary data, I wonder how much less practical difficulty there might be in practice in obtaining shorter Holter recordings compared to a 24 hour recording? The dog still has to have the monitor fitted and wear it for several hours (preferably from the point the dog is relaxed at home, not from the initial time of Holter fitting) – if the benefits are “cost, recording duration and owner compliance” how much difference would shorter recordings truly make? I don’t have a good feel for how much less companies would charge to analyse shorter recordings, unfortunately. The main advantage I can see would be in those cases that the leads became detached after less than 24 hours – if it could be shown that the data was valid if at least 2-3 hours of recording was available once the dog was at home and relaxed that could prevent the need to start all over again. My specific comments, questions and observations are detailed below.

Introduction

Line 62 – should read “…remain a concern.”

Lines 63-65 – this sentence is identical to lines 59-61. I recommend deleting the sentence in lines 59-61, as it makes most sense to keep this information at the end of the paragraph.

Lines 67-79 – you mention that pulse assessment can be used to assess heart rate, but do not discuss later in the paragraph whether this would provide an accurate reflection of heart rate (which seems unlikely, due to pulse deficits, etc.).

Lines 91-93 – how do you propose that the Holter is fitted without “the stress of hospital visits”?

Results

Line 151 – just an idle observation, but I’m surprised only 20 dogs met the inclusion criteria over a 7 year period. Were there a lot of recordings that were <24 hours when edited?

Lines 152-153 and 154-155 – personally, I would just report the range rather than the range and the IQR, as I don’t think the latter adds anything of real value.

Lines 177-180 – please don’t describe non-significant differences. This should simply read “There was no significant difference in heart rate between dogs receiving HR control therapy (121+/- 33bpm) and those not receiving HR control therapy (134 +/- 29 bpm).”

Lines 180-182 – Table 1 and Figure 1 essentially show the same information twice. Please remove either the Table or the Figures.

Lines 182-184 – I’m not sure why this correlation is clinically interesting or important – please explain why you performed this test.

Lines 184-186 – given that rate control status had no significant impact on heart rate, why would you imagine that it would have an impact on accuracy? Again, this seems to be a statistical test that isn’t testing a hypothesis.

Table 1

The information displayed represents “Median (95% CI)” NOT “(Median +/- CI)” – please edit this accordingly.

Discussion

Lines 206-207 – I don’t think that “agreement” changes – you are just being more lenient about what you are willing to accept as “accurate”.

Lines 209-215 – based on your stated mean heart rate of 126 bpm, a 20% inaccuracy gives a heart rate of 151 bpm, which is likely to be interpreted very differently than a mean of 126 by most clinicians. This is clearly potentially problematic – please expand the discussion to reflect this.

Lines 215-220 – this is the first time you have mentioned alternative methods of obtaining an ECG recording in the home environment – which potentially changes ho you might be positioning shorter recordings (although I don’t relish the idea of asking a client to hold an AliveCor against their dog for an hour!). Please add this information to the Introduction (with a brief summary of the work that has already been done looking at accuracy of such recordings in the home environment for monitoring of AF).

Lines 226-228 – is it not equally likely that these would consistently underestimate 24 hour averages (simply because they wouldn’t include the periods of exercise and excitement that also influence mean heart rate over 24 hours)? So you might be at risk of thinking that your rate control was better than it actually is?

Line 236 – please remove the grocer’s apostrophe (the “s” in ECGs denotes that this is plural rather than denoting possession).

Lines 237-248 – I am still not sure why you did this test in the first place (it feels like a fishing trip) so my preference would be to remove this from the discussion.

Lines 248-251 – this is possible, of course, but I think it’s very unlikely (see previous comment regarding lines 209-215).

Lines 255-257 – this would still rely on owners to record these times accurately – is there a way to mitigate this as a potential limitation to future studies?

Conclusions

Lines 260-262 – surely there is experimental evidence that would help determine guidelines for what is acceptable accuracy, rather than simply relying on the judgement of the clinician?

Reviewer #3: The purpose of this study was to determine if the heart rate measured for shorter time periods (5 minutes, one, two and three hours) would equate to the mean rate as determined by 24 hour electrocardiographic monitoring. The mean heart rate for each of these four time intervals was assessed for its ‘closeness’ (within 10%, 15% or 20%) to the 24 hour mean rate. The authors embarked on this investigation with the justification that performing a 24 hour Holter for shorter periods of time would be less problematic for owners and dogs. The conclusion of this paper is that none of the shorter time periods would equate to the mean 24-hour heart rate, but the longer the recording the closer the short surveillance heart rate was to the full recording.

