An Overview of the EKG
The Electrocardiogram (EKG) has been an immensely useful and practical tool in cardiology for over 120 years. Its longevity is amazing if one considers how quickly new technological advances make older tests completely obsolete.
EKG Machines show the heart’s electrical activity, printing the “spikes” on paper for the doctor to read.
EKG provides a snapshot of the heart's electrical activity. Human heart is an amazing high-tech organ that does a lot more than simply pumping blood through our arteries. The heart cells that do this heavy-labor, mechanical work will not function unless there is an electricity current flowing through them. The part of the heart that creates electricity (out of nothing!) is called the sinus node and is located in one of the upper chambers of the heart (the right atrium). It then spreads to the rest of the heart, including the bottom chambers (the ventricles) where the “heavy lifting” and pumping of our heart occurs. In case the sinus node cannot function properly, other heart cells can take over the electrical production, although not quite as efficiently as the sinus node can. If none of the heart cells can create the needed electrical beat then a pacemaker may become necessary.
The EKG reveals the electrical activity in the heart, but why is this so important? What can the heart's electrical activity tell us about our health? It can first tell us whether the heart rhythm is normal or abnormal: is the rhythm too fast? Too slow? Are there any extra or skipped beats or is the rhythm completely erratic, like in atrial fibrillation? Beyond information about the heart’s rhythm, the EKG allows us to diagnose previous heart attacks or, indirectly, severely clogged heart arteries. If a large part of the heart has been damaged by a previous heart attack that part is electrically silent and shows up on the EKG. The pattern of the heart's electricity also changes in hearts that, because of clogged arteries, receive less oxygen. This is how the stress test (also referred to as a treadmill test) can help diagnose heart disease: by recording the EKG of a patient who walks briskly on a treadmill for a few minutes while attached to an EKG monitor, the EKG pattern reveals any serious oxygen shortage to a large part of the heart. Consider that at a normal, resting heart rate, an 80-90% blockage in the arteries is usually not obvious on the EKG as the demand of the resting heart for oxygen is so low that a 10-20% opening of the artery is plenty to allow things to proceed normally. However, if we stress the heart and ask it to do more, such a blockage prevents the heart from meeting the increased oxygen demand and this problem usually becomes obvious on the stress EKG.
EKG also gives useful clues when the chambers of the heart (atria or ventricles) become enlarged, thick or weak. And while the EKG may not be a very precise test and can’t give us an answer for everything, it can tell us that something is wrong and point towards the need for more detailed testing. Frequently an abnormal EKG becomes the indication for more specialized heart testing like ultrasound of the heart, nuclear cardiology, CT or MRI of the heart or even invasive direct visualization of the heart and its arteries. As the mechanical behavior of the heart changes when heart disease occurs, so does its electrical behavior. In this way we get early clues from the inexpensive, quick, practical EKG and doctors make a decision whether more expensive, complex and riskier tests are necessary. EKG has stood the test of time: invented in the early 20th century has made it well into the 21st century. It's easy to perform, it requires no needles, no pain, and no radiation -- making it very useful for patients and doctors alike.
Shared Decision Making
In an era where there are so many options in the medical field, having the opportunity for shared decision making is more important than ever. Shared decision making is when a doctor and patient decide together on what needs to be done next. This contrasts with the more traditional practice of medicine in the 19th and 20th centuries, where the health care providers had the knowledge and dictated to the patients and their families of what needed to be done. Shared decision making is important when more than one option is being presented and it’s not 100% clear on what needs to be done. In a more “clear cut” situation, the role of shared decision making is less pronounced. For example, a young person comes in with acute appendicitis. We know that if we don’t operate and remove the appendix quickly, it can burst, cause peritonitis and ultimately lead to death. We wouldn’t converse about it for an hour with the patient and his family; we would say that this is what needs to be done and this is what we are going to do. Another common case (that I have often experienced as a cardiologist) is when someone is having a heart attack. We know that it’s important to move quickly and take care of the situation, and giving a variety of options is not the best use of time.
