Myocardial Infarction ===================== þ Atypical Early EKG signs of Impending MI þ Myeloperoxidase - released from ulcerated plaques - may be a marker for acute coronary syndrome, i.e., unstable angina - study looking @ troponin also looked at myeloperoxidase - troponin negative but ^ myeloperoxidase predicted adverse events - not diagnostic of infarction - better than C-reactive protein (CRP) - 35% of unstable angina patients had level less than average; not sensitive. þ Integrelin þ Differences between RV and LV infarcts - Right ventricular infarcts have been shown to have a better outcome and mortality if managed with PTCA rather than thrombolysis. In addition, RV infarcts are pre-load dependent. These are the patients who's blood pressure goes throught the floor when you give them nitro... thus you had better be ready for the pressure to drop in these patients. --Phillip L. Coule, M.D., EMT þ See also Chest Pain: þ Association of MI and cardiac arrest with Chlamydial infection þ ACC/AHA Guidelines - ACC/AHA Guidelines for the Management of Patients with Acute Myocardial Infarction. JACC 1996;28:1328-1419. and: ACC/AHA Guidelines for the Management of Patients with Acute Myocardial Infarction Executive Summary. Circulation 1996;94:2341-2350 ED-relevant excerpt of Executive Summary: Harvey Louzon's perceptive comments: þ Statistics - 5.5 million people present to EDs yearly with chest pain - 1.5 million people present to EDs with MIs; only a portion of these present with chest pain (?half). - Percentage of chest pain patients inappropriately discharged: + 1976: 7.7% (Schor) + 1987: 3.8% (Lee) + 1993: 1.9% [McCarthy. Ann Emerg Med 1993:22.] - Malpractice closed claims: missed MI 7% of cases, but 21% of $ paid. - From the Framingham study, of 708 patients who had MIs, 213 (30%) were only recognized later, in retrospect, on routine EKGs. Half had no symptoms and the other half had very atypical symptoms. [Kannel WB, Abbott RD. Incidence and prognosis of unrecognized MI. N Engl Med J 1992;311:1144-1147.] þ Effective Treatments for MI - Thrombolytics - Beta Blockers - Vasodilators - Aspirin - Magnesium (1.9 g in 50 cc D5W over 5 minutes, then 65 mmol [15.6g] in 500 cc D5W over 24 hours); appears to preserve myocardial function. [Woods KL, Fletcher S, Roffe C, et al. Intravenous magnesium sulphate in suspected acute myocardial infarction: results of the second Leicester Intravenous Magnesium Intervention Trial (LIMIT-2). Lancet 1992; 339:1433.] - oral anticoagulants [Lay J, Antman EM, Jiminez-Silva J, et al. Cumulative meta-analysis of therapeutic trials for myocardial infarction. N Engl J Med 1992; 327:248.] - angioplasty; is (slightly) better than thrombolysis. [Vaitkus PT. Percutaneous transluminal coronary angioplasty versus thrombolysis in acute myocardial infarction: A meta-analysis. Clin Cardiol 1995:18:35-38.] þ INeffective Treatments for MI - nifedipine [Goldbourt et al. Early administration of nifedipine in suspected acute MI. Arch Intern Med 1993 Feb 8:153(3):345-53.] Commentary: - Glucose, Insulin, Potassium (GIK): [Mehta SR et al. Effect of glucose-insulin-potassium infusion on mortality in patients with acute ST-segment elevation myocardial infarction: The CREATE-ECLA randomized controlled trial. JAMA 2005 Jan 26; 293:437-46.] - Heparin? þ Treatment for Nausea and Vomiting with MI - Compazine is safe [Wasserberger J, Ordog GJ, Lau JC, Gilston M, Herman LS. Intravenous prochlorperazine for the rapid control of nausea and vomiting in acute myocardial infarction: a clinical observation. Am J Emerg Med 1987 Mar;5(2):153-6.] - the new ACC/AHA recommendations suggest atropine but provide no references. þ MSO4 for MI pain relief þ Unusual Risk Factors for MI - Psychiatric illness in young women, probably due to use of benzodiazepines and tricyclics. One study found in age group 16-39 relative risk increased 17-fold by use of these drugs. Notes previous study indicated relative risk increased by 4x in those with panic disorder. [Thorogood M, Cowen P, et al. Fatal myocardial infarction and use of psychotropic drugs in young women. Lancet 1992;34:1067-1068.] þ MI Diagnosis in the ED - For clinical features of MI chest pain, see . - Time Course of Markers: Start Peak Fall + CK-MB 4 hr 18-24 hr 3-4 d + Troponin-I 3-6 hr ? 2 wk [more sens than CPK] + - role of EKG and CPK: - To R/O the patient yourself with serial ECGs and enzymes in the ED. - Newer tests for MI: Troponin, etc. - Deciding which chest pain patients need ICU admission. - Does an IM injection raise the CPK? - Diagnosing MI in the ED: value of single CPK and short "rule-out" protocols - Rate of Missed MIs - Right Ventricular Infarcts - Chest Pain from Cocaine - Computer programs aren't as good as good doctors. [Goldman et. al. A Computer-Derived Protocol to Aid in the Diagnosis of Emergency Room Patients with Acute Chest Pain. NEJM 1982:307;588-596.] þ Prognosis for MIs missed in ED, or patients with chest pain who leave AMA: - Because of high dollar loss that missed MIs represent from a legal standpoint much effort has been expended in an attempt to identify characteristics of this patient population. - One older study by Lee (1) found that 4% of their patients were sent home, from the ED, with an acute MI. This is consitent with a range of from 2% to 7% (the latter figure from an older Israeli study that used less specific criteria for diagnosing AMI). Analysis of these missed MIs revealed that 49% of them could have been averted had the physician not failed to correctly interpret the ECG nor failed to admit patients with recognized ischemic pain. Of 35 missed MIs, 5 had unrecognized ST segment elevations on the ED ECG. Failure to admit patients with recognized ischemic pain at rest (such as your patient) accounted for the remainder of the missed MIs. In a more recent study in the Annals substantially similar conclusions were reached (2). The missed MI rate in the latter study was only 1.9%. Twenty-five percent of the missed MIs were related to a failure to appreciate ST segment elevation (once again). An additional 25% were associated with failure to admit patients with recognized ischemia. --H. Louzon MD (1) Lee et. al. Clinical Characteristics and Natural History of Patients with Acute Myocardial Infarction Sent Home from the Emergency Room. Am J Card 1987;60:219-224 (2) McCarthy et. al. Missed Diagnosis of Acute Myocardial Infarction in the Emergency Department: Results from a Multicenter Study. Ann Emer Med 1993;22:579-582 - Missed MI patients have a very poor prognosis: [Lee et. al. Clinical Characteristics and Natural History of Patients with Acute Myocardial Infarction Sent Home from the Emergency Room. Am J Card 1987;60:219-224.] - AMA chest pain patients have an intermediate prognosis. [Lee TH, Short LW, Brand DA, et al. Patients with acute chest pain who leave emergency departments against medical advice: prevalence, clinical characteristics, and natural history. J Gen Intern Med 1988; 3:21-4.] Abstract: þ MI and Pregnancy