The Diagnosis of Acute Myocardial Infarction

SFK House Staff July 2009

Coronary Atherosclerosis: A Chronic Disease

0 – 20 yrs † ∞

Coronary Atherosclerosis: A Chronic Disease

*40 – 60 + yrs20 – 40 yrs

Nomenclature of ACS

The spectrum of clinically manifest Coronary Artery Diseasefrom UA to AMI is referred to as ACS.

Antman et al. Acute myocardial infarction. In: Braunwald EB, ed. Heart disease: a textbook of cardiovascular medicine. Philadelphia, PA: WB Saunders, 1997.

Criteria for Acute Myocardial InfarctionLaboratory evidence of myocardial necrosis with clinical myocardial ischemia.

Any one of the following criteria meets the diagnosis for myocardial infarction:

• Detection of rise and/or fall of biomarkers (preferably troponin) with at least one value above the 99th percentile of the upper reference limit (URL) together with myocardial ischemia with at least one of the following:

• Symptoms of ischemia;• New ischemic ST-T changes or new LBBB;• New pathological Q waves;• New loss of viable myocardium or regional wall motion abnormality by imaging techniques.

• Sudden unexpected death from cardiac arrest.

• For PCI patients, new elevations of biomarkers greater than 3x 99th percentile URL. A subtype related to stent thrombosis is recognized.

• For CABG patients, new elevations of biomarkers greater than 5x 99th percentile URL plus new pathological Q waves or new LBBB, or angiographically documented new graft or native coronary artery occlusion, or imaging of new loss of viable myocardium.

Thygesen, et al. J. Am. Coll. Cardiol. 2007;50;2173-2195

Types of Myocardial Infarction

Type 1: Spontaneous myocardial infarction related to ischemia due to a primary coronary event such as plaque erosion and/or rupture, fissuring, or dissection

Type 2: Myocardial infarction secondary to ischemia due to either increased oxygen demand or decreased supply, e.g. coronary artery spasm, coronary embolism, anemia, arrhythmias, hypertension, or hypotension

Type 3: Sudden unexpected cardiac death, including cardiac arrest, often with symptoms of myocardial ischemia, but death occurring before blood samples could be obtained or before the appearance of cardiac biomarkers in the blood

Type 4a: Myocardial infarction associated with PCI

Type 4b: Myocardial infarction associated with stent thrombosis as documented by angiography or at autopsy

Type 5: Myocardial infarction associated with CABG

Thygesen , et al. J. Am. Coll. Cardiol. 2007;50;2173-2195

“Ischemic” Symptoms

• Not all chest pain is cardiac• Not all cardiac pain is coronary insufficiency• Not all coronary insufficiency is atherosclerosis• Not all coronary occlusion is thrombosis• Not all ACS requires immediate coronary

angiography / reperfusion• 10-15% of myocardial infarctions are

asymptomatic

"False-Positive" Cardiac Catheterization Laboratory Activation Among Patients With Suspected ST-Segment Elevation Myocardial Infarction

D Larson, K Menssen, S Sharkey, et al. JAMA. 2007;298(23):2754-2760

1345 Patients over 3.5 Years1048 Transferred from 30 non-PCI hospitals

297 Presented initially to PCI hospital

10 Excluded5 Died

5 Angiography cancelled

1335 Underwent angiography

187 Had no culprit CAD

0 1 2 3 4 5 6 7 8

Cardiac troponin-no reperfusion

Cardiac troponin-reperfusion

CKMB-no reperfusion

CKMB-reperfusion

Days After Onset of Myocardial Infarction

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URL = Upper Reference LimitURL = Upper Reference Limit99%tile of Reference Control Group99%tile of Reference Control Group

100

Biomarkers in Acute Myocardial InfarctionBiomarkers in Acute Myocardial Infarction

Alpert et al. J Am Coll Cardiol 2000;36:959.Wu et al. Clin Chem 1999;45:1104.

Troponin-I Normal = ≤ 0.09 ng/mlCK-MB Fraction ULN = ≤6 ng/ml

Elevated Troponin Without Overt Ischemic Heart Disease

Cardiac contusion or other trauma, including surgery, ablation, pacing, etc.Congestive heart failure—acute and chronicAortic dissectionAortic valve diseaseHypertrophic cardiomyopathyTachy- or bradyarrhythmias, or heart blockTakotsubo stress cardiomyopathy (Apical ballooning syndrome)Rhabdomyolysis with cardiac injuryPulmonary embolism, severe pulmonary hypertensionRenal failureAcute neurological disease, including stroke or subarachnoid hemorrhageInfiltrative diseases, e.g. amyloidosis, hemochromatosis, sarcoidosis, scleroderma, neoplasia Inflammatory diseases, e.g. myocarditis, endocarditis or pericarditisDrug toxicity or toxinsCritically ill patients, especially with respiratory failure or sepsisBurns, especially if affecting 30% of body surface areaExtreme exertion

Modified from Jaffe et al. (4) and French and White (5).

ECG Manifestations of Acute Myocardial Ischemia(in Absence of LVH and LBBB)

ST elevation

New ST elevation at the J-point in two contiguous leads >0.2 mV in men or >0.15 mV in women in leads V2–V3, or >0.1 mV in other leads

ST depression and T-wave changes

New horizontal or down-sloping ST depression >0.05 mV in two contiguousleads; or T inversion >0.1 mV in two contiguous leads with prominentR-wave or R/S ratio ≥1

QRS Changes Associated With Myocardial Infarction

Any Q-wave ≥0.02 sec or QS complex in “anterior leads” V2 -- V3

Q-wave ≥0.03 sec and ≥0.1 mV deep or QS complex in any two leads of a contiguous lead group:

“lateral leads” I, aVL,V6 “anterolateral leads” V2–V6“inferior leads” II, III, aVF

R-wave ≥0.04 sec in “posterior leads” V1–V2 and R/S ≥1 with a concordant positive T-wave (in the absence of a conduction defect)

ECG Pitfalls in Diagnosing Myocardial Infarction

False positivesBenign early repolarizationLBBBPre-excitationBrugada syndromePericarditis, myocarditisPulmonary embolismSubarachnoid hemorrhageMetabolic disturbances such as hyperkalemiaFailure to recognize normal limits for J-point displacementLead transposition or misplacementCholecystitisTakotsubo stress cardiomyopathy

False negativesPrior myocardial infarction with Q-waves and/or persistent ST elevationPaced rhythmLBBB

Thygesen et al. JACC Vol. 50, No. 22, 2007

1 sec (25 mm / sec)

200 msec

40 msec

1 sec (25 mm / sec)

200 msec

40 msec

1 mv

0.1 mv or “1 mm”

1 sec (25 mm / sec)

200 msec

40 msec

1 mV (10 mm / mV)

0.1 mv or “1 mm”

0 300 150 100 75 60 50 BPM

?Ant-STEMI ?LVH ?HyperK+ ?LBBB ?WNL ?Pericarditis

? Takotsubo ?RBBB+STEMI ?Brugada ?Pul Embolism

Normal

Normal (Early

Repolari- zation)

Normal (Repolari-

zation Variant)

?Ant-STEMI ?LVH ?HyperK+ ?WNL ?LBBB ?Pericarditis

?Takotsubo ?RBBB+STEMI ?Brugada ?Pul Embolism

Brugad

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Peric

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Pulmonary Embolism

DC Cardio- version

RZ: 54 Latin-American male in ED (NOT SFK)

DR: 71 y male with chest pain in the Cardiac Procedures Unit

VP 32 y South Asian male surgical resident sought ED evaluation for chest pain and extreme fatigue. No significant past history. FH positive for premature CAD. CK and troponin-I elevated.

VP 32 y South Asian male surgical resident sought ED evaluation for chest pain and extreme fatigue. No significant past history. FH positive for premature CAD. CK and troponin-I elevated. Onset of pain after running a marathon, without training. Left AMA after overnight observation and IV hydration.

AR 96 y female with acute onset epigastric and substernal pain, nausea, onset 3:30 PM. In ED 6:54 PM, no history of coronary disease, +HTN, +PAF. Systolic murmur Ao valve. Trop-I 15.54 ng/ml, echocardiogram LVH, mild AS, inferoapical akinesis. CCL 7:20 PM.

10275665: NC 25 year old male with abrupt onset of severe chest pain. No substance abuse, no medications, no CV history. Cigarettes ½ ppd. Chol 157 mg/dl, LDL-C 80 mg/dl. CK 81 IU/L, troponin-I 0.05 ng/ml.

10275665: NC 25 year old male with abrupt onset of severe chest pain.No substance abuse, no medications, no CV history. Cigarettes ½ ppd.Chol 157 mg/dl, LDL-C 80 mg/dl. CK 81 IU/L, troponin-I 0.05 ng/ml.

Repeat CK 7668 IU/L, troponin-I >100 ng/ml. Echo LVEF 35% with apical clot.Symptoms began while driving home from first-time skydiving.

1-31-2006 0920 Hrs

34 y Asian F RN from UCSF. Presented to ED with acute onset severe chest pain 1 hr earlier. No CV history. Rare migraine headaches, most recently 5 d earlier. No medications. No illicit drug use, trauma, tobacco or alcohol. No hypertension, no diabetes, never obese, no FH atherosclerotic nor connective tissue vascular disease. No nocturnal chest pain nor palpitation. G2 P2 3 ½ yr post-partum, LMP 2 wks ago, HCG negative, no oral contraceptives.

Total choesterol 165 mg/dl, triglycerides 175 mg/dl, HDL-C 31 mg/dl, LDL-C 99 mg/dl. Troponin I 0.04 ng/ml (nl 0.0-0.09), CK-MB fxn 2.9 (nl <7.8).

DL 64y female hospital ward clerk with abrupt onset of chest pain and dyspnea while rushing to meet son at airport. No CV disease history. Maximum CK xxx IU/L, troponin-I 44.6 ng/ml. Cardiogenic shock required IABP.

RC 83 y male in CV – ICU, immediately post-op from aorto-coronary bypass

RF 82 y female in ED with acute onset epigastric pain and nausea and substernal chest pressure

JC 27 y male with no CV disease history presented to ED in RWC with acute chest pain and shortness of breath. Substance abuse denied, toxicology studies negative.

JC 27 y male with no CV disease history presented to ED in RWC with acute chest pain and shortness of breath. Substance abuse denied, toxicology studies negative. CK 1372 IU/L, troponin-I >50 ng/ml. Platelet count 1472 K/mm3. Emergent transfer to the CCL. Follow-up ECG 30 minutes later:

NW 36 y male alcoholic fell unconscious at home, ambulance to ED, intubated. CK 775 IU/L, troponin-I 0.14 ng/ml.

NW 36 y male alcoholic fell unconscious at home, ambulance to ED, intubated. CK 775 IU/L, troponin-I 0.14 ng/ml.

Repeat ECG 9 minutes later:

42 y Asian female on chemotherapy for metastatic breast carcinoma, acute onset chest pain and dyspnea, troponin-I 1.11 ng/ml

42 y Asian female on chemotherapy for metastatic breast carcinoma, acute onset chest pain and dyspnea, troponin-I 1.11 ng/ml.

Echocardiography revealed large pericardial effusion due to carcinomatosis.

AG 81 y male with chest pain worse with inspiration, sternal tenderness, elevated troponin-I.

AG 81 y male with chest pain worse with inspiration, sternal tenderness, elevated troponin-I.

Brought to ED by EMT from MVA. X-ray diagnosis of sternal fracture.

RH: 56 y male in ED with chest pain

DG: 58 y male in ED with lightheadedness and near syncope

JS: 84 y male in CV - ICU

How to Avoid Misdiagnosis

• Talk to the patient, take a history

• Examine the patient

• Obtain and review original documents

• Do not believe everything in the computer

• Consider the differential diagnosis

• Re-examine the patient

• Think

Questions to Ask Yourself

• Is my diagnosis correct?• Is my treatment plan appropriate for

this diagnosis?• Is my treatment plan appropriate for

this patient?• Does my patient understand and agree with the treatment plan?• Do I need help?

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