Prevalence, Clinical Characteristics, and Mortality Among Patients with MI Presenting Without Chest Pain
abstract & commentary
Synopsis: Chest pain was absent on initial presentation in 33% of nearly 435,000 patients later confirmed with acute myocardial infarctions (MIs) using a national registry of 1674 hospitals over four years. The group without chest pain tended to be older, female, have diabetes or prior heart failure or stroke, and have a noncaucasians racial/ethnic origin. Treatment delays and increased mortality were significant compared to other MI patients who presented with chest pain.
Source: Canto JG, et al. JAMA 2000;283:3223-3229.
Using hospital data from the national reg-istry of Myocardial Infarction 2 (NRMI-2), information was abstracted for all patients with confirmed acute myocardial infarctions (MIs) who were not involved with interhospital transfers from June 1994 through March 1998. More than 96% of these cases had the diagnosis made upon admission as opposed to during the hospitalization. Study variables included chest pain, age, sex, race, comorbidities, family and smoking history, previous cardiac procedures, lab and EKG results, hospital treatments and timing of treatments, and medical outcomes.
Analysis revealed only two of three patients had chest pain on initial evaluation. The group without chest pain were older (mean age, 74.2 years vs 66.9 years for chest pain), with 75 years and older more likely to have no chest pain compared to those 65 years of age who did have chest pain. Approximately 49% of the group were women without chest pain, compared to 38% with chest pain. Patients without chest pain generally were not in traditional high risk groups for acute MI; they were less likely to have a smoking history, hypercholesterolemia, positive family history for coronary artery disease, or any prior angioplasties or coronary artery bypass graft surgery than were the group that had chest pain. Slightly more African Americans and Asians presented without chest pain compared to Caucasians.
Patients without chest pain presented to the hospital later than those with pain (7.9 vs 5.3 hours), and if they were eligible for reperfusion therapy the time-to-treatment was longer (2.3 vs 1.1 hours for thrombolytic therapy, 4.7 vs 2.9 hours for angioplasty). They were also less likely to receive aspirin, heparin, or beta blockers within the first 24 hours.
Six variables were associated with the absence of chest pain, and patients with at least three of them had a 50% probability of no chest pain. In order of importance they were: prior heart failure, prior stroke, older age, diabetes, female sex, and non-caucasian racial/ethnic group. If a patient with acute MI had none of the six factors, only 17.5% of them presented without chest pain.
More than twice in-hospital mortality was found for patients presenting without chest pain, even when adjusted for differences in age, comorbidities, and severity of presentation. More than 23% died during the hospitalization compared to 9% for presentations with chest pain. Using multivariate logistic regression analysis, presentation without chest pain was one of the most important predictors of mortality. Further analysis linked 28% of the higher mortality to lower use of early pharmacological therapies (aspirin, heparin, beta blockers, ACE inhibitors, and IV NTG).
COMMENT BY MARY ELINA FERRIS, MD
Although chest pain has long been taught as the hallmark of acute MI presentation, this large study finds that one out of three patients did not have chest pain when first seen. Previous teaching that diabetes was the major cause of "silent" MI was also challenged, with less than one-third of the silent group having this diagnosis. Other important factors were found to be older age, female gender, prior CHF or stroke, and non-caucasian racial/ethnic group. Canto and colleagues claim this is the largest study ever published comparing presenting characteristics, treatments, and outcomes for acute MI patients.
The so-called "atypical presentations" of acute MI have scant published research literature in the last 10 years. We are still guided by a classic article nearly 25 years old, that reports the most common atypical signs as CHF, angina episodes that are not prolonged, arrhythmias, and unusual pain locations.1 Other studies have illustrated that resolution of chest pain may still be followed by occluded coronary arteries.2 This new article will hopefully stimulate more study into these atypical cases.
The association of delayed treatments with gender and racial disparities in non-chest pain presentations of acute MI may lead to new clues in this puzzling area. Recent attention to research in women’s health has confirmed that even among ideal candidates for acute MI therapy, women in all age groups were less likely to undergo diagnostic catheterization than men. The difference was especially pronounced among older women.3 Furthermore, strong evidence continues to show that African Americans are less likely than Caucasians to undergo invasive cardiovascular procedures, and Hispanics are less likely than Caucasians to have received catheterization and percutaneous transluminal coronary angioplasty.4
This study could be criticized because the patients they identified without chest pain may not have been able to give an accurate history of chest pain due to their shortness of breath, pulmonary edema, cardiac arrests, and stroke. Canto et al do not feel this limited their conclusions, and they further note that some acute MIs were missed altogether and not hospitalized due to lack of chest pain.
A major consequence of delayed diagnosis of acute MI was found to be significant delays in treatment, which was associated with greatly increased in-hospital mortality. This study should cause all health care providers to be more suspicious of acute MI in the absence of chest pain, and to further raise the index of suspicion in risk groups that include not only persons with diabetes but also older persons, females, those with a history of prior CHF and stroke, and persons from non-caucasian racial and ethnic groups.
References
1. Bean WB. Lancet 1977;1:1044-1046.
2. Califf RM, et al. Ann Intern Med 1988;108:658-662.
3. Gan SC, et al. N Engl J Med 2000;343:8-15.
4. Ford E, et al. Am J Public Health 2000;90:1128-1134.
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