Acute Coronary Syndromes. Erika Newton, MD Emergency Medicine July 2, 2009

Transcription

1 Acute Coronary Syndromes Erika Newton, MD Emergency Medicine July 2, 2009

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3 Pathophysiology 3 paths to ACS demand substrate acute blockage Acute blockage = unstable plaque. #1 unsolved problem in Cardiology: how to identify these lesions Nucleus Communications, Inc., 2003

4 The Vulnerable Plaque: A Visual Aid

5 ACS Terminology What are the acute coronary syndromes? How are they similar? How are they different? ACS = STEMI, non-stemi, unstable angina Same causes Can be clinically indistinguishable Differ in extent of damage Differ in ease of diagnosis

6 ?? What This Talk Should Teach You How to diagnose ACS to e f a s it's n e h W ge r a h c T C dis y r a ron o c a er d r o o t When How to treat ACS? ive g I d l u Sho lockers? beta-b H e d o C la l a c o t When?

7 Diagnosing ACS can be a Challenge Symptoms varied & nonspecific Available tests mostly inaccurate Admit-all strategy doesn't work And yet... Not a diagnosis you want to miss Mortality of untreated AMI 25% Missed MI #1 source of total malpractice payouts Many of your patients will have it 2 million cases per year in U.S. diagnosed #1 cause of death in U.S. & worldwide

8 Treating ACS can be a Challenge Evidence & guidelines keep changing ACS therapies have low therapeutic index Requires matching treatment to disease severity Diminishing returns since aspirin, lytics & PCI came along

9 Mortality in AMI: How Low Can it Go? Percent % s 1960s 1970s 1980s 1990s 2000s Mel Herbert, Jeffrey Tabas

10 Case 1 68 y/o man with crushing substernal chest pain & dyspnea x 1 hour

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16 Management of STEMI Rapid coronary reperfusion Cath lab (PCI) within 90 mins* Call Code H Or, Thrombolytics within 30 mins* Other meds Goals: Anti-platelet, pain relief, work of heart, anti-thrombotic AHA 2007: ASA, nitrates, heparin, clopidogrel, +/- B-blocker Supportive care ABC's detect & treat complications Dysrhythmia, pulmonary edema, shock, high-grade block *of 1st medical contact

17 PCI vs. Lytics PCI: lower mortality + reinfarct rate at 30 days Slight edge even if transfer required Advantage as time since symptom onset Lytics: still darn good NNT 40 to save one life (20 with aspirin) Preferred if patient presents early & PCI far away Absolute contraindications: risk of bleed active internal bleeding, bleeding disorder, aortic dissection, prior intracranial bleed, head trauma < 3 mos, brain aneurysm/avm/ca, ischemic CVA 3 mos-3 hrs prior

18 AHA 2007 Recommendations (STEMI, NSTEMI, UA) Morphine: Class I (STEMI), IIa (UA) NSAIDs: contraindicated ( mortality, AMI, CHF) Metoprolol: IV on arrival if BP else po by 24 hrs. Shock risk. Hold for signs/risks of shock, CHF, SBP < , age > 70, HR > 110 or < 60, heart block, asthma, time Facilitated PCI (STEMI): not recommended Heparin/enoxaparin: yes if lytics, PCI or neither. Bleed risk. Aspirin: mg po unless allergic Clopidogrel: mg po, age <75. Bleed risk. Platelet GP IIb IIIa inhibitors: soft evidence, soft guidelines, bleed risk

19 Case 2 History: 70 y/o woman with two prior MIs, no chest pain since stents placed last year, now with exertional chest pressure & dizziness for a few days, worse today. Exam: HR 80, BP 140/90, RR 20, sat 97% RA. Appears comfortable, normal heart/lung exam.

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21 ACS Risk Stratification Purpose: Assess risk of bad outcome from ACS Match aggressiveness of treatment to level of risk

22 Criteria for ACS Risk Stratification TRACK 5 ST Elevation Call Code H ST Elevation AMI New LBBB with sxs ST Depression in V1 - V3 c/w post. AMI + ACS sxs TRACK 4 High Risk ACS No ST Elevation No track 5 features ST Depression + ACS sxs T wave inversion + ACS sxs Intractable ACS sxs Hemodynamic instability + ACS sxs Acute CHF with ACS sxs Positive Troponin (NSTEMI) TIMI Risk 5-7 TRACK 3 Intermediate Risk ACS TIMI Risk 3-4 TRACK 2 Low Risk ACS TIMI Risk 0-2 TRACK 1 Non Cardiac Etiology No track 5 or 4 features Classic angina or new complaint angina <20 minutes at rest relieved by nitroglycerin Angina >20 minutes at rest now resolved Nocturnal or progressive angina No track 5, 4, or 3 features Atypical sxs with normal/unchanged EKG Cocaine abuse

23 Is it ACS? 58 y/o woman with occasional sharp left chest pains x months, slightly worse with breathing. Longer episode today. Normal stress test last month. PMH: fibromyalgia, thyroid dis., DM, HTN 80 y/o man whose home health aide called 911 when patient briefly appeared tachypneic. Now comfortable but just not myself today. PMH: BPH, DJD 40 y/o woman with frequent ED visits for minor complaints, now c/o chest pain, demanding morphine. Takes Xanax for anxiety.

