Postdischarge outcomes after percutaneous coronary intervention (PCI) are important measurements of quality of care and complement in-hospital measurements. We sought to assess in-hospital and postdischarge PCI outcomes to (1) better understand the relation between acute and 30-day outcomes, (2) identify predictors of 30-day hospital readmission, and (3) determine the prognostic significance of 30-day hospital readmission. We analyzed in-hospital death and length of stay (LOS) and nonelective cardiac-related rehospitalization after discharge in 10,965 patients after PCI in the Dynamic Registry. From 1999 to 2006 in-hospital death rate and LOS decreased. Thirty-day cardiac readmission rate was 4.6%, with considerable variability over time and among hospitals. Risk of rehospitalization was greater in women and those with congestive heart failure, unstable angina, multiple lesions, and emergency PCI. Conversely, a lower risk of rehospitalization was associated with a larger number of treated lesions. Patients readmitted within 30 days had higher 1-year mortality than those free from hospital readmission. In conclusion, although in-hospital mortality and LOS after PCI have decreased over time, the observed 30-day cardiac readmission rate was highly variable and risk of readmission was more closely associated with underlying patient characteristics than procedural characteristics.
Hospital length of stay (LOS) and in-hospital mortality after percutaneous coronary intervention (PCI) represent acute process and quality-of-care measurements, respectively. Important and complementary measurements of overall PCI quality are those that occur after hospital discharge. In fact, in-hospital and postdischarge metrics may be discordant because improvements in acute in-hospital process-of-care metrics may not translate to improvements in subsequent clinical events. In addition, the introduction of new technologies may affect acute process and 30-day outcomes differently. As such, there has been a renewed focus not only on LOS but also on postdischarge mortality and readmission rates after PCI. The latter was addressed in recently published data that suggested substantial and widely variable readmission rates among hospitals. Although the study of readmission rates likely provides an avenue for improving care, this metric leaves much to be desired because the nature of readmission is complex. Using a database designed specifically to prospectively assess PCI outcomes, we sought to assess in-hospital and postdischarge PCI outcomes, specifically 30-day rate of hospital readmission after PCI. In addition, we examined predictors of readmission at 30 days and the impact of hospital readmission on 1-year mortality.
Methods
Details of the purpose, structure, and function of the National Heart, Lung and Blood Institute–sponsored Dynamic Registry have been previously described. In total 10,965 patients undergoing PCI were consecutively enrolled in 5 recruitment waves from 1997 through 2006: 2,524 patients were recruited from 1997 to 1998, 2,105 patients were recruited in 1999, 2,047 patients were recruited from 2001 to 2002, 2,112 patients were recruited in 2004, and 2,177 patients were recruited in 2006. Patient- and lesion-level data were collected and component and composite rates recorded. Outcomes considered for this analysis included LOS as an acute process measurement and rates of in-hospital major adverse cardiac events including in-hospital death, myocardial infarction (MI), and any repeat target vessel revascularization procedure (acute quality measurements). For those patients discharged alive, 30-day cardiovascular readmission rates and 30-day and 1-year mortalities were determined. Cardiovascular readmission was defined as nonelective repeat hospitalization by 30 days in all patients alive at discharge for ≥1 of the following: angina, MI, coronary artery bypass graft surgery, nonstaged/nonindex artery PCI, heart failure, or stroke.
Patients participating in the Dynamic Registry consented to the collection of in-hospital and postdischarge data after the index procedure. Study coordinators at each site contacted patients multiple times in the first year and at 1 year to obtain vital status and information regarding intercurrent hospitalizations, cardiovascular events, or procedures. Dates corresponding to all reported outcomes were recorded and confirmed by requesting relevant records. Whenever possible, angiographic data pertaining to repeat PCI were collected and reviewed to determine target vessel revascularization. Postdischarge follow-up data were available for 97.5%, 94.9%, 90.2%, 99%, and 99% of patients for waves 1 to 5, respectively. The study protocol was approved by the institutional review boards of the coordinating center (University of Pittsburgh) and all clinical sites involved.
