Those curious cardiac enzymes

by Carolyn Thomas  ♥  @HeartSisters

When I showed up in the Emergency Department with textbook heart attack symptoms – central chest pain, nausea, sweating and pain radiating down my left arm – the hospital staff snapped to work and immediately ordered a flurry of diagnostic tests. These included an EKG (ECG, or electrocardiogram), blood tests, chest x-ray and a treadmill stress test. But all test results came back “normal”. I was then told that I was in the “right demographic” for acid reflux before being sent home – less than five hours after the onset of symptoms.

I left hospital that morning feeling terribly embarrassed for having made such a fuss over just a little case of indigestion.  It was only much later – after finally being correctly diagnosed, taken directly from the E.R. to O.R. and admitted to the cardiac intensive care unit for a myocardial infarction (MI, or heart attack) caused by a fully occluded Left Anterior Descending coronary artery – when I learned that my first “normal” blood tests may have been far less “normal” than I was told.  This is the part of my story where I like to insert a quick story – this one told to me by a woman in one of my Heart Smart Women presentation audiences. She described being an E.R. patient one day, and overhearing a conversation between the E.R. physician and the (male) patient lying in the bed next to her, behind the cubicle curtain. She heard the doctor telling the (male) patient:

“Your EKG is fine, and your blood tests are fine, too.  But we’re going to admit  you for observation just to make sure it isn’t your heart.”

Thus yet another male patient with symptoms but inconclusive cardiac test results is kept in hospital for observation, while I and countless other females with symptoms but inconclusive cardiac test results are misdiagnosed, patted on the head, and sent right home.

Turns out we’re not alone. A study published in The New England Journal of Medicine found that women in their 50s or younger presenting with cardiac symptoms were seven times more likely to be misdiagnosed and sent home from Emergency compared to their male counterparts.(1)

Here’s why that’s an important issue. The blood tests I mentioned look for specific cardiac enzymes in the bloodstream. This test will usually be ordered when a person like me with a suspected heart attack first comes into the Emergency Department. The blood test is usually repeated two more times over the next 12 hours.

One of these tests is for a specific cardiac biomarker called Troponinparticularly one called Troponin I that’s used to detect heart muscle damage that occurs during a heart attack. Ma Carolyn’s NOTE: although some consider the presence of this biomarker to be uniquely heart attack-related, increased blood concentrations of troponin are may also be detected in non-cardiac conditions (e.g. sepsis, hypovolemia, pulmonary embolism, or renal failure).

Patients who receive CPR, external defibrillation or shocks from an implantable cardioverter defibrillator may also have elevated troponin levels due to damage to the heart’s ventricular muscle. Medications and chemicals called “cardiotoxic” may also elevate troponins. Such agents include some chemotherapy drugs and chemicals such as carbon monoxide.

And some extreme endurance athletes – triathletes, for example – are even known to have temporarily detectable troponin levels in their blood.  As Dr. Malissa Wood explained in a Runner’s World interview, this is because their cell membranes may leak troponin, which is what cardiac muscle does when under extreme stress. Dr. Wood (who is the co-director of the Women’s Health Heart Center at Massachusetts General Hospital, teaches at Harvard, and has run many marathons herself), cites studies showing that the healthy heart (unlike the unhealthy heart in the throes of myocardial infarction  – heart attack) can almost always quickly repair these cell membranes, stem the troponin leakage, and suffer no permanent damage.

Many patients who experience a heart attack have increased troponin levels within six hours following the onset of symptoms.

This means that after 12 hours, almost everyone who has had a heart attack will exhibit raised troponin levels. Troponin levels may remain high for up to two weeks after a heart attack strikes. Many, but not all, Emergency Departments currently use a newer high-sensitivity diagnostic test for Troponins.

Cardiac troponin levels are normally so low they cannot be detected with most blood tests, so when they are detected, it’s usually significant in showing that heart muscle damage due to a myocardial infarction has occurred. Normal Troponin test results at 12 hours after the onset of symptoms typically mean that a heart attack is unlikely.

But I was already back home from the Emergency Department within five hours. No wonder it was “normal”.

Dr. Karin Humphries is a cardiac researcher in Vancouver whose studies include one of unique interest to women – especially women like me who were told in Emergency that their early diagnostic Troponin blood tests were “normal” – despite having a heart attack. As the Centre for Health Evaluation and Outcome Sciences described Dr. Humphries’ research:

“Cardiac Troponin is a protein that’s released into the blood by the heart muscle during a cardiac event, but the diagnostic threshold for this test is based on data from men.

“In fact, healthy women produce about half as much cardiac troponin as men, and many women who have had a heart attack show values below the diagnostic threshold of the current blood test. This has meant that women’s heart attacks have historically been underdiagnosed when it comes to heart attack, which can have serious implications for treatment and overall health. The CODE-MI Study, led by Dr. Karin Humphries, is addressing the diagnostic issue in heart attack by testing sex-specific thresholds for the cardiac troponin blood test, rather than one standard threshold.”

This difference is important for women to know. Being told your cardiac enzyme blood tests are “normal”  – especially in the absence of chest pain – will likely mean you can kiss a cardiac diagnosis goodbye.

(1) Pope JH, Aufderheide TP, Ruthazer R, et al. Missed diagnoses of acute cardiac ischemia in the emergency department. N Engl J Med. 2000;342:1163-1170.
(2) Fesmire et al. “Clinical Policy: Critical Issues in the Evaluation and Management of Adult Patients with Non–ST-Segment Elevation Acute Coronary Syndromes.” Annals of Emergency Medicine. Volume 48, No. 3. September 2006.

♥  See also:

36 thoughts on “Those curious cardiac enzymes

  1. The information you posted here has helped me understand what happened when my husband had a heart attack, followed by angioplasty & 3 stents.
    Thank you.

    Liked by 1 person

  2. I went to the GI doctor because I was having extremely weird heartburn. I was immediately told to go to the ER to have my heart checked. My troponin level was 0.15. I was then transferred to a Cardiac unit in another hospital. 10 hours later the team assured my parents that they were 99.9% sure I was not having a heart attack, but kept me overnight for observation. At 4:10 AM I woke up and I knew something was terribly wrong. I was sweating buckets, had intense chest pain, and my legs were flopping around like a fish. I was brought to the ER immediately. I had had a Widow Maker, my troponin levels never changed thru the 12 hours I was there. I had an 85% blockage, a piece of plaque broke off causing total blockage.

    If the ER had sent me home, I would not be here today. My question is why does my troponin level not change for the last 3 years it’s been 0.15? I’m a 53 year old women, I weighed 125 pounds at 5’5″ tall at the time of my MI. 3 years later I am now 88 pounds and was told I have a extremely rare heart disease that 1% of the population has. Today I have had chest pains for the last 4 hours, but the last 3X I’ve been to the ER they check my troponin level, keep me overnight and send me home. I’m so confused about troponin levels. Mine stays the same. Why would that happen?


    1. Hi Laureen – I’m not a physician so cannot comment on your specific case, but I can tell you that generally, it can happen, very rarely, that people who have a heart attack will have near-normal troponin concentrations in the blood, while other people with increased troponin concentrations have no apparent heart injury at all. I’m guessing that your EKG results were also “normal” before you’ve been sent home previously.


  3. I wanted to let you know that your experience is not one that only females experience. My father had a heart attack, the ER says he didn’t but they weren’t there and only kept him for 3-4 hours as well. I was with him when it happened and if it wasn’t a heart attack, what was it?! I’m sure you can identify with that feeling.

    Anyway, they didn’t waste any time rushing a 70 year old white male home either. Maybe that’ll make you feel a little better. I’m sure there are some sexists and racist doctors but I don’t believe the system is overwhelmingly flawed in this manner. As with any problem, if you go looking for more people with the same experience you will likely find it.(Referring to the journal article)

    I believe now more than ever we have to take charge over our healthcare and the healthcare of those we love.

    Liked by 1 person

    1. Hello Joshua – of course you are correct. There are indeed many cases of men being misdiagnosed in mid-heart attack too, including the famous case of the former U.S. Marine whose own longtime doctor (later proven very, very wrong) refused to refer him to a cardiologist because he simply would not believe that this fit, muscular and rugged-looking “healthy” patient could be having a heart attack. And sadly, no – it doesn’t make me feel one bit better to learn of anybody who has been misdiagnosed, male or female…

      You didn’t mention if your Dad was in fact later diagnosed with/treated for a heart attack (there are many non-cardiac conditions whose symptoms do mimic heart disease signs) but the stats on the cardiac gender gap are in fact significant. The recent American Heart Association’s major scientific statement on Women and Heart Attacks (the first in their 92-year history!) reported that women are indeed under-diagnosed compared to our male counterparts, and under-treated even when appropriately diagnosed. And I agree – all of us must take charge of our own health and of those we love!


  4. I was just at the hospital twice last week. They told me, on my second visit, that my troponin levels were elevated and they repeated the test and were still high, so that’s my normal number. What? I thought you didn’t even put out troponin unless you had a heart attack??

    Liked by 1 person

    1. Hi Denise – sorry to hear about your TWO trips to the hospital. I’m not a physician so cannot explain why the doctors told you what they did about your elevated troponins. Generally speaking, however, elevated troponins detected via blood tests are considered to be unique indicators of heart muscle damage. They can, however, less frequently be seen with conditions unrelated to the heart, such as severe infections or kidney disease (or, as mentioned above, in some endurance athletes). Just to confound us further, there ARE those rare types who have a heart attack but have normal troponin concentrations, and some people with increased troponins but NO apparent heart injury! Discuss the hospital test results with your physician. Best of luck to you…


  5. Hi,
    I had the experience of going to the ER just last night with very elevated blood pressure of 179/113 when I left home. I had taken 3 sets of BP for an hour and a half by that time, and the BP had steadily climbed from 151/105. One hour before I left, I had taken an extra dose of lisinopril because the BP was so high. When I got there, the BP was still 158/107 and I had a terrible headache. They did a few tests and an EKG which they said was normal (which I later learned was borderline) and NO CARDIAC ENZYMES. I didn’t realize until I got home that they had done no enzymes. I was shocked. The PA there inferred that I didn’t even need to have come and that I should manage my BP with my primary, which I do. By the time I left 5 hours later the BP had come down to normal, thanks to the lisinopril I had taken earlier, and the PA said I could go home. A few chemistry and hematology tests and 1 EKG and that’s it. Oh, well.


    1. I’m not a physician so cannot comment on your specific case, but I can say that generally, high blood pressure does not cause headaches except perhaps in the case of hypertensive crisis (systolic/top number higher than 180 OR diastolic/bottom number higher than 110) – a risk for stroke. Your numbers appeared to be near that range. Please see your GP right away to discuss this episode. Best of luck to you…


  6. I’m a med lab tech. Just to give my two cents, time between the troponin tests depends on the type of troponin the particular lab tests. For example, where I work, time is now more like 3 hours between draws. A more sensitive test means they can do this.

    Liked by 1 person

  7. In loving memory of my dear twin, thank you for your article.

    We were 66 years old. After complaining of severe heartburn she was sent home from the Dr.’s office with heartburn medication because her EKG was okay. Oh, how I wish I had been there to insist the doctor do more. Myocardial infarction (heart attack) was diagnosed 3 days later, stents were placed, but she died of cardiac tamponade two days after that.

    I’ll never know, but perhaps her telling the doctor she thought she had heartburn, he went with that without followup testing.

    Lesson: I think now I would try not to diagnose pain myself, have the doctor question my symptoms, and insist on follow up and then follow through.

