Hi Maciej,

It's a very good clinical question.

Although we have dozens of methods, HRV can be analyzed by different ECG Holter systems, there are number of scientific and some clinical papers on the value of HRV in post-infarction or heart failure patients, most probably HRV is not used on a daily clinical practice. The same is true for both older and more contemporary methods, including heart rate turbulence or phase rectified signal averaging, which have been shown to have outstanding prognostic value. We must carefully separate our attitude and hopes toward HRV, and the recommendations for it. So far, the HRV standards from 1996 do not recommend a routine use of HRV, and even very exciting papers from recent years have not changed our approach. Although I do a lot of research in HRV field, HRV itself still remains a research tool.

Maybe experts in the field of diabetic autonomic neuropathy could comment on it, as HRV is recommended as a diagnostic tool for this complication of diabetes.

Best regards,

Przemyslaw Guzik

HRV can be changed in SSS and OSAS but can it be used for diagnostic purposes in these clinical states? Could you, please, add some references supporting the view that HRV is useful (recommended) in diagnosis of sick sinus syndrome and obstructive sleep apnea syndrome?

Best regards,

Przemyslaw Guzik

Are you really asking about BEDSIDE use per se or about use in clinical practice?

Maciej - HR and HRV are variables (not parameters) of the heart and are useful in clinical patients. We take a nonlinear perspective on cardiac dynamics and RR intervals by employing Recurrence Quantification Analysis (RQA). I write about this in a new (2012) e-book on Pacemakers (attached). Free RQA software can be downloaded from my URL (link below). - Chuck Webber 09/28/12

http://homepages.luc.edu/~cwebber/

For diagnosis of OSA, yes, heart rate patterns are totally useful. I advocate looking at the heart rate patterns BEFORE you start generating numbers but unequivocally yes.. Here is a reference: Heart rate variability, sleep and sleep disorders. Stein PK, Pu Y. Sleep Med Rev. 2012 Feb;16(1):47-66. Epub 2011 Jun 11. Review.

For diagnosing of sick sinus syndrome please follow paper of Bergfeld et al., Sosnowski et al., Nicolin et al.

HRV at bedside can easily be detected during a deep breathing. However, the intence of the question was rather "in clinical practice" than "at bedside" itself.

I'm from Vietnam. These are some Holter system but the doctor do not use any HRV in this situation

I hope that we will be able to develop guidelines that will actually allow HRV to be included in patient assessment but right now the field suffers from bad data, overzealous vendors and a very simplistic understanding of what they would mean. There is a lot of work in the intensive care field both in adults and children where the clinicians really want to be able to use HRV to learn things about their patients that is not obvious from their other tools.

I agree with Phyllis Stein. HRV might be a very interesting tool for clinical and research work in a large number of fields. However I'm very much concerned about the validation of the methods used. Reading the literature, especially the "clinical" papers, often it is assumed as unquestionable that what comes out from a "black box" is correct and that it can be interpreted univocally to provide information of clinical relevance.

Instead the black boxes are often very different. Moreover, most of times, the end-users (clinicians) are very little confident with the ("mathematics and physics") background of what they use. For instance, in very few clinical papers one can find a clearcut definition of ECG recording bandwidth and of the sampling frequency used. Many clinicians blindly rely on HRV parameters calculated from 24-hours Holter recordings, but very few commercial Holter equipments provide a sampling frequency of 1 KHz, which is the standard for high-resolution ECG. Using a lower sampling the uncertainty/error in N-N detection increases.

Another problem is the concept of "stationarity", a prerequisite for appropriate application of the frequency domain analysis. Such stationarity in rare under clinical conditions, even within short intervals (the standard 5-minutes, according to ESC / NASPE guidelines). In fact if one scans a 5-minutes interval it is not unusual to observe sudden changes of the power spectra, which are very difficult to be explained.

Moreover Stein has clearly described the difference between true HRV and the "erratic rhythm", but such differentiation is practically impossible with the "black box" used by the majority of the clinicians.

Such kind of methodological pitfalls are not evident when HRV is calculated according to current clinical guidelines, because the selected long- and short-term intervals average everything inside the selected interval and provide and output which seems (patho)physiologically reasonable ( i.e. differences between day and night, or upright versus recumbent postures). However if one wants to be sure of the reproducibility/stationarity of happens within "that" analyzed time-interval, an honest analyst might face more often frustrating uncertainty than clearcut "diagnostic" evidence. The problem becomes more evident and critical if one is interested in using very/ultra-short-term HRV analyis, for instance to assess transient variations of sympatho-vagal interaction such as those induced by acute stress reactions.

Again I agree with Phyllis Stein that we need to develop guidelines, which must be based on more focused research work aimed to understand how to manage presently unclear items which migh affect the clinical use of HRV.

If the patient does not add any equipment line directly into the heart, can be used HRV. For medical electrical safety principles and avoid shock, shock patients does not allow to do so.

