Author + information
- Received November 24, 2014
- Revision received December 22, 2014
- Accepted January 13, 2015
- Published online March 31, 2015.
- Rajesh V. Swaminathan, MD∗∗ (, )
- Sunil V. Rao, MD†,
- Lisa A. McCoy, MS†,
- Luke K. Kim, MD∗,
- Robert M. Minutello, MD∗,
- S. Chiu Wong, MD∗,
- David C. Yang, MD∗,
- Paramita Saha-Chaudhuri, PhD‡,
- Harsimran S. Singh, MD, MSc∗,
- Geoffrey Bergman, MD∗ and
- Dmitriy N. Feldman, MD∗
- ∗Weill Cornell Medical College, New York-Presbyterian Hospital, Greenberg Division of Cardiology, New York, New York
- †Duke Clinical Research Institute, Division of Cardiology, Duke University Medical Center, Durham, North Carolina
- ‡Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, Canada
- ↵∗Reprint requests and correspondence:
Dr. Rajesh Swaminathan, Cardiac Catheterization Laboratories, Weill Cornell Medical College, 520 East 70th Street, Starr-431 Pavilion, New York, New York 10021.
Background There has been a decline in hospital length of stay (LOS) after primary percutaneous coronary intervention (PPCI) for ST-segment elevation myocardial infarction (STEMI).
Objectives The objective of this study was to examine whether shorter LOS is safe for older patients undergoing PPCI for STEMI.
Methods The study analyzed patients’ characteristics and 30-day outcomes by LOS (short, ≤3 days; medium, 4 to 5 days; long >5 days; where LOS was the discharge date minus the admission date plus 1) among 33,920 patients with STEMI in the linked CathPCI Registry-Centers for Medicare & Medicaid Services dataset who were ≥65 years of age and treated with PPCI from 2004 to 2009.
Results Percents of patients in each category were as follows: 26.9%, 46.3%, and 26.8% for short, medium, and long LOS, respectively. Patients with a long LOS were generally older, female, and had more comorbidities, including cardiogenic shock and multivessel disease. Patients with a short LOS generally had higher ejection fraction and single-vessel disease. There was no significant difference in 30-day all-cause mortality (hazard ratio [HR]: 1.00; 95% confidence interval [CI]: 0.74 to 1.34) or major adverse cardiac events (MACE) (death, readmission for myocardial infarction, unplanned revascularization: HR: 1.03; 95% CI: 0.86 to 1.25) for medium versus short LOS. There was a significant increase in adjusted mortality (HR: 2.30; 95% CI: 1.72 to 3.07) and MACE (HR: 1.75; 95% CI: 1.44 to 2.12) for long versus short LOS. Patients with a very short LOS (1 to 2 days) had significantly increased 30-day mortality and MACE compared with a 3- to 4-day LOS.
Conclusions Patients discharged as early as 48 h after PPCI have outcomes similar to patients who stay in the hospital for 4 to 5 days. Early, but not very early (<48 h), discharge may be safe among selected older patients with STEMI.
- length of stay
- myocardial infarction
- older patients
- primary percutaneous coronary intervention
- ST-segment elevation myocardial infarction
Hospital length of stay (LOS) is a critical measure of health care efficiency, yet it must be carefully balanced with health care quality. Reducing LOS is driven by financial pressures in the setting of decreasing reimbursements or bundled payment models proposed by the Centers for Medicare & Medicaid Services (CMS) (1). In contrast, longer LOS allows for improved patient-centered care and transition to the outpatient setting, which may result in lowered readmission rates and improved health outcomes (2). These issues are particularly germane to patients presenting with an ST-segment elevation myocardial infarction (STEMI), in whom in-hospital monitoring is important to detect arrhythmias and mechanical complications of myocardial infarction (MI), optimize secondary prevention, and provide education regarding risk factor modification, medication adherence, and rehabilitation. Although primary percutaneous coronary intervention (PPCI) is associated with improved survival and reduced risk of arrhythmic and mechanical complications compared with fibrinolytic therapy (3–7), there remains a substantial risk for subacute stent thrombosis and heart failure. In the current era of PPCI, there has been a decline in LOS in the United States after STEMI, with significant geographic variation in discharge practice patterns (8). Median LOS is shortest in the United States compared with other countries (9). Whether these shorter hospital stays are safe remains unclear.
