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Diagnosing Myocardial Infarction

Diagnosing Myocardial Infarction. Kimberly A. Dovin, MD, PGY3 Case Conference February 18, 2004. MI: Old Definition. Requires 2 of 3: Typical Sx Enzyme rise Typical EKG (Q waves). MI: Defined 2000. Acute, evolving or recent MI Requires 1 of 2:

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Diagnosing Myocardial Infarction

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  1. Diagnosing Myocardial Infarction Kimberly A. Dovin, MD, PGY3 Case Conference February 18, 2004

  2. MI: Old Definition • Requires 2 of 3: • Typical Sx • Enzyme rise • Typical EKG (Q waves)

  3. MI: Defined 2000 Acute, evolving or recent MI • Requires 1 of 2: • Typical rise and gradual fall (troponin) or more rapid rise and fall (CK-MB) of markers of myocardial necrosis with >= 1 of: • Symptoms • Q waves • EKG c/w ischemia • S/p coronary artery intervention • Pathologic findings of AMI

  4. MI: Defined 2000 Established MI One or more of - new Q waves on EKG - pathologic findings of healed/healing MI

  5. Symptoms of MI • Chest, epigastric, arm, wrist, jaw pain or discomfort w/ exertion or at rest • Usually lasts 20 min, but may be less • Associated sx: dsypnea, diaphoresis, nausea, vomiting, light-headedness • With or without chest discomfort

  6. Biochemical markers • Troponin: High sensitivity, high specificity for myocardial tissue • CK-MB: less tissue specific, but better specificity for irreversible injury • Myoglobin: for rapid diagnosis

  7. Biochemical Markers II

  8. Protein Molecular mass (kD) First detection Duration of detection Sensitivity Specificity Myoglobin 16 1.5–2 hours 8–12 hours +++ + CK-MB 83 2–3 hours 1–2 days +++ +++ Troponin I 33 3–4 hours 7–10 days ++++ ++++ Troponin T 38 3–4 hours 7–14 days ++++ ++++ CK 96 4–6 hours 2–3 days ++ ++ Biochemical Markers III

  9. Non MI Causes of Troponin Elevation • Tachycardia • PE w/ Right Vent infarct • Cardiac failure w/ myonecrosis • Cardiac surgery • Myocarditis • Renal failure

  10. EKG Findings: Ischemia • Patients with ST segment elevation: • New elevation at the J point in 2+ contiguous leads • >= 0.2mV in V1-3 • >= 0.1mV in all others • Patients without ST segment elevation: • ST segment depression • T wave abnormalities

  11. EKG Findings: Established MI • ANY Q waves in V1-3 • Q wave >= .03s in I, II, aVL, aVF, V4-6

  12. Coronary Angiogram • Observer variability • Discordance betw severity of lesion and physiologic effects • Greater stenosis vs more unstable plaques? • 2-D picture of a 3-D problem • Diffuse disease may limit estimation of “abnormal segments” • Missed lesions

  13. “ It is now clear that any amount of myocardial damage, as detected by cardiac troponins, implies an impaired clinical outcome for the patient.” “A review of currently available data demonstrates no discernible threshold below which an elevated value for cardiac troponin would be deemed harmless.”

  14. Bibliography • Elliott Antman MD, Jean-Pierre Bassand MD, Werner Klein MD, Magnus Ohman MD, Jose Luis Lopez Sendon MD, Lars Rydén MD, Maarten Simoons MD and Michal Tendera MD Myocardial infarction redefined––a consensus document of The Joint European Society of Cardiology/American College of Cardiology committee for the redefinition of myocardial infarction Journal of the American College of Cardiology Volume 36, Issue 3 , September 2000, Pages 959-969 • John K French and Harvey D White Clinical implications of the new definition of myocardial infarction Heart 2004;90:99-106 • Steven E. Nissen MD, FACC Pathobiology, not angiography, should guide managementin acute coronary syndrome/non–ST-segment elevation myocardial infarction*1The non-interventionist's perspective Journal of the American College of Cardiology Volume 41, Issue 4, Supplement 1 , 19 February 2003, Pages S103-S112

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