24 How helpful are clinical factors?

25 Symptoms Crushing substernal chest pressure Or, nonspecific discomfort in the chest, arm, neck, jaw, back, abdomen Or... Dyspnea Nausea Fatigue Syncope Malaise Dizziness Paresthesias/numbness No symptoms Diaphoresis

26 Atypical ACS Symptoms: Just How Atypical Are They? 40% of AMI patients presented w/ atypical pain & 35% without AMI had typical pain Lee, Arch Int Med 1985 Only 50% of 721 AMI patients, many elderly, presented w/ any chest pain Gupta, Ann EM 2002 Of 550 MIs, chief complaint = dyspnea in 17%, cardiac arrest 7%, dizzy/weak/syncope 4% Milner, Am J Card 1999 Of non-chest-pain chief complaints, 54% had dyspnea, 19% abdominal pain, 15% fatigue Uretsky, Am J Card 1977

27 Do Any Pain Characteristics Help? Lee et al, Arch Int Med 145:65, 1985

28 Is it ACS or Esophageal Pain? Davies et al, J Clin Gast 7:477, 1985

29 How We Fare With Atypical ACS We underdiagnose & undertreat Mortality 3x as high up to 30%! 2% MIs missed in ED, patient sent home

30 Who Are We Missing and Who's Missing Them? ACS patients we tend to miss Younger, female, nonwhite, no chest pain, normal EKG ACS patients who present atypically Older, female, diabetic, prior CHF In 65 cases of missed AMI, physicians Documented less detail about pain Documented risk factors less often Were less experienced Rusnak, Ann EM 1989

31 Risk Factors Demographics: age, sex Traditional risk factors smoking, family history, HTN, DM, cholesterol Cocaine use Other PMH & comorbidity Think secondary ischemia

32 No Risk Factors No ACS Risk factors raise odds of CAD over a lifetime Han et al. Ann EM Feb N = 10,806 registry patients with suspected ACS # of risk factors as predictors of ACS, by age <40 yrs: 0 LR LR yrs: 0 LR LR 2.13 >65 yrs: 0 LR LR 1.09

33 Physical Exam May identify: The acutely ill patient ACS complications Contraindications to specific ACS therapies Another cause of chest pain

34 How helpful are diagnostic tests?

35 Normal or Abnormal?

36 Same Patient, Old EKG

37 EKGs in ACS Can be... Normal Code H!-worthy A bn orm al Almost but not quite normal...but are under no obligation to be impressive.

38 What the EKG Can Tell You Does the patient need immediate reperfusion? STEMI, new LBBB, posterior wall MI Any potentially unstable ACS complications? Dysrhythmias, high-grade blocks Any other abnormalities that could be ischemic? Ischemic ST & T wave changes often subtle 30-day death or reinfarction rate, by initial EKG: 5.5% if T-waves 10.5% if STs (p < 0.001) Savonitto, JAMA 1999

39 .And what it can't: You can't rule out ACS with an EKG. MI: initial EKG nondiagnostic in 30-60%, normal in 10%! nstable angina: EKG even less helpful often nonspecific or norm

40 Biomarkers Role of troponin in the ED Positive troponin diagnoses AMI, level prognostic Troponin measurable some time after 4 hrs Sensitivity with time, depends on cut-off Negative trop-i 6-12 hrs after symptoms rules out MI Why not use other biomarkers? Myoglobin: nonspecific, gone in 24 hrs CPK-MB: less specific & less sensitive New markers actively sought

41 Prognostic Value of Initial Troponin Morality rates according to initial troponin I level. Antman, NEJM 335:1342, 1996

42 And yet... You can't rule out ACS with enzymes. (Negative enzymes don't rule out unstable angina.)

43 Patients who can be Discharged if Enzymes are Negative Low-risk; no symptoms in 12 hrs; normal EKG* Single troponin rules out MI (but not ACS) Low-risk; atypical symptoms; normal EKG* Two troponins, 4 hrs apart, one > 6-8 hrs after sxs Low-risk; prolonged, ongoing pain; normal EKG* Two troponins +/- resting sestamibi *& early stress test can be assured

44 Non-Invasive Tests & Cardiac Cath Treadmill test: a coin toss Stress-echo, nuclear stress Negative testing & enzymes in low-risk chest pain work-up predicts very low subsequent event rate Prior negative test: no value in ruling out ACS now Resting sestamibi: during pain 92% sensitive CT: OK for low-risk patient with negative troponin Normal CT predicts very low event rate can DC home Significance unclear if +plaque; cut-off arbitrary Cardiac cath: gold standard but just how good?

45 A New View of CAD Driven by the ascendancy of angiography and the success of revascularization strategies that target arterial stenoses, the degree of arterial narrowing dominated our thinking about the pathophysiology of CAD for decades. We viewed the risk of events as dependent on the degree of stenosis and envisioned atherosclerosis as a segmental or focal disease...we now recognize that for much of its life history, the atherosclerotic lesion grows outward, or abluminally, rather than inward...even portions of the coronary arterial tree that appear perfectly normal by angiographic criteria often harbor a substantial burden of atherosclerosis...stenoses represent the 'tip of the iceberg' of atherosclerosis...[this will mean] considerable consequences for our current understanding of the acute coronary syndromes... Libby & Theroux, Circulation 2005

46 ACS Testing: The Next Wave? Inflammatory markers Intravascular ultrasound Angioscopy Optical coherence tomography Thermography Raman/near-infrared spectroscopy Electron beam computed tomography Magnetic resonance imaging

47 ed the unsettling prevalence of atherosclerotic lesion

48 Last But Not Least Well Maybe Least Can Treatment Response Tell Us Who Has ACS? No: Of 250 patients admitted with chest pain, 88% of ACS patients, 92% non-acs, had a favorable response to nitrates Shry AmJCard 2002 ACS patients, inconveniently, found to have high rate of favorable responses to GI meds Failure to respond to nitrates not found helpful in ruling out ACS

49 The Bottom Line So we miss a few... At least 2% of patients with acute MI are missed & sent home from the ED with twice the mortality. There are about 2 million MIs every year. What's 2% of 2 million? Missed MIs are the #1 contributor to total malpractice payouts. Question: What's an acceptable MI miss rate? There isn't one.

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