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Posted on Thursday October 31, 2024 in Naked Heart
An article written by Dr Edward Leatham, Consultant Cardiologist
Tags: Podcast, Faints, Vasovagal, Bradycardia, NH1 search website using Tags to find related stories.
Bradycardia, or a slow heart rate, is a term you might have come across in a medical report or perhaps during a routine checkup. For many, hearing that their heart rate is “too low” can trigger concern. But what does bradycardia actually mean? And when does a slow pulse become something to address with a healthcare professional? Let’s dive deeper into the causes, symptoms, and treatment options, to help demystify bradycardia and highlight when it is a natural variation and when it requires medical attention.
In simple terms, bradycardia means that your heart rate is lower than what is considered typical. For adults, a resting heart rate of 60 to 100 beats per minute (bpm) is considered within the normal range. Bradycardia is usually defined as a resting heart rate below 60 bpm. However, this definition varies slightly depending on the individual and the context, as lower heart rates can be normal in certain situations, particularly for well-trained athletes, those who regularly engage in physical fitness routines and is also within the normal range for non athletic people who are regarded as simply having ‘high vagal tone’.
A slower-than-average heart rate may, in many cases, be perfectly benign. Yet, in some individuals, bradycardia can lead to symptoms such as dizziness, fatigue, shortness of breath, or fainting, which could indicate an underlying problem.
Your heart rate, or pulse, is a reflection of your heart’s activity and an important metric of cardiovascular health. By taking the pulse, we can gain insight into the body’s autonomic nervous system balance—between the parasympathetic (“rest and digest”) and sympathetic (“fight or flight”) systems—and how the body is adapting to stressors and changes in health.
Normal resting heart rate varies significantly between individuals due to genetic, physiological, and lifestyle factors. The rate is typically determined by a balance of “vagal tone” (the effect of the vagus nerve that slows the heart rate) and sympathetic activity (the body’s natural accelerator). In people with higher vagal tone, for instance, the resting heart rate might naturally be lower, whereas those with a predominantly sympathetic tone may have a higher resting heart rate.
Thus, knowing your typical or “baseline” resting heart rate can be a valuable way to monitor your own health. If your rate suddenly varies significantly from this baseline, it could be a signal that something more serious is going on.
It’s important to recognise that what may seem “too slow” in terms of heart rate is not necessarily abnormal. For instance:
In these situations, a slow heart rate is simply a reflection of the body’s adaptation to physical training or natural physiological adjustments and does not necessarily indicate a health problem. However, when bradycardia leads to symptoms, it is important to evaluate for underlying causes and consider appropriate treatment.
Several factors can lead to a lower-than-normal heart rate, some benign and some requiring medical intervention:
Simple faints
Many people experience a reflex known as vasovagal syncope. This occurs when a specific trigger, like standing still for a long time at events or being in medical situations (such as blood tests or dental procedures), causes them to feel faint or “squeamish.” During this reaction, the heart rate gradually drops, sometimes even leading to a brief pause, which can seem alarming. Symptoms often build up over a few minutes, allowing people to recognise and prepare for them, which is why vasovagal syncope is generally not a concern for driving. Remarkably, even severe episodes are rarely life-threatening, as the gradual onset and predictability help individuals manage the situation.
Medical Conditions Affecting the Heart’s Electrical System:
The heart has its own electrical wiring that controls how and when it beats. Bradycardia often results from problems in this electrical system.
Sinoatrial (SA) Node Dysfunction: Known as the heart’s natural pacemaker, the SA node sets the rhythm. If it starts to slow down or pause, the heart rate can decrease.
Heart Block: This occurs when the electrical signals from the atria (upper chambers of the heart) to the ventricles (lower chambers) are delayed or blocked. In cases of advanced heart block, the ventricles do not receive signals to beat at the normal rate, leading to a slower pulse.
Hypothyroidism: An underactive thyroid gland can reduce metabolism and slow down heart rate.
Electrolyte Imbalances: Potassium, calcium, and magnesium play critical roles in heart function, and imbalances can lead to slower heart rates.
Infections and Fevers: Certain infections, including bacterial and viral, may result in a temporary increase or decrease in heart rate.
Medications:
Common medications such as beta-blockers or certain types of calcium channel blockers used to control high blood pressure or heart rhythm can reduce heart rate.
Other drugs, including some used for anxiety or eye drops used for glaucoma, can also affect heart rate and contribute to bradycardia.
Age-Related Changes:
Aging can cause natural changes to the heart’s electrical pathways, leading to a slower resting heart rate.
Congenital Heart Conditions:
Some people are born with heart conditions that predispose them to a slower heart rate.
A slow heart rate may not cause symptoms in many people. However, when bradycardia leads to insufficient blood flow, symptoms may arise, including:
For many, bradycardia is a natural and non-threatening condition. However, it can become a medical concern if:
When bradycardia is suspected, a cardiologist may recommend a series of tests to assess heart function and uncover any underlying issues. These tests are designed to capture the electrical activity, structure, and function of the heart. Here are some of the most common diagnostic tools for evaluating bradycardia:
These diagnostic tools help cardiologists determine the cause and severity of bradycardia, allowing for an informed approach to treatment and management tailored to each patient’s specific needs.
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The Naked Heart is an educational project owned and operated by Dr Edward Leatham. It comprises a series of blog articles, videos and reels distributed on Tiktok, Youtube and Instagram aimed to help educate both patients and healthcare professionals about cardiology related issues.
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