Correspondence

Specialty of Ambulatory Care Physicians and Mortality after Myocardial Infarction

N Engl J Med 2003; 348:1288-1289March 27, 2003

Article

To the Editor:

Patient factors that influence physicians' referrals may have exaggerated differences in outcomes between generalists and specialists in the study by Ayanian and colleagues (Nov. 21 issue).1 Results from observational studies such as this one will be convincing only when they comprehensively assess patient factors that are central to the generalist's role in prioritizing complex problems in ill patients. Most generalists are unlikely to pursue ongoing care with cardiologists for patients with severe coexisting illnesses who are poor candidates for revascularization. Because this study did not include measures of the severity of coexisting illnesses, unmeasured severity may have substantially affected referral and mortality rates. Additional, inadequately measured factors that may have influenced results in favor of specialty consultation are socioeconomic status and area of residence (rural vs. nonrural).2-4

Our concern is that this study and others comparing specialists' care to generalists' care will be used to make policy, even though the results may be misleading or may not apply to important subgroups of patients.5 In particular, we do not believe that this study convincingly supports the need for all patients to be referred to a cardiologist after myocardial infarction. Generalists alone can often provide compassionate, efficient, and high-quality health care for patients with heart disease who are poor candidates for revascularization.

Paul A. James, M.D.
Arthur J. Hartz, M.D., Ph.D.
Barcey T. Levy, Ph.D., M.D.
University of Iowa, Iowa City, IA 52242
paul-james@uiowa.edu

5 References

1. 1

   Ayanian JZ, Landrum MB, Guadagnoli E, Gaccione P. Specialty of ambulatory care physicians and mortality among elderly patients after myocardial infarction. N Engl J Med 2002;347:1678-1686
   Full Text | Web of Science | Medline

2. 2

   Auerbach AD, Hamel MB, Davis RB, et al. Resource use and survival of patients hospitalized with congestive heart failure: differences in care by specialty of the attending physician. Ann Intern Med 2000;132:191-200
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3. 3

   Frances CD, Shlipak MG, Noguchi H, Heidenreich PA, McClellan M. Does physician specialty affect the survival of elderly patients with myocardial infarction? Health Serv Res 2000;35:1093-1116
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4. 4

   Chen J, Radford MJ, Wang Y, Krumholz HM. Care and outcomes of elderly patients with acute myocardial infarction by physician specialty: the effects of comorbidity and functional limitations. Am J Med 2000;108:460-469
   CrossRef | Web of Science | Medline

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   Jollis JG, DeLong ER, Peterson ED, et al. Outcome of acute myocardial infarction according to the specialty of the admitting physician. N Engl J Med 1996;335:1880-1887
   Full Text | Web of Science | Medline

Author/Editor Response

To assess whether differences in the severity of illness could explain differences in mortality associated with physicians' specialties, we examined three measures of severity that we had previously dichotomized (serum creatinine level) or not included (left ventricular ejection fraction and blood hemoglobin level) when matching patients who did or did not see a cardiologist after discharge. Among patients with renal insufficiency, the mean serum creatinine level was very similar in the two subgroups (3.44 mg per deciliter in those who saw a cardiologist vs. 3.47 mg per deciliter in those who did not; P=0.69). Among those with congestive heart failure while hospitalized, the mean ejection fraction was also similar (40.0 percent vs. 40.6 percent, respectively; P=0.21). In the overall matched cohort, the mean hemoglobin level was nearly identical in the two subgroups (13.87 g per deciliter vs. 13.90 g per deciliter, respectively; P=0.92). These findings suggest that by incorporating an extensive set of clinical factors when matching patients according to their propensity to see a cardiologist for ambulatory care, we also closely balanced key severity measures that have been shown to affect survival.1-3

We agree with James and colleagues that unmeasured socioeconomic factors, such as the level of education or availability of supplemental insurance, may be associated with care by cardiologists and may explain some of the differences in mortality that we observed.4 However, as we found in a sensitivity analysis, controlling for a plausible unmeasured socioeconomic effect would have reduced but not eliminated the increased mortality among patients who did not see a cardiologist. Therefore, in the absence of randomized trials, we believe that rigorous observational studies can provide useful guidance to patients, physicians, and policymakers about the roles of primary and specialty care for patients with coronary heart disease.

John Z. Ayanian, M.D., M.P.P.
Mary Beth Landrum, Ph.D.
Peter Gaccione, M.A.
Harvard Medical School, Boston, MA 02115
ayanian@hcp.med.harvard.edu

4 References

1. 1

   Krumholz HM, Chen J, Chen YT, Wang Y, Radford MJ. Predicting one-year mortality among elderly survivors of hospitalization for an acute myocardial infarction: results from the Cooperative Cardiovascular Project. J Am Coll Cardiol 2001;38:453-459
   CrossRef | Web of Science | Medline

2. 2

   Shlipak MG, Heidenreich PA, Noguchi H, Chertow GM, Browner WS, McClellan MB. Association of renal insufficiency with treatment and outcomes after myocardial infarction in elderly patients. Ann Intern Med 2002;137:555-562
   Web of Science | Medline

3. 3

   Wu W-C, Rathore SS, Wang Y, Radford MJ, Krumholz HM. Blood transfusion in elderly patients with acute myocardial infarction. N Engl J Med 2001;345:1230-1236
   Full Text | Web of Science | Medline

4. 4

   Blustein J, Weiss LJ. Visits to specialists under Medicare: socioeconomic advantage and access to care. J Health Care Poor Underserved 1998;9:153-169
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