Diagnosing Coronary Artery Disease

Chest pain from Coronary Artery Disease (CAD) is either:

  • Myocardial Infarction (M.I.), a Heart Attack.  Part of the heart muscle has died; OR
  • Angina.  Blood can’t deliver enough oxygen to heart muscle, but nothing has died yet.
  • The term โ€œAcute Cardiac Syndromeโ€ means itโ€™s hard to tell, at least at first.
  • Symptoms & most tests are the same (as opposed to other causes of “chest pain”)

If we think a patient having chest pain today may be in the midst of an acute M.I., we call 911 and let the ER handle everything.  But if the patient had pain suggestive of Angina, and isnโ€™t having active symptoms at the moment, or if we work in an ER, we proceed as follows:

Suspect CAD By Patient’s Symptoms & Medical History

1.  Pain feels heavy, dull, achy, squeezing, or pressure.  NOT sharp or stabbing.  NEVER worse with breathing or coughing

  • Mid- or left-chest.  Maybe left shoulder, jaw, or upper arm.  Maybe upper abdomen.  Rarely right chest.  NOT numbness in left arm, or pain below elbow.
  • Lasts 45 secs. to 5 minutes if Angina; ongoing if M.I.  Never just a few seconds.
  • Worse with exertion.  An acute M.I. also hurts at rest.
  •  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; should be in an ER)
  • Pain thatโ€™s worst at rest, & not felt with significant exertion, probably ISNโ€™T cardiac.

2.  Other Symptoms.  The more that are present during pain, the more we suspect CAD as cause:

  • 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)

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

  • Main Hard Risks:  Age: Men over 40; Post-menopausal Women; Smokers; Hypertension; Diabetes; High Cholesterol
  • Also: Strong Family History of CAD; Same-day stimulant use (cocaine or amphetamine); HIV Infection (mainly if not being treated)
  • Obesity & sedentary life-style are soft risks, donโ€™t factor into clinical decision-making.

Conclusion:  The more of the above that are present, the more we want to order tests for CAD. Note that Physical Examination, like with a stethoscope, doesn’t help much at all.

Tests

1.  The Electrocardiogram (EKG).  This is the first test we do.

  • Can identify actual M.I. (if “S-T Elevation”); old M.I. (“Q-Waves”); other findings suggesting Angina (“upside-down T-waves”); other findings suggesting an abnormal heart
  • Problems with False-Negatives  —  1) EKG can be normal in the midst of an M.I.; 2) With Angina, EKG is normal at rest, abnormal (positive) during exercise.
  • Problems with False-Positives  —  EKG can be abnormal in a perfectly healthy person.  See why we should NEVER do any Test if we DON’T THINK a Patient has That Disease

2.  Cardiac Enzymes  —  Blood test for Troponins, only done if we suspect M.I. here & now

  • High Troponins mean damage to heart muscle  =  M.I.
  • Different types of Troponins, need to be drawn several hours apart
  • Elevated Troponins with S-T Elevation on EKG  =  STEMI  (“S-T Elevation M.I.“);  Elevated Troponins  with normal EKG  =  NSTEMI  (“Non-STEMI” M.I.) (still an M.I.)
  • “Troponin Leak”  =  Only slight elevation in Troponins.  Less diagnostic.
  • We NEVER order Cardiac Enzymes outside a hospital (if we suspect M.I. here & now, we call 911 & send to ER).

3.  Stress Tests  —  Utilizing exercise to diagnose Angina if patient is pain-free at rest.  Several Types:

  • Treadmill  —  EKG while exercising on a treadmill, if EKG at rest is normal
  • Stress Echo (echocardiogram) or Nuclear Medicine Perfusion Scan, during exercise, if EKG at rest is abnormal
  • If patient can’t exercise (frail, bad knee, etc.), inject a drug instead to rev up the heart during Stress Echo or Perfusion Scan (“Pharmacologic Stress Test“)
  • If Stress Echo or Perfusion Scan is abnormal in part of heart during exercise / stress, that’s Angina (due to blocked coronary artery in that area)
  • If same abnormality present when test also done at rest (no exercise or stress), that’s a  Scar from Old M.I. (over & done with, not the cause of patient’s current symptoms)
  • Some ERs may do Echo or Perfusion Scan at rest, without stress, if patient still having ongoing chest painNegative test means NOT Angina; positive may be either active Angina or merely Old M.I.

4.  Cardiac Catheterization (“Cardiac Cath”)  —  Invasive, but best test for Coronary Arteries

  • Also called an Angiogram (โ€œangioโ€ = โ€œarteriesโ€)
  • Usually only done if either the initial EKG or Stress Test is abnormal
  • Tiny catheter threaded from an artery in groin, up into heart, to squirt dye & see on x-ray what the coronary arteries actually look like (blockages)
  • Can sometimes open blockages with tiny metal stents at same time (angioplasty)
  • Risks of Cardiac Cath:  Death (1/1,000), M.I. (1/1,000, Stroke (1/300-500).  Risks higher in older & sicker people, lower if younger & generally healthy [but undiagnosed coronary artery disease is also risky]

5.  Coronary Artery Calcium Scan (various types)  —  NOT at all useful in diagnosing cause of chest pain.  Only used to evaluate risk of coronary artery disease without necessarily having symptoms.  Controversial as to usefulness.

See Diagnosing Coronary Artery Disease — Full Text for more in-depth discussion.

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