To the Editor: Kostis et al. (March 15 issue),1 who report thatmortality among patients admitted for acute myocardial infarctionis higher on weekends than on weekdays, provide strong evidencethat this finding may be due to a lack of invasive cardiac serviceson weekends. However, if hospitals that lacked the ability toprovide these services on weekends also tended to lack otherimportant characteristics influencing mortality (e.g., the staffingof superior nurses or better cardiac surgeons), then the apparentassociation of lower rates of invasive cardiac services on theweekends with higher mortality may be a spurious one. The authorsshould have provided a fixed-effects analysis (controlling foreach hospital in their models). If the lack of invasive serviceson weekends truly leads to worse outcomes, such weekend differencesin mortality should occur within hospitals. As reported, onecannot rule out the possibility that much of the observed weekendeffect may be due to the admission of patients to worse hospitalson weekends as compared with weekdays. Establishing that theweekend effect persists after controlling for each hospitalwould have strengthened the case for changing current staffingpatterns.
Jeffrey H. Silber, M.D., Ph.D. Children's Hospital of Philadelphia Philadelphia, PA 19104 silber{at}email.chop.edu
References
Kostis WJ, Demissie K, Marcella SW, Shao Y-H, Wilson AC, Moreyra AE. Weekend versus weekday admission and mortality from myocardial infarction. N Engl J Med 2007;356:1099-1109. [Free Full Text]
To the Editor: The article by Kostis et al. does not reflectthe dramatic changes that have occurred in the treatment ofmyocardial infarction in New Jersey. The study focused on patientswho were treated between 1987 and 2002. During this interval,few patients underwent immediate angioplasty for ST-elevationmyocardial infarction, even at institutions that had such acapability. In 2002, New Jersey began to allow community hospitalsto perform primary angioplasty for ST-elevation myocardial infarction.This change resulted in a major increase in the availabilityof immediate angioplasty. In addition, public reporting of so-calleddoor-to-balloon times has fostered an intense focus on the timelytreatment of ST-elevated myocardial infarction.
I suspect that if Kostis et al. extended their study to thepresent day, they would see a smaller gap between weekday andweekend outcomes and a much higher utilization of invasive procedureson the weekends. Patients with symptoms of myocardial infarctionon weekends should be immediately taken to a facility capableof performing primary angioplasty so that they can receive optimaltreatment at all times.
Henry Altszuler, M.D. Muhlenberg Regional Medical Center Plainfield, NJ 07061
To the Editor: Kostis et al. document increased mortality frommyocardial infarction, persisting at 1 year, among patientspresenting on weekends as compared with weekdays and suggesta causal association with reduced availability of invasive careon weekends. However, their data show that mortality at 365days changed little during the 16-year period they studied,despite a major increase in the use of invasive procedures.For example, the weekday mortality from 1987 to 1990 was 23.7%,as compared with a weekend mortality of 23.9% from 1999 to 2002,despite an increase in the proportion of non–Q-wave myocardialinfarctions from 20.5% to 51.0% during this time. Only 5953of 42,076 patients (14%) underwent coronary-artery bypass grafting(CABG) or percutaneous coronary intervention (PCI) on weekdaysduring the period from 1987 to 1990, whereas in the period from1999 to 2002, the corresponding weekend figure was 6884 of 15,542(44%). These data and the increased mortality with weekend admissionsof patients with other conditions that do not all require invasivetherapy1 suggest that the increase in mortality may be due tothe decreased weekend availability of cognitive skills and otherhospital services rather than to fewer invasive procedures directly.
Stephen P. Fitzgerald, F.R.A.C.P. Royal Adelaide Hospital Adelaide 5000, Australia stephenpfitzgerald{at}yahoo.com
References
Bell CM, Redelmeier DA. Mortality among patients admitted to hospitals on weekends as compared with weekdays. N Engl J Med 2001;345:663-668. [Erratum, N Engl J Med 2001;345:1580.] [Free Full Text]
To the Editor: Kostis et al. report that for patients with acutemyocardial infarction, hospitalization on weekends, as comparedwith weekdays, is associated with increased mortality. A lowerrate of performance of invasive procedures on weekends partlyexplains the difference. We analyzed mortality and invasiveprocedures on weekends and weekdays for hospitalizations fora first acute myocardial infarction, using the National Cause-of-Death,Swedish Myocardial Infarction, and Swedish Hospital Dischargeregisters.1 The Swedish data confirm the increased mortalityon weekends (Table 1). Revascularization procedures were performedmore frequently on weekdays, as reported by Kostis et al. However,our data suggest that the difference in mortality can be explainedonly in part by differences in invasive procedures, since sucha difference also existed during periods when PCI and CABG werenot available. In addition, statistical adjustment for PCI andCABG during the 48 hours after acute myocardial infarction resultedin only a moderate decrease in the modeled difference in theperiod from 2000 through 2005 (hazard ratio for death at 2 days,1.16; 95% confidence interval, 1.10 to 1.22). On the basis ofautopsy records that were available from 1987, we found no differencebetween weekends and weekdays in rates of sudden death fromacute myocardial infarction among patients who never reachedthe hospital.
