New research from Virginia Tech has revealed why certain heart rhythm medications, like flecainide, can become risky when blood sodium levels drop.
These drugs are commonly used to treat atrial fibrillation and other irregular heartbeats, but under certain conditions, they may actually disrupt the heart’s electrical signals rather than help them.
Sodium is a crucial electrolyte in the body that helps with nerve and muscle function, including how the heart beats.
When sodium levels in the blood get too low—a condition called hyponatremia—it can create problems for people who are taking medications that block sodium channels in the heart.
Until now, doctors have known that both low sodium and sodium channel blockers can affect the heart, but they didn’t fully understand why the combination of the two can be so dangerous. This new study helps explain that.
The research team studied how electrical signals move through the heart using guinea pig hearts.
They found that when sodium channels are blocked, as they are with medications like flecainide, the heart must rely on backup systems to keep its rhythm going.
One of those systems involves close contact between heart cells in tiny spaces, a process known as ephaptic coupling. Another system involves potassium ions that help reset the heart’s electrical signals between beats.
However, when sodium levels in the blood are too low, these backup systems don’t work as well. That means the electrical signals in the heart slow down more than expected, raising the risk of dangerous rhythm problems.
In simpler terms, if you’re on a medication like flecainide and your sodium levels drop—even slightly—your heart may have trouble keeping a stable rhythm.
The good news is that the researchers also discovered ways to potentially reduce this risk. They found that if certain pathways in the heart, like the ones involving potassium or ephaptic coupling, are supported or adjusted, the heart becomes less sensitive to low sodium levels, even when sodium channels are blocked by medication.
This could help doctors develop better treatment strategies in the future.
Lead researcher Steven Poelzing, a professor at Virginia Tech, emphasized that while not every patient needs to worry, the findings are especially important for older adults or hospitalized patients who are more likely to have low sodium levels. For patients on rhythm-control medications, it may be just as important to monitor sodium levels as it is to treat the irregular heartbeat.
Talking to your doctor about how your medications interact with your body’s electrolyte balance—especially sodium—could help prevent serious heart problems before they happen.
Source: Virginia Tech.