In the current study, we used the linked national CathPCI Registry with the CMS claims data to examine LOS of older patients with STEMI and associated 30-day clinical outcomes, including mortality and combined major adverse cardiovascular events (MACE: mortality, readmission for MI, or unplanned revascularization) during the period from 2004 to 2009. We hypothesized that early discharge was as safe as longer LOS with respect to clinical outcomes at 30 days.
The CathPCI Registry, co-sponsored by the American College of Cardiology and the Society for Cardiovascular Angiography and Interventions, is a large, national registry of patients undergoing diagnostic cardiac catheterizations and/or percutaneous coronary intervention (PCI) that captures ∼85% of PCI procedures performed at >1,400 hospitals. Details of the registry, data collection, and monitoring have been previously described (10–13). This study used version 3.0 of the CathPCI Registry, which is the latest version linked to CMS claims. Procedure codes were used to identify index procedures in the Medicare files, which were then linked to the CathPCI Registry by using indirect identifiers. Linking rules were applied using a hierarchical matching algorithm (14,15), until a match was achieved. The feasibility of linkage to CMS claims has been previously described (14), and it has been used by other analyses of CathPCI data that sought long-term outcomes (15). The Institutional Review Board of Duke University Medical Center in Durham, North Carolina approved the study after determining that the study met the definition of research not requiring informed consent.
Study population, definitions, and outcome measures
We included patients who had electrocardiographic evidence of ST-segment elevations on presentation to emergency departments at acute care hospitals with PPCI capabilities and who subsequently underwent PPCI from January 6, 2004 to December 31, 2009. We excluded the following patients: those <65 years of age or >90 years of age (n = 1,208); STEMI transfers from centers without PPCI capabilities; patients receiving thrombolysis (n = 1,030); patients who were discharged to extended care, other facilities, or nursing homes (n = 4,297); and patients with in-hospital death (n = 3,736) or coronary artery bypass grafting (CABG) (n = 1,862). The final study population totaled 33,920 patients who were discharged home alive. LOS was defined by the standard CMS definition, as reported in LOS published data (16), as the discharge date minus the admission date plus 1. In other words, a LOS of 3 is actually 2 days after the day of admission/PCI (e.g. Wednesday discharge after Monday admission/PCI). Given the discrete nature of LOS, we stratified LOS into approximate tertiles: short (≤3 days), medium (4 to 5 days), and long (>5 days). We also separately analyzed the group of patients with very short LOS (1 to 2 days) relative to other LOS days.
Our primary outcomes were post-discharge 30-day clinical events stratified by LOS, including mortality and MACE (defined as a composite of mortality, readmission for MI, or unplanned repeat revascularization). Secondary outcomes included the incidence of 30-day readmission for MI, unplanned revascularization, and bleeding events (accounting for death as a competing factor). All-cause mortality was obtained from the claims data. Readmissions for MI and unplanned revascularization that occurred during follow-up were obtained from claims data using the International Classification of Diseases-Ninth Revision-Clinical Modification (ICD-9-CM) diagnosis code 410.X1 (MI) and ICD-9-CM procedure codes 36.00, 36.06, 36.07, 36.09, and 36.10 to 36.19 (revascularization). Unplanned repeat revascularization was defined as readmission with a PCI or CABG procedure and a principal discharge diagnosis that was clearly not consistent with an elective readmission (17): specifically, heart failure, acute MI, unstable angina, arrhythmia, or cardiac arrest. Readmissions for bleeding were identified from claims data using the following ICD-9-CM diagnosis codes: 430 to 432, 578.X, 719.1X, 423.0, 599.7, 626.2, 626.6, 626.8, 627.0, 627.1, 786.3, 784.7, or 459.0.
For descriptive analyses, baseline characteristics, procedural characteristics, in-hospital adverse events, and hospital characteristics were compared among patients grouped by LOS. Continuous variables are presented as medians with 25th and 75th percentiles, and categorical variables are presented as frequencies (percents). Differences among patient groups were compared using Pearson chi-square tests for categorical variables and Mann-Whitney Wilcoxon rank sum test for continuous variables.
