Published online before print February 10, 2009, doi: 10.1161/CIRCINTERVENTIONS.108.826172
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Original Articles |
Trends in the Association Between Age and In-Hospital Mortality After Percutaneous Coronary Intervention
National Cardiovascular Data Registry Experience
From the Division of Cardiovascular Diseases (M.S., D.R.H), Mayo Clinic, Rochester, Minn; Duke Clinical Research Institute (M.T.R., F.-S.O., E.D.P.), Durham, NC; Mid America Heart Institute/UMKC (J.A.S.), Kansas City, Mo; Denver VA Medical Center (J.S.R.), Denver, Colo; University of Texas Health Science Center (H.V.A), Houston, Tex; Rush University Medical Center (L.W.K.), Chicago, Ill; and Beth Israel Deaconess Medical Center (K.K.L.H.), Boston, Mass.
Correspondence to Mandeep Singh, MD, MPH, Mayo Clinic, 200 First Street SW, Rochester, MN 55905. E-mail singh.mandeep{at}mayo.edu
Received October 7, 2008; accepted November 24, 2008.
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Abstract |
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Background— Temporal trends and contemporary data characterizing the impact of patient age on in-hospital outcomes of percutaneous coronary interventions are lacking. We sought to determine the importance of age by assessing the in-hospital mortality of stratified age groups in the National Cardiovascular Data Registry.
Methods and Results— In-hospital mortality after percutaneous coronary intervention on 1 410 069 patients was age stratified into 4 groups—group 1 (age <40, n=25 679), group 2 (40 to 59, n=496 204), group 3 (60 to 79, n=732 574), and group 4 (
80, n=155 612)—admitted from January 1, 2001, to December 31, 2006. Overall in-hospital mortality was 1.22%; in-hospital mortality was 0.60%, 0.59%, 1.26%, and 3.16% in groups 1 to 4, respectively, P<0.0001. Overall temporal improvement per calendar year in the adjusted in-hospital mortality after percutaneous coronary intervention was noted in most groups; however, this finding was significant only in the 2 older age groups, group 3 (odds ratio, 0.94; 95% CI, 0.92 to 0.96) and group 4 (odds ratio, 0.95; 95% CI, 0.92 to 0.97). The absolute mortality reduction was greatest in the most elderly group, those over the age of 80 years.
Conclusions— In-hospital mortality after percutaneous coronary intervention has fallen for all age groups over the past 6 years. However, the largest absolute reduction was seen among patients 80 years of age or older.
Key Words: age • percutaneous coronary interventions • mortality • temporal trends
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Introduction |
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With improving life expectancy, it is projected that over the next 30 years, the proportion of people
65 years of age will increase from 12.4% to 19.6% in the United States.1 During the same time interval, the absolute number of the oldest old (85 years of age) will double, from 9.3 to 19.5 million. Coronary heart disease is the leading cause of death among patients in the United States and with changing demographics the burden of ischemic heart disease will be experienced most by the elderly population. Increasing age is a powerful predictor of adverse events in patients with coronary heart disease, including patients undergoing coronary revascularization.2–5 The time trends in decline in heart disease-related mortality over the past 2 decades have demonstrated disparities with lesser decline noted in heart disease–related mortality in older compared with younger ages.6
Clinical Perspective see p 20
Although, percutaneous coronary intervention (PCI) has been established as an excellent revascularization strategy for higher risk patients, older age is known to influence short- and long-term outcomes after PCI both in the setting of acute myocardial infarction (MI) and during elective percutaneous intervention.7,8 Age is an important covariate that determines death and other major adverse cardiovascular events in all risk adjustment revascularization models.9–13 Much of the data on the effect of age as an independent determinant of outcome are relatively old and are derived from late 1990s and early 2000, and therefore, do not include patients receiving current therapies, including drug-eluting stents. Temporal improvement in the outcomes after PCI has been documented in various risk groups undergoing PCI, however, such trends in various age groups are not well studied.14–16 To that end, we examined the influence of patient age on in-hospital mortality from a contemporary cohort, and analyzed the temporal trends in stratified age groups included within the National Cardiovascular Data Registry (NCDR) Cath PCI registry.
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Methods |
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The NCDR Cath PCI registry is designed to evaluate patient and lesion selection criteria and in-hospital outcomes/complications using standardized data definitions in a large sample with wide geographic diversity.17
We studied in-hospital mortality in 1 410 069 patients undergoing PCI. We age stratified the study sample into 4 groups—group 1 (age <40, n=25 679), group 2 (40 to 59, n=496 204), group 3 (60 to 79, n=732 574), and group 4 (80, n=155 612)—from January 1, 2001, to December 31, 2006. The authors had full access to and take full responsibility for the integrity of the data. All authors have read and agree to the manuscript as written.
Definitions
Death was defined as all-cause mortality during each hospital stay. Procedural success was defined as residual stenosis 
50% with thrombolysis in myocardial infarction (TIMI) 3 flow and decrease in stenosis 20% in all lesions attempted.
