Atrial fibrillation is a disturbance in the normal process for awakening a heartbeat.
The heart is separated into two upper chambers (atria) that receive blood and two lower chambers (ventricles) that forcefully eject blood into arteries. The movement of upper and lower must be coordinated to achieve an effective heartbeat. Thus, each beat is complex and highly organized, beginning with an intrinsic biological bandleader known as the sinus node.
Without external influence, the heart repeats the motions of a beat unceasingly unless it is deprived of energy. The sinus node is at the topmost point of the heart, where it functions like a clock to undergo a periodic electrical change. That change spreads outward from cell to cell and awakens atrial muscle, causing it to contract and gently coax blood into the ventricles. The awakening does not spread directly to the lower chambers because heart muscle cells of the atria are separated from the heart muscle cells of the ventricles in all but one location.
When the electrical awakening reaches the center of the heart, between the two upper and two lower chambers, it arrives at another focus of special heart cells called the “junction” or Atrio-Ventricular (AV) node. The junction spreads out into the ventricles as a specialized network of cable-like cells that pass along the awakening and coordinate the muscular action of these pumping chambers.
The natural basis for the timing with which the sinus node drives the heart is based largely upon the mechanical coupling between the heart and arteries. Eons of evolution have tuned the heart’s rhythm to match perfectly with dance of the bouncy, springy arteries that it fills. However, the tempo of the node also changes to match the mood of the body, synthesized from needs, hormonal urgings (such as adrenalin) and the brain’s commands.
In atrial fibrillation, a single point in the atrium is no longer responsible for awakening. There may be many points awakening independently of each other, no longer clockwork in their behavior. Alternatively, the electrical message that spreads through the atria may get caught in a circle, like a dog chasing its tail or the message may become fractured as it spreads. In any case, the atria are undergoing a constant electrical change that is roiling and chaotic like bubbles of boiling water. Facing such noise from above, the junction is overwhelmed. Its design is to pass along a message, but only a fraction of the chaotic messages of atrial fibrillation are allowed to pass through.
A heart driven by atrial fibrillation is robbed of order and efficiency to beat with erratic haste. It no longer responds to the body’s wants and needs. The effect is to sap stamina from the healthy and make the ill worse.
The sensation most commonly bringing atrial fibrillation to light is an awareness of the heartbeat. It may be described as a fluttering inside of the chest, the movements soft and irregular. This is in contrast to the regular pounding of a heart driven by exercise or fright.
If you lie motionless and pay close attention, you will feel your heart break the calm. The heart makes a tight fist that tilts and moves about in the chest while at its task. The whole body moves with it. The movement is generally ignored because our brain has the ability to filter sensations that are regular, consistent or expected. Perception of these sensations requires concentration.
During severe infection or under the influence of invigorating hormones, like that of the thyroid gland, the heart rate remains high at all times, often more than 100 beats each minute. Although there may be a generalized sensation of being ill at ease, the heart rate is rarely the focal point. In someone with low blood counts or with a heart that is severely diseased, blood delivery and heart rate at rest may be sufficient but reserve is immediately spent with the slightest movement. There is no place to call upon for reserve blood flow to the body but an increase in heart rate. For many people in these extremes, a hunger for breath is a more pressing concern than the pounding heart.
Irregularity is the principle indication that atrial fibrillation may be present. However, irregularity may be easily ignored. An occasional, brief change in the heart’s rhythm, for one beat or so, is universal. Like a missed musical note, attention to it is fleeting. The heart rate during or between episodes is normal. A single mistimed beat is usually described as extra because it originates from somewhere other than the heart’s normal bandleader. The off-timed work of the heart may occur with such short notice that no blood has been able to enter the main pumping chamber. The resultant heartbeat passes along no, or minimal impulse to the arteries. One may feel as if the heart had stopped, or the need for and act of a short intake of breath. In some, the pause is unnoticed, but the following beat produces discomfort. The bandleader, momentarily stunned by the effrontery of this “other” part of the heart that has chosen to speak, pauses. The intermission allows time for extra blood to enter the heart, making the next beat more forceful. The sensation has been described as an instant of fatigue, of breathlessness or as though the heart had “flopped” inside of the chest.