Estimates of the event rates for primary endpoints at 30 days post-discharge were determined on the basis of weights that were functions of Kaplan-Meier censoring estimates; the log-rank test was used to assess differences by LOS group. The cumulative incidence differences for time-to-event clinical outcomes were assessed using Gray’s method (18). Both the unadjusted and adjusted hazard ratios (HRs) were estimated for comparison of LOS groups along with a 95% confidence interval (CI) on the basis of the sandwich estimator of standard errors to account for within-hospital correlation. The adjusted analysis included the variables adopted in the validated CathPCI Registry all-cause mortality model as covariates, which consisted of age, race, sex, body mass index, glomerular filtration rate, presence of cardiogenic shock at admission, medical history (i.e., congestive heart failure, diabetes, valvular surgery, cerebrovascular disease, peripheral vascular disease, chronic lung disease, dialysis, PCI), highest-risk lesion characteristics, New York Heart Association (NYHA) functional class, and pre-procedure intra-aortic balloon pump (IABP), ejection fraction (19), as well as in-hospital bleeding, vascular complications, need for transfusions, and hospital characteristics.
To examine factors associated with longer LOS (defined as greater than the median LOS of 4 days), a multivariable logistic regression with generalized estimating equations was used. The generalized estimating equations method was used to account for within-hospital clustering (20), because patients at the same hospital are more likely to receive similar treatment relative to patients in other hospitals (i.e., within-center correlation for response). The adjusted analysis included covariates from the CathPCI Registry mortality model as well as in-hospital complications (i.e., bleeding, need for transfusions, vascular complications, renal failure).
To evaluate mortality and MACE rates of the very short LOS group relative to other LOS days further, we also performed a propensity-matched analysis to account for differences in case mix between the very short LOS group (LOS 1–2) and other LOS days (LOS 3–4) more robustly. We used the “gmatch” macro from the Mayo Clinic, which performs greedy matching of cases to control subjects (LOS 3–4 vs. LOS 1–2) within a pre-specified caliper having a width of 0.2 times the SD of the logit of the propensity score. In the propensity score model, we adjusted for the variables in the NCDR mortality model, hospital characteristics, and additional patient and procedural factors including in-hospital complications of bleeding, transfusions, vascular complications, and renal insufficiency. To estimate the LOS 3–4 versus LOS 1–2 effect on outcomes among the propensity matched sample, we present the odds ratio (OR) from a logistic regression model stratified by matched pair. We were able to match 85% of the patients with a very short LOS within the pre-specified caliper for analysis.
To assess LOS trends over time, we calculated percentiles of the distribution of LOS by discharge year. A p value <0.05 was considered significant for all tests. The Duke Clinical Research Institute performed all statistical analyses using SAS software version 9.2 (SAS Institute, Cary, North Carolina).
Baseline characteristics by LOS
During the study period, 33,920 patients with STEMI presented to 1,028 sites after inclusion and exclusion criteria were applied to the linked dataset, where the matching algorithm successfully linked 70% of eligible patients (Figure 1). The distribution of LOS is displayed in Figure 2, and the proportion of patients in each LOS category was as follows: short LOS (26.9%, n = 9,135), medium LOS (46.3%, n = 15,704), and long LOS (26.8%, n = 9,081).
There were differences in baseline demographics among the 3 examined groups, with short and medium LOS groups having fewer comorbidities compared with the long LOS group (Table 1). Overall, patients with longer LOS were older and more frequently had prior MI, heart failure, diabetes, renal failure, cerebrovascular disease, peripheral vascular disease, chronic lung disease, hypertension, and shock. In addition, symptom onset to admission time was generally shorter in short and medium LOS groups (18.0% and 18.5%, respectively) compared with the long LOS group, in which presentation >6 h from symptom onset was more frequent (21.5%).
There were also differences in procedural characteristics and in-hospital adverse events. Patients in the short LOS group were more likely to have preserved left ventricular function (median ejection fraction 50%), non–left anterior descending (LAD) culprit vessel, TIMI (Thrombolysis In Myocardial Infarction) flow grade 1 to 3 before PCI, and were more likely to have a successful PCI procedure. Patients in the long LOS group had more multiorgan derangements and anatomic features associated with worse outcomes, such as the following: multivessel disease, complex (type C) coronary lesions, LAD culprit vessel, TIMI flow grade 0 before PCI, shock or heart failure, IABP placement, and in-hospital bleeding or vascular complications.
