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Clinical Characteristics, Management Strategies and Outcomes of Acute Myocardial Infarction Patients With Prior Coronary Artery Bypass Grafting

      Abstract

      Objective

      To investigate the management strategies, temporal trends, and clinical outcomes of patients with a history of coronary artery bypass graft (CABG) surgery and presenting with acute myocardial infarction (MI).

      Patients and Methods

      We undertook a retrospective cohort study using the National Inpatient Sample database from the United States (January 2004–September 2015), identified all inpatient MI admissions (7,250,768 records) and stratified according to history of CABG (group 1, CABG-naive [94%]; group 2, prior CABG [6%]).

      Results

      Patients in group 2 were older, less likely to be female, had more comorbidities, and were more likely to present with non-ST-elevation myocardial infarction compared with group 1. More patients underwent coronary angiography (68% vs 48%) and percutaneous coronary intervention (PCI) (44% vs 26%) in group 1 compared with group 2. Following multivariable logistic regression analyses, the adjusted odd ratio (OR) of in-hospital major adverse cardiovascular and cerebrovascular events (OR, 0.98; 95% CI, 0.95 to 1.005; P=.11), all-cause mortality (OR, 1; 95% CI, 0.98 to 1.04; P=.6) and major bleeding (OR, 0.99; 95% CI, 0.94 to 1.03; P=.54) were similar to group 1. Lower adjusted odds of in-hospital major adverse cardiovascular and cerebrovascular events (OR, 0.64; 95% CI, 0.57 to 0.72; P<.001), all-cause mortality (OR, 0.45; 95% CI, 0.38 to 0.53; P<.001), and acute ischemic stroke (OR, 0.71; 95% CI, 0.59 to 0.86; P<.001) were observed in group 2 patients who underwent PCI compared with those managed medically without any increased risk of major bleeding (OR, 1.08; 95% CI, 0.94 to 1.23; P=.26).

      Conclusions

      In this national cohort, MI patients with prior-CABG had a higher risk profile, but similar in-hospital adverse outcomes compared with CABG-naive patients. Prior-CABG patients who received PCI had better in-hospital clinical outcomes compared to those who received medical management.

      Abbreviations and Acronyms:

      CABG (coronary artery bypass graft), MI (myocardial infarction), OR (odds ratio), PCI (percutaneous coronary intervention)
      Coronary artery bypass grafting (CABG) is one of the most common surgical procedures in the United States.
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      Percutaneous coronary intervention in native arteries versus bypass grafts in prior coronary artery bypass grafting patients: a report from the National Cardiovascular Data Registry.
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      The occlusive disease of grafts and native coronary arteries may result in increased risk of recurrent ischemic events, including angina (>6% at 1 year), myocardial infarction (MI) (>7% after 6 years, or >10% within 10 years), and death (>2% at 1 year, increase 4% to 9% after 5 years).
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      Because of a large number of CABG survivors worldwide, the proportion of patients admitted with acute MI with history of CABG has increased in recent years.
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      • et al.
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      Current American and European guidelines provide class 1 recommendation for early invasive assessment with a coronary angiogram and revascularization for high-risk patients presenting with acute MI.
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      • et al.
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      However, some of the key randomized controlled trials that have established the evidence basis of an invasive approach in acute MI have excluded patients with previous CABG.
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      Furthermore, inconsistent findings have been reported associated with an invasive approach in different studies; for instance, in a Swedish registry of 10,837 patients with prior CABG, 1-year adjusted mortality was 50% less in those who received revascularization compared with those who were treated conservatively.
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      In contrast, a post hoc analysis of the Acute Catheterization and Urgent Intervention Triage Strategy (ACUITY) trial, found that adjusted 30-days and 1-year risk of major adverse cardiovascular events were increased in prior CABG patients treated with revascularization rather than medically.
      • Nikolsky E.
      • McLaurin B.T.
      • Cox D.A.
      • et al.
      Outcomes of patients with prior coronary artery bypass grafting and acute coronary syndromes: analysis from the ACUITY (Acute Catheterization and Urgent Intervention Triage Strategy) trial.
      In an analysis of 3853 patients who had acute coronary syndrome (ACS) with prior CABG in the Global Registry of Acute Coronary Events (GRACE) registry data, the 6-month adjusted mortality outcomes were similar in patients who received revascularization versus those who treated medically.
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      • et al.
      Invasive vs non-invasive treatment in acute coronary syndromes and prior bypass surgery.
      Optimal treatment strategy and clinical outcomes are not well defined in prior CABG patients who present with acute MI.
      The objective of this study was to investigate treatment strategies and clinical outcomes of patients presenting with acute MI with a history of CABG in contemporary clinical practice and to study the in-hospital clinical outcomes associated with an invasive or conservative approach (medical management) using national data from the United States.

