Bradyarrhythmias

Bradyarrhythmias

Bradyarrhythmias refer to a group of heart rhythm disorders characterized by a slower than normal heart rate. The term "bradyarrhythmia" is derived from "brady," meaning slow, and "arrhythmia," meaning irregular heart rhythm. These conditions can lead to insufficient blood flow to the body and may cause symptoms such as fatigue, dizziness, and fainting.

Etiology

Bradyarrhythmias can result from a variety of causes, including:

• Sick sinus syndrome
• Atrioventricular block
• Hypothyroidism
• Myocardial infarction
• Medications such as beta-blockers and calcium channel blockers

Pathophysiology

The heart's electrical system controls the rate and rhythm of the heartbeat. Bradyarrhythmias occur when there is a disruption in the normal conduction pathways, leading to a slower heart rate. This can occur at the level of the sinoatrial node, the atrioventricular node, or the His-Purkinje system.

Sinoatrial Node Dysfunction

The sinoatrial (SA) node is the heart's natural pacemaker. Dysfunction of the SA node can lead to sinus bradycardia or sinus arrest, where the heart rate is abnormally slow or pauses occur.

Atrioventricular Block

Atrioventricular (AV) block occurs when the conduction between the atria and ventricles is impaired. AV block is classified into three degrees:

• First-degree AV block: Prolonged PR interval without missed beats.
• Second-degree AV block: Intermittent failure of conduction, further divided into Mobitz type I (Wenckebach) and Mobitz type II.
• Third-degree AV block: Complete heart block with no conduction between atria and ventricles.

Clinical Presentation

Patients with bradyarrhythmias may present with a variety of symptoms, including:

• Fatigue
• Dizziness or lightheadedness
• Syncope (fainting)
• Shortness of breath
• Chest pain

Diagnosis

The diagnosis of bradyarrhythmias typically involves:

• Electrocardiogram (ECG) to assess heart rhythm
• Holter monitor for continuous ECG monitoring
• Electrophysiological study in complex cases

Treatment

Treatment of bradyarrhythmias depends on the underlying cause and severity of symptoms. Options include:

• Discontinuation or adjustment of medications causing bradycardia
• Pacemaker implantation for symptomatic bradycardia or high-degree AV block
• Treatment of underlying conditions such as hypothyroidism

Prognosis

The prognosis for patients with bradyarrhythmias varies depending on the cause and treatment. With appropriate management, many patients can lead normal lives. However, untreated severe bradyarrhythmias can lead to complications such as heart failure or sudden cardiac arrest.

See Also

• Tachyarrhythmia
• Cardiac electrophysiology

References

• Bradyarrhythmias - American Heart Association
• Bradyarrhythmias - NCBI Bookshelf