Hospital, geographic variation, and trends in LOS
Patients in the short LOS group were more likely to be treated at smaller hospitals with fewer beds and annual PCI cases. Discharging patients with STEMI early was also more commonly practiced in hospitals in the West and Midwest regions compared with the South and Northeast (Table 1). The median LOS over the 6-year period was 4 days; however, the relative frequency of patients in each LOS category changed with a trend toward earlier discharges over time. In 2005, 24% of discharges in older patients with STEMI were in patients with a short LOS; this percent increased to 30% by 2009. Conversely, 47% and 29% of discharges in patients with STEMI were in patients with medium and long LOS, respectively, and these percents decreased to 45% and 25% by 2009, respectively.
The 30-day mortality and MACE rates were 0.9% and 1.9% for short LOS, 1.0% and 2.2% for medium LOS, and 3.5% and 5.0% for long LOS, respectively (p < 0.0001) (Figures 3A and 3B). A multivariable Cox regression analysis (Table 2) demonstrated similar adjusted rates of death and MACE within 30 days for medium versus short LOS (mortality, HR: 1.00; 95% CI: 0.74 to 1.34; MACE, HR: 1.03; 95% CI: 0.86 to 1.25).
The incidence of readmissions for MI at 30 days was 1.0% for short LOS and 1.1% for medium LOS, but it was significantly higher at 1.6% for long LOS (p = 0.001) (Figure 3C). The rates of 30-day readmissions for unplanned revascularizations were not significantly different across LOS categories (0.7% for short LOS and 1.0% for both medium and long LOS; p = 0.23) (Figure 3D). The frequency of bleeding events requiring readmission after initial discharge was relatively low, but it increased across all LOS categories: 0.2%, 0.4%, and 0.6% for short, medium, and long LOS, respectively (p < 0.001) (Figure 3E).
Factors associated with longer LOS
Table 3 displays independent predictors of longer LOS (>4 days) after controlling for baseline characteristics, variables from the NCDR mortality model, and in-hospital complications. The factors associated with longer LOS included pre-operative IABP, transfusion, vascular complication, cardiogenic shock, renal insufficiency, and bleeding. Hospitals located in the West and Midwest regions were 24% and 28% more likely to have short versus longer LOS than hospitals located in the South, respectively, whereas hospitals in the Northeast had longer LOS versus hospitals in the South (see Table 3).
Very short LOS and outcomes
Very short LOS (1 to 2 days), which represents discharge on the day of PCI or the day after PCI (similar to the practice for elective PCIs) was infrequent and present in 1,244 patients (3.7%). The relationship between distribution of LOS and clinical outcomes (MACE) is shown in Figure 4 and reveals that very short LOS is associated with significantly worse 30-day clinical outcomes. A “U-shaped” curve for MACE events was noted with a nadir at LOS 3–4, where overall unadjusted 30-day MACE rates were similar for LOS of 3 or 4 days. Compared with LOS 3–4 (Online Table 1), patients in the very short LOS group were of similar age, but more commonly they were male with hypertension, hyperlipidemia, chronic lung disease, diabetes, and earlier PCI or CABG. Patients in the very short LOS group were more likely to have TIMI flow grade 1 to 3 pre-PCI and a lower frequency of LAD culprits, cardiogenic shock, any bleeding, or vascular complications. The PCI procedural success rate was similar. Guideline-directed post-STEMI discharge medications including antiplatelet agents, beta-blockers, and statins were less frequently prescribed in patients in the very short LOS group. Compared with very short LOS, patients with a 3- to 4-day LOS had >50% reduction in adjusted mortality (OR: 0.47; 95% CI: 0.27 to -0.82 for LOS 3 vs. LOS 1–2; OR: 0.46; 95% CI: 0.27 to 0.79, for LOS 4 vs. LOS 1–2) and a more than 40% reduction in MACE (OR: 0.59; 95% CI: 0.40 to 0.86 for LOS 3 vs. LOS 1–2; OR: 0.56; 95% CI: 0.38 to 0.82 for LOS 4 vs. LOS 1–2) (Table 4). Similarly, among propensity-matched cohorts, the risk of death (OR: 0.41; 95% CI: 0.21 to 0.81) and MACE (OR: 0.52; 95% CI: 0.33 to 0.80) remained significantly lower for LOS 3–4 versus LOS 1–2.
