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Acute Coronary Syndrome: Interview With Dr Alexander C. Fanaroff
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Acute Coronary Syndrome: Interview With Dr Alexander C. Fanaroff
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>> The Rational Clinical Examination Series was begun many years ago to try to reconcile what we all learned in medical school regarding the clinical presentation of disease. We were all taught that certain diseases presented in a variety of ways and that there were certain signs and symptoms that were characteristic for those diseases. But when one goes back to the medical literature to find out where people came up with these ideas, one is hard pressed to find much evidence to support these notions. [ Music ] >> Hello. I'm Ed Livingston, Deputy Editor of Clinical Reviews and Education for JAMA.
And welcome to this edition of the JAMA Evidence Podcast. Today we take on how patients present when they are having a heart attack. Classically, a patient reports having substernal chest pain and will describe feeling like an elephant is sitting on their chest. The pain radiates to the left arm and the left neck. This will be associated with shortness of breath and diaphoresis. At least that's what we are taught. Let's consider the following patient He is 40 years old and healthy. He had no family history of significant disease.
He went to his doctor every year for an annual physical. About a year ago he described some musculoskeletal pain in his right chest. And for some reason his physician was suspicious and got a EKG, which was normal. But he also went ahead and got a treadmill test, which was also normal. A year after that, he described the following. >> I was experiencing some right arm discomfort. And it was similar to that if you ever tried to, you know, start a lawn mower that didn't want the cooperate and stuff like that.
So the next day or, you know, worked in the yard for a little bit too much, and you've had some soreness in your right arm, is what I was experiencing. It was, like, in my shoulder in the meaty part of your shoulder, not like in the shoulder blade. So that had continued for a couple of days. And the only way I could find relief, really any type of relief was elevating my arm above my head and stretching it that way would give me some type of relief. But once I lowered my arm, it would return and that continued on.
>> He had this pain for several days. It worried him, so he did an internet search to try to find the cause of the pain. He found the usual descriptions of heart attacks on the internet which described the classical presentation of substernal chest pain radiating to the left arm and neck and decided that his problems were probably related to strain and anxiety and not his heart. But on Father's Day, the following happened. >> The discomfort got excruciating, and it radiated over my shoulder and into my chest and to the center of my chest.
And it wasn't so much as a pain. It was like someone had, you know, there is a belt around me and somebody was slowly tightening down the belt. And I decided to drive myself to the ER and by the time I had gotten in my car, it was like there was a very small strong person sitting on my steering wheel pushing both feet into my chest. So it became very hard to breathe. [ Music ] >> When our patient arrived in the emergency room, he had a normal EKG and a normal cardiac echo.
He didn't get a diagnosis of myocardial infarction until his troponins came back, and they were elevated. A cardiac catheterization showed that he had an occluded circumflex artery, and two other coronary arteries had 99% and 70% occlusions. He then underwent a four-vessel cardiac bypass and did well. This patient's story shows how important it is to recognize that so-called classic symptoms of disease are not so classic and that it's necessary to critically evaluate them, as is done in the Rational Clinical Examination articles.
In this article on the diagnosis of acute coronary syndrome, we are going to learn that the classic signs and symptoms of having a heart attack, such as chest pain and arm pain, are very poor indicators of actually having a heart attack. Summary scores, such as the HEART score or TIMI score, do a lot better. They are very good at predicting that someone is not having a heart attack and less good at predicting that they actually are having a heart attack. Before we get too deep into how a heart attack presents and how the diagnosis is made, let's define the terms.
>> So acute coronary syndrome is a clinical diagnosis. And as you can tell from the name, it's a syndrome that really incorporates three separate diagnoses. And the diagnoses are ST elevation myocardial infarction, or STEMI; non-ST segment elevation myocardial infarction, or NSTEMI; and unstable angina. And acute coronary syndrome encompasses all three of those diagnoses. >> Why are they aggregated into one diagnosis? >> They have been aggregated into one diagnosis because pathophysiologically all three of those entities are the same thing and that has important implications for treatment.
Now pathophysiologically, all of them involve plaque rupture, a rupture of atherosclerotic plaque within a coronary artery lumen, with formation of a thrombus, which occludes blood flow and causes both symptoms and the negative consequences of an acute coronary syndrome. >> So they have a common pathophysiology, but there's three manifestations of that pathophysiology. So could you tell us a little bit about what those three mean? What's the difference between a STEMI and a non-STEMI?
>> So in STEMI, you have plaque rupture with total occlusions of the coronary artery with no blood flow to the affected coronary territory, which causes infarction that involves the entirety of the myocardial wall. In non-STEMI and unstable angina, which have kind of been in the most recent set of AHA/ACC guidelines and aggregated into this concept of non-ST segment elevation or acute coronary syndrome, in non-ST segment elevation and acute coronary syndrome, you have plaque rupture with thrombus formation and near-total occlusion of the coronary artery.