Atrial fibrillation is a sustained irregularity. The sensation accompanying its presence is often described as fluttering, racing, hammering, or even a “glimmer”. It is disquieting, if not uncomfortable. Anxiety accompanies the irregularity causing restlessness, while urging stillness. At onset, many will sit upright, as if at attention, soon changing position, seeking comfort that will not come, while the dominant hand unconsciously seeks the chest. Sweat comes to the brow and a breath will simply not make it all the way in. In some, the strangeness compels them to test its gravity by walking about, albeit cautiously. The loss of cardiac efficiency is sudden and may be profound. Any physical activity will require greater effort resulting in the sensation of fatigue. A day may seem to drag on without end and soon it becomes apparent that the night holds no promise of rest.
At first, such episodes may be brief. Someone who appears pale, breathless and seemingly incapacitated in one moment may look and feel quite normal an hour later. The sense of normality may last days, weeks, even months so that with the next occurrence, the prior event is a vague memory. Intermittence and our natural tendency to minimize sensations that have passed without a specific remedy are part of the reason that atrial fibrillation may be intermittently present for years before it is discovered.
Stay tuned for more on ATRIAL FIBRILLATION.
Say coronary artery disease in a crowded room and very soon the conversation will turn to surgery and stents: who got one, who needed one and the inevitable, who was perfectly fine until it was found that one of these procedures was necessary. You may wonder how things could get so bad that you need an operation without realizing that there is any problem and how the decision to recommend a stent or bypass surgery comes about.
Does every narrowed spot in the coronary arteries have to be treated to prevent a heart attack?
The answer has changed quite a bit over the past 40 years because the understanding of coronary artery disease has changed. At the dawn of the 20th Century, coronary artery disease was thought to be a gradual encrustation of arteries that choked off heart muscle, much like the corrosion of the pipes in your home. The treatment seemed obvious. When the narrowing gets bad, clean it out or go around the problem. Deliver blood where it is needed and heart attack will be prevented.
It took about 50 years for bypass surgery to come to fruition and it worked. The operation was a grand success. People who had the surgery were relieved of the symptoms of coronary artery disease. Some of them even lived longer than they might have otherwise. However, the surgery was not very effective in preventing heart attacks. With a little more observation came the irony. Even though the operation became a very important part of the treatment of coronary artery disease, the idea that drove the development of the procedure was not completely accurate.
It’s not always the devil you know…
For many years and even most of the time today, coronary artery disease was discovered because it caused symptoms. It made someone short of breath during usual activities or it created chest discomfort with movement or anxiety. In any case, a narrowed artery brought the disease to recognition and a narrowed artery was what everyone thought needed to be addressed.
What we know today about Atherosclerosis is that the disease that gets into the walls of your arteries is substantially different from the corrosion of your plumbing. The first difference (or maybe it’s a similarity) is that if the disease is at one place, it is almost certainly everywhere else as well. Where one narrowing is discovered, there are ten other places in the artery that have disease as well, but are not narrowed. Atherosclerosis rots the walls of arteries from within, simmering for some time before obstructing the channel for blood flow. Therefore, where a narrowing of an artery is discovered is just the tip of the iceberg, quite literally.
The second and most important difference is that any site in the arteries where disease is present can become very inflamed and make blood clot. This means that arteries may become narrowed or closed in an instant, anywhere. The spot in an artery likely to cause a heart attack may be the narrowed spot that is visible or, more often, some other diseased site with no visible narrowing at all before the blood clot forms. This is the reason that bypass surgery was not a very effective protection from heart attack for most people.
This does not mean that bypass surgery and stents are not useful. It just means that, under most circumstances, surgery and stents are not used to prevent heart attack. About 1/3 of people with chest discomfort due to coronary artery disease are unhappy with symptom control. Despite the use of medicines, chest discomfort prevents normal daily activities, rising and grooming in the morning or even taking a short walk. Facing such limitations, the choice to have a procedure performed is driven by the wish to resolve symptoms.
