Editing Holter monitor

{{Short description|Portable device for cardiac monitoring}}
{{more citations needed|date=October 2020}}
{{Infobox medical intervention (new)|Name=Holter monitor|Speciality=[[Cardiology]], [[electrophysiology]]|image=HolterAFT1000.jpg|caption=3-lead Holter monitor|image_size=220}}

In [[medicine]], a '''Holter monitor''' (often simply '''Holter''') is a type of ambulatory [[electrocardiography]] device, a portable device for [[cardiac monitoring]] (the [[monitoring (medicine)|monitoring]] of the [[electrical conduction system of the heart|electrical activity of the cardiovascular system]]) for at least 24 hours.

The Holter's most common use is for monitoring ECG [[heart]] activity (electrocardiography or ECG). Its extended recording period is sometimes useful for observing occasional cardiac [[arrhythmia]]s which would be difficult to identify in a shorter period. For patients having more transient symptoms, a cardiac event monitor which can be worn for a month or more can be used.<ref>{{cite web|url=http://www.heart.org/HEARTORG/Conditions/HeartAttack/DiagnosingaHeartAttack/Holter-Monitor_UCM_446437_Article.jsp|title=Holter Monitor|work=www.heart.org|access-date=8 April 2018|archive-date=16 July 2018|archive-url=https://web.archive.org/web/20180716135958/http://www.heart.org/HEARTORG/Conditions/HeartAttack/DiagnosingaHeartAttack/Holter-Monitor_UCM_446437_Article.jsp|url-status=bot: unknown}}</ref>

When used to study the heart, much like standard electrocardiography, the Holter monitor records electrical signals from the heart via a series of [[electrode]]s attached to the chest. Electrodes are placed over bones to minimize artifacts from muscular activity. The number and position of electrodes varies by model, but most Holter monitors employ between three and eight. These electrodes are connected to a small piece of equipment that is attached to the patient's belt or hung around the neck, keeping a log of the heart's electrical activity throughout the recording period. A 12-lead Holter system is used when precise [[ECG]] information is required to analyse the exact origin of the abnormal signals.<ref>Herzschrittmacherther Elektrophysiol. 2013 Jun;24(2):92-96. {{doi|10.1007/s00399-013-0268-4}}. Epub 2013 Jun 19. 12-lead Holter electrocardiography. Review of the literature and clinical application update.  Su L1, Borov S, Zrenner B.</ref>

==History==
The Holter monitor was developed at the Holter Research Laboratory in [[Helena, Montana]], by experimental physicists [[Norman Holter|Norman J. Holter]] and Bill Glasscock,<ref name=Meldrum>{{cite journal|last1=Meldrum|first1=Stuart J|title=Obituary for Wilford "Bill" Glasscock|journal=Journal of Ambulatory Monitoring|date=1993|volume=6|issue=3|page=243|quote=with the passing of Bill Glasscock, we have lost the second half of one of the most successful partnerships ever to exist in the field of biomedical engineering}}</ref><ref>{{Cite web|url=http://americanhistory.si.edu/blog/2011/11/at-the-heart-of-the-invention-the-development-of-the-holter-monitor-1.html|title=At the Heart of the Invention: The development of the Holter Monitor|website=National Museum of American History|access-date=13 August 2016|date=2011-11-16}}</ref> who started work on radio [[telemetry]] in 1949. Inspired by a suggestion from cardiologist [[Paul Dudley White]] in the early 1950s, they redirected their efforts toward development of a wearable cardiac monitoring device.<ref name=Herzschritt>{{cite journal| last = Hilbel | first= Thomas |author2=Thomas M Helms |author3=Gerd Mikus |author4=Hugo A Katus |author5=Christian Zugck | date = 10 January 2008 | title= Telemetry in the clinical setting | journal  = [[Herzschrittmachertherapie & Elektrophysiologie]] | volume= 19 | issue = 3 | pages = 146–64 | issn = 0938-7412 | url = https://www.researchgate.net/publication/23423927 | access-date  = 4 August 2009 | doi = 10.1007/s00399-008-0017-2| pmid= 18956161 }}</ref> The Holter monitor was released for commercial production in 1962.<ref name=Herzschritt/>

== Data storage ==
[[File:Holter Atrialfibrillation.jpg|thumb|[[Atrial fibrillation]] recorded by a Holter monitor]]
Older monitors used [[Reel-to-reel audio tape recording|reel-to-reel tapes]] or C90 or C120 [[audio cassette]]s, moving at a 1.7&nbsp;mm/s or 2&nbsp;mm/s speed to record the data. The recording could be played back and analyzed at 60 times the recording speed, so 24 hours of recording could be analyzed in 24 minutes. Modern monitors record [[European Data Format|EDF-files]] on digital [[flash memory]]. The information is loaded on a computer, which counts ECG complexes; calculates summary statistics, such as average, minimum, and maximum heart rate; and finds parts of the recording that are worthy of further study.