In this large, contemporary national registry, we found that a majority of older patients with STEMI (46%) had a medium LOS, whereas 27% of patients had a short LOS. After adjustment, patients with short LOS had similar mortality and MACE rates as those with medium LOS. These data suggest that selected patients with STEMI who do not develop post-procedural complications may be eligible for an earlier discharge without an increase in 30-day adverse events (Central Illustration). Furthermore, from 2004 to 2009, the proportion of patients undergoing earlier discharges increased. This pattern may reflect the increasing safety of PCI in general (21), the use of bleeding avoidance strategies (22), and the financial pressures for hospitals to reduce inpatient LOS.
In contrast to established guidelines for “door-to-balloon” times, current guidelines do not provide criteria for determining an optimal LOS or “balloon-to-door” time for patients with STEMI. Large-scale changes in the way post-STEMI care is delivered and reductions in LOS nationally may be accompanied by unintended consequences (23). Therefore, it is critical to examine the safety and understand the effects of such changes, particularly among Medicare beneficiaries with substantial comorbidities. It is reassuring that in broadly representative older patients at more than 1,000 centers in the United States, 30-day mortality and MACE outcomes were similarly low among patients with short and medium LOS. It remains unknown whether shorter LOS and reduced hospital costs align with effects on care continuity and patients’ preferences.
We found that patients with long LOS (27%) had the highest rate of 30-day mortality and MACE. Given the observational nature of our study, these data should not be interpreted to mean that keeping a patient with STEMI in the hospital beyond 5 days would translate into poor outcomes. Rather, this group was a sicker cohort of patients with substantial comorbidities and in-hospital complications relative to those with short and medium LOS, and thus these patients would be expected to have more readmissions within 30 days. An early discharge strategy would apply only to patients who do not develop post-procedural complications, and recuperation at home would attenuate nosocomial infection and delirium, to which older patients are prone.
Patients with short LOS had less complicated presentations. The safety of early discharge for such patients is in line with previous prospective studies (24,25), which were limited by small sizes and single-center experiences. The PAMI-II (Primary Angioplasty in Myocardial Infarction -11) study from 1998 implemented a strategy of early identification of low-risk patients with STEMI to receive accelerated care in a non–intensive care unit setting with hospital discharge on day 3 without noninvasive testing or traditional care (24). The study showed that the accelerated group had similar in-hospital and 6-month outcomes, yet these patients were discharged 3 days earlier than the traditional group (4.2 ± 2.3 days vs. 7.1 ± 4.7 days; p = 0.0001). Similarly, the Safe-Depart trial (25), a small, single-center study, identified 54 low-risk patients with STEMI on the basis of the Zwolle Primary PCI Index (26), after these patients underwent primary or rescue PCI, and found that an early discharge strategy with rapid follow-up was feasible.
An important finding of our study is that very early discharge (same-day or overnight stay after PCI) is associated with an increase in 30-day mortality and MACE. Risks associated with PCI, such as acute stent thrombosis, bleeding, and renal failure, are highest within the first 24 to 48 h (27); thus, longer observation may be required to avert these complications. Furthermore, optimal post-MI medications were less frequently prescribed on discharge in patients with very short hospital stays. The current data highlight the importance of implementing standardized protocols for STEMI discharge and post-discharge follow-up in patients with very short LOS, in addition to the need for further clinical evidence that a very early discharge strategy can be safely applied in contemporary practice. From a hospital policy standpoint, this finding supports justification for “inpatient” monitoring and reimbursement under the recently introduced CMS “2-midnight rule.” The concept and safety of an “outpatient STEMI PCI” when the patient stays <2-midnights would require further investigation and policy discussion because clearly there would be a disconnect between the level of monitoring required and the time spent in the hospital.
We also found geographic and hospital-level variation that affected LOS. Hospitals with smaller numbers of beds had greater proportion of patients in the short LOS group, a finding that may reflect pressure to expedite bed availability. Of interest, hospitals in the West and Midwest had significantly shorter LOS compared with the Northeast and South. Such variation has been seen in earlier studies for STEMI (8) and elective PCI (28), and it may be a reflection of hospital discharge policy or institutional culture, unrelated to medical or logistical factors. This finding highlights potential areas for improvement and cost savings within certain regions.