The hobbled heart
Heart muscle that is repeatedly shorted in its energy supply weakens and participates less in every heartbeat. Over time and with more than one artery narrowed, large segments of heart muscle may weaken substantially, hobbling the heart’s ability to pump blood. There are many people who have more than one narrowed artery by the time that their problem is first recognized. Months, or maybe years of little physical activity allow the disease to silently tighten its noose. When the heart is rarely asked to work hard, it will hardly warn of its jeopardy. The danger of disease that has reached this point is that a bleeding ulcer, a case of the flu, an angry gall bladder or worse, a tiny heart attack that might have been survived will all prove much more difficult to face than would have been the case with a heart that could pump normally.
A heart that is hobbled can be recognized, even when chest discomfort does not warn of a problem. This is the basis for the exercise tolerance test (ETT). Sometimes referred to in error as an exercise treadmill test, measurement of physical fitness can be performed with a treadmill, bicycle or virtually any type of exercise. The goal is to uncover hidden limitation that may be due to heart disease. Alternatively, there are several methods used by physicians to measure the heart muscle’s strength. When physical fitness and/or the strength of the heart muscle are abnormal, the next heart attack or other major illness will be trouble.
Restoring normal blood flow to heart muscle may allow it to recover. That means that any future illness may be faced with a heart that is more capable of doing its job and the next heart attack might just be survivable. Stress tests and measurements of the heart’s strength are the tools used to identify the hobbled heart that may improve with a repair of its arteries. This does not mean that every person with limited exercise capacity or abnormal heart strength needs surgery. No two people with severe coronary artery disease face exactly the same challenges or have exactly the same wants, needs or concerns. Therefore, the most important aid for the decision to undergo stent or bypass surgery under these circumstances is the advice of a trusted physician.
Unstable: The devil you know.
There is one setting where a specific site in an artery can be recognized as the potential source of a heart attack. That setting is unstable disease. When an angry artery causes blood to clot, the blood clot takes a life of its own. It may grow rapidly and close the artery. The result is a heart attack. Just as often, the blood clot grows rapidly, but only to the point that it narrows the artery severely and stops there. Heart muscle may not suffer severe damage. Instead, the result is symptoms that get increasingly worse, often to the point that they will appear with little or no effort. The problem with a blood clot is that it is completely unpredictable. Having narrowed the artery and come to the precipice of a heart attack, the blood clot may stop and heal. On the other hand, it may not. If the decision is not, then anytime from the first change in symptoms until about two months later, the clot may grow again and fulfill its capacity to cause that heart attack.
Someone with symptoms that have just appeared for the first time, or that occur at rest or are worsening may have a blood clot that ceased its growth for a time. Symptoms like this are called “unstable” because they may represent the unstable behavior of a blood clot. Within thirty days of the onset of unstable symptoms, the chance of a major problem or damage to the heart is about one in three.
Medication can usually calm a blood clot and stop its growth. However, when symptoms persist or there are other signs of potential danger, the artery may have to be treated with a stent or bypass surgery. Under these very specific circumstances, treating the narrowed site in an artery to improve blood delivery can, in fact, prevent a heart attack.
The abbreviated version is: When symptoms are unstable, call your physician. The narrowing responsible for symptoms may need treatment. He or she may want to perform testing to assist in that decision. When no symptoms are present, or when symptoms have been the same for quite some time, any narrowing that is present is already healed. The decision to have treatment beyond medication depends upon the outcome of testing that your physician has requested and your discussion with him or her about control of symptoms.
The essential treatments for coronary artery disease and heart attack are to maintain our body’s inner environment near design conditions with a controlled diet, regular physical activity, weight management and carefully chosen medications. The most basic aspect of that treatment, the part that applies to everyone, is to follow a healthy lifestyle.
Surgical bypass and stent-assisted angioplasty of severely narrowed arteries are extremely important tools to restore normal blood flow to heart muscle. Either can be used to relieve changing or unstable symptoms and potentially derail a heart attack in evolution. In someone who has stable symptoms, or none at all, invasive treatments are needed only if symptoms are unmanageable with medication or when disease is crippling the heart’s ability to perform.
