What is heart block
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Understanding Heart Block: Types, Causes, and Implications
Definition and Types of Heart Block
Heart Block Overview
Heart block is a condition where the electrical impulses that control the heartbeat are partially or completely interrupted as they travel from the atria to the ventricles. This interruption can occur at various points in the heart's conduction system, including the bundle of His and its branches.
Bundle-Branch Block
A specific type of heart block, known as bundle-branch block, involves partial or complete interference in the transmission of impulses down either the right or left branch of the bundle of His. This can occur in conjunction with other forms of heart block.
Complete Heart Block
Complete heart block, or third-degree heart block, occurs when the electrical signals from the atria do not reach the ventricles at all, causing the atria and ventricles to beat independently of each other. This can result in a significantly slowed heart rate (bradycardia) and is often symptomatic .
Causes of Heart Block
Surgical Heart Block
Heart block can be a serious complication following surgical procedures for congenital heart defects. It is often caused by direct trauma to the central conduction bundle during surgery. While some patients may revert to a normal sinus rhythm within weeks post-operation, others may require a pacemaker due to the persistence of the block.
Coronary Artery Disease
Acute heart block can be a complication of myocardial infarction, although survivors often return to sinus rhythm. Chronic heart block, particularly in the elderly, is frequently associated with coronary artery disease and coronary sclerosis .
Autoimmune and Congenital Factors
Autoimmune congenital heart block (CHB) is caused by the transference of maternal antibodies to the fetus, leading to inflammation and fibrosis of the fetal conduction tissues. This type of heart block is usually diagnosed in utero or shortly after birth and can result in irreversible complete AV block. Additionally, congenital complete heart block can occur without any anatomical abnormalities and may remain unnoticed until adulthood.
Genetic Syndromes
Heart block can also be associated with genetic conditions, such as the 18p-syndrome, where it may present with other cardiac abnormalities like atrioventricular node calcification. Progressive familial heart block type I (PFHBI) is another genetic form, linked to mutations in the TRPM4 gene, which affects ion channel function and leads to progressive conduction system disease.
Clinical Implications and Management
Symptoms and Diagnosis
Patients with heart block may experience symptoms such as dizziness, breathlessness, chest pain, excessive palpitation, vertigo, and sweating. These symptoms are due to the reduced efficiency of the heart's pumping action.
Management Strategies
Management of heart block often involves the use of pacemakers, especially in cases where the block is persistent or symptomatic. Temporary pacing may be used immediately post-surgery, with permanent pacemakers being implanted if normal rhythm does not resume .
Conclusion
Heart block is a complex condition with various types and causes, ranging from surgical complications and coronary artery disease to autoimmune and genetic factors. Understanding the underlying mechanisms and appropriate management strategies is crucial for improving patient outcomes. Further research is needed to develop effective preventive and therapeutic approaches, particularly for autoimmune and congenital forms of heart block.
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