Association of Asymptomatic Bradycardia with Incident Cardiovascular Disease and Mortality
What is Asymptomatic Bradycardia?
Asymptomatic Bradycardia refers to the heart rate which is very slow than the normal heart rate. The slow rate depends on the age factor and physical condition of the person. In average people, the heart rate less than 60 BPM (beeps per minute) is considered a condition of bradycardia. It is commonly found in athletes.
Asymptomatic Bradycardia in some countries is said to have been interconnected with lower cardiovascular disease risk and increased mortality. A Multi-Ethnic Study of Atherosclerosis was done to check whether the asymptomatic bradycardia is associated with incident cardiovascular disease and mortality or not. Before we discuss about the study in detail, let us first understand the symptoms, causes and complications of asymptomatic bradycardia and its association with cardiovascular diseases and related mortality.
Symptoms of Asymptomatic Bradycardia
- Breath shortness
- Cardiac Arrest
- Problems while exercising
- The symptoms may vary from person to person.
Causes of Asymptomatic Bradycardia
Bradycardia can be caused by the following conditions:
- Damaged heart tissues
- A complication because of heart surgery
- Inflammatory disease
- Heart block
- The side-effect of certain medications
Complications of Asymptomatic Bradycardia
Untreated or severe bradycardia can cause problems like:
Research on the Asymptomatic Bradycardia
Numerous studies demonstrated that a higher resting heart rate shows a bad cardiovascular outcome. This resting heart rate has been known to be modifiable with time, with respect to genes and environmental factors like exercise and medications. This impact of bradycardia is not very clear as bradycardia is found in athletic individuals and is asymptomatic. The effects of bradycardia on non-athletic individuals are unclear. Tresch et. al observed a group of 96 people and described that sinus bradycardia in healthy non-athletic individuals having an age greater than 40 years did not have any association with Cardiovascular Disease and morbidity1. On the contrary, some other studies showed implications of the association between bradycardia and mortality. Kolloch et. al demonstrated an increased risk of coronary artery disease with a heart rate less than 50 beats per minute2.
The Multi-Ethnic Study of Atherosclerosis (MESA)(3)
Importance of the Study
In some regions or populations, bradycardia has been seen associated with a lower risk of cardiovascular disease.
The Objective of the Study
To check whether asymptomatic bradycardia is associated with lower cardiovascular disease risk or decreased incident cardiovascular disease or mortality.
Participants in the Study
The research included 6,733 participants. They invited men and women who were not the patients of cardiovascular disease of ages 45 to 84 in 2000-2002 and recorded and followed them for over 10 years to discover incident cardiovascular disease and mortality4. Patients who had atrial arrhythmias were not included.
Methods of the Study
The participants’ heart rate was measured with the help of baseline electrocardiogram. Resting heart rate was regulated on a 12-lead electrocardiogram. The analysis was done in June 2014.
In a study, 6733 individuals between the ages of 45-84 years took part. This group consisted of individuals of multi-ethnicity mainly considering 4 ethnic groups which included 38 percent people of white origin, 28 percent African American, 22 percent Hispanic and 12 percent Chinese population.
They were not diagnosed with Cardiovascular Disease (CVD). The presence of CVD was higher for the individuals with bradycardia but after adjustment for CVD risk factors and potential risks, the risk quotient was reduced. Resting heart rate was determined with the help of a 12-lead electrocardiogram. Patients previously diagnosed with an arrhythmia or having a pacemaker system attached to them were not included. Although bradycardia was conventionally defined for a heart rate less than 60 beats per minutes or 50 beats per minute it was considered that the patients having a resting heart rate of less than 50 bpm were said to be suffering from bradycardia. These participants were tracked for the next 9 to 12 months for any cardiovascular events and mortality.
Cox proportional hazards model was used to measure the association between Cardiovascular Disease events and mortality.
The results were observed which showed that the mean age of the participants was 62 years out of which 47 percent were males. The participants who did not take a heart rate modifying drugs showed a mean heart rate of 63+10 bpm and 5 percent of them had a resting heart rate less than 50 bmp. On the other hand, the participants who took the drug showed a mean heart rate of 60+10 bpm and 11 percent were diagnosed with bradycardia. The mortality in individuals who took the heart rate modifying drugs was 69 percent higher in people having an HR between 50 and 59 bpm and 142 percent higher in the population with an average heart rate of 60 to 69 bpm. The mortality risk among the individuals who did not take the drug was similar to the individuals with bradycardia. On the contrary, the individuals who took the drug showed a higher mortality rate both for HR<50 bmp and HR>80 bmp.
It was then observed that bradycardia was not associated with an increase in mortality for patients without Cardiovascular Disease. These finding gave a sigh of relief to the patients with bradycardia but don’t have cardiovascular disease. Only the individuals who took prescribed drugs to slow the heart rate have been proven to be relevant to determine the association between bradycardia and mortality. The main limitation of this study was that the individuals who did not have Cardiovascular Disease were taking heart rate modifying drugs were also included. It was then concluded that bradycardia was not associated with incident Cardiovascular Disease or mortality except having an adverse effect on the individuals taking HR modifying drugs.
