Bradyarrhythmia - Causes, Symptoms, Diagnosis, and Treatment

Introduction:

A bradyarrhythmia is slower than usual because of an irregular heart rhythm. Healthy people can also have slow heart rates. People with bradyarrhythmia have a slower heart rate because of a medical condition or defect that can affect the rhythm. When bradyarrhythmia is diagnosed, a treatment plan may include implantable devices or lifestyle changes depending upon severity.

What Are the Causes of Bradyarrhythmia?

1. Intrinsic Causes:

• Aging: Aging is considered a primary cause.

• Heart Failure: Congestive heart failure occurs when the heart is not able to pump adequate blood in response to the body's demand.

• Ischemic Heart Disease: Heart problems caused by the narrowing of heart arteries.

• Myocardial Infarction: Blood flow to the heart muscle is blocked due to a lack of oxygen.

• Congenital Heart Disease: A congenital disability that alters the functioning of the heart.

• Infiltrative Cardiac Disorder: A diverse group of cardiac diseases characterized by the deposition of abnormal substances within the heart tissue.

• Sarcoidosis: Abnormal collections of inflammatory cells form a lump in any body part.

• Amyloidosis: A rare disease that occurs when an amyloid protein builds up in organs.

• Fibrosis: Scarring and damage of the cardiac muscle tissue.

• Myocarditis: Inflammation of the heart muscle (myocardium).

• Lyme Disease: Lyme disease is an infectious disease of bacterial origin.

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2. Extrinsic Causes:

• Medications: Beta-blockers, calcium channel blockers, etc.

• Hyperthyroidism: When the thyroid gland produces excessive thyroid hormones than required, it is known as hyperthyroidism.

• Hypothyroidism: When the thyroid gland fails to produce enough hormones.

• Hypokalemia: Hypokalemia means low blood potassium levels.

• Hyperkalemia: A medical problem in which blood has too much potassium.

• Hypothermia: Hypothermia is a potentially grave condition where there is a significant drop in body temperature.

• Surgery: Post-surgical bradyarrhythmia is common due to the anesthesia and certain medications that may slow the heart rate.

• Obstructive Sleep Apnea: When the muscles in the back of the throat relax too much to allow normal breathing.

Common symptoms of Bradyarrhythmia may include vomiting, coughing, dizziness, fainting, fatigue, shortness of breath, and weakness.

What Are the Types of Bradyarrhythmias?

Different types of bradyarrhythmias have their causes, but all result in a slower-than-typical heart rate. Some of the kinds of bradyarrhythmia are:

1. Sinus Node Dysfunction: Also known as sick sinus syndrome. The sinus node is also known as the heart’s natural pacemaker. They send out the electrical impulse that triggers the heart to beat. A disease or defect that affects the sinus node may result in sick sinus syndrome.

2. Heart Blockage: It is a condition that results from impaired cardiac electrical signals that restrict the electrical impulses in the heart from moving as usual. It may result in a slow heart rate or skipped heartbeats.

3. Bradycardia or Tachycardia Syndrome: In some patients, sinus node dysfunction leads to alternating periods of slow and fast heart rates. Atrial fibrillation (Afib) is one of those symptoms.

The blockage of AV node can be in different ways :

• First-Degree Heart Block: It is a less severe form of heart block caused by delayed conduction of electrical impulses from the atria to the ventricles.

• Second-Degree Heart Block: If the impulses slow so much, resulting in the heart skipping a beat (type I), or some notions never get to the ventricles, an arrhythmia develops (type II).

• Third-Degree Heart Block: There is a complete interruption of the electrical impulses and almost no communication between the atria and the ventricles. This is the most severe form.

Second and third-degree heart blocks mostly require a pacemaker, an electrically charged device implanted under the chest skin, and help manage heartbeats.

What Are the Methods for Diagnosis of Bradyarrhythmia?

Cardiac tests are done to detect bradyarrhythmia. Some of them are as follows:

• ECG (Electrocardiogram): A test to check the heart's rhythm and electrical activity.

• Holter Monitor: A small, wearable device that records the heart's rhythm.

• Loop Recorder: A heart recording device implanted in the body underneath the chest skin.

• Post-event Recorder: Post-event monitor records irregular heartbeats that last slightly longer than a few seconds.

• Electrophysiologic Study (EPS): A test to evaluate the heart's electrical system and abnormal heart rhythms.

• Exercise Stress Test: A cardiac stress test is a diagnostic test used to measure cardiac activity in response to external stress.

Some additional cardiac tests are :

• Cardiac Magnetic Resonance: Cardiac magnetic resonance imaging is a non-invasive diagnostic tool to assess the structure and function of the heart and its associated structures.

• Cardiomyopathy Test: A heart biopsy, or myocardial biopsy, is used to diagnose types of cardiomyopathy.

Laboratory tests done for bradyarrhythmias are:

• Metabolic Panel: A blood test that provides information about the body's fluid balance, levels of electrolytes, and kidney and liver functions.

• Thyroid Function: Testing the levels of thyroid hormones.

• Serologic Testing: Antibody test.

• Polysomnography: A comprehensive test used to diagnose sleep disorders.

What Is the Management of Bradyarrhythmia?

Management depends upon the condition of patients. For example, hemodynamic stable and unstable patients have different modes of control.

Hemodynamically Unstable Patient:

1. 1st line - 0.5 mg intravenous (IV) Atropine is given. If instability is still present, transcutaneous pacing is followed by transvenous pacing, followed by Dopamine and Epinephrine.

2. Once the patient is stable, management is turned toward the methods for hemodynamically stable patients. If the patient is hemodynamically stable, then:

• Search for reversible causes, if any.

• Treatment of the reason.

• Permanent pacemakers are placed if showing persistent symptoms.

Treatment During Pregnancy Needs Specific Considerations:

Depending upon the type of bradyarrhythmia, the baby's gestational age, any associated conditions, and the overall health of the fetus and mother, the treatment are advised accordingly. In addition, the baby’s heart rate and well-being are closely monitored throughout pregnancy for any signs of fetal hydrops or heart failure.

Treatment strategies include:

• In mild cases, treatment is not required, but the baby is closely monitored from time to time.

• Medications.

• Steroids.

• Premature or emergency deliveries.

What Are the Complications?

If a pacemaker is implanted, annual follow-up is advised to check the proper functioning of the leads, battery life, and if there are any other symptoms. Pneumothorax and haemothorax can occur to the venous access technique, preferably if the subclavian vein is punctured. This leads to complications such as cardiac perforation, diaphragmatic stimulation, and venous thrombosis.

What Are the Recent Advances in Therapy?

There has been tremendous advancement in pacemakers and other treatment methods for bradyarrhythmia. Some of them are as follows:

• Leadless Pacemaker: A leadless pacemaker is a small self-contained device inserted in the heart's right ventricle.

• His Bundle Pacing: His bundle pacing is an alternative technique for delivering cardiac resynchronization therapy.

Conclusion:

Bradyarrhythmias may be caused for various reasons, although acute myocardial infarction, hypoxia, sepsis, and hypothermia should be considered. Emergency department therapy treats the underlying cause, pharmacologic interventions, and temporary pacing. It is essential to conclude if the bradyarrhythmia will not be able to resolve spontaneously or with the alleviation of a condition that is the likely cause of the bradyarrhythmia.