Patients were stratified by 30-day readmission status. Continuous data were summarized as mean ± 1 SD. Categorical variables are summarized as counts or percentages. Overall differences between proportions were assessed by chi-square test, continuous variables were compared by Kruskal–Wallis test, and the test for trend was assessed with Mantel–Haenszel test for categorical variables and ordered Jonckherre–Terpstra test for continuous variables. Similar methods were used for lesion-level analyses. Cumulative event rates at 30 days and 1 year were calculated by the Kaplan–Meier method and compared using log-rank statistic. Patients who did not have the outcome of interest were censored at the last known date of contact or at 30 days or 1 year if contact extended beyond that point. All rates are reported as point estimates. Rates were also adjusted for imbalances in important covariates among waves using general linear modeling methods. To examine risk factors associated with a cardiovascular readmission within 30 days of PCI, a model was built using important clinical, demographic, and procedural factors using Cox proportional hazards method. Hazard ratios and their corresponding 95% confidence intervals are reported. All statistical analyses were performed using SAS 9.2 (SAS Institute, Cary, North Carolina), and a 2-sided p value ≤0.05 was considered to indicate statistical significance.
Results
Over successive periods from 1997 through 2006, there were significant increases in patient age, body mass index, previous revascularization, percentage with concomitant noncardiac disease, diabetes mellitus, hyperlipidemia, heart failure, and hypertension and a decrease in percentage with previous MI ( Table 1 ). Overall stent use increased over time. No drug-eluting stents were used before 2004, whereas such stents were used preponderantly in the 2004 and 2006 recruitment periods. Procedural success remained unchanged ( Table 2 ). Radial artery access was used in 3.1% overall, with a trend toward increasing use that peaked at 6.6% in the final 2006 recruitment wave (p <0.0001).
| Characteristic | 1997–1998 | 1999 | 2001–2002 | 2004 | 2006 | p Value ⁎ |
|---|---|---|---|---|---|---|
| (n = 2,483) | (n = 2,077) | (n = 2,026) | (n = 2,083) | (n = 2,161) | ||
| Age (years), mean, median | 62.5, 63 | 62.9, 63 | 64.3, 65 | 63.6, 64 | 63.9, 64 | <0.001 |
| Age >65 years | 44.1% | 45.2% | 48.8% | 46.3% | 46.5% | 0.066 |
| Women | 35.2% | 36.1% | 36.0% | 32.6% | 32.9% | 0.013 |
| Race | ||||||
| White | 80.0% | 78.1% | 79.1% | 76.9% | 75.1% | 0.982 |
| Black | 7.8% | 12.1% | 12.9% | 14.7% | 16.2% | |
| Asian | 4.8% | 3.9% | 3.8% | 3.0% | 2.1% | |
| Hispanic | 7.2% | 5.7% | 4.1% | 5.3% | 5.8% | |
| Other | 0.2% | 0.2% | 0.1% | 0.0% | 0.7% | |
| Body mass index (kg/m 2 ), mean, median | 28.2, 28 | 28.8, 28 | 29.3, 28 | 29.2, 28 | 29.7, 29 | <0.001 |