First, because the CathPCI registry accounts for only in-hospital events, we linked the database to CMS claims data to obtain 30-day clinical outcomes. This limited our population to patients older than 65 years and subjects the data to coding bias and possibly missing events. However, older patients are at higher risk for in-hospital complications after PPCI (29–31), so it is likely that a higher proportion of younger patients would be eligible for earlier discharge. Second, our study period ended in 2009, after which further evolution in care models for patients with STEMI, advances in bleeding avoidance strategies including increased use of radial access for STEMI (32), and use of newer-generation drug-eluting stents may have led to continued reductions in LOS with a positive impact on 30-day outcomes. Third, although our robust statistical approach using validated risk models and propensity matching accounted for some of the potential bias inherent to observational analyses, there remains risk of unmeasured confounders. Fourth, some patients after STEMI may return to the hospital within 30 days for elective or “staged” revascularization of a nonculprit artery. To minimize counting this as an unplanned revascularization, we defined repeat revascularization as readmissions with PCI or CABG that were associated with a principal discharge diagnosis that was clearly not consistent with an elective readmission. This methodology has inherent limitations because it is based on administrative data; however, it is currently the most reliable algorithm available and has been utilized in other published registry data. For this reason, we also analyzed each component of the combined MACE separately as secondary endpoints. Furthermore, miscoding the second admission, given that it is linked so closely to the index admission for STEMI, may have increased readmission event rates; however, miscoding would likely be similar across the various LOS categories. Finally, we could not account for patients who may have very short stays as a result of leaving against medical advice, a factor that may also portend worse outcomes secondary to medication noncompliance. These factors, in combination with the overall small sample size of the very short LOS group, preclude any definitive conclusions about the potential safety of a very early discharge strategy. Our analysis therefore raises an important question that needs to be addressed in future studies, particularly those that use chart reviews to examine why certain patients have a very short hospital LOS after STEMI.
Nearly one-half of the older patients with STEMI in the United States who are undergoing PPCI have a 4- to 5-day LOS, yet patients discharged earlier have similar 30-day mortality and MACE. These data suggest that early discharge (but not within 48 h after PPCI) may be safe among selected older patients undergoing PPCI for STEMI who do not develop in-hospital complications.
COMPETENCY IN SYSTEMS-BASED PRACTICE: The importance of in-hospital monitoring for patients with MI and appropriate reasons for variation from the mean 4- to 5-day inpatient stay on the basis of risk factors and comorbidities should be made clear to patients, family members, other caregivers, and payers. Earlier discharge (still no <48 h after PCI) may be safe in selected older patients undergoing uncomplicated primary PCI.
TRANSLATIONAL OUTLOOK: Early discharge strategies could be developed that promote safe transitions to the outpatient setting, optimize efficiency, and enhance patient-oriented outcomes.
This research was supported by the American College of Cardiology Foundation’s National Cardiovascular Data Registry (NCDR). The views expressed in this article represent those of the authors and do not necessarily represent the official views of the NCDR or its associated professional societies identified at www.ncdr.com. The CathPCI Registry is an initiative of the American College of Cardiology Foundation and the Society for Cardiovascular Angiography and Interventions. Dr. Feldman is a consultant and Speakers Bureau member for Abbott Vascular, Eli Lilly, Daiichi-Sankyo, Bristol-Myers Squibb, and Pfizer. Dr. Bergman is a proctor for transcatheter aortic valve replacement. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- Abbreviations and Acronyms
- American College of Cardiology
- American Heart Association
- coronary artery bypass grafting
- Centers for Medicare & Medicaid Services
- intra-aortic balloon pump
- International Classification of Diseases-Ninth Revision-Clinical Modification
- left anterior descending
- length of stay
- major adverse cardiac event(s)
- myocardial infarction
- percutaneous coronary intervention
- primary percutaneous coronary intervention
- ST-segment elevation myocardial infarction
- Received November 24, 2014.
- Revision received December 22, 2014.
- Accepted January 13, 2015.
- 2015 American College of Cardiology Foundation
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