==Components==
Each Holter system has hardware (called monitor or recorder) for recording the signal, and software for review and analysis of the record. There may be a "patient button" on the front that the patient can press at specific instants such as feeling/being sick, going to bed, taking pills, marking an event of symptoms which is then documented in the symptoms diary, etc.; this records a mark that identifies the time of the action on the recording. Advanced Holter recorders are able to display the signal, useful for checking the signal quality.

===Recorder===

The size of the recorder differs depending on the manufacturer of the device. The average dimensions of today's Holter monitors are about 110x70x30&nbsp;mm, but some are only 61x46x20&nbsp;mm and weigh&nbsp;99 g.<ref>[http://www.superecg.com/en/hearthbug/reliable-and-accurate/ HeartBug technical specifications] {{webarchive|url=https://web.archive.org/web/20131004213531/http://www.superecg.com/en/hearthbug/reliable-and-accurate/ |date=2013-10-04 }}</ref>

Most Holter Monitors monitor the ECG via two or three channels. Depending on manufacturer, different lead systems and numbers of leads are used; the number of leads may be minimised for patient comfort. Two or three channel recording has been used for a long time in the Holter monitoring history; 12-channel Holters were introduced later, using either the standard 12-lead electrocardiograph or the modified (Mason-Likar) [[Cardiac stress test|exercise lead]] system.<ref>{{cite journal | last1=Papouchado | first1=M. | last2=Walker | first2=P. R. | last3=James| first3=M. A. | last4=Clarke | first4=L. M. | title=Fundamental differences between the standard 12-lead electrocardiograph and the modified (Mason-Likar) exercise lead system | journal=European Heart Journal | publisher=Oxford University Press (OUP) | volume=8 | issue=7 | date=1 July 1987 | issn=0195-668X | doi=10.1093/eurheartj/8.7.725 | pages=725–733| pmid=3653124 }}</ref> 

These Holters can occasionally provide information similar to that of an [[ECG]] stress test examination. They are also suitable when analyzing patients after [[myocardial infarction]]. Recordings from these 12-lead monitors are of a significantly lower resolution than those from a standard 12-lead ECG, and in some cases have been shown to provide misleading ST segment representation, even though some devices allow setting the sampling frequency up to 1000&nbsp;Hz for special-purpose examinations such as detection of "late potential".

Another innovation is the inclusion of a triaxial movement sensor, which records the patient's physical activity and, on examination and software processing, extracts three movement statuses: sleeping, standing, or walking. Some modern devices can record spoken patient diary entries that can be listened to.

===Analyzing software===

[[File:Cubeholter.jpg|thumb|250px|Screenshot of Holter ECG software]]
After the recording of ECG signal for typically 24 hours, the signal must be analysed. A person would have to listen for the full 24 hours; instead integrated automatic analysis determines different sorts of heart beats, rhythms, etc. The success of the analysis is closely associated with the signal quality, which mainly depends upon the attachment of the electrodes to the patient's body. Incorrect attachment allows electromagnetic disturbance to add noise to the record, particularly with rapid patient movement, impeding processing. Other factors can also affect signal quality, such as muscle tremors, sampling rate and resolution of the digitized signal (high quality devices offer higher sampling frequency).

The automatic analysis commonly provides the physician with information about heart beat morphology, beat interval measurement, [[Heart rate monitor|heart rate variability]], rhythm overview and patient diary (moments when the patient pressed the patient button). Advanced systems also perform spectral analysis, ischemic burden evaluation, graph of patient's activity or PQ segment analysis. Also possible is the ability to monitor and analyse [[pacemaker]] impulse detection, useful for checking pacemaker function.

==Gallery==
<gallery mode="packed">
File:Alex CM4000.jpg|A 5-lead placement EASI configuration Holter monitor
File:Holter-Underwear.jpg|A Holter monitor can be worn for many days without causing significant discomfort.
File:Holter monitor on canine.jpg|Canine Holter monitor with DogLeggs Vest
File:Holter Monitor.jpg|A Holter monitor with a US quarter dollar coin to show scale
File:Holter Monitor On Female With Belt.JPG|Holter monitor can be worn with bra, with no discomfort.
File:Tlakový Holter.png|Holter monitoring of [[blood pressure]]
File:Event Recorder relativ weit kranial 81W - CR - 001.jpg|[[Implantable loop recorder]]
</gallery>

==See also==
* [[Wireless ambulatory ECG]]
* [[BodyKom]], a heart monitoring service transmitting data via the mobile cellular telephone network

==References==
{{reflist}}

==External links==
{{Commons category|Holter monitors}}
* [https://www.nlm.nih.gov/medlineplus/ency/article/003877.htm Holter monitor – MedLine Plus]
* [https://www.mybiocalculus.com Holter monitor – Biocalculus] {{Webarchive|url=https://web.archive.org/web/20220215022638/https://mybiocalculus.com/ |date=2022-02-15 }}

{{Cardiac procedures}}
{{Authority control}}

[[Category:American inventions]]
[[Category:Diagnostic cardiology]]
[[Category:Medical monitoring equipment]]