First-degree AV block:
In this condition, there is a delay of the electrical impulse reaching the lower chambers of the heart. It is not a complete heart block, merely a delay in conduction producing prolongation of the PR interval on the surface electrocardiogram. First-degree AV block is rare but may be seen in young, healthy adults, especially well-trained athletes owing to an increase in vagal tone. Patients are generally asymptomatic. In pediatrics it may be seen with certain types of congenital heart defects, after heart surgery or closure of an atrial septal defect, following catheter ablation, muscular dystrophy, rheumatic fever, lupus, rheumatoid arthritis, Lyme disease, tuberculosis, endocarditis, diphtheria, medications, coronary disease, heart failure and degenerative diseases of the electrical conduction system.
Most asymptomatic patients without an underlying cause do not require any treatment or follow-up.
Complete Heart Block:
Complete heart block is also called complete AV block or third-degree AV block. It means that the heart’s electrical signal can’t pass normally from the upper to the lower chambers. It does not mean the blood or coronary flow is blocked. It means that conduction of the electrical signal within the heart is completely blocked. As a result, the ventricles are stimulated by a back-up but slower pacemaker resulting in a slow pulse rate. Heart block may be present at birth (congenital heart block) or be acquired (after heart surgery, heart attack, muscular dystrophy, systemic diseases, underlying electrical disorder, inflammation or infection of the heart and others. Transient heart block may be seen with Lyme disease, side effects to medications, inflammation of the heart and others. The mother of an infant with congenital heart block should be checked for a collagenous disease such as Lupus.
A pacemaker is usually indicated, especially in patients with electrical disorders, symptoms, heart failure, complex heart defects or very slow pulse rates.
Patients with complete heart block may develop heart failure, fainting spells, lethargy, seizures and even sudden death. Optimal work-up and follow-up should be done by a pacemaker specialist such as Dr. Villafañe.