GRID VIEW
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Electricity is essential for most modern-day activities. We use it for lights, air conditioning, and watching cat videos. We also use it to keep our hearts beating. Electricity coordinates the heart and causes it to contract into its familiar wub-dub. Why do we need electricity in the heart, and what can we do when the zips don’t zap properly?
Shockingly, we’ll start with a broad overview. The heart is an organ made of several billion cells. These are organized into many structures, including chambers. There are two small upper chambers called atria, which is the plural word for the left atrium and right atrium. There are also two large lower chambers called ventricles, which are again separated into left and right. The set on the left pumps fresh, oxygenated blood from the lungs to all the cells in the body. The set on the right pumps deoxygenated blood to the lungs to get more oxygen. It is a little strange to describe the heart only as a series of chambers, as the actual structure of the heart is a giant, very strong, coiled muscle. In order for muscles to contract and produce power, electricity is needed. Electricity tells the muscles they need to move. In most of the body, the electrical signals for muscles to contract are delivered by the brain. The heart is a little different.
The heart is involuntary, meaning we have no direct control over when it beats. We can send signals to the heart by breathing deeply or jumping, but the electrical signal that tells the heart to beat comes from within the heart itself. Near the top is a collection of cells called the sinoatrial (SA) node. Here resides a group of cells called pacemaker cells. These cells produce a small electrical zippy zappy signal around once per second. This signal rapidly amplifies and spreads throughout the atria, causing them to contract. This spreading comes out like a wave, which allows all the atrial muscle cells to contract in a big, coordinated manner. Soon after, the signal travels through the atrioventricular (AV) node into the ventricles, propagating outward. This takes a fraction of a second, so we hear wub-dub instead of just one big beat. This also gives blood time to travel from the atria to the ventricles, ensuring it goes correctly.
This system is pretty amazing, but it’s not foolproof. Many things can go wrong. The electrical signal might be disrupted, the heart might be too slow, or it might beat at a bizarre rhythm. When this happens, the heart pumps less efficiently than it needs to, and sometimes can’t pump enough blood for oxygen to get around the body. Unlike a heart attack, where heart cells die immediately, electrical problems can often be alleviated. When the electricity in our heart doesn’t behave correctly, we can put in artificial electricity.
When the heart’s pacemaker cells aren’t successfully sending coordinated signals to the whole heart, an artificial cardiac pacemaker (often just called a pacemaker) can be implanted. Temporary pacemakers may sit outside the body, but permanent ones are installed inside our body cavities. These are made of materials our bodies don’t find threatening, like titanium. They can be attached to the heart through wires called leads, mounted on the heart surface, or inside the heart muscle. Each patient will have electrical problems in specific areas; maybe the pacemaker cells aren’t working properly, or maybe electricity can’t travel to the ventricles, or maybe it can’t cross from the left to the right side. Because of this, pacemakers can attach to either an atrium, a ventricle, or to both ventricles.
Because the electrical problems are so varied, artificial pacemakers have many different patterns for firing. Artificial pacemakers don’t just cause beating; they also detect it. Little electrodes can tell when the heart has fired, and internal circuitry can measure this against when the cardiologist thinks a beat should have happened. Most will detect when a shock is needed and fire on demand, but some fire all the time. Pacemakers can respond to changes in heart rate, can sense abnormal rhythms, and have special modes for things like surgery. On top of all of this, medical professionals can often remotely monitor artificial pacemakers and adjust the pacemaker’s programming without surgery! This can be used to make sure heart rhythms stay ideal, but can also help alleviate the side effects of artificial pacemakers, which include chest pain, dizziness, fatigue, and shortness of breath. Pacemakers are amazing wonders of the modern era. As time goes on, scientists are developing new and more specific programs to zap the heart without zapping our fun. It’s nice to know that when you watch a video of a funny cat falling off the dresser, electricity makes your heart happy inside and out.