| Previous percutaneous coronary intervention | 28.2% | 30.7% | 33.2% | 31.9% | 35.4% | <0.001 |
| Previous coronary artery bypass surgery | 16.4% | 17.0% | 19.6% | 19.9% | 17.8% | 0.147 |
| Previous myocardial infarction | 39.1% | 32.5% | 27.6% | 26.2% | 22.6% | <0.001 |
| Severe noncardiac concomitant disease | 29.4% | 33.6% | 38.4% | 36.7% | 36.0% | <0.001 |
| Cerebrovascular | 6.0% | 6.4% | 6.8% | 8.0% | 6.8% | 0.042 |
| Renal | 3.3% | 4.8% | 7.1% | 8.3% | 8.7% | <0.001 |
| Peripheral vascular | 7.1% | 7.1% | 9.0% | 8.7% | 7.4% | 0.176 |
| Pulmonary | 6.8% | 8.8% | 8.2% | 7.6% | 7.7% | 0.613 |
| Cancer | 5.6% | 6.7% | 7.6% | 7.7% | 7.4% | 0.006 |
| Other | 8.4% | 10.6% | 15.4% | 14.5% | 11.2% | <0.001 |
| Diabetes mellitus | 27.5% | 28.5% | 30.2% | 33.2% | 34.2% | <0.001 |
| Congestive heart failure | 9.7% | 9.3% | 12.4% | 9.2% | 10.1% | 0.694 |
| Hypertension | 59.2% | 64.4% | 74.7% | 77.1% | 78.2% | <0.001 |
| Hyperlipidemia | 61.3% | 63.6% | 71.7% | 75.2% | 79.2% | <0.001 |
| Smoking | ||||||
| Never | 34.4% | 32.1% | 33.3% | 37.5% | 36.0% | 0.041 |
| Current | 25.4% | 27.1% | 24.0% | 22.6% | 25.6% | |
| Former | 40.1% | 40.8% | 42.7% | 39.9% | 38.4% |
⁎ Test for trend in patients from successive recruitment periods discharged alive.
| Characteristic | 1997–1998 | 1999 | 2001–2002 | 2004 | 2006 | p Value ⁎ |
|---|---|---|---|---|---|---|
| (n = 2,483) | (n = 2,077) | (n = 2,026) | (n = 2,083) | (n = 2,161) | ||
| Abnormal left ventricular ejection fraction | 26.8% | 27.1% | 31.1% | 30.7% | 28.7% | 0.044 |
| Left ventricular ejection fraction, mean, median | 55.2, 56 | 53.3, 55 | 51.6, 55 | 51.8, 55 | 52.7, 55 | <0.001 |
| Number significant lesions, mean, median | 2.9, 2 | 2.9, 2 | 3.1, 3 | 3.1, 3 | 3.1, 3 | <0.001 |
| Amenable to complete coronary artery bypass surgery revascularization | 87.4% | 85.4% | 82.6% | 76.0% | 72.1% | <0.001 |
| Amenable to complete percutaneous coronary intervention revascularization | 81.4% | 81.2% | 81.8% | 87.0% | 90.2% | <0.001 |
| Revascularization reason | ||||||
| Asymptomatic | 2.2% | 4.7% | 8.5% | 10.1% | 14.5% | <0.001 |
| Stable angina pectoris | 25.1% | 20.6% | 20.0% | 23.0% | 18.8% | <0.001 |
| Unstable angina pectoris | 47.3% | 45.8% | 41.9% | 34.9% | 32.7% | <0.001 |
| Acute myocardial infarction | 18.5% | 25.7% | 27.8% | 27.8% | 28.8% | <0.001 |
| Other | 6.9% | 2.7% | 1.4% | 1.7% | 1.8% | <0.001 |
| Cardiogenic shock | 1.1% | 1.4% | 1.6% | 0.7% | 1.1% | 0.282 |
| Circumstances of procedure | ||||||
| Elective | 66.7% | 51.7% | 51.9% | 77.8% | 65.9% | 0.001 |
| Urgent | 16.2% | 41.7% | 27.8% | 15.9% | 25.9% | |
| Emergency | 17.2% | 6.7% | 20.4% | 6.3% | 8.2% | |
| Lesion American College of Cardiology/America Heart Association classification | ||||||
| A | 10.0% | 13.1% | 16.2% | 10.6% | 11.6% | 0.013 |
| B1 | 29.3% | 32.8% | 34.2% | 35.9% | 29.7% | |
| B2 | 39.8% | 38.2% | 30.3% | 32.3% | 29.5% | |
| C | 20.9% | 15.9% | 19.3% | 21.1% | 29.2% | |
| Treatment strategy | ||||||
