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I bought a blood pressure monitor (A&D UA-851) which has the option to measure irregular heartbeat. I do understand what 'irregular' means, but why do irregular heartbeats happen and what are it's implications short and long term?

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I wouldn't put too much trust in the option to measure irregular heartbeats. Its specificity shouldn't be too high, especially when you consider that some more advanced digital monitors used in hospitals give a lot of false positives. – Tivie Jun 25 '14 at 11:06
I understand the OP wants to understand how his blood pressure monitor works. Some of you are thinking that it works by just interpreting cardiac rhythm. This is false! It is done by interpreting the frequency space of regular/irregular heartbeats. Please, note the difference between irregular cardiac rhythm and irregular heartbeat. – Masi Jan 8 '15 at 17:28
Masi - I understand something completely different from the question. He is not asking how his blood pressure monitor works, he is asking in layman's terms why an irregular heartbeat happens. I haven't voted your post down, but I think if you answered the question and were less confrontational and aggressive in comments you may get more upvotes. – Rory Alsop Jan 9 '15 at 12:07
I think you should re-think the accepted answer for one of the other answers. – dustin Jan 11 '15 at 22:26
@dustin are you telling me what to do? I understand Masi's answer and see that he's passionate about answering it right. – Matas Vaitkevicius Jan 12 '15 at 7:54
up vote -6 down vote accepted

There are many parts in the OP's question. One is about indications. However, since the device of question is subjective in determining irregular heartbeats or heart rhythms, it provides only subjective results, particularly about irregular heartbeats and irregular heartrhythms. I focus on my answer why it does so and how it could be designed better for objective results.

Listing indications based on subjective measurements have high risk of false negative and false positive results. Also, the other fact is that since we do not know what does the irregular heartbeat really looks like, I think, it is too early to provide indications and can be very error-prone.

Definition of Heartbeat

Heartbeat has amplitude and characteristic energy levels in time. One unit of the Cardiac rhythm is the pulse wave or in other words heartbeat. The amplitude and time interval of the pulse wave can be palpated, not only either one, subjectively by hand.

Limitations about detecting irregular heartbeats with subjective blood pressure devices

  • You cannot return energy spectrum of heartbeat from cardiac rhythm and time interval as two separate units. In other words, you cannot return the blood pressure with little errors this way, only very rough approximation. Therefore, I skip the description of the cardiac rhythm which is not heartbeat. See the Rags' answer for his simplistic and wrong definition of the irregular heartbeat as an irregular cardiac rhythm where he also skips sporadic type - better in the book (1) for the full descriptions.
  • I skip the physiology of cardiac cycle here for simplicity because it is not needed for explicit definition of heartbeat, but can be used for implicit definition from one-sided and wrong view as in Tivie's answer. You can see in one answer of revision history where I describe how to define little more explicitly the cardiac cycle with seven distinct phases but not relevant to this answer so left out.
  • The blood pressure machines are not for detecting irregular heartbeats like in Rags' biased comment here.

One heartbeat can consists of many energy levels from different origins. However, there are often characteristic energy levels with greatest energy in the normal heartbeat.

Irregular heartbeat

Irregular heartbeat has irregularities in energy level and time interval. In contrast, cardiac rhythm can have irregularities only in time interval, which is the reason why we do not look the case here from the view.

Irregular heartbeat for the blood pressure monitor -machine

I now describe how the heartbeat is detected simplistically and giving you an overview about how these machines work.

The blood pressure monitors detect first the amplitudes of the heartbeat in time interval. They convert the data into different energy levels and do analysis based on both energy level and time interval.

Irregular heartbeats form from the Pacemaker cells (SA node, AV node and Purkinje fibers) which maintain the cardiac rhythm and the energy of the heartbeat. They can be arrythmic (rarely benign) or tachycardic.