Further work is suggested to be conducted in other cohorts and a different number of databases to perfectly conclude that these results are true if they can be replicated.
Preventions for Asymptomatic Bradycardia
The following are some of the preventions of bradycardia:
- Taking a balanced diet and eating healthy can prevent bradycardia.
- Smoking should be avoided
- Regular check-ups should be taken so that if there is a symptom of bradycardia, it can be treated on time.
- Regular exercise is a must for everyone
- The person should control his/her blood pressure.
- The cholesterol should be kept in check
It is a general term for various disorders related to heart and blood vessels. They include:
- Coronary Heart Disease
- Peripheral Arterial Disease
- Deep Vein Thrombosis
- Pulmonary Embolism
- Congenital Heart Disease
- Cerebrovascular Disease
- Rheumatic Heart Disease
Treatment, Diagnosis, and Prognosis of Bradycardia
The organs cease to operate when there is no enough oxygen reaching the organs which happens due to an extremely low heart rate. However, athletes with a low heartbeat is normal because of their over activity. When problem occurs in the sinus node, which is the natural pacemaker of the heart, it is known as the sinus bradycardia. Bradycardia may occur here when the electrical rhythm is not recorded as it should. The signs and symptoms of bradycardia are dizziness, near fainting, unexpected fatigue, lack of energy, pain in the chest, problems with memory, forgetting easily, and respiratory problem, symptoms of underlying illness, lightheadedness, and fainting spells.
Sleep apnea, myocarditis, certain medication or lupus can cause bradycardia. Treatment depends on the underlying cause of the low heart rate and by inserting a pacemaker by a surgical procedure. A heart beat recording 60 per minute is considered abnormal and refers to as bradycardia or sinus bradycardia5. Underlying heath conditions such as Cardiac arrhythmia, typhoid fever, narcotics, hypothermia, and endocarditis, a heart surgery complication, etc. can cause bradycardia. The risk factor which can cause bradycardia are smoking, damage of the heart, anxiety, use of heavy alcohol, heavy drug use, diabetes, high blood pressure, coronary artery disease, psychological stress and renal insufficiency.
The electrical signals that signifies the heart rhythm is measured by ECG or electrocardiogram. Electrocardiogram is essential for the diagnosis of bradycardia along with medical history and some physical examinations. The heart rhythm may not get recorded under emotional stress of physical examination which is one of the challenges in diagnosing bradycardia. Another diagnosis includes providing a portable ECG machine by the doctor which is also known as cardiac event motor where heart rhythm data is collected over come days. Sometimes an underlying illness is responsible for the low heart beat for which some doctor may refer to a blood test. It is very important to inform the respective doctor about the different medications the patient consumed or is consuming and the dosage too. Any information about the herbal or vitamin supplements being consumed by the patient should also be informed to the doctor. Many supplements and medications can cause fluctuation in the heart rate including bradycardia.
In case of any heart disease or problem, the primary thing to focus is the diet of the patient. Any underlying illness should be treated to bring the overall functioning and the health of the heart in proper condition. Symptoms would be naturally relieved and the heart rate will return to normal.
Diet should be essentially changed if it’s a concern of high blood pressure or cholesterol as according to American heart association one’s diet can improve heart functioning by fighting cardiovascular diseases. Different kinds of nutrient foods are recommended such as wild caught fish and lean proteins, vegetables and organic fruits, and whole grains, salmon and mackerel, walnuts, egg yolks etc. Foods rich in omega – 3s are highly helpful to our body as it lowers blood pressure, rejects the bad cholesterol and increases the good cholesterol level. COQ10 supplements which are rich in essential fats such as cabbage, sesames seeds, oranges, broccoli, pistachio nuts etc. can reduce heart attack risks, lowers the blood pressure and lowers the level of certain substances which are seen to increase the risk of cardiovascular disease. Intake of magnesium can also help in having sleep, relieve muscle aches and spasms.
Acupuncture is very helpful in some of the patients to reduce the risk of heart disease in patients with fibromyalgia and it also lowers stress level. Reducing the stress level is very important for people with heart disease. Pilates, yoga and meditation induces calmness and wellbeing. Vitamin B complex helps to reduce depression symptoms in people. Inhaling lavender essential oil is also another way of coping with anxiety through the therapeutic effect of smell. Sleep apnea causes bradycardiac symptoms. Thus one should know ways of getting sufficient sleep. Exercising daily is a must as it keeps a body active and improves cardiovascular health, lowers stress level facilitating a good amount of sleep and also reduces symptoms of sinus bradycardia. It also increases the level of vitamin D by exposing oneself to the sunlight.
Bradycardia is a condition in which heart rate is very slow than the normal heart rate. The slow rate depends on the age factor and physical condition of the person. Athletes experience it commonly as their resting heart rate is lower than the normal heart rate.
Cardiac arrest and dizziness are two of the symptoms of bradycardia. Its causes include damaged heart tissues, complication after heart surgery and inflammatory disease.
It can be prevented by avoiding smoking, getting regular check-ups, exercising regularly, and eating healthy food. If the bradycardia left untreated it can cause various complications including severe chest pain, heart failure, high or low blood pressure.