A new research team is on a quest to collapse a tiny pocket between cardiac cells that can cause big problems. Called the perinexus, the structure spans only tenths of a millimeter all the space it needs to disrupt a person's heartbeat. The researchers were the first to identify the perinexus in humans. The study was published in Frontiers in Physiology.
Typically, the heart beats in a steady "lub-dub" rhythm. The upper chambers of the heart, called atria, receive blood from the lungs and the veins and pass it to the lower chambers of the heart that's the lub. In the dub, the valves close and the lower chambers pump the blood out to the rest of the body. All of the cardiac cells move in a carefully choreographed dance of electrical impulses, making the heart contract at the right time, in the right order.
They found that people who have atrial fibrillation before surgery have structural derangements outside of their cardiac cells. By identifying which structure outside of the cell is deranged, we think we can target it to reduce the burden or risk of atrial fibrillation.
Small channels, called gap junctions, allow for the electrical communication between cells to ensure the continued contractile wave. Electrical communication can also occur through a spark outside of the cell in the nanodomain space of the perinexus. The tiny pocket is right next to the gap junctions and is so small that a spark can jump across the extracellular space, continuing the contractile wave from one cell to another.
The researchers found that in patients with atrial fibrillation, the perinexus appears permanently expanded, and the spark can't clear the jump. When the communication whether through the gap junctions or the spark across the perinexus — is disrupted, it slows the electrical wave and increases the risk for atrial fibrillation.
Genetics and risk factors, such as aging, obesity, sleep apnea, can lead to an irregular, rapid heartbeat typically the first symptom of atrial fibrillation, which is the most common arrhythmia. The lub-dub breaks pattern, significantly decreasing the efficiency with which the heart pumps blood.
The researchers are collaborating further to determine if pharmaceutical intervention can force a perinexal collapse and correct the irregular heartbeat.
These data support a novel concept of perinexus expansion as a potential explanation for electrical remodeling, conduction slowing and their link with increasing age, each of which is known to contribute to the epidemic of atrial fibrillation.
By further understanding this mechanism, Poelzing may be able to develop a monitoring system for patients with atrial fibrillation as well. They might be able to examine a person's blood chemistry to see how their salt levels are noting that cellular communication channels are controlled via levels of sodium, potassium, and calcium.
Particular combinations of those three could cause or increase a person's risk for miscommunication between cardiac cells. By monitoring the levels, we might be able to stop or even prevent an atrial fibrillation episode.