This is a very focused study to determine if short recordings are adequate in the evaluation of rate during atrial fibrillation. The authors state that there are no other methods currently available to determine heart rates in a dog for longer than one hour. However, an Internet search will reveal that individuals are adapting noninvasive monitoring such as Fit Bits for dogs. Additionally, other devices have been developed. (See reference: Yasin Cotur, Michael Kasimatis, Matti Kaisti, Selin Olenik, Charis Georgiou, Firat Güder. Stretchable Composite Acoustic Transducer for Wearable Monitoring of Vital Signs. Adv. Funct. Mater. 2020, 30, 1910288. Doi.org/10.1002/adfm.201910288) These may serve as a way to get minimal information (and likely inadequate when monitoring arrhythmias) regarding heart rate. Such devices could provide data for specific questions such as heart rate. Comparison of these devices with established methods such as 24 hour Holter monitoring would be important to document. It is not clear how this study could be used in such a situation. Authors need to further justify this study.

From an implementation component there are no striking errors in this manuscript. It should be noted however that the average heart rates of the dogs examined are actually low for atrial fibrillation. Dogs that have high ventricular response rates are of course the more critical for monitoring and this paper does not address that kind of patient. Differences between low and high ventricular response rate heart rates over 24 hours is likely meaningful.

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: Yes: Mark Rishniw

Reviewer #2: No

Reviewer #3: No

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

PONE-D-20-23023R1

Comparison of heart rate obtained from shorter duration Holter recordings to 24-hour mean heart rate in dogs with atrial fibrillation

PLOS ONE

Dear Dr. Sanders,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Your manuscript was sent back to 2 of the previous Reviewer's who, together with myself, appreciate the modifications you have made to the the original manuscript. However, there are still a number of outstanding questions that should be resolved, particularly regarding statistical analysis.

Please submit your revised manuscript by Oct 19 2020 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

We look forward to receiving your revised manuscript.

Kind regards,

Daniel M. Johnson, PhD

Academic Editor

PLOS ONE

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: (No Response)

Reviewer #2: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: (No Response)

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: (No Response)

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: (No Response)

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: (No Response)

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The authors have addressed most of my concerns. The only concern that I have is that individual dogs might have had "better agreement" than other dogs. A more complex analysis, where "dog" is inserted as a random variable into the model, might help demonstrate this.

To highlight this, one dog might have had agreement within 10% for 70% of the 5 minute segments, while another dog (for whatever reason) might have had agreement within 10% for only 10% of the 5 minute segments. A dog with an average AF rate of 230 bpm would have a higher probability of agreeing than one that still had considerable vagal influence on the AV nodal conduction.

This type of approach will likely require consultation with a statistician/epidemiologist. The authors might consider plotting the % agreement for each shorter period against average 24hr HR to see if there is any relationship.

Reviewer #2: General comments: thank you for the opportunity to read this revised version of the manuscript – I would like to thank the authors for addressing the majority of my previous comments and concerns. I have some remaining questions, which are detailed below.

Abstract

Line 40-41 – you say in lines 37-38 that “nearly 100% of heart rate averages obtained from 2 hour ECG recordings fell within 20% range” – but here you says that all of them did – please clarify this inconsistency.

Materials and Methods

Lines 158-159 – I’m still not sure why you are reporting both the range and the IQR. It seems superfluous to me – I would just report the range.

Lines 161-163 – it is not clear from this whether you mean “within 10% of the mean” (i.e. mean +/- 5%) or “mean+/- 10%” (which is what it says in the abstract) – please reword this to improve clarity.

Lines 161-163 – I assume that you mean that you are reporting the percentage of HR averages falling within 10%, 15% and 20% of the 24 hours mean HR FOR THAT DOG (rather than the average mean HR for all dogs)? Please clarify.

Results

Line 174 – again, I don’t know why you are reporting both range and IQR.

Lines 198-200 – again, the “10% range” is not the same as “mean +/- 10%”; it is mean +/- 5%. Please make sure that the wording is clear throughout the manuscript.

Lines 198-201 – an additional way to look at this would be to report the percentage of measurements that would have resulted in a different clinical decision being taken. For example, if (for the purposes of the study) we take 125bpm as a cut-off for deciding whether or not to change medications, you could report what percentage of the shorter recording were above this cut off if the 24 hour mean was <125 (and vice versa). This would be easier for clinicians to interpret, I think.