Staff Writer / Editor Benton Lowey-Ball, BS, BFA
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References:
Buckberg, G. D., Nanda, N. C., Nguyen, C., & Kocica, M. J. (2018). What is the heart? Anatomy, function, pathophysiology, and misconceptions. Journal of cardiovascular development and disease, 5(2), 33. https://www.mdpi.com/2308-3425/5/2/33
Lak, H. M., & Goyal, A. (2020). Pacemaker types and selection. https://www.ncbi.nlm.nih.gov/books/NBK556011/
Sundnes, J., Lines, G. T., Cai, X., Nielsen, B. F., Mardal, K. A., & Tveito, A. (2007). Computing the electrical activity in the heart (Vol. 1). Springer Science & Business Media.
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I recently went to a dessert party. That’s a party where everyone brings a dessert. I, naturally, arrived with cookies while others brought cakes and pies. Surprisingly, there was one attendee who presented a bowl of berries, another who showcased a sweet potato casserole, and a third who simply brought avocado with a dash of salt. Do these all count as desserts? What is a dessert? A word that was clear at the outset was quickly confusing in how broad it was. Unfortunately, that confusion can also happen with medical terms. Take cardiovascular disease. It’s got something to do with the heart, but sometimes it includes strokes in the brain. So what is cardiovascular disease?
“Cardiovascular” is a word made of two component parts: cardio- means “heart” and vascular indicates blood vessels. Together, cardiovascular disease is that which affects the heart and/or blood vessels. The heart and blood vessels carry oxygen to the cells and keep them alive. Since we’re made of cells, keeping them alive is pretty important. Therefore, the heart and blood vessels are also quite important, and cardiovascular disease can be dangerous if not managed.
Cardiovascular disease is more common than apple pie in the United States. Data from the CDC show that nearly HALF of adults over 20 have some form of cardiovascular disease. With a prevalence that high, it’s no surprise that cardiovascular disease is the leading cause of death in America and around the world. Unfortunately, as noted above, the exact definition of “cardiovascular disease” is very broad. In researching this article you are currently reading, I consulted the World Health Organization, the American Heart Association, and the National Institute of Health (part of the CDC). These organizations listed the various diseases included in cardiovascular disease, and only agreed on two conditions:
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- Coronary artery disease – when the blood vessels to the heart are narrowed by plaques
- Cerebrovascular disease including stroke – where the vessels to be brain are blocked
Other diseases that at least two agreed on include:
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- Arrhythmia – an irregular heartbeat
- Congenital heart defects – heart defects occurring from birth
- Heart attack – also called a myocardial infarction, where the blood flow to the heart is blocked
- Hypertension – high blood pressure
Though all these diseases may seem different, they are all part of the same system. Narrow blood vessels to the heart or brain cause oxygen loss. This narrowing can be caused by plaque formed when cholesterol lodges in the vessel wall. If some of this plaque dislodges, it can lead to heart attacks and strokes. Irregular heartbeats and heart attacks can lower the amount of blood (and oxygen!) delivered around the body. Hypertension stresses the whole system and can lead to heart attack, stroke, and damage to other organs like the kidneys. Additionally, they may have similar risk factors, outcomes, and treatments.
There is a genetic component to cardiovascular disease. This is evident with congenital heart defects, which occur during development. It is also evident looking at who is at risk of developing cardiovascular disease. African Americans are at the highest risk, while people who identify as Hispanic have the lowest risk. Big modifiable risks include cholesterol, smoking, and hypertension (which is itself a form of cardiovascular disease!). Other risks include diabetes, being overweight, poor diet, low exercise, alcohol consumption, and low sleep. Research is ongoing into the cycle of mental health and cardiovascular disease as well. Mood and anxiety disorders, PTSD, and chronic stress can cause direct damage to the cardiovascular system while simultaneously increasing behaviors that compound the danger, including smoking and failing to take medicines.
Lowering the modifiable risks above is, unsurprisingly, one of the best ways to fight cardiovascular disease. Managing cholesterol, blood pressure, and diabetes can help. Cutting smoking and lowering alcohol intake can make a big difference. Getting help with mental health (and getting a good night’s sleep) may help your heart relax as well. Maintaining a healthy weight through a good diet and dynamic exercise is vital. Unfortunately, without management, cardiovascular disease is more like a desert than a dessert: it can kill you.
