Progressive familial heart block

On this page:

What is progressive familial heart block?

Progressive familial heart block is a genetic condition that alters the normal beating of the heart. A normal heartbeat is controlled by electrical signals that move through the heart in a highly coordinated way. These signals begin in a specialized cluster of cells called the sinoatrial node (the heart's natural pacemaker) located in the heart's upper chambers (the atria). From there, a group of cells called the atrioventricular node carries the electrical signals to another cluster of cells called the bundle of His. This bundle separates into multiple thin spindles called bundle branches, which carry electrical signals into the heart's lower chambers (the ventricles). Electrical impulses move from the sinoatrial node down to the bundle branches, stimulating a normal heartbeat in which the ventricles contract slightly later than the atria.

Heart block occurs when the electrical signaling is obstructed anywhere from the atria to the ventricles. In people with progressive familial heart block, the condition worsens over time: early in the disorder, the electrical signals are partially blocked, but the block eventually becomes complete, preventing any signals from passing through the heart. Partial heart block causes a slow or irregular heartbeat (bradycardia or arrhythmia, respectively), and can lead to the buildup of scar tissue (fibrosis) in the cells that carry electrical impulses. Fibrosis contributes to the development of complete heart block, resulting in uncoordinated electrical signaling between the atria and the ventricles and inefficient pumping of blood in the heart. Complete heart block can cause a sensation of fluttering or pounding in the chest (palpitations), shortness of breath, fainting (syncope), or sudden cardiac arrest and death.

Progressive familial heart block can be divided into type I and type II, with type I being further divided into types IA and IB. These types differ in where in the heart signaling is interrupted and the genetic cause. In types IA and IB, the heart block originates in the bundle branch, and in type II, the heart block originates in the atrioventricular node. The different types of progressive familial heart block have similar signs and symptoms.

Most cases of heart block are not genetic and are not considered progressive familial heart block. The most common cause of heart block is fibrosis of the heart, which occurs as a normal process of aging. Other causes of heart block can include the use of certain medications or an infection of the heart tissue.

How common is progressive familial heart block?

The prevalence of progressive familial heart block is unknown. In the United States, about 1 in 5,000 individuals have complete heart block from any cause; worldwide, about 1 in 2,500 individuals have complete heart block.

What genes are related to progressive familial heart block?

Mutations in the SCN5A and TRPM4 genes cause most cases of progressive familial heart block types IA and IB, respectively. The proteins produced from these genes are channels that allow positively charged atoms (cations) into and out of cells. Both channels are abundant in heart (cardiac) cells and play key roles in these cells' ability to generate and transmit electrical signals. These channels play a major role in signaling the start of each heartbeat, coordinating the contractions of the atria and ventricles, and maintaining a normal heart rhythm.

The SCN5A and TRPM4 gene mutations that cause progressive familial heart block alter the normal function of the channels. As a result of these channel alterations, cardiac cells have difficulty producing and transmitting the electrical signals that are necessary to coordinate normal heartbeats, leading to heart block. Death of these impaired cardiac cells over time can lead to fibrosis, worsening the heart block.

Mutations in other genes, some of which are unknown, account for the remaining cases of progressive familial heart block.

Read more about the SCN5A and TRPM4 genes.

See a list of genes associated with progressive familial heart block.

How do people inherit progressive familial heart block?

Progressive familial heart block types I and II are inherited in an autosomal dominant pattern, which means one copy of an altered gene in each cell is sufficient to cause the disorder. Some people withTRPM4 gene mutations never develop the condition, a situation known as reduced penetrance.

In most cases, an affected person has one parent with progressive familial heart block.

Where can I find information about diagnosis or management of progressive familial heart block?

These resources address the diagnosis or management of progressive familial heart block and may include treatment providers.

You might also find information on the diagnosis or management of progressive familial heart block in Educational resources and Patient support.

General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.

To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.

Where can I find additional information about progressive familial heart block?

You may find the following resources about progressive familial heart block helpful. These materials are written for the general public.

MedlinePlus - Health information (4 links)
Additional NIH Resources - National Institutes of Health
National Heart, Lung, and Blood Institute: What is Heart Block?
Educational resources - Information pages (15 links)
Patient support - For patients and families (4 links)

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

Genetic Testing Registry - Repository of genetic test information (3 links)
ClinicalTrials.gov - Linking patients to medical research
PubMed - Recent literature
OMIM - Genetic disorder catalog (3 links)

What other names do people use for progressive familial heart block?

bundle branch block
HBBD
hereditary bundle branch defect
hereditary bundle branch system defect
Lenegre Lev disease
Lev-Lenègre disease
Lev's disease
Lev syndrome
PCCD
progressive cardiac conduction defect

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines and How are genetic conditions and genes named? in the Handbook.

What if I still have specific questions about progressive familial heart block?

Ask the Genetic and Rare Diseases Information Center

Where can I find general information about genetic conditions?

The Handbook provides basic information about genetics in clear language.

These links provide additional genetics resources that may be useful.

What glossary definitions help with understanding progressive familial heart block?

arrhythmia ; atrioventricular node ; autosomal ; autosomal dominant ; bradycardia ; cardiac ;cardiac arrest ; cell ; channel ; fainting ; familial ; fibrosis ; gene ; hereditary ; His ; infection ;inherited ; obstructed ; pacemaker ; palpitations ; penetrance ; prevalence ; sinoatrial node ; syncope ;syndrome ; tissue

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.

References (10 links)

The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook