Diagnosing Coronary Artery Disease — Full Text

There are lots of types of heart disorders, but when it comes to โ€œchest pain,โ€ weโ€™re mainly dealing with โ€œCoronary Artery Diseaseโ€ (see Diagram — Heart Anatomy).  And thatโ€™s either:

  • An acute Heart Attack (a.k.a. โ€œMyocardial Infarction,โ€ or โ€œM.I.โ€) right here & now; OR
  • Partial blockage in the coronary arteries that nourish the heart (โ€œAngina Pectoris,โ€ a.k.a. โ€œAnginaโ€)

The difference is that โ€œInfarctionโ€ means that part of the heart muscle is dead & gone, forever.ย  Angina is when the muscle isnโ€™t getting enough oxygen via its blood supply, but hasnโ€™t died yet, & can still be saved with treatment.ย  Insufficient oxygen to a part of the body is called โ€œIschemiaโ€ (iss-KEE-mee-uh).ย  Both Angina and M.I. are manifestations of the same illness: Coronary Artery Disease (CAD).ย 

If the patient is having active pain right now, we use simply one expression to include both Infarction & Ischemia: โ€œAcute Cardiac Syndromeโ€ (ACS).  Only time will tell if any heart muscle has actually died.  When the patient feels fine today, but has chest pain here & there, if that winds up due to CAD (blockage of the coronaries), we call it Angina.  Angina may remain stable, or the blockage may progress to an eventual M.I.

We diagnose Angina & M.I. the same way we diagnose everything; by a combination of history-taking, physical exam, & testing.  While women may have slightly different symptoms than men overall, there’s not much difference when it comes to individual patients with chest pain.

HISTORY

Clinically, we tell the difference between Angina (ischemia) and an acute M.I. (infarction) by whether the pain has been present and ongoing the last few days or not.  Anginal pain only lasts 1-5 minutes, but can keep recurring.  Pain from an M.I. is ongoing.

  • Chest pain all day, or on-and-off daily for the last week?  Could be an M.I.
  • Short-lived chest pain a few days (weeks, months) ago?  Might be Angina.
  • Persistent chest pain a month ago, lasted 1-2 weeks?  Perhaps an old M.I.
  • Chest pain that lasts seconds:  Neither.
  • Chest pain all day long the last 1-2 months?  Wonโ€™t have a thing to do with the heart.

To determine whether โ€œchest painโ€ has anything to do with the heart, we ask 3 types of questions: 1) Symptom Description; 2) Other โ€œAssociated Symptomsโ€; and 3) Risk Factors for coronary artery disease (CAD).

Symptom Description of cardiac chest pain (either ischemia or infarction):

** Quality:  Heavy, dull, achy, squeezing, pressure-like, or something similar.

  • NOT sharp or stabbing.
  • NEVER โ€œpleuritic,โ€ i.e. hurts with each breath, cough, or movement of torso.

** Location: Usually mid- or left-chest

  • Maybe the left shoulder, jaw, or upper arm (even occasionally right chest or upper belly).
  • DONโ€™T WORRY about numbness in the left arm, or pain below the elbow.

** Duration: 1-5 minutes for Angina

  • A frank M.I. lasts longer (indefinitely)
  • Occasional recurrent chest pains lasting 30-60 minutes wonโ€™t be the heart
  • Pain that lasts seconds isnโ€™t cardiac
  • Beware: everyone is notoriously inaccurate at estimating time.  We practically need a watch to know for sure.

** Exertional:  Cardiac chest pain hurts worse with exertion.

  • With Angina, the degree is usually predictable, like one flight of stairs, two city blocks, three minutes of sex, etc.
  • โ€œUnstable Anginaโ€ means occurring with less & less exertion time after time, or even at rest (dangerous, because a complete M.I. may soon occur)
  • An acute M.I. also hurts at rest.
  • Pain thatโ€™s worst at rest, & not felt with significant exertion, probably isnโ€™t cardiac.

Associated Symptoms: Cardiac chest pain is usually accompanied by one or more of the following:

  • Shortness of breath
  • Nausea or vomiting
  • Burst of Cold Sweat (โ€œdo cold, wet, drops of sweat break out on your forehead?โ€)
  • Lightheadedness or dizziness (not room-spinning vertigo)

The more of these symptoms that come and go together with the chest pain, the more we worry that itโ€™s the heart.  These symptoms are also called โ€œangina equivalents;โ€ if they occur during exertion even without chest pain, it could be Angina.

Risk Factors for Coronary Artery Disease (CAD):  The 5 main hard risks —

Other equally-hard risks include:

  • Strong Family History of CAD: like a heart attack within a few years of patientโ€™s current age.  For women, a maternal family history is particularly concerning.
  • Same-day stimulant use (cocaine or amphetamine).
  • HIV Infection (maybe; especially if not being treated)
  • History of typical angina, i.e. exertional chest pain, even if thatโ€™s not the pain a patient is seeking care for today.

Obesity & sedentary life-style are soft risks.  Theyโ€™re certainly something to avoid, but donโ€™t factor in during clinical decision-making.

PHYSICAL EXAMINATION  — 

Not much help.  There are virtually no clues we hear with a stethoscope to tell us if someone is having a heart attack.  Sometimes we detect other cardiac conditions, & wonder, โ€œwell if they have that, they may also have CAD.โ€  But in the midst of an acute M.I., the heart sounds perfectly normal!

If we find signs of Heart Failure, that concerns us because an M.I. may be causing it. These include rales at the bottom of the lungs (heard by stethoscope), or swollen legs.

THE WORK-UP

A 25-year old comes in with chest pain.  It occurs in bed at night, never hurts while jogging, and there are no risk factors for CAD.  We listen carefully to the heart, & announce, โ€œYour heartโ€™s perfectly normal.โ€  The patient leaves reassured.

We didnโ€™t lie.  Is it a little bit phony?  Maybe.  But the worst thing we could do would be to order tests.  Thatโ€™s because when thereโ€™s very little chance that a person has a disease, any abnormal tests are most likely wrong!  False-positives, far & away!!!  Click for a simple explanation why we should Never Test People with Low Likelihood of Disease.

So who do we work-up?  People with a combination of risk factors & clinical clues.  Sometimes itโ€™s the person with crushing chest pain, shortness of breath, a cold sweat, and no CAD risks.  Or maybe a person with new not-so-typical symptoms that donโ€™t sound like Angina or an M.I., but theyโ€™re an older smoker with diabetes, high blood pressure, & just snorted some stimulant.  Or somewhere in-between.

But thereโ€™s an uncommon newly-recognized condition, not well understood, called Spontaneous Coronary-Artery Dissection (SCAD).  Thereโ€™s no blockage, but rather a coronary artery suddenly splits apart lengthwise, causing an M.I.  It mostly occurs among people with other unusual diseases (e.g. Fibromuscular Dysplasia, affecting arterial walls), but can occur disproportionately among younger women.  So even if a woman has no CAD risk factors, if she describes typical symptoms of an M.I., itโ€™s important to pursue the diagnosis. See the link for more information.

Tests

If we think a patientโ€™s chest pain may be due to coronary artery disease (either Angina, or a frank M.I.), we proceed as follows:

If we have strong suspicion they may be in the midst of an acute M.I., we call 911 and let the nearest ER handle everything.  But if the patient had pain suggestive of Angina, and isnโ€™t having active symptoms at the moment [or if we suspect M.I. and work in an E.R.], we proceed as follows:

**  Electrocardiogram (EKG)  —  The โ€œKโ€ in the abbreviation comes from the German word for “heart”; โ€œEKGโ€ seems to ring clearer than โ€œECG,โ€ so thatโ€™s the most common term.  By attaching electrodes to a patientโ€™s limbs & chest, we can get 12 different tracings of a heartโ€™s own innate electric current moving through cardiac muscle.  Itโ€™s called a โ€œ12-lead,โ€ in contrast to continuous monitors that only detect heart rhythms.

An EKG can suggest the following possibilities related directly to chest pain:

  • โ€œInjuryโ€ to muscle, suggesting an acute M.I. in progress (finding “S-T elevation”)
  • โ€œIschemiaโ€: insufficient circulation, but no imminent muscle damage (yet)
  • Old M.I.: over & done with; nothing to do with current symptoms (but indication that the patient certainly has CAD)
  • Unrelated findings indicating the patient has an unhealthy heart (so todayโ€™s symptoms might or might not be related)

Some big problems with the EKG:

  • The EKG can be normal in the midst of an acute M.I.
  • With Angina, i.e. partial blockage of a coronary artery, the EKG can be normal at rest, & only turn positive during exercise (when the heart needs more blood for the work-out, but canโ€™t get it)

If a patient has chest pain, we do an EKG and announce โ€œitโ€™s normal,โ€ they feel very reassured.  We clinicians, however, feel reassured by our history-taking that the heart is fine.  When it comes to coronary artery disease, the medical history is much more accurate than an EKG.  Back-room medical humor includes the concept of โ€œtherapeutic EKG,โ€ i.e. we knew all along they were OK, but the test was actually a โ€œtreatmentโ€ (i.e. reassurance).

And of course, another big problem: False-positives can be common.  Also, lots of EKG findings are โ€œnon-specific,โ€ very hard to tell if theyโ€™re false-positives or truly diagnostic.  Women have more false-positive & false-negative EKGs than men.

Moral  —  we’re always cautious about ordering & interpreting EKG’s.  See again our explanation of Why NOT to do a Test if we DON’T THINK the Patient Has the Disease.

**  Cardiac Enzymes  —  With an M.I., enzymes leak out of heart muscle, and can be detected by blood tests.  The main ones used today are Troponins.  An older one was the โ€œCKโ€ or “CK-MB Band”.  Timing is important, since eventually high troponins wash out of the blood & results return to normal.  There are two different types of troponins, that show up at different time frames, so patients are often held around the ER for hours to repeat the test.