Staff Writer / Editor Benton Lowey-Ball, BS, BFA
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References:
Centers for Disease Control and Prevention. (July 19, 2021). Coronary artery disease (CAD). U.S. Department of Health and Human Services. https://www.cdc.gov/heartdisease/coronary_ad.htm
National Center for Chronic Disease Prevention and Health Promotion, Division for Heart Disease and Stroke Prevention. (May 15, 2023). About heart disease. U.S. Department of Health and Human Services. https://www.cdc.gov/heartdisease/about.htm
American Heart Association. (May 31, 2017). What is cardiovascular disease? https://www.heart.org/en/health-topics/consumer-healthcare/what-is-cardiovascular-disease
Tsao, C. W., Aday, A. W., Almarzooq, Z. I., Alonso, A., Beaton, A. Z., Bittencourt, M. S., … & American Heart Association Council on Epidemiology and Prevention Statistics Committee and Stroke Statistics Subcommittee. (2022). Heart disease and stroke statistics—2022 update: a report from the American Heart Association. Circulation, 145(8), e153-e639. https://www.ahajournals.org/doi/full/10.1161/CIR.0000000000001123
National Heart, Lung, and Blood Institute. (n.d). Heart and vascular diseases. U.S. Department of Health and Human Services. https://www.nhlbi.nih.gov/science/heart-and-vascular-diseases Accessed on September 12, 2023.
The World Health Organization. (June 11, 2021). Cardiovascular diseases (CVD). https://www.who.int/news-room/fact-sheets/detail/cardiovascular-diseases-(cvds)
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When EMTs arrive on the scene of an emergency, they have to remember their ABCs. These are Airway, Breathing, and Circulation. The absolute top priority for any patient is to ensure they have an open airway to breathe, that air is entering the lungs, and that the heart is pumping blood to the brain and other organs. This is also the most important thing our body does in daily life as well. We can go weeks without food, days without water, hours without ice cream, and minutes without oxygen.
In order to get oxygen from the lungs to our brain and organs, we rely on one of the most remarkable organs in our body: the heart. The heart pumps automatically, nonstop, 24/7, from womb to grave. It consists of four chambers, two on top, and two on the bottom. Each heartbeat pulls blood into the top two chambers and pumps it out of the bottom two. The bottom two are more muscular and do the heavy lifting. Unfortunately, the heart can deteriorate and lead to heart failure.
Heart failure is a condition where the heart can’t pump well enough to deliver oxygen to the organs effectively. The heart is still pumping, but organs are not receiving enough oxygen to function. This is not good. Heart failure affects over six million Americans and ten times as many people worldwide. Risk factors for heart failure include:
- Heart disease, including Coronary Artery Disease
- High Blood pressure
- Tobacco
- Excessive alcohol
- Poor diet
- Lack of exercise
- Obesity
- Diabetes
Heart failure has several signs and symptoms. Some of the most consistent are edema and shortness of breath. Edema is fluid trapped in the body’s tissues and most often pools in the lower extremities and the abdomen. Shortness of breath is due to the heart failing to deliver enough oxygen. This is particularly prevalent when trying to do activities or when lying down. Shortness of breath can keep patients from exercising or sleeping, which only exacerbates problems. Patients who have limited exercise in their routine may not be aware of progressive difficulty, masking this important symptom.
Other symptoms can be broad and nonspecific. They include:
- Sudden weight gain
- Persistent coughing or wheezing
- Lightheadedness and fainting
- Depression
- Nausea and loss of appetite
- Irregular heartbeat, high pulse, and palpitations
- Fatigue
If you have heart failure and find yourself experiencing several of these conditions simultaneously, especially with edema and shortness of breath, we urge you to contact your physician immediately. Additionally, you may want to keep track of your level of fatigue because this symptom increases as the heart failure progresses. The excellent news is that new and exciting monitoring devices are currently being developed to help patients manage their heart failure and determine if their condition is deteriorating.
