Rate of Missed MIs in ED ======================== þ How many people in the hospital with MI had no chest pain? - 25% [Uretsky BF, Farquhar DS. Symptomatic myocardial infarction without chest pain: Prevalence and clinical course.] þ How many people have an MI and it's only found on a routine EKG later? - 30% of those with MIs (half with no symptoms, half with very atypical symptoms) [Kannel WB, Abbott RD. Incidence and prognosis of unrecognized myocardial infarction. N Engl J Med 1992;311:1144-1147.] Many studies have documented a missed diagnosis rate (of MI) of from 5 - 8% in ED patients presenting with chest pain. Upon analysis several of these studies have determined that approximately half of these cases could have been picked up had the physician either not misinterpreted the EKG, not failed to admit patients with recognized ischemia at rest nor ignored ECG changes not known to be old (1). If you miss 1 low risk patient in 40 per year who turns out to have an MI and you proceded to admit 20 or so MIs per year (personally) through your ED then you have met your quota for the year. Similar analysis has also revealed that patients with missed MI also are generally younger and present with more atypical histories (this is your classic low risk group--so what did you expect?). KC> OK, let's accept this 5-8% number. It always seemed to me, based on what you describe above, that if you are really "good" then you can cut this down to the 2.5-4% figure. "Good" means being obsessive about admitting patients with any EKG changes, or any abnormality on the EKG if you don't have a previous one, or anyone who might have rest pain. And getting a reputation of being a "softie" to those to whom you're admitting the patients. And occasionally have to do a hard-sell job to get a patient admitted. So, down to the 2.5-4% range. I doubt this figure includes much if any use of a single enzyme test. Assuming the timing is right, then, one should be able to get this "miss" rate down a bit more -- not sure our data justifies trying to calculate the exact numbers, but significantly below this, maybe 1-2%? I firmly believe that if one insists upon no more than a 1 in 1000 (0.1%) rate of missed MI in the ED then the only way to accomplish this is to indiscriminantly admit every patient over the age of 35 who presents with chest pain irrespective of history, enzyme level, risk factors or ECG. The current state of the art (standard of practice) is far worse than this (it's 5 - 8%). That doesn't mean we should not try to improve upon this statistic. A simple way of halving it,as I mention above, is to carefully scrutinize the ECG and resist the temptation to try outpatient management when ischemia at rest is strongly suspected. KC> Agreed. But my "comfort zone," based primarily on personal factors, would be about 1:1000 for missing MIs. I can't quite get there, but I suspect, and hope, that by observing the above, I can get reasonably close: a factor of 10 or so away. A cost effectiveness analysis indicates that an infarction admission rate of from 5 to 10% is appropriate (2). As a corollary, admission of patients with a 2 to 3% likelihood of MI cannot be justified. KC> Hmm. Is my role in life to be a patient advocate, and do what is best for the patient, or to be cost-effective? "You have about a 3% chance of this chest pain being an MI. You'd be better off in the hospital, but the New England Journal says it's not cost-effective for me to admit you, so you've got to go home. Don't worry, there's only about a 1:10,000 chance you'll have an arrythmia and wake up dead." An old caricature of the grumpy, sleepy physician has him telling the patient to 'take an aspirin and call me in the morning.' In the case of ischemic heart disease this is not bad advise. Aspirin may not be quite as good as heparin for the treament of unstable angina but it's not bad at all (3,4). In the case of acute MI the use of aspirin is every bit as good as streptokinase as a single agent (although, admittedly the combination of both is better than either one alone) (5). KC> "I think there's only a 1:1000 chance that this pain is related to your heart. That's pretty unlikely. And I think that if we admitted you to the hospital for this, and do all sort of fancy tests now, you're more likely to have some sort of problem from the tests and being in the hospital than if you were at home. Like I said, I really don't think it's your heart. I can only be 99.9% sure, but that's pretty good. And if we give you an aspirin now -- you've heard that aspirin is a blood thinner, right? -- if we give you an aspirin now, and have you take one a day from now on, it is good to protect against heart attacks, and is unlikely to cause any problems for you. Your doctor will recheck you tomorrow in the office, OK?" KC> Try that with different numbers and see how it feels if someone is telling it to you. Attempting to 'catch' every single patient with ischemic chest pain is a quest for the Holy Grail. It leads to untenable situations such as that described by James Li in a recent post where a dozen patients are loitering in the ED for 20 hours awaiting their 'rule out'. H. Louzon MD KC> Agreed. You can't catch all of anything, unless maybe it's arrows sticking out of the chest. But you can try to reduce it to acceptable limits -- acceptable to patients as well as doctors. KC> Now, what about PEs? If someone asks "Doctor, could this chest pain be a blood clot in my lung?" what do we say? "Duh, I dunno." --Keith Conover, M.D. (1) Lee et. al. Clinical Characteristics and Natural History of Patients with Acute Myocardial Infarction Sent Home from the Emergency Room. Am J. Cardiology 1987;60:291-224 (2) Fineberg et.al. Care of Patients With a Low Probability of Acute Myocardial Infarction: Cost Effectiveness of Alternatives to Coronary Care Unit Admisions. NEJM 1984;310;1301-7 (3) Theroux et. al. Aspirin, Heparin, or Both To Treat Acute Unstable Angina. NEJM 1988;319:1105-11 (4) Theroux et. al. Aspirin Versus Heparin to Prevent Myocardial Infarction During the Acute Phase of Unstable Angina. Circulation 1993;88(1):2045-48 (5) ISIS-2 Collaborative Group: Randomized Trial of IV Streptokinase, oral Asirin Both or Neither Among 17,187 Cases of Suspected Acute Myocardial Infarction. LAncet 1988;2:349-60 ------------------------------------------ McCarthy BD, Beshansky JR, D'Agostino RB, Selker HP Missed diagnoses of acute myocardial infarction in the emergency department: results from a multicenter study [see comments] Ann Emerg Med 1993 Mar;22(3):579-82 STUDY OBJECTIVE: To determine the rate of missed acute myocardial infarction (AMI) in the emergency department and the factors related to missed diagnoses. STUDY DESIGN: Observational and case-control study. SETTING: Data were analyzed from a multicenter study of coronary care unit admitting practices that included patients who presented to the ED with chest pain or other symptoms suggestive of acute cardiac ischemia (N = 5,773). Patients with missed AMI (cases) were compared with control patients admitted with AMI and to a second control group of patients discharged without AMI. RESULTS: Of 1,050 patients with AMI, 20 (1.9%; 95% confidence interval, 1.2-2.9%) were not admitted. Patients with missed AMI were significantly less likely to have ECG changes and a history of AMI or nitroglycerin use than patients admitted with AMI. However, they were significantly more likely to have ECG changes than patients discharged without AMI. Five patients with missed AMI (25%) had ST-segment elevation, and seven (35%) were discharged with a diagnosis of ischemic heart disease by the physician in the ED. Death or potentially lethal complications occurred in 25% of missed AMI patients. CONCLUSION: The rate of missed AMI in the ED was only 1.9%. However, 25% of these might have been prevented had ST-elevation not been missed, and another 25% might have been prevented had patients who were recognized to have ischemic heart disease by the physician in the ED been admitted.