Statistical Methods
For descriptive analyses, baseline characteristics, angiographic characteristics, procedure use, and clinical outcomes were compared between age groups. Continuous variables are presented as mean with standard deviation and categorical variables are expressed as frequencies with percentages. To test for independence of a patient’s baseline characteristics, angiographic characteristics, and outcomes with respect to different age groups, Kruskal-Wallis tests were used for continuous variables and Pearson 
2 tests were used for categorical variables.
Overall mortality rate was calculated for each age group. To graphically display the temporal trend of mortality, the mortality rates were also calculated for each age group in a given year and plotted on the same graph.
In examining the association between year effect and outcome in different age groups, a multivariable logistic regression was used to estimate the effects of 1-calendar-year increases in each age group. Variables of interest in the model are age group (4 levels), year (continuous variable), and the interaction between age group and year. The generalized estimating equation18 method was used to account for within-hospital clustering, because patients at the same hospital are more likely to have similar responses relative to patients in other hospitals (ie, within-center correlation for response). The method produces estimates similar to those from ordinary logistic regression, but the estimated variances of the estimates are adjusted for the correlation of outcomes within each hospital. Variables adjusted in the model are body mass index, ST-elevation MI, cardiogenic shock, previous congestive heart failure, previous valve surgery, cerebrovascular disease, peripheral vascular disease, chronic lung disease, previous PCI, preprocedure intra-aortic balloon pump, diabetes/treatment, renal failure/dialysis, smoker, PCI status, and highest risk lesion features (pre-TIMI flow, Society for Cardiovascular Angiography and Interventions lesion class, and lesion segment).
Mortality trend over time was also analyzed and stratified according to presentation as elective or urgent/emergent/salvage PCI. To demonstrate any influence of introduction of drug-eluting stents on mortality, linear spline was used in the multivariable model. Year 2004 was chosen to be the knot for linear spline. For each age group, we now have 2 sets of odds ratio (OR), one for the year effect before 2004 and the other for the year effect after 2004. If drug-eluting stent (DES) has an impact on mortality trend, then the OR for year effect before 2004 will be different from the year effect after 2004.
ORs and 95% CIs were presented for per-1-calendar-year increases in each age group to examine the strength of its influence on mortality. A probability value <0.05 was considered significant for all tests. All statistical analyses were performed by the Duke Clinical Research Institute using SAS software (version 9.0, SAS Institute, Cary, NC).
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Results |
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Of 1 410 069 consecutive procedures from 677 sites performed between 2001 and 2006, only 5 were excluded due to missing age information. We also excluded patients older than 100 years (n=56). Patient characteristics and angiographic features, stratified by age-specific groups, are shown in Table 1. Older age groups (3 and 4) had a lower proportion of men and had higher prevalence of several comorbid conditions. Presentation with congestive heart failure was more common in older patients (9.41% and 15.92% in groups 3 and 4 versus 4.19% and 5.38% in groups 1 and 2, respectively, P<0.0001). Cardiogenic shock was more frequent in group 4 (2.67% versus 2.12%, 1.82%, and 1.97% in groups 1 to 3, respectively, P<0.0001); however, the presentation with ST elevation MI was lower in the older groups (10.51% and 11.35% in groups 3 and 4 versus 27.91% and 17.62% in groups 1 and 2, respectively, P<0.0001).
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In-Hospital Outcomes
The overall mortality was 1.22% and was noted to be higher with older age (Figure 1). The procedural success was lower in the older age group, P<0.0001. Other complications namely periprocedural MI, stroke, renal failure, vascular occlusion, and bleeding complications were higher in older age, Table 2.
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Temporal Trends
The effect of time on mortality after PCI differed according to age. Figure 2A demonstrates the temporal trends in mortality from 2001 to 2006. The decline in mortality was greater in patients in the older 2 age groups, when compared with younger 2 groups. Table 3 illustrates the unadjusted and adjusted outcomes for mortality per 1 year increase in calendar year in different age groups. These data suggest improvements in acute outcomes after contemporary PCI compared with earlier experiences. However, the decrease in risk-adjusted mortality was only statistically significant among patients in group 3 (OR, 0.94; 95% CI, 0.92 to 0.96) and group 4 (OR, 0.95; 95% CI, 0.92 to 0.97). Although reduction in odds of mortality was greatest in young patients, absolute mortality reduction was greatest in the elderly (Table 3).
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Subgroup Analyses
We stratified the 4 age groups into 2 distinct categories, elective or urgent/emergent/salvage, based on the presentation at the time of PCI. Figure 2B and 2C demonstrate the temporal trends in mortality from 2001 and 2006 in patients undergoing elective (Figure 2B) or urgent/emergent/salvage PCI, Figure 2C. The decline in mortality was greater in the older 2 age groups, Table 3. To note the effect of introduction of drug-eluting stents on outcomes, we arbitrarily chose the year 2004 as in 2003 this technology became available. Table 4 summarizes the results. There was no mortality reduction noted after the year 2004 when compared with the earlier years.