Each machine is designed little differently but they have some components the same. They are designed for the normal physiologic condition at rest, not often for different pathologies, arrhythmias, tachycardia, fast respiration, temporary diseases and accelerative movements. They try to skip some major distractions in doing the calculation. I skip the specific algorithms in doing these simplifications and approximations, see the revision history for a stub about this topic.

The blood pressure monitors detect arterial blood pressure, do analysis based on it and its applications, and estimates blood pressure. Good machines use the characteristic energy levels and time interval together in analysis. The characteristic energy levels can be differentiated to the origin, since we know which frequency corresponds to each pacemaker:

  • Sinoatrial node (70-80 Hz)
  • AV node beating too early (40-55 Hz)
  • Bundle of His (40 Hz)
  • Purkinje fibers (15-40 Hz)

The good machine has to be able to distinguish between pulse (P) and respiratory waves (R). It ignores most often the vasomotor wave (V) because the interval of measurement is so short. See the Figure for those waves in one picture:

enter image description here

where the vasomotor wave can be deduced by trendline or appropriate time-series analysis.

Summary. Good blood pressure monitoring machines estimate the blood pressure of the heartbeat through the characteristic energy levels in time interval. The analysis and diagnosis of the irregular heartbeat is however much more difficult. My skipped factors and many others should be considered if such a device is wanted.


  1. Guide to Physical Examination and History-Taking, Lynn Bickley MD. 2012.
  2. Physiology, 4th edition, Linda Costanzo.
  3. Guyton. About different types of waves in indirect measurement of arterial blood pressure.
  4. My notes about types of waves in Physiology courses (three different universities) during years 2012-2014
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There are a number of inaccuracies within this answer - statins are not prescribed for the control of arrhythmias for example – Rory M Jun 25 '14 at 10:02
@Masi Arrhythmias are not physiological responses to stress nor a compensatory mechanism. They arise from interference in the electrical conductivity of the heart. While some are, in fact, benign, most arrhythmias require chronic aggressive treatment. Statins are HMG-CoA reductase inhibitors, which inhibit the synthesis of cholesterol. Statins do not regulate directly the cardiac cycle. Other classes of drugs are used such as Na+, K+ and Ca+ channel blockers, beta-blockers and Digoxin. – Tivie Jun 25 '14 at 10:36
I think there is a bit too much convolution of the terms arrhythmia and tachycardia. Arrhythmias may be tachycardic but not all tachycardia is arrhythmic. Take the example, when you do intense exercise you will become tachycardic (>100bpm), but this a regular sinus tachycardia and not an arrhythmia. – Spinorial Jun 25 '14 at 12:55
There are still a number of issues remaining. Could you clarify what you mean by "too high T waves"? The only T wave related arrhythmia I'm aware of is T wave alternans, which certainly isn't benign. White coat syndrome might be expected to raise a persons blood pressure (partially through a rate increase) but I don't think it causes paroxysmal arrhythmias. – Rory M Jun 25 '14 at 19:32
@Masi I've read through the entire answer again from the start a couple of times to try and offer some help but if I'm honest to me it makes no sense at all. I did some searching using the terms you use and didn't really get anywhere. I'm not convinced that the 30th revision will be the charm and, whilst I didn't cast them, I do understand the thinking behind the deletion votes. I also don't understand why the bounty was placed? – Rory M Jan 8 '15 at 20:02

The normal cardiac cycle is comprised of two distinct phases: the systolic phase in which the heart contracts, ejecting the blood, followed by the the diastolic phase when the cardiac muscle relaxes, refilling the heart with blood.

This cycle is assured by specialised cardiomyocytes (Cardiac muscle cells) that conduct electrical impulses through the heart. When there's interference in this electric activity, the cycle becomes irregular or arrhythmic.

Arrhythmias can be divided by their place of origin:

  • Atrial (atria are the upper chambers of the heart)
  • Ventricular (ventricles are lower chambers of the heart)
  • Junctional (the junction between the two)
  • Heart blocks (caused by a blockade in the conductivity of the electrical specialised cardiomyocytes)

Some arrhythmias are physiological, such as the Respiratory sinus arrhythmia, a naturally occurring variation in heart rate that occurs during a breathing cycle. Also, in healthy individuals, some extra sistoles might occur without being the translation of a subjacent heart condition and have benign prognosis in individuals without other conditions.