Check out clinical research options available to you with ENCORE Research Group on our enrolling studies page.
By Benton Lowey-Ball, BS Behavioral Neuroscience
Sources:
Albert, N., Trochelman, K., Li, J., & Lin, S. (2010). Signs and symptoms of heart failure: are you asking the right questions?. American Journal of Critical Care, 19(5), 443-452. https://doi.org/ajcc2009314
Groenewegen, A., Rutten, F. H., Mosterd, A., & Hoes, A. W. (2020). Epidemiology of heart failure. European journal of heart failure, 22(8), 1342-1356. https://doi.org/10.1002/ejhf.1858
U.S. Department of Health & Human Services/Centers for Disease Control and Prevention (October 14, 2022). Heart failure https://www.cdc.gov/heartdisease/heart_failure.htm
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Heart failure is quite frankly, a terrifying sounding condition. It is severe, but not as immediately drastic as it sounds. Put simply, heart failure is when the heart fails to pump as much blood as the body will need long-term. The heart works like a balloon, filling with blood and contracting to pump it out. Ejection fraction is a term used to describe the amount of blood pumped out compared with the total the heart can hold. In a normal heart, 50-70% of blood is ejected with each heartbeat. When this amount falls below 40%, a person has a reduced Ejection Fraction (the rEF of HFrEF). This is a serious condition.
The heart pumps blood to every cell in the body. This is how cells receive oxygen and nutrients, and how they get rid of waste products. Without enough blood, cells suffocate. Oxygen isn’t reaching cells and the brain interprets this as being short of breath. Common symptoms of HFrEF include:
- Fatigue
- Difficulty breathing, especially when lying down or sleeping
- Inability to exercise
- Ankle swelling
Inside the body, doctors can also look for diagnostic markers. These may include structural changes to the heart and increased natriuretic peptides. Natriuretic peptides are hormones that regulate the amount of salt and water in the blood. They act as vasodilators, opening blood vessels which can be helpful in compensating for heart failure. The body attempts to compensate for the loss of oxygen and nutrients in the blood in many ways, but long term the body has trouble sustaining with heart failure.
Who is at risk of developing HFrEF? Unfortunately, it is more prevalent in the United States than almost anywhere else, affecting 6.5 million Americans each year. Risk factors include age, being male, obesity, and smoking. Additionally, other medical conditions increase your risk of developing Heart Failure with reduced Ejection Fraction. Previous heart attacks, coronary heart disease, diabetes, and hypertension are some associated conditions. All told, HFrEF leads to around a million hospitalizations every year, and being hospitalized for HFrEF comes with a low 5-year survival rate.
What can be done? There are several methods of dealing with a reduced ejection fraction. Some methods treat symptoms, such as diuretics, and others can help reduce mortality, such as beta-blockers. There are several other medications and even some implantable devices that can help with HFrEF. These can help improve your ejection fraction or health outcomes but are not yet a silver bullet. New medications with increased outcomes and fewer side effects are entering clinical trials and may help with the underlying condition. To learn more about current heart failure research options, call our office today.
Written by Benton Lowey-Ball, BS Behavioral Neuroscience
Bloom, M. W., Greenberg, B., Jaarsma, T., Januzzi, J. L., Lam, C. S., Maggioni, A. P., … & Butler, J. (2017). Heart failure with reduced ejection fraction. Nature reviews Disease primers, 3(1), 1-19. https://www.nature.com/articles/nrdp201758
Martinez-Rumayor, A., Richards, A. M., Burnett, J. C., & Januzzi Jr, J. L. (2008). Biology of the natriuretic peptides. The American journal of cardiology, 101(3), S3-S8. https://doi.org/10.1016/j.amjcard.2007.11.012
Murphy, S. P., Ibrahim, N. E., & Januzzi, J. L. (2020). Heart failure with reduced ejection fraction: a review. Jama, 324(5), 488-504. https://doi.org/10.1001/jama.2020.10262
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November 7, 2024