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Discussion |
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These results obtained in over 1 million PCI patients enrolled in the NCDR demonstrates the continued adverse effect of increasing age on in-hospital outcome after PCI in contemporary practice using current interventional techniques and pharmacological therapy but also shows declining mortality rates over time. Although reduction in mortality after adjustment is noted in all age groups undergoing PCI in the modern era, the absolute reduction is greatest in the most elderly, those 80 years old or greater.
Age and Outcome
The relationship between age and outcome after PCI has been previously reported.4,5,7,8,19,20 In this study, the mortality rate in octogenarians was 5 times higher compared with the younger population and represents almost 30% of all deaths after PCI. Age in other studies was an independent predictor of outcomes after percutaneous coronary revascularization overall, and also in the setting of primary PCI. Despite higher in-hospital mortality in elderly, we previously demonstrated survival at follow-up after primary PCI similar to expected survival in the general US population.5 Similar observations were made by Cohen et al8 from the National Heart, Lung, and Blood Institute Dynamic Registry. They demonstrated that although the adjusted risks of in-hospital and 1-year mortality rates increased with age, the relative magnitude of excess mortality rates at 1 year was comparable with that observed by age in the US general population.
Effect of age on outcomes was evaluated in the NCDR dataset in the past. Shaw et al17 analyzed the NCDR demonstrated age among other risk factors predictive of adverse outcomes. Klein et al specifically evaluated the outcomes of PCI in octogenarians in this registry at an earlier time frame and found age to be an independent risk factor for in-hospital mortality after PCI; the OR was 1.03 (95% CI, 1.00 to 1.07) for each additional year of age >80.21 The results of this study are consonant with the recent studies demonstrating higher in-hospital mortality in older age groups. Increased in-hospital mortality in the elderly is likely due to higher prevalence of cardiac risk factors, comorbid conditions, and lower procedural success with PCI. In addition, the prevalence of acute coronary syndrome was higher in older age groups. These findings assume importance with limited randomized clinical trial data to guide care in elderly patients and answer some of the lingering uncertainties about benefits of coronary angioplasty in this population. In addition to chronologic age, biological age, comorbid conditions, frailty, quality-of-life indicators, and other age-associated impairment might be more relevant in elderly in decision making for revascularization procedures.22–25
Temporal Trends
The available data on age as a predictor of adverse outcome are relatively old, and recent temporal trends in various age groups in patients with coronary heart disease undergoing PCI are lacking. Our study demonstrated significant improvement in the in-hospital mortality in all the age groups during the study period. Even though the reasons for decline in the younger groups are uncertain, the relative risk reduction was most notable in the younger patients. The elderly patients undergoing PCI had the greatest absolute mortality reduction. With higher proportional mortality in older group, the temporal decline in this high-risk subgroup is of great importance. The reduction in mortality is likely due to improvement in operator and technology and availability of evidence-based medications, including glycoprotein IIb/IIIa inhibitors, dual antiplatelet therapy, β-blockers, and statins.26 This reduction in mortality was noted despite higher prevalence of comorbid and angiographic risks. The observed temporal improvement in the mortality after PCI as demonstrated by our study is consonant with other studies demonstrating significant improvements in outcomes noted in various high-risk clinical and angiographic subsets, eg, older age, unstable angina, angiographic thrombus, and MI, underscoring significant technological and pharmacological advances, including higher use of evidence-based medications, glycoprotein receptor inhibitors, and stents.5,6,14–16 Despite noting significant improvements in the in-hospital outcomes after PCI, one recent study from the Mayo Clinic could not demonstrate additional reduction in mortality in the 2 recent time periods (1996 to 2003 and 2003 to 2004) with in-hospital mortality of 1.7% and 1.8%, respectively.27 No reduction in other major adverse cardiac end points was noted, in fact, the incidence of Q-wave MI and stroke increased in the most recent group.
Limitations
The limitations inherent to retrospective design are applicable to this study. Even as we establish temporal decline in the in-hospital mortality in all age groups undergoing PCI, causality cannot be determined from our analyses. We may not have accounted for some unmeasured confounders, however, that would bias the results toward the null. It is difficult to determine the relative importance of better operator skills, improvement in technology, use of stents, and improved antiplatelet and other adjunctive therapy in improving the results in the most recent period. We realize that the increase in levels of cardiac biomarkers is an important prognostic marker; however, because of the inherent complexity of this large data set, the nonavailability of these markers in the early time periods, and changing definitions, we chose not to elaborate on the temporal trends of MI across various age groups.
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Conclusions |
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Advancing age continues to be associated with adverse outcomes after PCI; however, from 2001 to 2006, in-hospital mortality rates have declined. The temporal decline in this particular adverse outcome after PCI was seen in all age groups and was most evident in the older age groups.
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Acknowledgments |
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Disclosures
None.
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References |
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Footnotes |
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Guest Editor for this article was Antonio Colombo, MD.
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