Named the condition under which heart medications become dangerous

Blood sodium level is a key indicator that patients taking medications to control heart rhythm, such as flecainide, should pay attention to. A new study by American scientists from Virginia explained why even a moderate decrease in blood sodium can sharply worsen heart conduction in such patients. The work was published in the journal Heart Rhythm (HR).

Researchers conducted experiments on guinea pig hearts, a model that is close to human hearts. Scientists showed that when taking sodium channel blockers, the heart becomes particularly vulnerable to decreases in sodium concentration. This can occur, for example, during vomiting, diarrhea, when taking diuretics or other medications, as well as in hospitalized and elderly patients.

"Doctors have long known that sodium channel blockers slow conduction, and low sodium is a risk. But now we have shown why their combination is particularly dangerous," explained the lead author of the study, Steven Poelzing from the Fralin Institute at Virginia Tech.

When sodium channels are partially blocked, the heart tries to conduct electrical signals through bypass routes. One such mechanism is the interaction between cells through narrow intercellular spaces. Another is the outflow of potassium ions, which is responsible for restoring the electrical potential. But when sodium decreases, both mechanisms begin to work less effectively, causing the electrical signal to pass through the heart with a delay.

Scientists also found that intervention in these bypass pathways can reduce the heart's sensitivity to sodium reduction, potentially opening the way to new treatment methods.

Although this does not mean that every patient on antiarrhythmics should urgently check their sodium, doctors should consider electrolyte balance when prescribing such medications, especially for vulnerable groups.

"Sometimes a simple analysis and conversation with a doctor can prevent a serious problem," emphasized Poelzing.