So some blood is still getting by. And you have either subendocardial infarction in the case of non-STEMI or subendocardial ischemia in the setting of unstable angina. >> So when do the ST segments go down? >> So ST segment depression is generally a feature of non-ST segment elevation acute coronary syndrome, and it's a, it's an indication of ischemia rather than infarction, and it's subendocardial ischemia or subendocardial infarction.
>> Heart disease is very common. It's responsible for about a quarter of all deaths in the United States. A recently published article in JAMA by Jamal from the American Cancer Society showed that there has been a very marked reduction in deaths from cardiac disease. There is a clinical reviews podcast on that subject, and I'd encourage you to listen to it. But even though mortality is decreasing, there are still about 600,000 patients who die a year from heart disease. One of the most common causes is heart attack.
Most people just don't drop dead from a heart attack, and usually there is some kind of warning before it happens. Most develop some kinds of symptoms, and it's important that people recognize these symptoms and seek care early in the disease's course so that they can get early treatment and have good outcomes. But the disease's presentation isn't straightforward. As we'll see, many of the signs and symptoms we're told are characteristic for having an MI are not seen with patients actually having an MI. Yes, some patients do present like one would expect from textbook descriptions of MI; but most don't.
There's 8 million ER visits for chest pain every year. Of these, only about 13% actually have an acute coronary syndrome. So how do we keep the other 90%, or about 7 million people, out of the hospital and not having them go home and drop dead from an MI? There is a way. And in this Rational Clinical Exam, Fanaroff and colleagues investigated the ER presentation of acute coronary syndrome and how to best determine who needs hospitalization and who doesn't. We tend to think of acute coronary syndrome presenting as substernal chest pain radiating to the left arm and neck.
It also may be described as a feeling like having an elephant sitting on one's chest. But many, if not most, patients don't present this way. Especially notorious for presenting in odd ways are patients with diabetes and older women. In fact, about 20% of all MIs that occur are only identified after they have occurred. So in the Rational Clinical Exam article in the ACS that you authored, what I found quite striking is that the most classic symptoms that are associated with acute coronary syndrome are not so classic. That in point of fact, many of them, like classic chest pain or left arm pain, had likelihood ratios that were not all the impressive, you know, in the 2 range, something like that.
So how do you explain that? >> I think that in general patients sometimes don't do the best job explaining their symptoms, and physicians don't do the best job listening to patients. And I think that one patient's typical chest pain or crushing substernal chest pain may be an entirely different thing. >> I would have thought that a patient who has typical chest pain, whatever "typical" means, but typical for ACS, would be very, very predictive of having acute coronary syndrome.
But in your analysis, you found that the likelihood ratio of having that symptom is only 1.9 as it relates to a patient having acute coronary syndrome. And I would have thought it would be like 19, not 1.9. So why is that? >> I think that's a very good question. But I think also that a lot of the things that we classically think of as typical chest pain syndromes came about because that's just what people thought they were anecdotally.
They were classic symptoms. But when you actually look at the literature, you find that they are not as strongly associated with the diagnosis as you might expect. >> The analysis presented in this Rational Clinical Examination article shows that none of the typical signs or symptoms for acute coronary syndrome, such as chest pain, pain radiating into the arm, shortness of breath, or any other symptom can reliably predict that a patient is or isn't having a heart attack. That's because these symptoms can be associated with a lot of other diseases like GERD or arthritis.
The best guess that a patient is having an MI comes from combinations of symptoms and lab tests. Various combinations of these exist, and the ones that work the best are the TIMI and HEART scores. >> So what we have found to be the best tool for evaluating the patient with possible acute coronary syndrome were these risk models. And the two that I think are probably most useful are the TIMI risk score and the HEART risk score. >> The HEART and TIMI scores are very good at predicting when patients are not having a heart attack.
They work OK, but are not perfect at predicting who is having heart attack. They are most useful for evaluating emergency department patients and identifying those who can be sent home with little risk of having missed a diagnosis of acute coronary syndrome. So it's important to know what's in these scores and how to calculate them. Dr. Fanaroff. >> So the TIMI risk score initially came from a clinical trial enrolling patients that all had acute coronary syndrome, then was a prognostic tool to assess for 14-day outcomes.
It's subsequently been evaluated multiple times in the unselected chest pain population. But the TIMI risk score assesses for the presence of seven variables and each one, if present, gets 1 point. And the seven variables are age greater than 65, three or more cardiac risk factors, known coronary disease, aspirin use, greater than or equal to 2 episodes of angina in the preceding 24 hours, ST segment elevation or depression greater than 1/2 millimeter, or elevation in cardiac biomarkers. And again, it gives a score between 0 and 7.