Realizing what arteries do...
If we take the wayback machine to well... wayback, people didn’t know how the heart worked, what arteries do or even that their dysfunction could cause disease. Of course, people have been talking or writing about arteries for millenia. At first, arteries weren’t really seen for what they are. They were felt as the pulse. Chinese physicians pored over the pulse to seek any clue to internal disquiet. Was it fast, slow, regular, irregular, strong or weak? Did it push hard or simply tap and how did it change? Greeks physicians were equally interested but only briefly and moved on to other pursuits. On both fronts, there were some interesting observations. They gave pulses a host of clever names (some of which we still use) and realized that something about the pulse was important. They just were not certain exactly what that important thing might be.
The general sense of things (in this discussion, things are the heart and arteries, mostly) went something like this. From food and air, our bodies somehow distilled an essence that fueled life. This mixed in blood which contained life’s most basic and necessary essence. Blood moved, partly of its own accord. It animated the body and provided the fuel for physical activity. In doing so, blood also provided the essential nature of what we are, how we feel and behave. The dispensation of life into the body could be felt in the pulse. The heart was somewhere in this mix. Exactly what it was doing wasn’t completely clear. Altogether, this scenario is pretty decent guesswork, considering that there was not a wealth of information to guess from.
Leonardo looks for life and points at arteries
Fast forward to the Renaissance. By this time, most people who were interested in the human body had taken the old understanding of how things worked and found the explanations to be seriously wanting. In part, this was because many of the “experts” expounding upon how things worked liked to sprinkle their writing with personal opinion and some seriously bizarre ideas. The weight of crazy so badly encumbered explanations of the natural world that the scientific method of thought was born. Scientific method meant that if you wanted to put forth an idea, you had to let other people–who might not buy your explanations or even like you–test it and make fun of you when you were wrong.
Leonardo da Vinci (just Leonardo apparently) was of this time. In some respects, he probably is the best representative of this time, in that he observed, he described and he explored ideas by putting them to the test. One of his most important contributions to the new way of thinking was to accurately describe normal and variant human anatomy. His beautiful drawings capture his exploration of the mechanics of how and why different parts of us work as they do.
At the time, there was a general understanding that blood moved through the body with arteries as the highways. The heart was in some way integral to the process, but the mechanics were a mystery. In Leonardo’s drawings and writing concerning circulatory anatomy, it is clear that he knew of heart valves, that blood really went in only one direction and that arteries were responsible for the distribution of energy. With energy, he included the body’s heat, the still undefinable essence of life because it was all too clear that, should blood escape through an open artery, the heat of life would go with it.
Famously curious and undoubtedly consulted to explain any mystery, Leonardo’s interest was piqued when he was offered the opportunity to examine an old man who had died peacefully. His purpose was to find where life’s heat escaped at a peaceful end. He examined the anatomy in great detail and reported his observations and musings. From the many observations, one stands out as the beginnings of an idea. Leonardo reported that the supple, straight vessels of youth had been thickened, gnarled, and bent with age, leaving little room remaining for blood.
In today’s world, we would interpret this description as evidence of arterial disease. The old man died peacefully, probably having a heart attack as he slept. Thickened and deformed arteries probably signified more than simply age, but also atherosclerosis, the disease of arteries that plagues so many of us. No one really knows what conclusions Leonardo drew from his observations about arteries. He may very well have believed that part of our aging is an attenuation of the channels blood can take to keep us moving and alive. What is most important is that his observations represent the the first inkling that arteries might fail of their own accord and cause disease.
Within a relatively short time (in historical terms) arterial failure would be seen more clearly and blamed for an odd type of chest discomfort that eventually became known as heart attack.
