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?
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
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 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:
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:
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.
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:
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).
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: