Must-Know Facts About AFib
How and why rhythm disorders like atrial fibrillation begin and more.
The heart is a pretty incredible organ when you think about it. It’s finely tuned and works in synchronicity: the timing of every action of the heart needs to be perfectly in sync in order for it to function properly. It’s this timing where problems with heart rhythm come in.
Heart beat impulses begin in the brain.
The command center for the heart is the brain in an area called the medulla (where the brain meets the spinal cord). It’s the medulla that regulates critical bodily functions we don’t need to think about: heart rhythm, as well as breathing, blood flow, blood pressure, and digestion.
It’s the medulla that sends out signals to have your heart beat at a faster or slower rate. It does so through two nerves: the sympathetic nerve and the parasympathetic nerve. These nerves send impulses or signals to the heart to beat with the help of chemical messengers called neurotransmitters.
The sympathetic nerve releases the neurotransmitter noradrenaline, or norepinephrine, to increase heart rate, usually in response to stressful stimuli. The parasympathetic or vagus nerve releases the neurotransmitter acetylcholine to decrease heart rate, calming down the body as necessary. These two nerves work together to keep the heart beating in normal rhythm, and any imbalance in this signaling can lead to an irregular rhythm.
The heart is a life-giving electrical pump.
Every heartbeat is a contraction of the heart muscle, squeezing out oxygen- rich blood to the lungs and the rest of the body through the arteries. These heartbeats are regulated by the heart’s own electrical conduction system, whereby cells in the heart transmit electrical impulses to each other to pump out blood and result in a heartbeat. (It’s these electrical impulses or signals that are measured by an EKG; they’re shown in waves.)
Once the heart receives “commands” from the brain, electrical signaling begins in a group of cells collectively called the sinus node (aka sinoatrial node or SA node), located in the upper right chamber or atria of the heart. When the heart is beating normally, this part of the heart generates an electrical signal about 60 to 100 times per minute. The AV node, located between the atria and the ventricles, controls the passage of this electrical signal from the atria to the ventricles.
Each lightning-fast electrical signal activates first the atria (the two upper chambers of the heart that receive blood from the veins), which then squeeze and pump blood to the ventricles— the two bottom chambers of the heart that pump out blood to the arteries. The blood flows from the atria to the ventricles through valves: the tricuspid valve on the right side of the heart and the mitral valve on the left side.
When the electrical signals that coordinate the heartbeats don’t work properly, an irregular heartbeat occurs. This irregular heartbeat could either be tachycardia, when the heart beats too fast (over 100 beats per minute), or bradycardia, when the heart beats too slow (less than 60 beats per minute).
Atrial fibrillation can be symptomless.
The most common symptoms of AFib include an irregular heartbeat, the sensation of a racing heart (heart palpitations), chest pain, shortness of breath, weakness, a reduced ability to exercise, fatigue, confusion, and/or lightheadedness. Some people experience more than one of these symptoms; others, however, don’t experience any, making them unaware they have the condition.
While an irregular heartbeat isn’t serious on its own, it can trigger more serious problems like a stroke. Instead of forcibly contracting and squeezing blood out of the heart, the heart’s chambers quiver instead of beating, reducing the heart’s pumping ability. Not fully pumping all of the blood out of the chambers can cause the blood to become sluggish, pool, and potentially clot, increasing the risk of stroke. This is why people with AFib have a five times greater risk of stroke than those without the condition. If you have any of these symptoms, it’s important to see a doctor to start treatment and prevent a potential heart attack or stroke.
Your risk increases with age.
The older you get, the more you’re prone to atrial fibrillation. This is why it’s more common in those who are 65 and older. Other risk factors include:
• a history of heart disease, heart attack, heart surgery, or heart valve problems.
• a family history of AFib. If family members have it, you’re more likely to get it too.
• alcohol consumption. Drinking alcohol seems to increase the risk of an irregular heart rhythm.
• obesity. Being overweight can cause an increase in the size of the left upper chamber of the heart. The result: the heart doesn’t work efficiently to pump blood, triggering an irregular heartbeat.
• high blood pressure. Hypertension occurs when the blood flows with more force than usual, pushing on the artery walls and forcing the heart to work harder. Over time, this causes the heart muscle to thicken and stiffen. The result: electrical signals can’t move through the heart as easily, causing an irregular heartbeat.
• chronic conditions such as thyroid problems and sleep apnea can increase your risk. When it comes to the thyroid—a small butterfly-shaped gland
in the neck—too much thyroid hormone (a condition known as hyperthyroidism or overactive thyroid) can increase heart rate, causing palpitations and abnormal heart rhythm.
Sleep apnea occurs when breathing stops or becomes too shallow during sleep for up to ten seconds at a time reducing the flow of oxygen to the brain, the body, and the heart. Some experts believe that mechanical stresses and chemical changes occur in the heart each time a person is startled awake by a lack of oxygen, contributing to AFib. Kidney disease can also trigger AFib as can diabetes and lung disease.
Atrial fibrillation is treatable.
There are different treatments your doctor may discuss with you:
• Ablation: a procedure used to remove or get rid of faulty electrical connections in the heart that may be triggering an irregular heartbeat or arrhythmia.
• Antiarrhythmic medications: medications used to maintain a normal heart rhythm and reduce blood pressure. These interfere with the effect of hormones like adrenaline on the heart’s cells and stop electrical impulses that trigger irregular heartbeats.
• Beta blockers: medications used to control heart rhythm, as well as to treat angina, or chest pain, and reduce high blood pressure. These block the effects of the hormone epinephrine (aka adrenaline) on the heart.
• Blood thinners: medications that prevent blood from clotting, thereby preventing heart attack and stroke (a risk factor for
AFib). These work by blocking or weakening vitamin K, important for blood clotting; by impeding proteins or enzymes that cause blood cells to stick together forming blood clots; or by keeping platelets (blood cells that form clots) from sticking together on the walls of blood vessels.
• Calcium channel blockers: medications used to control heart rate by relaxing and opening the arteries, making it easier for the heart to pump blood and reducing blood pressure. These prevent calcium from entering the cells of the heart and arteries (calcium triggers the heart and arteries to contract, or squeeze out blood).
• Cardioversion: a treatment used to reset the heart rhythm either by electric shocks through paddles or patches attached to the chest or through medications given intravenously or by mouth.
• Digoxin: a medication that improves the strength and efficiency of the heart, helping to control AFib. It’s commonly taken with calcium channel blockers or beta blockers. Digoxin affects sodium and potassium levels inside heart cells to reduce strain on the heart, thereby slowing down and controlling heart rate.