However, some arrhythmias can have a wide range of health implications, from asymptomatic, to a mild intolerance to exercise, to Cerebrovascular Accident (CVA or stroke) or even sudden death due to cardiac arrest.

Therapeutic varies with the underlying cause but can be medical (with drugs such as Na+, K+ and Ca+ channel blockers, beta-blockers and Digoxin) or surgical (ie: Artificial pacemaker).

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Great answer but it would be fantastic if you added some references. – Bez Jun 25 '14 at 12:30
-1 This answer is about the origin of the cardiac rhythm with major simplifications in the cardiac cycle. Irregular heart beat is not the same thing as arrythmias, also dangerous overloading of tachycardia with arrythmia. Focus on the explicit classification of heartbeat based on origin, not how those machines work. – Masi Jan 8 '15 at 18:54
I think it's a very good answer - although references would be ideal all the content is factual as far as I can see. – Rory M Jan 8 '15 at 20:05
@Masi well, this is a Biology Q&A site so answers should really focus on the biological aspects of the question. The original question "why do irregular heartbeats happen and what are it's implications short and long term" is succinctly answered in the above without over complication. – Rory M Jan 9 '15 at 14:48
@Masi What on earth does "dangerous overloading of tachycardia" mean? (I don't even mention tachycardia anywhere!) – Tivie Jan 10 '15 at 17:10

Very simply putting, irregular heat beat means that the pulse is not regular. It can be diagnosed by checking your pulse clinically.

Irregularities are further classified as:

  1. Regularly Irregular: this occurs in heart blocks where every second or third beat is skipped regularly causing a pattern. Usually as time progresses the degree of block worsens and result in the final form which is complete block (fourth degree heart block)

  2. Irregularly Irregular: this occurs in arrhythmia where there is total dissociation between atria and ventricles and the ventricles beat very irregularly with no pattern. The ventricles don't follow intrinsic rhythm because every SA nodal impulse that occurs at the end of latency of AV node will get conducted. Thus the heart rate is very high without any pattern. (Here heart rate means ventricular rate)

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-1 because it is not correct answer to the functioning of the blood pressure monitoring. This answer emphasizes the melodies that are events in time interval of the heartbeat. There are also irregularities in the amplitudes of the heartbeat. There can be many amplitudes or energy levels in one heartbeat. Those machines do not only consider cardiac rhythm in making the diagnosis. They consider the energy levels and cardiac rhythm together. Without energy, you cannot even get pressure! – Masi Jan 8 '15 at 18:51
@Masi, you cannot measure irregular heart beat using blood pressure. Even a BP monitoring machine can measure irregular heart beat using pulse only. The only other way is using an ECG or echo cardiography. Irregular heart beat is a defined medical term. And my answer is the correct one. – One Face Jan 9 '15 at 0:35
5… what I said is correct. No one measures irregular heart rate using bp. Bp measuring in a patient with irregular heat rhythm is only done to prevent shock. Echo cardiogram can visualize heart beats thus irregularities can be seen and diagnosed. Please check thoroughly before telling someone is wrong. – One Face Jan 9 '15 at 6:19
@Masi read the sentence how you deem fit. The question is clear cut. From your profile, it says you are in medical school. Then you should know from case studies that there is information put in them that is irrelevant. When you do your differential diagnoses, I hope you don't include the useless information. The same is occurring here. The question is: why do irregular heartbeats happen and what are it's implications short and long term? The question came about due to a setting on a BP. The question doesn't say anything about relating the two. – dustin Jan 9 '15 at 21:47
@Masi no one is saying give medical advice. Read my comment one more time. Again, I am telling you to re read something. – dustin Jan 9 '15 at 22:19

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