Atrial fibrillation, often called AFib, is the most common long-term heart rhythm disorder, affecting an estimated 10 million Americans.
It happens when the upper chambers of the heart beat in an irregular way instead of working smoothly with the lower chambers.
This can reduce blood flow and greatly increase the risk of stroke, heart failure, and other serious problems.
Most cases develop later in life because of aging, high blood pressure, diabetes, or heart disease. However, some people inherit rare genetic changes that cause AFib decades earlier. Researchers have long wondered why some people carrying these mutations become sick much sooner than others.
A new study led by researchers at Penn State College of Medicine provides an important clue. Published in Nature Communications, the research shows that rare disease-causing mutations can work together with many common genetic differences carried by millions of people. Together, these inherited changes may greatly increase the risk of developing AFib at a young age.
Every heartbeat begins with an electrical signal produced by specialized heart cells. This signal spreads through the upper chambers before reaching the lower chambers, allowing the heart to pump blood in a regular rhythm. In AFib, many abnormal signals appear at the same time, causing the upper chambers to quiver instead of contracting properly.
The team focused on a rare mutation in a gene called LMNA. This gene helps organize DNA inside cells and has already been linked to inherited heart disease. Using laboratory-grown heart cells created from donated blood samples, the scientists discovered that the LMNA mutation changed how DNA was packaged, affecting genes that control the heart’s electrical activity.
The researchers also analyzed genetic information from more than 500,000 people in the UK Biobank. They found that people carrying many common genetic risk variants had about twice the risk of developing early-onset AFib when combined with a rare mutation. This demonstrates that overall genetic background can strengthen the effects of a harmful mutation.
One important discovery involved genes that regulate sodium movement into heart cells. Sodium is essential for creating the electrical signals that allow the heart to beat normally. When these pathways were disrupted, the risk of abnormal heart rhythms increased.
Professor Dawood Darbar explained that many patients first learn they have AFib only after suffering a stroke. Detecting people at high genetic risk before symptoms appear could allow doctors to monitor them more closely and begin treatment much earlier.
This laboratory study provides valuable insight into why inherited AFib develops earlier in some people than others. Although the findings are not yet ready for routine patient care, they strengthen the case for combining rare mutation testing with broader genetic analysis.
If confirmed in future clinical studies, this approach could improve screening, prevent strokes, and allow doctors to identify high-risk families much earlier.
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