What is a correlation between your pulse rate and your heart health? How can on-time regular HRV measuring help to detect CVDs?
Did you know that cardiovascular diseases, or CVDs, are the leading causes of death and morbidity in industrialized nations, accounting for 32% of all deaths? It is the unfortunate truth, that despite the major advancements in healthcare accessibility, technology and improved medical treatments over the last decades, the frequency of cardiovascular conditions as well as the associated mortality rates continue to increase. The risk of developing CVDs also rises with age, and patients who suffer from CVDs often require chronic or recurrent hospitalization and long-term medical treatment, with all the costs that this implies for the healthcare systems.
There is a strong link between heart health and heart rate variability (HRV), as well as the value of the latter as a direct indicator of autonomic nervous system (ANS) disbalance. Let us explain what each of these terms means. HRV represents the variability in the time intervals between successive heartbeats while ANS is responsible for key physiological functions in the body, including cardiovascular activity. It regulates heart contractions and heartbeat, as well as blood pressure, which explains its essential role in maintaining cardiovascular functioning and health.
The amount of currently available research on the relationship between CVD and unbalanced sympathetic-vagal outflow to the heart confirms the important influence of the ANS on cardiovascular health. HRV is an established marker of how both branches of ANS (sympathetic and parasympathetic) work. Tracking HRV levels can play a key role in understanding cardiovascular risk factors, as well as the onset of the cardiovascular disease itself.
Today, HRV is an acknowledged index for cardiovascular science and diagnostics. It has become a standard non-invasive metric for evaluating the autonomic nervous system, serving as a convenient and relatively cheap tool for ANS function assessment and tracking. This has led to an increase in the development of devices that can track HRV levels, like smartphone-integrated apps and tools, or wearable devices. Available to the vast population, such consumer tools can have an exceptional impact on HRV monitoring, cardiovascular disease diagnostics and care.
The correlation between HRV and CVD
HRV serves as an indicator of the activity levels of the sympathetic and the parasympathetic branches of the ANS, as well as of the way these two branches modulate together the heart activity. A high HRV is a sign that the heart is operating well, and that it adapts to various stressors quickly and efficiently. In contrast, a low HRV can be an indicator of reduced cardiovascular fitness and of too much stress, when the sympathetic nervous system is constantly activated. Dysfunction of the ANS plays a major role in the development and progression of cardiovascular diseases, including myocardial infarction, heart failure, and sudden cardiac death.
In normal conditions, HRV values are constantly fluctuating throughout the day, as they are highly dependent on the interaction between the two branches of the ANS – sympathetic and parasympathetic. When the body is under stress, the sympathetic branch promotes the release of stress hormones, putting the body in the “fight-or-flight” mode. On the other hand, the parasympathetic branch is activated during more relaxed and less stressful times, turning on the “rest-and-digest” mode. When the sympathetic branch is strongly activated HRV values are low. A low resting HRV can serve in certain cases also as an indicator of cardiovascular risk factors, along with others, such as unhealthy lifestyle habits (like a sedentary lifestyle) and additional health conditions (like diabetes).
It is already well known that patients who exhibit low HRV levels following a CVD-related event (e.g. heart attack) have a more difficult recovery process and higher mortality risk. Therefore, tracking HRV levels can help not only to detect the early onset of CVD but also serve as a prognostic factor for patients with ongoing or past CVD conditions.
From a preventive perspective, routine HRV monitoring is meaningful also for individuals who had no previous history of cardiovascular conditions. Research shows that individuals who show fewer fluctuations in the heart rate and exhibit enhanced HRV values are overall healthier. In these individuals, a sudden change in the HRV values can act as an immediate and direct indicator of declining health status.
In general, a low HRV usually means that the sympathetic branch of the ANS is dominating and preparing the heart and the body to take on more stress than normal, which makes the heart beat faster and with less variability.
However, in cases of strenuous exercise, a decreased HRV is not a bad sign, but only an indicator that the body is dealing with physical exertion. In this case, ANS signals to the heart that the focus should be turned to uttermost parts of the body rather than internal processes.
Impact of HRV metrics on CVD detection
HRV is one of the most informative indicators of risks linked to cardiovascular disease and therefore, received a lot of attention in the last couple of years. New methods for both tracking and analyzing HRV metrics are being developed to offer healthcare providers a convenient and easily accessible method of detecting and monitoring various health conditions. The final goal is to alleviate the burden on the healthcare system by bringing health tracking methods closer to actual patients and raising their awareness about CVD risk factors.
In the last decade, thanks to automated analysis methods, HRV has become a regular part of the routine examination of patients with cardiovascular risks and chronic cardiovascular disease. HRV represents a useful tool for documenting events in various clinical settings, and remarkably low HRV measurements have been clearly linked to the severity of CVD, additionally proving how strong HRV and CVD correlate.
HRV could therefore become a valuable tool for assessing the health of the general population, as well as offer a method for detecting risk factors for cardiovascular disease. Previous studies did prove that HRV measurements can be used to predict increased mortality risk in patients who suffered from a heart attack or heart failure. However, the research available today on the link between HRV, ANS and CVD is still partial, and requires further studies before tools for CVD risk factors can be derived and fully accepted.
Alternative ways to measure HRV
24h-long monitoring is considered to be the optimal length for reliably tracking the changes in HRV metrics. Usually, such long measurements are performed with special ECG devices. However, given the time that such monitoring duration requires, other approaches need to be considered and developed. Particularly, using a smartphone or another wearable device to measure HRV in shorter or selected intervals throughout the day. It is a desirable alternative that is much more convenient and economical and delivers long-term measurement benefits.
Furthermore, the onset of cardiovascular disease can be the result of a combination of various factors, which must always be taken into consideration. HRV, therefore, should not be treated as an exclusive indicator of heart-related health issues, but rather as a valuable addition and a convenient tool for monitoring the efficiency of cardiovascular regulation.
HRV metrics need to be smartly integrated with the existing tools for identifying, tracking, and quantifying risk factors of CVD. However, an overestimation of the HRV as a predictor for lifetime risk of CVD should be avoided. Nevertheless, in combination with regular and specific checkups with medical professionals, HRV has immense potential in helping the general population take better care of their health and build lifestyle habits that enhance both life expectancy and quality
About KENKOU: Kenkou works across multiple platforms, solutions and technology sources to coherently integrate cardiovascular vital data measurement into existing health solutions. We provide an SDK (software development kit) for easy integration of HRV-measurement across a spectrum of use-cases. To find out how cardiovascular vital data can boost your app, contact us at [email protected] We will be happy to talk to you.