| Stent use (overall) | 67.6% | 79.2% | 86.1% | 93.3% | 95.6% | <0.001 |
| Eluting stent use (overall) | 0% | 0% | 0% | 65.2% | 82.8% | <0.001 |
| In-hospital myocardial infarction | 2.6% | 2.7% | 1.8% | 2.4% | 1.7% | 0.0919 |
| In-hospital Q-wave myocardial infarction/emergency coronary artery bypass surgery | 0.7% | 0.5% | 0.2% | 0.2% | 0.1% | <0.001 |
| Overall angiographic success | ||||||
| None | 3.3% | 2.7% | 2.2% | 2.2% | 2.1% | <0.001 |
| Partial | 4.2% | 4.2% | 3.2% | 2.3% | 1.6% | |
| Total | 92.5% | 93.1% | 94.7% | 95.5% | 96.3% | |
| Procedure success (angiographic, without death/Q-wave myocardial infarctions/emergency coronary artery bypass surgery) | 96.3% | 97.0% | 97.6% | 97.6% | 97.8% | 0.0069 |
⁎ Test for trend in patients from successive recruitment periods discharged alive.
Over time, in-hospital mortality improved significantly and LOS shortened. Over the same period, there was considerable variability in 30-day cardiac readmission rates ( Figure 1 ). The cardiac-related readmission rate in those discharged alive was 4.6% (95% confidence interval 3.5 to 5.7) and ranged from 0% to 14.3% across the 27 sites. Cardiac readmission rate for 2001 to 2002 (where only 90.2% follow-up was achieved compared to 95% to 99% follow-up rates for the rest of the recruitment periods) was estimated by imputation to be 4.9% to 5.2%. Cardiac readmission rates for those <65 years old (n = 5,835) and those ≥65 years old (n = 4,985) were similar ( Figure 2 ). Distribution of cardiac-related reasons for readmission is presented in Figure 3 .
Tables 3 and 4 present demographic, angiographic, and procedural characteristics for those patients discharged alive according to 30-day readmission status. Those characteristics independently associated with rehospitalization by 30 days of discharge are listed in Table 5 . As shown, there were no procedural predictors but several patient-related variables associated with risk of rehospitalization. Although female gender, congestive heart failure, acute coronary syndromes, co-morbid conditions, a larger number of significant lesions, and emergency PCI were associated with a greater risk of rehospitalization, increasing numbers of lesions treated by PCI was associated with a lower risk of readmission.
| Characteristic | Total (n = 10,829) | Rehospitalization | p Value ⁎ | |
|---|---|---|---|---|
| No | Yes | |||
| (n = 10,345) | (n = 484) | |||
| Age (years), mean, median | 63.4, 64 | 63.4, 64 | 63.2, 63 | 0.9147 |
| Age >65 years | 46.1% | 46.1% | 45.5% | 0.7803 |
| Women | 34.6% | 34.2% | 41.5% | 0.0010 |
| Race | ||||
| White | 77.9% | 78.0% | 77.1% | 0.8037 |
| Black | 12.6% | 12.6% | 12.0% | |
| Asian | 3.5% | 3.5% | 4.3% | |
| Hispanic | 5.7% | 5.6% | 6.4% | |
| Other | 0.2% | 0.3% | 0.2% | |
| Body mass index (kg/m 2 ), mean, median | 29.0, 28 | 29.0, 28 | 28.7, 28 | 0.1814 |
| Previous percutaneous coronary intervention | 31.7% | 31.6% | 35.2% | 0.1218 |