    Liked by 1 person

    1. Sharon, my condolences to you and your family on the death of your twin sister. Many people in mid-heart attack start off their conversation with doctors by saying things like: “It’s probably nothing, just a pulled muscle from lifting heavy boxes, maybe indigestion from too much spicy Thai food, etc etc” (not wanting to make a fuss). But even without self-diagnosing like that, doctors are far more prone to dismiss the possibility of heart problems once that EKG comes back “normal”. Unlike your sister, I walked into the ER and said very clearly: “I think I’m having a HEART ATTACK!” – but again, my “normal” EKG started a whole new non-cardiac discussion. So whatever your sister may or may not have said to that first doctor, we can’t know for sure that he wouldn’t have sent her home anyway. Thanks so much for getting in touch on such an important subject. Sorry for your loss…


    1. Hi Georgia,
      Yes. According to Medtronic, one of the world’s largest manufacturers of pacemakers: “A pacemaker is not a cure. It will not prevent or stop heart disease, nor will it prevent heart attacks.”


  8. How long after this happened did you actually get admitted to the OR and diagnosed as having a heart attack? Yesterday I went into the ER for the exact same symptoms and they sent me home right away too with the SAME diagnosis. It didn’t feel like it was Acid Reflux related…. and I still had chest tightness the rest of the night. I have some today, but not as bad. I just want to know if I should be looking further into this. I have a follow up with my Primary doctor next Thursday. I’m wondering how long it took you to get that diagnosis and if I should be still worried or watching it since it was less than 24 hours ago, or if you went in again later that night within a 12 hour period.

    Liked by 1 person

    1. Hello Tia,
      I was sent home from the ER and did not return for TWO WEEKS (a very bad decision on my part, by the way – I was so embarrassed for having made a big fuss over “nothing” – plus I’d been told very clearly by a man with the letters MD after his name: “It is NOT your heart!”) So no way was I going to go back just to be embarrassed again – until my increasingly debilitating cardiac symptoms got so bad I couldn’t even walk five steps. What I SHOULD have done was to go back the minute the same symptoms returned.

      Do not be like me. If your symptoms return, seek immediate medical help. Good luck at your doctor’s follow-up visit.


  9. Nice article. I’m curious to know why the protocol has such a long time between tests.

    When I went to the ER with obvious symptoms, my blood tests and ECG were normal. They convinced me to stay so they could test my blood 6 hours later (turned out to be 7 hours). The second test confirmed a heart attack. My questions are (1) how much was my heart damaged in those 7 hours (2) why wait so long between tests? They start the 6-hour timer at the the time of the first test, as if the heart attack happened at that time. If the heart attack started 2 hours before the first test, a second test would be positive long before 6 hours passes. Seems like a dangerous protocol. Why not test every hour? Yes, it costs money. But,this is the heart we’re dealing with. Rant over.

    Liked by 2 people

    1. Mike, I’m not a physician – your cardiologist is your best resource for these questions. But my understanding is that it’s all about time needed before cardiac enzymes indicating heart muscle damage are detectable in the blood. The ER could test for cardiac enzymes every hour on the hour, but it takes a certain amount of time for enzymes like troponin to even appear in the bloodstream at all. A second test MIGHT be “positive long before six hours passes” but evidence suggests it’s not more likely to confirm the sooner you retest.

      Diagnostic testing is NOT consistent from hospital to hospital despite diagnostic/treatment protocols. For example, I was back home within five hours of the onset of my textbook MI symptoms – far too early to see elevated enzymes in blood test results in my two back-to-back tests one hour apart, both “normal” (and this timing was NOT in line with treatment protocols, of course, which normally recommend 12 hours of observation to rule out MI when patients present with clear cardiac signs).

      How much was your heart muscle damaged in those seven hours? Impossible to say, although the higher your troponin numbers, the higher the likelihood of muscle damage. If your ejection fraction numbers now appear normal, chances are your muscle damage was minimal.


  10. Blood tests can reveal the overall health of your body, therefore, it is necessary to get a blood test at least once a year. ..*;.

    Warm regards


  11. Carolyn,

    A physician told me that hospital protocols can vary. At her hospital, troponins are drawn 3 times, every 8 hours. At the minimum, troponins should be done twice from 6 to 8 hours apart. This gives an opportunity to see if there are rising values. Now that I know this, I would insist on the 2 or 3 times protocol.