A short time ago, my email inbox contained a query from one of those online information sites. The question posed was, “Do stents prevent heart attack?” My initial impulse was to ignore the question altogether. It is too broad and too general for a simple answer. But then again, it is exactly what most people who are worried about coronary artery disease would like to know the answer to. What makes the question so difficult is that the answer is different, depending upon your perspective. This was my attempt at a reasonably complete, but concise answer.
The short answer
Yes. Without question, placement of a stent is an important part of the treatment options to prevent a heart attack. However, the complete answer is important.
The long answer
A stent is used to reduce narrowing, open an artery and improve blood flow to heart muscle. For everything, there is a season and for the stent, that season is when the heart is in need of rescue.
In order to review the idea of rescue as it pertains for stents, two major concepts require definition. They are angina and stability.
A narrowed artery to the heart may cause symptoms of chest discomfort during physical activity, with anger or other types of emotional stress. The particular type of chest discomfort (an uncomfortable uneasiness that doesn’t always hurt) is called angina pectoris, or just angina. The symptoms usually mean an artery is narrowed, but don’t tell you what the narrowing is made of.
When people experience angina, the discomfort may follow different patterns. The pattern of symptoms provides a clue as to what a narrowing that is causing the symptoms might be made of. Symptom patterns are generally condensed for descriptive purposes.
To the point of our discussion, some people have discomfort that they have noticed for at least two or more months. The discomfort is fairly consistent in its return with repetition of specific physical activity; for example walking up a hill or sweeping a room. This is called stable angina. “Stable” symptoms, or stable angina, is usually an indication that the narrowing responsible for the symptoms made of scar tissue. Scar tissue is relatively dormant and unlikely to change rapidly causing a heart attack.
On the other hand, some people experience symptoms that they have never felt before, that come on for no reason, or keep going away only to return slightly worse. These symptoms are said to be unstable. Unstable symptoms suggest that a blood clot is part of the narrowing responsible for symptoms. Blood clots are unpredictable, prone to grow very rapidly and are the cause of most heart attacks.
The important point is that the pattern of symptoms, stable or unstable, provides the indication as to whether or not a heart attack is threatened.
People who have stable symptoms are not facing imminent harm. Stable symptoms that are encountered only during time of great effort are easily managed. On the other hand, some people with stable symptoms find it difficult to shower and groom in the morning without stopping to rest. A person who is so limited, even after trying medication, may seek a rescue from his or her disease-imposed prison. By restoring blood flow to heart muscle and relieving symptoms, a stent may hold the key to that prison. This is very much a rescue and the proper use of a stent. However, the use of a stent for this purpose does not prevent a heart attack.
People who have unstable symptoms face the threat of a heart attack in the very near future. In fact, in some, the unstable symptoms are an indication of a heart attack that is under way. Since the heart is being damaged by a misbehaving artery, it is in need of rescue from harm. This is the type of rescue where a stent can stop or prevent a heart attack. Unstable symptoms fall into three major categories.
ST-segment Elevation Myocardial Infarction (STEMI) is a heart attack that is immediately apparent on an EKG. The diagnosis is recognized while damage is underway, triggering emergency treatment. Medicines that dissolve clot (Thrombolytic drugs) can be given very quickly. In hospitals with the capacity to perform emergency angioplasty, a balloon procedure and stent placement is preferred over thrombolytic drugs.
Non-ST-segment Elevation Myocardial Infarction (NSTEMI) is a heart attack that was not apparent on an EKG and recognized only after the fact by finding blood-test evidence of heart muscle damage in someone with unstable symptoms. Thrombolytic drugs are not useful, but rescue treatment with other medications, stents or sometimes surgery may be necessary to prevent additional damage and to speed healing.
Unstable Angina (USA) refers to unstable symptoms without evidence of a heart attack on the EKG or blood testing. The evidence of an unstable artery in need rescue is the discovery of a severely narrowed coronary artery that explains the unstable symptoms. In someone with unstable angina, placement of a stent, in addition to equally important medical therapy (cholesterol lowering, blood pressure control, diabetes control, aspirin and related drugs) unquestionably prevents heart attack.
For more information, stay tuned for “Heart Attack: The science and the story of what it is, why it happens and what to do about it.”
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