If troponins are high enough, they mean the patient is having a Myocardial Infarction (M.I.).  If the EKG also shows it, with “S-T Elevation,” the patient has a “STEMI” (S-T Elevation M.I.).  If the EKG doesn’t show it, it’s a “N-STEMI” or “Non-STEMI,” which is still a heart attack (M.I.).

If troponins are just a little high, it’s called a “troponin leak,” jargon for “we’re not sure.”  Other diseases can raise troponins a little, as can a normal degree of expected lab error.  If the EKG also suggests an M.I., that’s most likely the diagnosis.  If the EKG is normal, it’s hard to know.

We NEVER EVER order cardiac enzymes outside a hospital.  They only help tell if a patient is having an actual heart attack, & if thatโ€™s what we thought, well, why didnโ€™t we call 911?  A lawyerโ€™s dream (plaintiffโ€™s lawyer).

**  Stress Tests  —  Often, the EKG is normal at rest, the chest pain is gone, but we suspect our patient might have coronary artery disease causing Angina.  So we order a Stress Test to see if EKG abnormalities arise during exertion.  There are a few ways to do this.

1.  The standard stress test is the โ€œExercise Treadmill Testโ€ (โ€œETTโ€) — a regular EKG while walking on a treadmill that inclines steeper & steeper.

2.  If there are non-specific abnormalities on our initial EKG (when the patient is resting peacefully on a table), the ETT result will be uninterpretable.  So the patient must exercise during either of the following:

  • Echocardiogram (โ€œStress Echoโ€): to see if any part of the cardiac muscle (called the “heart wall”) fails to contract enough, indicating a blockage in circulation of blood to it (“wall motion abnormality”); OR
  • Perfusion Scan: inject a radioactive tracer which shows up by a Nuclear Medicine scan, & see if a blockage prevents it from circulating into a part of the heart muscle during exercise.

If the Echo or Perfusion Scan is abnormal during rest, it just indicates a scar, permanent damage from  an old M.I.  But if it’s normal at rest, and abnormal with exercise, that’s Ischemia  —  a blockage in coronary arteries, that shows itself under stress (exertion), and may eventually get worse to cause a frank M.I. (Infarction, with permanent damage) in the future.

Some ERs do Echo’s or Perfusion Scans without stress in patients who have ongoing chest pain but normal EKGs and normal Cardiac Enzymes.  A negative test during ongoing pain is very reassuring that symptoms are not due to ischemia (i.e. not active coronary artery disease).  A positive test during chest pain may mean either active ischemia, or old M.I., as described above.

3.  If the person canโ€™t exercise (bad knee, too frail, etc.), we do a โ€œPharmacologic Stress Test.โ€  Inject a drug to rev up the heart (dobutamine, dipyridamole, adenosine, etc.), & then do an Echo or a Perfusion Scan to see what’s happening in the coronary arteries.

Like the regular resting EKG, all stress tests carry a certain chance of being false-positive or false-negative.  The problem is greater in women than men.

While weโ€™re in the process of ordering stress tests, we give our best medical treatment for coronary artery disease, just in case.  This includes a daily aspirin, high-dose โ€œstatinโ€ (to lower cholesterol, even if cholesterol is normal, since the statin protects the heart), and maybe a โ€œbeta-blocker” medication to protect the heart.

**  Cardiac Catheterization (“Cath”; Angiogram)  —  Ordered & performed by cardiologists, itโ€™s the best test to find blockage in the coronary arteries.  A thin catheter is inserted into the femoral artery in the groin, threaded upstream & guided by fluoroscopy (x-ray) into the coronary artery.  Dye is injected, & x-rays can trace its flow through all the branch arteries.  Blockages can often be treated on the spot, with stents (which open up the artery).

A Cardiac Cath is performed for patients with chest pain and obviously abnormal EKGs, elevated cardiac enzymes (troponins), or those with positive stress tests.  It might rarely be done if EKG & stress tests are normal but the patient’s symptoms are extremely suggestive of CAD.  A Cardiac Cath is invasive, with almost a 1% risk of some major complication.  These include:

  • Death (1/1,000)
  • M.I. (1/1,000)
  • Stroke (1/300-500)

Risks are higher in older & sicker people, lower in generally healthy people.  But undiagnosed coronary artery disease is also risky.

**  Coronary Artery Calcium Scan  —  Various types of tests exist to determine how much calcium has built up in the coronary arteries.  This test is NOT USEFUL for diagnosing the cause of chest pain.  It’s meant as a tool to evaluate risk of a future heart attack.  If the scan is completely negative, well, that would surely mean a patient’s chest pain has nothing to do with the heart.  But if there’s any degree of calcium build-up, there’s no way whatsoever to know if it’s at all related to a patient’s symptoms.

See also Diagnosing Coronary Artery Disease for the clinicianโ€™s condensed thought-process when face-to-face with a patient.

Thatโ€™s it for Heart Attacks & Angina.  For other causes of chest pain, select either:

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