Bradycardia

Overview

Bradycardia is a condition characterized by a slow heart rate, with the heart beating fewer than 60 times per minute. In most cases, adults have a resting heart rate between 60 and 100 beats per minute. When bradycardia occurs, it can lead to insufficient pumping of oxygen-rich blood throughout the body, which can be a serious problem. Symptoms of bradycardia may include dizziness, fatigue, weakness, and shortness of breath. However, sometimes bradycardia may not cause any noticeable symptoms or complications.

It’s important to note that a slow heart rate is not always a cause for concern. During sleep or in certain individuals, such as healthy young adults and trained athletes, it is quite common to have a resting heart rate between 40 and 60 beats per minute. In these cases, bradycardia is not typically associated with any adverse effects.

However, when bradycardia becomes severe and leads to symptoms or complications, medical intervention may be necessary. In such cases, the placement of an implanted pacemaker can help regulate and maintain an appropriate heart rate. This device helps regulate the heart’s rhythm and ensures that it beats at a rate that adequately meets the body’s oxygenation needs. Overall, bradycardia is a condition characterized by a slow heart rate, typically below 60 beats per minute. While it can be a serious problem if it prevents the heart from pumping sufficient oxygenated blood, it can also occur without causing any harmful effects, particularly in individuals who are physically active. When symptoms are present, bradycardia is usually a treatable condition with a positive prognosis.

Symptoms

Most cases of bradycardia do not have any symptoms, especially for those who are physically active since their hearts are more efficient. However, in some cases, bradycardia can hinder the brain and other organs from receiving enough oxygen, leading to the following signs and symptoms:

• Chest discomfort, or angina
• Breathing difficulties, or dyspnea
• Confusion or memory issues
• Difficulty concentrating
• Dizziness, lightheadedness, and fainting (syncope)
• Heart palpitations
• Easily exhausted when moving
• Fatigue
• Irritability, agitation, or other personality changes

If you notice any signs or symptoms of bradycardia, it’s crucial to seek a timely and accurate diagnosis as well as appropriate care. If you have concerns about a slow heart rate, it’s advisable to consult your healthcare provider. In the event that you experience fainting, difficulty breathing, or persistent chest pain lasting more than a few minutes, it is important to immediately call emergency medical services.

Causes

Bradycardia happens when the signals originating from the sinus node in the right atrium of the heart slow down or experience blockages. In a normal heart, there are four chambers: two atria (upper chambers) and two ventricles (lower chambers). The sinus node, a cluster of cells located in the upper right chamber, acts as the heart’s intrinsic pacemaker. It generates the electrical impulses that initiate each heartbeat.

Generally, bradycardia can be a result of:

• Aging-related heart tissue deterioration
• Electrolyte deficiencies, such as calcium, magnesium, and potassium
• Heart tissue damage caused by heart disease or a heart attack
• Congenital health defect
• Inflammation in the heart, such as endocarditis, myocarditis, and pericarditis
• Heart surgery or repair
• Hypothyroidism
• Obstructive sleep apnea
• Sedatives, opioids, and pharmaceuticals used to treat heart rhythm abnormalities, high blood pressure, and some mental health disorders
• Infections, such as rheumatic fever, rheumatic heart disease, and Lyme disease
• Heart block (atrioventricular block): Bradycardia refers to the interruption of the heart’s electrical system, causing a blockage or reduction in the flow of electrical current during the heart’s beating process. These blocks can occur at various points within the heart’s electrical conduction system. The heart consists of four chambers – two atria (upper chambers) and two ventricles (lower chambers). The sinus node, located in the upper right chamber (right atrium), is a cluster of cells responsible for generating the heart’s natural pacemaker signal, initiating each heartbeat. However, in cases of bradycardia, these signals slow down or encounter blockages. There are three types of heart blockages:
  • First-degree heart block: If there is no underlying problem with electrical signaling, first-degree heart block rarely causes symptoms and usually does not require therapy. In this degree, the electrical impulse still reaches the ventricles, but it passes more slowly through the AV node than usual. The impulses are delayed.
  • Second-degree heart block: In this degree, the impulses are intermittently inhibited which means not all electrical signals are received by the ventricles. Some beats are skipped, resulting in a slower and occasionally irregular heartbeat. This heart block is categorized into two: the Mobitz Type I and Mobitz Type II.
  • Third-degree heart block: The electrical transmission from the atria to the ventricles has been completely blocked. When this occurs, the ventricles normally begin to beat on their own, but the heartbeat is slower, erratic, and unreliable. Third-degree block severely impairs the heart’s ability to pump blood throughout the body.

Risk factors

Bradycardia can occur to anyone at any age. However, certain risk factors may contribute to a higher risk. Since this condition is linked with cardiac tissue damage caused by some form of heart disease, anything that raises the risk of heart disease increase the risk of bradycardia.
Several risk factors include:

• Older age, usually over age 65
• Hypertension
• Smoking
• Excessive alcohol consumption
• Drug abuse
• Stress and anxiety
• Trauma or injury