In instances that have more than one option and are not as acute (or urgent), shared decision making is a very ethical option and practice with most physicians. Here’s an example of how this tends to play out: say we have a patient who comes in for an appointment. She feels fine, and has no symptoms of an impending heart attack or stroke, but is considered high risk. As a doctor, I offer the option of prescribing a statin (which lowers cholesterol). These medications have been widely used since the 1980s and have been credited for cutting the number of heart attacks in half. They have been very powerful and useful, but they need to be taken on a daily basis. While they are generally safe to use, it’s important to remember that there are no medications without side effects. Statins are not “muscle friendly”, and approximately 1 in 5 patients develops muscle aches while taking this medication. This is not life-threatening, but it can inhibit daily activities. It becomes a back and forth discussion that takes time and effort from both the patient and the doctor. Of course, it is much easier for a doctor to say “here is your prescription, take this daily and come back in two months so I can check your cholesterol levels”. But the approach where the physician invites the patient to make decisions together based on the patient’s comfort level can be extremely beneficial. On one hand, we want to educate the patient on what we think is best; but on the other hand, we want him to be able to follow through with that decision.
Shared decision making is a wonderful thing. It’s what patients deserve, but it takes time and a good attitude from both the patient and the physician. It takes the realization from the patient that there are no easy fixes in medicine and that prevention is the first line of defense. Does your doctor practice shared decision making? If you’re not sure, have a discussion with her and find what fits your needs the best.
To your health!
Dr. Anthony
Should we be taking aspirin daily to prevent heart attacks and strokes?
Aspirin is a medication we have been using for over one hundred years. At a low dose, which averages between 40-100 mg a day, aspirin has been used in the last two to three decades primarily for the prevention of heart attacks and strokes.
We know that heart attacks and strokes can occur when cholesterol plaque in one of our major heart or brain arteries first develops, then matures (which can take decades!), and -- without warning -- becomes unstable and cracks. When it reaches this point, the blood flow over the unstable plaque recognizes the situation as “bleeding” or a “hole” in the artery. It tries to repair the situation by flowing very quickly to where it believes the problem is happening, and in the process can form a clot over the unstable plaque in less than one minute. So here we have a situation where a cholesterol plaque may only obstruct 10-20% of the opening (lumen) of a heart or brain artery. When this plaque becomes unstable, the blood forms a clot over it and within a minute there is a 100% obstruction of the blood flow. Because there is no blood flow through the artery, the cells start dying in a matter of 3 minutes for the brain and 30 minutes for the heart. This is how most heart attacks and strokes can occur.
A low dose of aspirin works by inhibiting the sticky cells in the blood, called platelets, from sticking together and forming a clot. However, at a high dose, aspirin also inhibits various enzymes and good cells. While a low dose would protect the arteries from clotting, a higher dose would not. This is why we have been using a low dose for the prevention of heart attacks and strokes. If too much aspirin is taken, it can cause bleeding, which has the reverse effect and can encourage clotting of the arteries.
Those who have had a heart attack or stroke are instructed to continue taking a low dose of aspirin every day for the rest of their lives. However, we must remember that science has no “last word”: it’s all based on the function of time and the evaluation of the available evidence.
So let’s say that the evidence from twenty years ago overwhelmingly supported using aspirin for the prevention of heart attacks and strokes -- not only for secondary prevention (meaning you’ve already had a heart attack or stroke and you’re taking it as a way to prevent this from happening again), but for primary prevention, which means you never had a heart attack or stroke, but you were deemed to be at a higher risk for suffering from one. This includes people with diabetes, smokers, those with high LDL or high blood pressure, a family history of heart disease, etc. For all of these people, we thought it made sense to give a low dose every day for the rest of their lives to prevent heart attacks or strokes from ever occurring in the first place.
A few months ago, science came forward and said that this is not correct. We have reevaluated the evidence, and in the modern era of medicine-- with better use of “statins” (Lipitor, Crestor, etc), medications that lower the LDL (bad cholesterol), and improved treatment of high blood pressure-- we don’t think the benefits of taking aspirin for primary prevention outweigh the risks. This is big news for patients and doctors!
Randomized trials and observations from the American College of Cardiology and the American Heart Association, which included tens of thousands of patients for years, have concluded that the use of aspirin is no longer appropriate for primary prevention of heart attacks and strokes -- except for those at very high risk (meaning those who have at least a 10% risk of developing heart attacks or strokes over the next ten years). The studies indicated that patients who have already had a heart attack or stroke should absolutely continue taking aspirin for secondary prevention. But for using aspirin for primary prevention, we have to really dive into the risk factors of the patient (age, family history, lifestyle, blood pressure level, cholesterol level) and determine if this is appropriate. Only if we evaluate these factors as being high, and the risk of bleeding from aspirin is low, then it is ok to use aspirin for primary prevention.
As with any kind of medication or regimen, please speak with your doctor before determining whether you should start or stop taking aspirin.
To your health!
Dr. Anthony