Nearest May Not be Best for Patients with AMI
Abstract & Commentary
To determine whether the volume of cases treated influences mortality following acute myocardial infarction (AMI), Thiemann and colleagues analyzed outcomes in 98,898 Medicare patients older than 65 years of age using data collected over an eight-month period (2/94-7/95). Patients were identified using discharge codes. Photocopies of charts were then reviewed to verify the diagnosis of AMI. AMI was deemed present if patients had a creatine kinase MB fraction higher than 0.05 or at least two of the following: chest pain, serum creatine kinase at least two times the upper limit of normal, or diagnostic EKG findings. Patients were excluded if they were admitted from any site other than home, were comatose on arrival, had dementia, or terminal illness. Outcomes were analyzed after dividing the sample into quartiles according to the number of AMI patients seen each week (i.e., < 1.4, 1.4-2.5, 2.6-4.4, and > 4.4, respectively).
Patients admitted to hospitals in the lowest quartile were 17% more likely to die within 30 days of admission compared to patients admitted to hospitals in the highest quartile (P < 0.001), a difference of 2.3 deaths per 100 patients. At one year, mortality was 29.8% among patients admitted to the lowest-volume hospitals, compared to 27.0% in the highest-volume hospitals. Survival at high-volume hospitals remained better when the data were analyzed by subgroups (e.g., age, history of cardiac disease, Killip class of infarction, the presence or absence of contraindications to thrombolytic therapy, and time from the onset of symptoms). Most patients had an internist (37%) or cardiologist (30%) as their attending physician. There was a small long-term survival advantage for patients managed by a cardiologist (P = 0.02), but physician specialty did not affect the association between hospital volume and survival. Whether patients received aspirin and thrombolytic medications on admission, and beta-blockers or angiotensin-converting enzymes (ACE) inhibitors at discharge, reduced, but did not eliminate, survival differences. Availability of invasive procedures (angioplasty, bypass surgery) was not associated with a significant survival advantage, independent of hospital volume. (Thiemann DR, et al. N Engl J Med 1999;340:1640-1648.)
COMMENT BY LESLIE A. HOFFMAN, PhD, RN
By virtue of geography and the policy of the emergency medical system, most patients with AMI are taken to the nearest hospital. The findings of this study call this practice into question. In this nationwide sample of elderly patients with AMIs, improved survival was associated with admission to hospitals that treated a greater number of patients with AMIs compared to hospitals that treated fewer cases. Further, these findings remained true when subgroups reflecting factors that might be expected to influence outcome were examined (e.g., age, type of infarction, delay from onset of symptoms, availability of invasive procedures, and physician specialty). Use of aspirin, thrombolytic agents, beta blockers, and ACE inhibitors accounted for about one-third of the survival benefit but did not eliminate the influence of volume.
Concerns about increased mortality, morbidity, and, in particular, delay of thrombolysis, influence policies regarding the preferred hospital destination. However, relatively few patients receive thrombolytics (19.3% in this study), and high-volume hospitals may be able to compensate for short transport delay by earlier thrombolytic administration. It is also questionable whether much time was saved by choosing a closer hospital. In metropolitan areas, 22% of admissions to a smaller volume hospital occurred within the same zip code as a high-volume hospital. Within two zip code integers, 74% of patients could have received treatment at a high-volume hospital. With the exception of rural areas, any advantage from a shorter transport time would appear to be easily offset by benefits from a more experienced healthcare team.
There are several limitations to this study. It was retrospective and did not include managed care patients or patients younger than 65 years of age. The study also had a number of major strengths, including a large, nationally representative sample, blinded data abstraction, a relatively short data collection interval, and long-term follow-up. Of eligible patients, only 3.8% were excluded for missing data. Thus, the study included nearly 100% of Medicare patients with fee-for-service insurance who were admitted from home with an AMI. Given this, it is highly likely the findings are representative. These findings suggest the need to re-examine policies that dictate taking patients to the nearest facility, particularly in metropolitan areas, where differences in transport time are likely to be minimal or nonexistent.
Patients who received care from a cardiologist:
a. were more likely to receive thrombolytics.
b. had a small long-term survival advantage.
c. had improved care regardless of volume.
d. had no change in morbidity.
e. None of the above
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