Best Heart Rate Variability App – Rigid Rhythm

A healthy heart does not always beat in the same rhythm but adapts variably to the current load. This shows the heart rate variability (HRV), which can also be measured in the general practitioner’s practice with common EKG devices, smartphones, and apps, such as Welltory. Welltory is a smartphone app for iPhones and Android phones which helps the users or potential patients to know various health parameters, including heart rate monitor (HRV), stress measuring, even an energy level scale sleep quality analysis, and much more. Also, it’s a pulse oximeter app. Although the HRV can be used to reliably predict cardiovascular events, it is currently not paid for by the health insurers, via a non-invasive measuring method with high informative value for cardiovascular diseases. It can be useful on apple watch HRV.

The ability of the heart to change the time interval from one heartbeat to the next depending on the load was already described in the third century. This is called heart rate variability (HRV) or heart rate variability. In an HRV analysis, the intervals between the R waves of normal cardiac actions are recorded and their variance is evaluated (NN interval, also beat-to-beat interval). A healthy heart does not beat like clockwork, but is subject to the influence of the autonomic nervous system: Both sympathetic and parasympathetic fibers influence the heart’s activity, noticeable through an acceleration of the pulse when breathing in and by slowing it down when exhaling. This respiratory sinus arrhythmia (RSA) is common in young healthy people and provides information about the heart health of an elastic heart and the sympathovagal balance. A multitude of influences (e.g., stress, physical strain, illnesses, and medication) can seriously disrupt this balance.

The variability of the heartbeat represents a global indicator for the psychological and physical condition of people in their living environment. In neonatology, too, recording HRV is part of routine diagnostics, including diagnostics for neonatal sepsis. Some specialist societies have already included the HRV analysis in their guidelines (e.g., American Society for Occupational and Environmental Medicine, program for national health care guidelines). In general medicine, it is useful for stratifying the risk of cardiovascular diseases, diabetic neuropathy, and depression.

HRV as A Prognostic Marker

In general, restricted regulation of the autonomic nervous system is associated with a lower life expectancy. The reason for this is stress, which is a risk factor for coronary artery disease (CHD) due to chronic overactivation of the sympathetic nervous system. In addition to this over-activation of the sympathetic nervous system, the reduced parasympathetic activity also represents a risk factor for incipient or already existing CAD. A reduced vagal tone is typically shown by special changes in the HRV spectral analysis in both CAD and its progression, angina pectoris. 

If myocardial infarction has taken place, the HRV is reduced and the sympathetic activity increased. The complication rate for tachyarrhythmia events, re-infarcts, and cardiac mortality increase three to four-fold in these patients. The increased sympathetic tone often leads to an increase in the heart rate, which is decisive for the prognosis. Heart failure also leads to increased heart rate and reduced HRV. After an acute myocardial infarction, the recording of the HRV has a predictive value for serious complications, death in hospital, and the probability of re-infarction. The relevance of HRV as a prognostic marker after acute myocardial infarction has been confirmed in a large number of large cohort studies. Heart attack patients, those who also suffer from depression have a significantly worse prognosis (as well as a limited HRV) than patients without depression. The mortality of bypass patients is also related to reduced-HRV. Abnormalities in the low-frequency range (LF) of the frequency spectrum are also considered to be predictors of atrial fibrillation. A large number of studies have shown that hypertension is associated with reduced HRV. The HRV is therefore an important risk factor for arteriosclerosis, arrhythmias, heart failure, Myocardial infarction, and sudden cardiac death. Limited heart rate variability increases cardiovascular risk.

HRV values ​​are subject to numerous influencing factors that must be taken into account when interpreting them. Children and adolescents have a pronounced variability in heart rate; this decreases with increasing age. Women up to the age of 30 show lower values ​​than men. After the age of 50, however, these gender effects disappear. Internal diseases usually cause a reduction in HRV. This is the case with CHD, hypertension, heart failure, metabolic syndrome, and diabetes mellitus. Hyperthyroidism and hypothyroidism are also associated with reduced HRV. Depressed patients often have increased HR and reduced HRV (sympathy-adrenergic overactivation). Drinking alcohol in the evening also affects the nighttime activation of the parasympathetic nervous system, which leads to a weakened RSA and an only slowly decreasing pulse rate. A variety of drugs also influence heart rate variability, tricyclic antidepressants, SSRIs, and atypical neuroleptics. Beta-blockers can have different effects, diuretics and alpha-receptor blockers (vasodilators) increase HRV.

So, are you still thinking of how to measure heart rate variability? The Welltory app can be used as a heart rate device. 

Analysis of the HRV

The evaluation of the HRV takes place after the measurement via the PC-supported analysis. There are three analysis methods:

1. Time-related analysis – a measurement of heart rate fluctuations from beat to beat over time. Statistical parameters:

• SDNN: Standard deviation of all NN intervals as a measure of variability (synonym SDRR), an indicator for total variability
• RMSSD: Square root of the mean of the sum of all squared differences between neighboring NN intervals, an indicator of short-term variability, parasympathetic activity, respiration (RSA)
• EI-Difference between the highest and lowest heart rate in a breathing cycle
• HFmean mean heart rate

2. Frequency-related analysis – spectral analysis (e.g., Fast Fourier Transformation), i.e., frequency representation of the frequency bands. A distinction is made here between three important frequency ranges that represent different physiological processes:

• VLF-BandVery Low Frequencies <0.04 Hz | Sympathetic nerve (including thermoregulation)
• LF-Band Low Frequencies 0.04 – 0.15 Hz | Baroreflex loop (especially enter  blood pressure regulation)
• HF band High Frequencies 0.15 – 0.4 Hz | Parasympathetic Nervous System, Respiration (RSA)
• LF / HF LF / HF ratio | Sympathovagal balance

3. Non-linear analysis – analysis of Poincare plots, i.e. two- or multi-dimensional point cloud representations:

• SD1 (ms) Width of the point cloud | Rapid changes in heart rate
• SD2 (ms) length of the point cloud | Long-term HRV
• Dyx | Density of the point cloud

Guidelines for HRV analyzes were drawn up in 1996 by the Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology.

Conclusion for Practice

1.The prognostic and predictive power of the HRV has been well studied.

2. HRV is subject to a large number of external influences (e.g. caffeine, beta-blockers).

3. HRV is restricted in a number of diseases (e.g. depression, diabetes, cardiovascular diseases).

4. HRV analysis:

• Is recommended in guidelines by leading specialist societies.
• Is a non-invasive, painless, quick, and uncomplicated examination.
• RSA 1 minute, short-term HRV approx. 5 minutes, long-term HRV for up to 24 hours.
• Suitable for risk stratification in cardiovascular diseases.
• Can be delegated and settled as IgeL.
• Can be carried out with common ECG devices, if necessary with additional software and apps.

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