How Valuable is the Initial ECG Recorded in the ED?
February 28, 2002 4 minutes read
How Valuable is the Initial ECG Recorded in the ED?
Abstract & Commentary
Synopsis: Patients with an initially normal ECG suffer a substantial mortality rate.
Source: Welch RD, et al. JAMA. 2001;286:1977-1984.
Although only 2.1% of patients with acute myocardial infarctions (AMI) were discharged from the emergency department (ED) with a normal electrocardiogram (ECG), it should be noted that the 30-day mortality rate among these patients has proved to be high, in the range of 10.5%.1 Multiple studies have suggested that a normal or nonspecific ECG portends a low rate of mortality and/or life-threatening complications;2-5 however, to date, there have been no large multihospital studies of patients with AMI that have addressed the independent prognostic value of a normal or nonspecific initial ECG.
The National Registry of Myocardial Infarction (NRMI) is an observational database of hospitalized patients with confirmed AMI that was instituted in 1989. These data have permitted cardiologists to compare the risk of in-hospital death and life-threatening complications among patients with both normal and diagnostic initial ECGs. Welch and colleagues reported their analysis of 391,208 patients with AMI whose initial ECG in the ED recorded between June 1994 and June 2000 was within normal limits or demonstrated the presence of only nonspecific abnormalities. In-hospital mortality rates proved to be 5.7%, 8.7%, and 11.5%, while the rates for the composite of mortality and life-threatening adverse events were 19.3%, 27.5%, and 34.9% for the normal, nonspecific, and diagnostic ECG groups, respectively, in patients who proved to have AMI. After adjusting for other predictor variables, the odds for mortality for the normal ECG group was 0.59 and the odds for mortality for the nonspecific group was 0.70 compared with the diagnostic ECG group. Therefore, it would appear that in this large cohort of patients with AMI, patients presenting with normal and nonspecific ECGs had significantly lower in-hospital mortality rates and adverse events than did those patients with diagnostic ECGs.
Comment by Harold L. Karpman, MD, FACC, FACP
More than 5 million patients per year are seen in EDs for chest pain or related symptoms, and it has been clearly determined the initial ECG recorded is the first and most effective tool for risk-stratification of these patients.7 It is clear that AMI patients presenting with normal or nonspecific abnormalities on ECGs have a lower in-hospital mortality rate than do patients with ECGs diagnostic of acute MIs. However, the data presented by Welch et al now clearly demonstrate that patients with initially normal ECGs suffered a substantial mortality rate, in fact, one that approximates the 30-day risk of AMI patients with ST segment elevations treated in recent perfusion therapy trials.8 The results also reveal that the combined mortality and potential life-threatening adverse event rates in AMI patients were 19.2% in those patients with normal ECGs and 27.5% in those who demonstrate only nonspecific abnormalities on their initial ECG.
Furthermore, the data presented by Welch et al has important implications for the approximately 2-4% of patients with AMI who are inadvertently discharged from the ED (eg, it should be noted that the rate of inappropriate discharge is 7.7 times more likely for patients with normal initial ECGs).1 These patients sustained short-term (ie, 30 day) mortality rates of a minimum of 10.5% to as high as 26% and have a risk-adjusted mortality ratio of 1.9 times those of patients with AMI who had not been discharged.1 It should, therefore, be clear that a normal ECG recorded in an ED must be evaluated along with the entire clinical picture, which may include such variables as the age and sex of the patient, the character of the presenting symptoms, a full evaluation of the past history, and a careful review of all risk factors such as cigarette smoking, cholesterol levels, lack of exercise, family history, exposure to stress, inadequate exercise history, etc. It must be fully recognized by all physicians that an initial normal ECG may reduce but not eliminate the possibility that a patient presenting with chest pain is suffering an AMI, especially those patients whose risk factor profile places them at higher risk of having symptomatic CAD.
In 1998, more than 5.3 million patients sought emergency care for chest pain or related symptoms. The increasing use of newer biochemical markers in association with physiological testing (ie, treadmills, nuclear studies, etc) will undoubtedly help identify more of the at-risk patients even though their initial electrocardiogram may prove to be normal. Hopefully, these abnormalities detected in the ED will initiate a course of appropriate medical investigation and therapy at an earlier stage that undoubtedly will lead to reduced mortality and life-threatening adverse events both in the hospital and after discharge.
Dr. Karpman, Clinical Professor of Medicine, UCLA School of Medicine, is Associate Editor of Internal Medicine Alert.
References
1. Pope JH, et al. N Engl J Med. 2000;342:1163-1170.
2. McCullough PA, et al. Clin Cardiol. 1998;21:22-26.
3. Karlson BW, et al. Am J Cardiol. 1991;68:171-175.
4. Zalenski RJ, et al. Ann Emerg Med. 1988;17:221-226.
5. Rouan GW, et al. Am J Cardiol. 1989;64:1087-1092.
6. Slusarcick AL, McCaig LF. Adv Data. 2000;317:1-23.
7. Goldman L, et al. N Engl J Med. 1996;334:1498-1504.
8. N Engl J Med. 1997;336:1621-1628.
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