| Previous coronary artery bypass surgery | 17.9% | 17.7% | 20.9% | 0.1299 |
| Previous myocardial infarction | 29.9% | 29.9% | 30.5% | 0.7865 |
| Severe noncardiac concomitant disease | 34.6% | 34.2% | 42.3% | 0.0003 |
| Cerebrovascular | 6.8% | 6.7% | 9.1% | |
| Renal | 6.4% | 6.4% | 6.2% | 0.8750 |
| Peripheral vascular | 7.8% | 7.8% | 9.5% | 0.1525 |
| Pulmonary | 7.9% | 7.8% | 10.0% | 0.0892 |
| Cancer | 7.0% | 7.0% | 6.4% | 0.6461 |
| Other | 11.8% | 11.6% | 17.0% | 0.0003 |
| Diabetes mellitus | 30.6% | 30.5% | 34.0% | 0.1039 |
| Congestive heart failure | 10.1% | 9.9% | 14.3% | 0.0019 |
| Hypertension | 70.3% | 70.2% | 73.5% | 0.1222 |
| Hyperlipidemia | 70.1% | 70.0% | 71.2% | 0.5830 |
| Smoking | ||||
| Never | 34.7% | 34.5% | 38.2% | 0.0518 |
| Current | 25.0% | 24.9% | 27.0% | |
| Former | 40.3% | 40.6% | 34.9% | |
| Characteristic | Total (n = 10,829) | Rehospitalization | p Value ⁎ | |
|---|---|---|---|---|
| No | Yes | |||
| (n = 10,345) | (n = 484) | |||
| Abnormal left ventricular ejection fraction | 28.9% | 28.7% | 33.5% | 0.0479 |
| Left ventricular ejection fraction, mean, median | 52.9, 55% | 52.9, 55% | 52.0, 55% | 0.1985 |
| Number significant lesions, mean, median | 3.0, 2 | 3.0, 2 | 3.4, 3 | <0.0001 |
| Amenable to complete coronary artery bypass surgery revascularization | 80.6% | 80.7% | 79.5% | 0.5443 |
| Amenable to complete percutaneous coronary intervention revascularization | 84.4% | 84.5% | 81.7% | 0.1103 |
| Revascularization reason | ||||
| Asymptomatic | 8.0% | 8.1% | 6.0% | 0.1011 |
| Stable angina pectoris | 21.6% | 21.9% | 15.3% | 0.0005 |
| Unstable angina pectoris | 40.7% | 40.5% | 45.0% | 0.0480 |
| Acute myocardial infarction | 25.5% | 25.2% | 31.6% | 0.0017 |
| Other | 2.8% | 2.9% | 1.7% | 0.1131 |
| Cardiogenic shock | 1.2% | 1.1% | 2.7% | 0.0017 |
| Circumstances of procedure | ||||
| Elective | 58.3% | 58.8% | 49.6% | <0.0001 |
| Urgent | 31.0% | 30.9% | 34.5% | |
| Emergency | 10.6% | 10.4% | 15.9% | |
| Lesion American College of Cardiology/American Heart Association classification | ||||
| A | 12.2% | 12.2% | 13.4% | 0.2813 |
| B1 | 32.2% | 32.4% | 29.1% | |
| B2 | 34.2% | 34.1% | 36.3% | |
| C | 21.3% | 21.3% | 21.2% | |
| Treatment strategy | ||||
| Stent use (overall) | 77.8% | 77.8% | 78.3% | 0.7552 |
| Eluting stent use (overall) | 28.2% | 28.0% | 32.5% | 0.0123 |
| In-hospital myocardial infarction | 2.3% | 2.2% | 3.3% | 0.1106 |
| In-hospital Q-wave myocardial infarction/emergency coronary artery bypass surgery | 0.4% | 0.4% | 0.4% | 0.8991 |
| Overall angiographic success | ||||
| None | 2.5% | 2.4% | 3.9% | 0.0733 |
| Partial | 3.1% | 3.1% | 2.3% | |
| Total | 94.4% | 94.4% | 93.8% | |
| Procedure success (angiographic, without death/Q-wave myocardial infarction/emergency coronary artery bypass grafting) | 97.2% | 97.3% | 95.7% | 0.0289 |
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