Acute Coronary Syndromes - part III
Nov 26th, 2008 by sandnsurf
RISK STRATIFICATION OF PATIENTS WITH SUSPECTED AMI
- Less than 30% patients currently admitted to CCU have final diagnosis AMI. Conversely 2-5% AMI patients are inadvertently sent home, accounting for 25% of all emergency care malpractice dollars awarded in litigation.
- Twenty-five percent AMI patients have atypical symptoms and signs, 50% an initial non-diagnostic ECG. EDs +/- chest pain evaluation units (CPEU) care for the low and intermediate risk chest pain patients.
Swap C, Nagurney J. Value and limitations of chest pain history in the evaluation of patients with suspected acute coronary syndromes. JAMA 2005;294:2623-29. [Reference]
- Risk stratification pathway using an Accelerated Chest Pain Assessment Protocol (ACPAP) has been validated using enzymes and ECG at 0 and 6-8 hours and EST.
Aroney C, Dunlevie H, Bett J. Use of an accelerated chest pain assessment protocol in patients at intermediate risk of adverse cardiac events. MJA 2003; 178:370-4. [Reference] (Editorial Fitzpatrick M. MJA 2003; 178:364-5). [Reference]
- High risk applies if have any one or more of: repetitive or prolonged (>10 min) chest pain; raised troponin or CK-MB on arrival or at 6 / 9 hours; ECG changes; haemodynamic compromise with SBP <90 mmHg, cool peripheries, sweating, Killip Class >1 heart failure; new-onset mitral regurgitation; VT; syncope; LVEF <40%; prior PCI in last 6 months or prior CABG ever; and diabetes or chronic renal failure (eGFR <60ml/min) with typical ACS symptoms. They all need CCU.
- Intermediate risk applies if have no high-risk features + had chest pain in last 48 hrs that occurred at rest or was repetitive or prolonged, but now resolved; age > 65 yrs; known CAD eg prior AMI; ≥ 2 risk factors of hypertension / family history / smoker / hyperlipidaemia; and diabetes or chronic renal failure (eGFR <60ml/min) but atypical ACS symptoms. They should all have a stress test (exercise ECG or myocardial perfusion scan)before discharge, providing serial cardiac enzymes and ECGs were normal on arrival and at 6 / 9 hrs.
- Low risk only applies to patients with clinical features consistent with ACS withoutintermediate or high-risk features (see above); and also a neg troponin + normal ECG at 0 and 6 / 9 hours. They do not need immediate stress testing, but can be discharged to outpatient care.
National Heart Foundation of Australia; The Cardiac Society of Australia and NZ. Guidelines for the management of acute coronary syndromes 2006. Med J Aus 2006;184 :S1-S29 [Reference].
- Interest in earlier ‘rule-out’ of myocardial damage with ECG and bedside testing on arrival and at 90-120 minutes of myoglobin, CK-MB and troponin, or change in (∆) troponin. All rapidly available as a bedside Point-of-Care Test (POCT). Many other markers being studied such as BNP, IMA etc.
McCord J, Nowak R, McCullough P et al. Ninety-minute exclusion of acute myocardial infarction by use of quantitative point-of-care testing of Myoglobin and troponin I. Circulation 2001;104:1483-88. [Reference]
- Still need to rule out inducible ischaemia by stress testing, ideally prior to discharge from hospital, or within 72 hours as an outpatient.
Meyer M, Mooney R, Sekera A. A critical pathway for patients with acute chest pain and low risk for short-term adverse cardiac events: role of outpatient stress testing. Ann Emerg Med 2006;47:427-35. [Reference]
- Early discharge at 2-3 hours has been proposed in very low risk patients with normal initial ECG, no previous ischemic chest pain, and age younger than 40 years, or if over 40 years negative markers at 0 and 2 hours. NB: not prospectively validated yet.
Christenson J, Innes G, McKnight D et al. A clinical decision rule for early discharge of patients with chest pain. Ann Emerg Med 2006;47:1-10. [Reference]
- Therefore study underway to derive a robust, highly sensitive clinical decision rule to identify low risk patients safe for early discharge.
Hess E, Wells G, Jaffe A et al. A study to derive a clinical decision rule for triage of emergency department patients with chest pain: design and methodology. BMC Emergency Medicine 2008;8:3.1-10 [Reference].
- Chest pain evaluation unit (CPEU) appropriateness undeniable; staffing, facility and cost issues more complex. Overall care and algorithms for risk stratification must be collaborative between disciplines.
Body R. Emergent diagnosis of acute coronary syndromes: Today’s challenges and tomorrow’s possibilities. Resuscitation 2008;78:13-20 [Reference]. (Excellent overview of current difficulties in risk-stratification).
- Note that patients discharged after a ‘possible AMI’ ruled out still have a higher mortality compared to a matched population, or those who did have an AMI!
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