Table 1. Hazard Ratios for Death from Myocardial Infarction on Weekends, as Compared with Weekdays, in Sweden from 1968 to 2005, Adjusted for Age and Sex.
Rickard Ljung, M.D., Ph.D. Max Köster, B.Sc. National Board of Health and Welfare SE-106 30 Stockholm, Sweden rickard.ljung{at}socialstyrelsen.se
Imre Janszky, M.D., Ph.D. Karolinska Institutet SE-171 76 Stockholm, Sweden
References
Hammar N, Nerbrand C, Ahlmark G, et al. Identification of cases of myocardial infarction: hospital discharge data and mortality data compared to myocardial infarction community registers. Int J Epidemiol 1991;20:114-120. [Free Full Text]
To the Editor: Although I draw qualitative conclusions thatare similar to those of Kostis et al. in a study of data onnational Medicare claims,1 the mortality effects shown by Kostiset al. are much larger than those in the Medicare study (0.9%vs. 0.2% at 30 days) and raise concerns regarding unobservedpatient heterogeneity.
Several commentators2,3 have suggested that higher weekend mortality4may result from the delayed hospitalization of persons who hadan onset of less severe symptoms on weekends. Although the acutenature of myocardial infarction suggests little opportunityfor elective deferral, the data indicate otherwise. Poolingall the years in Table 1 of the article by Kostis et al. showsthat 26.5% of hospitalizations for myocardial infarction occurredon weekends, considerably less than the 28.6% that would haveoccurred if the incidence had been uniform. The authors observedhigher rates of complications on weekends, which is consistentwith the hypothesis that a reduced rate of weekend hospitalizationleads to a weekday caseload of patients with more severe symptoms.Differences in observable measures of the severity of patients'symptoms suggest the presence of unobservable differences aswell.
David J. Becker, Ph.D. University of Alabama at Birmingham School of Public Health Birmingham, AL 35294 dbecker{at}uab.edu
References
Becker DJ. Do hospitals provide lower quality care on weekends? Health Serv Res (in press).
Halm EA, Chassin MR. Why do hospital death rates vary? N Engl J Med 2001;345:692-694. [Free Full Text]
Bell CM, Redelmeier DM. Mortality among patients admitted to hospitals on weekends as compared with weekdays. N Engl J Med 2001;345:663-668. [Erratum, N Engl J Med 2001;345:1580.] [Free Full Text]
The authors reply: Silber notes that hospital-specific characteristicsother than the ability to perform PCI may explain the differencein mortality between weekend and weekday admissions. The increasedhazard ratio for 30-day mortality due to weekend admission wasobserved when the analysis was restricted to hospitals thatcould perform PCI (hazard ratio, 1.08) and when the availabilityof PCI was included in the Cox model (hazard ratio, 1.04). Adjustmentfor individual hospitals, as suggested, yielded a similar result(hazard ratio, 1.04). These analyses also suggest that althoughthe use of PCI is now more widespread, as noted by Altszuler,increases in the rate of PCI may not eliminate the differencein mortality between weekend and weekday admissions. In fact,we recently examined data from 2001 through 2004 (the latestavailable) and found a persistent difference in 30-day mortalityfor weekend admissions (12.1%) versus weekday admissions (11.4%)(P=0.02).
We agree with Fitzgerald that there may be differences in thebreadth of expertise and the availability of certain medicaltherapies between weekdays and weekends. Nevertheless, the sequentialCox proportional-hazard models suggest that differential useof invasive cardiac procedures is one of a number of causesof the difference in mortality. Ljung et al., who also foundhigher mortality for weekend admissions, concur on this point.
Fitzgerald makes the excellent point that 1-year mortality didnot change markedly in the 16-year period, whereas there wasa substantial increase in the use of revascularization. We hypothesizethat the reasons for the attenuation of the reduction in mortalityat 1 year include the older age of patients in more recent years,the higher rate of coexisting illnesses, and possibly the discontinuationof beneficial pharmacologic therapies (e.g., angiotensin-converting–enzymeinhibitors, beta-blockers, and statins) after discharge.
As noted by Becker, we found that the highest proportion ofpatients with myocardial infarction were admitted on Monday(16.1%) and the lowest on Saturday (13.1%) and Sunday (13.4%).The higher rates of complications with weekend admissions maybe attributable to more severe infarction, as Becker suggests,but could also be due to differences in management. In addition,the higher mortality for weekend admissions persisted afteradjustment for complications as well as for demographic characteristics,coexisting illnesses, and the type and site of myocardial infarction.However, as noted, we could not control for unmeasured factors,including the time from symptom onset to admission. Furtherexploration of the factors underlying the difference in outcomesbetween weekend and weekday admissions may lead to the implementationof measures designed to mitigate the difference.
William J. Kostis, M.D., Ph.D. Robert Wood Johnson Medical School New Brunswick, NJ 08903 kostiswj{at}umdnj.edu
Kitaw Demissie, M.D., Ph.D. University of Medicine and Dentistry of New Jersey Piscataway, NJ 08854
Abel E. Moreyra, M.D. Robert Wood Johnson Medical School New Brunswick, NJ 08903
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