A closer look at heart block and what causes it

In a normal heartbeat, an electrical signal comes from the sinoatrial (SA) node or the heart’s natural pacemaker, and it travels through the atria and reaches the atrioventricular (AV) node. Once it crosses the AV node, it goes through the bundles of His, which part into bundle branches or thin and wire-like structures that continue into the right and left ventricles. After journeying down the bundle branches, it reaches the ventricles’ muscle cells and leads them to contract and pump blood to the body.

This is a highly efficient process, according to cardiac electrophysiology specialist Dr. Ian Weisberg. Yet something called heart block can occur when the passage of electricity from the heart’s top to bottom becomes delayed or disrupted. This disorder of the cardiac electrical system has three degrees, namely first degree, or delayed conduction between the atria and ventricles but with all beats conducted; second degree, where some beats aren’t conducted to the ventricles; and third degree, where the atria and ventricles beat entirely independently of each other.

Both first-degree and higher-degree heart block are common, but the former typically presents no apparent sign or symptom, while the latter is particularly more prevalent among the elderly. It’s not uncommon for a previous heart attack, heart failure, rheumatic heart disease, congenital heart diseases, and conduction-interfering medications to cause heart block.

While people with heart block can be asymptomatic, it’s also possible to experience symptoms such as fainting, shortness of breath, lightheadedness or dizziness, and a decline in the ability to exercise. A doctor, adds Dr. Ian Weisberg, can accurately diagnose heart block through blood tests that rule out electrolyte imbalance as well as thyroid function testing that looks at thyroid hormone levels.

Dr. Ian Weisberg is a Pensacola, Florida-based cardiac electrophysiology specialist who performs more than 200 than 200 ablation of atrial fibrillation procedures every year. For similar reads, visit this page.