    ERs have a “person can only be in the ER 23 hours” by insurance. Anything more requires hospital admission. This may drive the “get em out” quickly if the person looks like they don’t fit the profile.

    I will add as well, that patients are also eager to leave, as lying in an ER for 23 hours is tedious, hard to sleep and certainly no TV to while away the hours. It’s an ordeal. That may drive the patients to choose to leave prematurely, particularly if they are being told they “probably” don’t have an MI problem, and instead it’s GI or anxiety. This also makes it hard for the patient to return (emotionally speaking) and worried about being perceived as imagining things.

    All in all, it’s a complicated decision – but it shouldn’t be.



    1. Hi Mary – all excellent points. That’s quite the variation in E.R. protocol, isn’t it? A common practice, I’ve been told, is to do cardiac enzyme blood tests at 4 and 6 hours after admission. Or 3x q8h. Or 2x 6 and 8 hours after admission. Good grief….


  12. How do you pronounce “troponin”? I’m not kidding – I want to know! If I’m going to meet up with the “pat on the head and send home” syndrome, I’ll need to be able to demand the right thing.

    Thanks again for all you do, Carolyn.


  13. There’s a confusing message in that time is heart muscle and that clarity of diagnosis takes time when the EKG and other earlier signs are within normal. Once again the importance of advocating for oneself to know that there needs to be follow up testing/observation for women as well as men.

    Thanks for providing the rationale for those with concerns to insist on necessary observation. You are an advocate through cyberspace who provides us with ways to advocate for ourselves.


    1. Thank you for your comment, Dina. You raise an important point. For example, had I known more about these blood tests at the time, I could have requested a follow-up test later that day. Staff could have actually discharged me and just had me return later – no need to even take up a bed in the E.R all day! Anything would have been better than sending a patient presenting with textbook heart attack symptoms home with a GERD misdiagnosis.


      1. I was told for months that my symptoms were not related to my heart, despite the fact that I could no longer walk around the block, play badminton, was in a nauseous state etc. I had been to see four different doctors, three heart, pulmonary, renal, etc. I too passed treadmill testing. On the morning that I again called my heart doctor begging for help, the message was: You have no stenosis! I am sending you back to the Pulmonary doctor.

        I decided at 12 midnight to drive myself to the hospital. I made copies of all my medical records, had a flat tire on the way, which could not be fixed, found a man pulling out of the last emergency parking space and into the hospital I took myself to. Lo and Behold.

        The doctors on duty knew it was my heart. A 98% blockage in the main artery. While waiting overnight, I had a very unpleasant experience in that I was given an overdose of NitroGlycerine; no one on duty could hear me calling for help, the monitor was not being watched. The problem: for my size and weight, the dose was too strong.

        I thought what I experienced was the big bang and away you go. The symptoms were classic for someone having heart problems. A friend with a Hollywood Doctor in NYC just had a quintuple byass operation; his doctor was hearing for months of the same symptoms and fluffed it off.

        The problem: today’s doctors do not know or recognize the typical symptoms of heart disease. These symptoms are typical. They rely on stress test (most pass these) and I could go on and on. Many of us are dead or dying because the doctors are ignorant of typical signs of heart trouble Stop relying on stress testing. Do the right thing: “Angiogram!! What is the difference if it is risky? Which is worse, dying with blocked arteries or complications from the procedure? At least you are in the hospital and they can try to save your life.

        Liked by 1 person

        1. Yikes – what a story, Tully (including the bits about driving yourself to hospital at midnight, getting a flat tire, snagging the last available parking space, that overdose of nitro – WOW!!) For some patients (the estimate is as high as 20%), treadmill stress tests may not necessarily be accurate in identifying cardiac issues. Personally, I’m skeptical that angiography will ever become the default diagnostic test to rule out heart attack (it’s not only invasive and risky, but very expensive and less accurate at diagnosing certain microvascular or spasm disorders of the coronary arteries). In the past several years, we’ve also seen distressing examples of “stent-happy” cardiologists implanting unnecessary stents inappropriately in patients whose symptoms could have been more effectively (and safely) managed with cardiac meds.


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