In addition, with tracking HRV signals with time up to a few days and also to diagnose one of the results is not enough to convince team doctors do this.

In Vietnam, the overload of patients still show through current routine should not have any intention to measure and monitor the patient's HRV parameters.

I with the great pleasure following to the point of view Phyllis Stein and Riccardo Fenici that "the field suffers from bad data, overzealous vendors and a very simplistic understanding of what they would mean" and "most of times, the end-users (clinicians) are very little confident with the ("mathematics and physics") background of what they use". These are two fundamental pitfalls which are present at many studies. We may say without impropriety that, the perception of pacemaker physiology through studying HRV is the nearest purpose of the researcher in this field. Understanding of mathematical apparatus of HRV is the following necessary stage. Moreover, now the most of researchers have a greatest preoccupation with searching of new (necessarily new!) mathematical approaches to HRV analysis. I have feeling that we search for The Holy Grail and everyone keeps the in mind own unique and undoubtedly correct way.

I am very satisfied with the discussion. However, as I am clinician I would like to use a relatively simple parameter that provides a description of global HRV and adds information beyond HR itself. Of course, as HR limits the range of its variation, a reduction of HRV in the presence of HR accleleration does acutally add nothing, as well as increased HRV in a patient with bradycardia. However, if lower HR is associated with an HRV reduction it inform that autonomic control is insufficient and clearly indicate pathology (chronotropic insufficiency). On opposite, faster HR coincided with an HRV increment also indicates abnormal heatbeats formation.

Use of more sofisticated methods with complicated physics and mathematics should be still examined, as novel features of neurocardiology can be unveliled. As a science itself there should be no forbidden zones of exploration. However, clinical use should be limited to a well defined standardized resproducible variable, for which the clinical awarness might really influence patients' management.

There is one very interesting application of HRV which is a kind of clinical breakthrough and came from the neonatology field. Moorman and coworkers built a scoring system for early SEPSIS detection in neonates (especially low weight). They observe sudden drops in tachograms and apply suitable mathematics in order to detect and count them automatically. Last year he has published the results of a large multicenter study that he did in the US, including some hundreds or even thousands of neonates. The results show that the method they developed is able to identify patients in whom SEPSIS may develop many hours before other clinical symptoms are possible to be detected. What is also interesting, they identified a biophysical mechanism in which the heart rate is affected by the presence of pathogenes. As far as I remember the study is extended towards adults as well.

I am not familar with other fields' experience in HRV. However, there are several HRV studies in neonatology which shows very impressive correlation with morbidity and outcome.

Dear dr Teng, I'd be personally greatful for some good reference on that, ideally a review. There is a decades-long discussion on usage of HRV in cardiology so such a material would be quite appreciated.

Dear All,

There is a new publication with numbers of reviews on Holter ECG, including HRV:

http://www.sciencedirect.com/science/journal/00330620/56/2

Phyllis Stein is one of the co-authors :)

This is a really good book and you should download it for free.

Best regards,

Przemyslaw Guzik

Sorry if I insert here such my suggestion.

I am not here to outline you the importance of the HRV current studies and I have not to remember you that the current linear or non linear methodologies are not completely satisfactory. Of course every day we find papers published also in valuable international journals that continue to use standard linear indexes and FFT or DFT for their clinical investigations and conclusions. Non linear methodologies have their valuable content also if currently they still do not find a continuous clinical appreciation. Usually three bands are considered in the frequency domain , as you well know, the VLF, the LF , and the HF for short 5-6 minutes recording. We need to remain in this framework, we need to use such bands for our estimations but my modest opinion is that the basic methodology as well as the physiological setting need to be advanced. This is the reason because we have studied for several years a new method, called the CZF method. We have verified, however, that such method, although of great interest, results of difficult interpretation for some clinicians. Consequently we have elaborated a new method, the new CZF version , that , in addition to the rigour of the previous formulation , gives results that give immediate clinical interpretation.

The method as well the software for your experimentation are given in our site www.saistmp.com Consequently I invite all you to visit the site and go to use such new method in your experimental as well as clinical conditions and verify directly its interest. The present software is the primary elaboration. Within a brief time we will give the complete version responding to all the formulation of the method. All the researchers that , at this time, will result using currently such new CZF method will receive obviously automatically the updates.

A final question. We have experienced the method on a large number of subjects and in some different pathological conditions. Consequently don’t hesitate to contact me if you need help, suggestions, questions, previous results that may help you in your use of the method ([email protected])

I was hoping in my Masters thesis on heart rate variability in students at risk of cardiovascular disease to be able to use it as a clinical tool, but found that it is simply too complicated. I have found the only use in clinical setting is in monitoring over- training- syndrome, but it cannot be used as a "once off" measurement. One needs daily measurements of the same athlete, together with a training log to pick up that person's own pattern before one can start to identify trends in response to training. It is a long an arduous procedure, but I don't think it is practical in high care situations.