>> Which biomarker? Troponin? >> Actually, when the TIMI risk score came out, troponin was not in as wide use as it is today. So it allows for the use of any cardiac biomarker. And in the studies that we looked at, they used either troponin or CK-MB. Most of the studies we looked at did use troponin. >> So that was the HEART score? >> That was the TIMI risk score. >> How does the HEART score differ?
>> The HEART score differs from the TIMI risk score in a couple of ways. The first is the HEART risk score is newer than the TIMI risk score. And it was derived a priori based on what people thought might be important elements to determining whether or not somebody had an acute coronary syndrome. And in the HEART risk score, there are five categories, each of which is scored on a scale of 0 to 2 to give a score from 0 to 10. And HEART is actually an acronym that stands for History, EKG, Age, Risk factors, and Troponin.
So a patient with an unconcerning history or history incompatible with ACS gets a score of zero. A patient with a history highly suggestive of ACS gets a score of 2. And a patient with a history somewhere between gets a score of 1. And I should say that "history" in this case refers only to their description of their chest pain. You know, if they said they had crushing substernal chest pain, you'd give them, radiating to the left arm and neck, you'd give them 2 points. And if they said, you know, "I got punched in the chest, and now my chest hurts," you'd give a score of zero.
E for EKG, they get zero points for a normal EKG, 1 point for an EKG with nonsignificant repolarization abnormalities, and 2 points for an EKG with ST-depressed or transient ST elevation. A for Age, zero points for age less than 45, 1 point for age 45 to 65, and 2 points for age greater than 65. R for risk factors, zero points for no risk factors, 1 point for one to two risk factors, and 2 points for three or more risk factors or known coronary disease. And the risk factors that the HEART score takes into account are hypertension, hyperlipidemia, diabetes, and obesity.
And T for troponins, so zero points for a normal troponin, 1 point for troponin one to three times different than normal, and then 2 points for a troponin greater than three times different normal. And for both the TIMI risk score and the HEART risk score, the troponin that we take into account is the very first troponin that the patient has drawn on arrival to the emergency department. >> So which is better the HEART or the TIMI score? >> I think that from our study, you'd be hard-pressed to find a difference in the HEART and the TIMI risk scores.
Both of them broke patients into four categories Low risk with a likelihood ratio approaching 0.2 or 0.3, indeterminate risk with a likelihood ratio approaching 1, intermediate risk with a likelihood ratio approaching 2 and 1/2 or so, and then high risk with a likelihood ratio greater than 6.8. And so this is the TIMI risk score, 13, and this is the HEART risk score. But the confidence interval for all those likelihood ratios overlap, and I think you'd be hard-pressed to say one or the other is better. I would add I personally find the HEART risk score easier to remember the components of, so that's the one that I use when I see patients.
But I don't think that there is any reason to prefer one or the other. >> Like so many diseases, acute coronary syndrome has a classic presentation, but this presentation is sort of an average presentation that occurs in some patients but not all of them. Life's much more complex than that. No one thing can tell you a patient is having a heart attack. Instead, you need to take into consideration a set of factors and put them together in your head and let your gestalt tell you what's the most likely thing going on with the patient.
The likelihood ratios put numbers to your gestalt and help you decide what's going on so you can decide what the next best step for the patient is. For acute coronary syndrome, no classic symptoms for MI are reliable for making the diagnosis of MI. Rather, clinical signs and some tests are best aggregated into the HEART or TIMI scores. These work pretty well, and clinicians will be well served by using them when evaluating patients for chest pain in the emergency department. They are at their very best for establishing a very low likelihood for having an acute coronary syndrome.
[ Music ] We get feedback from our readers. They tell us they get confused by likelihood ratios. Even though they are not used as often as sensitivity and specificity for tests, they are actually much more useful than those measures. Listen to Part 2 of this podcast, where the Rational Clinical Examination Editor, Dr. David Simel, explains how to use likelihood ratios for evaluating acute coronary syndrome tests. [ Music ] If you enjoyed this podcast and would like to hear more, go to itunes.com/JAMAnetwork. While you are there, check out our entire roster of JAMA Clinical Reviews Podcasts.
Subscribe, and leave a review. All of our podcasts are also available in Stitcher. I welcome your questions, comments, and feedback. The best way to reach me is on Twitter. I am @ehlJAMA. CME for listening to this podcast and reading the related review article is available at JAMAnetworkcme.com. I'm Ed Livingston, Deputy Editor of Clinical Reviews and Education for JAMA and I'll be back soon with another edition of the JAMA Evidence Podcast.
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