Table 1 – the poor accuracy for 3 hour recordings in the 10% range column is intriguing – the range includes 50% (i.e. no better than flipping a coin) – can you comment on the possible reasons for this apparent anomaly?

Discussion

Lines 232-234 – I appreciate what you are saying here (clearly, 20% of a larger number is bigger than 20% of a smaller number). However, I still think that even at lower heart rates 20% is too inaccurate – even at 120bpm, if you are talking about +/20% (which remains unclear – see previous comments) then this would go as high as 144bpm (which would almost certainly be interpreted differently). Even if you mean “within 20% of the mean” that would take you to 132bpm, which may well be interpreted differently from 120bpm. Personally, on the basis of your results I would want at least a 3 hour recording.

Lines 247-250 – I sincerely hope that clinicians do not accept wider limits of accuracy! See previous comments.

Lines 251-257 – these two sentences appear to contradict one another – if the other at home tools have the capacity to record continuous ECG for more than one hour, why is it not feasible to use them to make recording >1 hour long? Should it not say “…do not have the capacity to record continuous ECG for more than one hour duration”?

Conclusions

Lines 289-290 – that is a fair interpretation of your results – but I still maintain that the level of inaccuracy is potentially dangerous in terms of its impact on how the clinician might choose to manage the case (e.g. make dose adjustments to rate control medications (or not)). I think that it is very important that you acknowledge this overtly in the text – this is not simply a mathematical problem, but something that potentially impacts on how well patients are managed clinically.

Lines 290-292 – I think that it is really important that you provide more information that helps the reader understand better what 20% inaccuracy actually means for their patients; otherwise how can they judge what an acceptable level of error is?

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

PONE-D-20-23023R2

Comparison of heart rate obtained from shorter duration Holter recordings to 24-hour mean heart rate in dogs with atrial fibrillation

PLOS ONE

Dear Dr. Sanders,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Although the Reviewers and myself feel the changes you made much improved the manuscript, Reviewer 2 has a number of outstanding issues that need to be addressed before the manuscript can be accepted for publication in PLOS ONE.

Please submit your revised manuscript by Nov 21 2020 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

We look forward to receiving your revised manuscript.

Kind regards,

Daniel M. Johnson, PhD

Academic Editor

PLOS ONE

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: (No Response)

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: (No Response)

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: (No Response)

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: (No Response)

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: (No Response)

Reviewer #2: General comments – thank you for responding to the majority of my previous comments and questions. I have a few remaining comments, which are detailed below.

Results

Lines 224-227 – surely the purpose of measuring the shorter duration heart rate averages is to try to predict the 24 hour mean heart rate; this analysis is therefore back-to-front.

Lines 227-229 – what is the P value for this effect?

Lines 229-232 – apologies if I have missed something, but I don’t understand where this information comes from – please can you explain how you derived this (i.e. where the information that “on…average 60% of the HR averages obtained from short duration ECG recordings fall within +/-10% of the 24 hour mean HR” comes from – I can’t figure it out from the preceding sentences).

Discussion

Lines 244-257 – I appreciate what you are trying to say – but this argument feels somewhat circular (essentially you can’t know what level of accuracy you need until you know what the 24 hour mean is, by which point you have done a 24h Holter, so the question becomes moot). Given this, can you suggest any situations in which a shorter recording WOULD be valuable? After all, surely the point of doing a 24h Holter in dogs with AF is that you don’t know what the 24h mean heart rate is and you want to find out? After all, even if you have previously Holtered a dog, surely the point of re-Holtering them is to see if anything has changed, so you don’t know what the mean HR is going to be before you do the Holter.

Conclusions

Lines 307-309 – I would still prefer this sentence to be edited or removed, as I don’t think that clinical functionality is determined by the clinician’s judgement (if something is wildly inaccurate that doesn’t change just because the clinician has decided that they are happy to accept a wildly inaccurate result).

Lines 309-314 – thank for adding this information – I think it provides very valuable context.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: Yes: Mark Rishniw

Reviewer #2: No

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

Comparison of heart rate obtained from shorter duration Holter recordings to 24-hour mean heart rate in dogs with atrial fibrillation

PONE-D-20-23023R3

Dear Dr. Sanders,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Daniel M. Johnson, PhD

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #2: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #2: Thank you for your clear and comprehensive responses to my previous comments - I have no remaining questions.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #2: No