      Patients and Methods

      Study Settings

      National Inpatient Sample (NIS) is the largest publicly available all-payer inpatient health care database of the United States designed by the Healthcare Cost and Utilization Project and supported by the Agency for Healthcare Research and Quality.
      • Deyo R.A.
      • Cherkin D.C.
      • Ciol M.A.
      Adapting a clinical comorbidity index for use with ICD-9-CM administrative databases.
      The NIS records discharge level data on diagnosis and procedures from approximately 1000 hospitals, including 20% of all community hospitals in the United States and 7 million hospitalizations annually.
      • Rashid M.
      • Fischman D.L.
      • Gulati M.
      • et al.
      Temporal trends and inequalities in coronary angiography utilization in the management of non-ST-Elevation acute coronary syndromes in the U.S.
      The NIS dataset constitutes a 20% stratified sample of US community hospitals and discharge weights are used to determine national estimated and weighted data, which represents more than 95% of the US population. As NIS is an anonymized publicly available database, ethical approval was not required for this study.

      Study Design

      This is a retrospective cohort analysis of all records in the NIS database of patients admitted with acute MI, non-ST segment elevation MI (NSTEMI), and ST segment elevation MI (STEMI) from January 2004 to September 2015. We used the International Classification of Disease, Ninth Revision, Clinical Modification (ICD-9-CM) codes to identify patients. Records with missing data for age, sex, primary diagnosis, and inpatient mortality were excluded from this study (Supplemental Figure 1, available at http://www.mayoclinicproceedings.org).
      Data regarding patients’ clinical characteristics, comorbid conditions, and in-hospital clinical outcomes were extracted by using the ICD-9-CM diagnosis and procedures codes provided in Supplemental Table 1 (available online at http://www.mayoclinicproceedings.org). We also collected information regarding hospital characteristics including number of beds, location, region, and teaching status. Hospital bed sizes within NIS are defined using different regions of the United States and ranges from 1 to 249 beds for a small hospital, 25 to 449 beds for a medium hospital, and 50+ to 450+ beds for a large size hospital.
      Patients with acute MI were stratified into two groups according to background history of CABG. Group 1 was CABG naive; group 2 had prior CABG. Clinical outcomes of interest included in-hospital all-cause mortality, major acute cardiovascular and cerebrovascular events (MACCE: defined as a composite of all-cause mortality, stroke, and cardiac complications), acute ischemic stroke, and major bleeding. Major bleeding was defined as a composite of gastrointestinal, retroperitoneal, intracranial, and unspecified hemorrhage.

      Statistical Analysis

      Descriptive statistics were performed to compare differences in baseline demographics, clinical characteristics, and crude outcomes between two cohorts. Continuous variables are presented as median and interquartile ranges (IQRs). To determine statistical differences between two groups, χ2 and Wilcoxon rank sum test were used. We performed temporal analysis to assess management strategy during the study period from 2004–2015 and assessed statistical significance by P for trend. Logistic regression models were fitted using maximum likelihood estimation and described as odds ratios (ORs) with 95% CIs. Analysis was initially crude, followed by adjustment for; age, sex, year of procedure, comorbidities (anemia, arthritis, congestive heart failure, coagulopathy, chronic lung disease, depression, diabetes mellitus, diabetic chronic complications, drug abuse, hypertension, hypothyroidism, liver disease, lymphomas, fluid and electrolyte disturbances, metastatic cancer, neurologic disorders, obesity, paralysis, peripheral vascular disease, psychosis, renal failure, solid tumor without metastasis, and weight loss), hospital bed size, hypercholesterolemia, history of coronary artery disease (CAD), family history of CAD, previous MI, previous cerebrovascular accident, previous percutaneous coronary intervention (PCI), shock during admission, use of intra-aortic balloon pump, atrial fibrillation or flutter (AF), ventricular tachycardia (VT), ventricular fibrillation or flutter (VF), NSTEMI presentation, STEMI presentation, and procedures such as coronary angiogram, PCI, or CABG undertaken during admission. We also performed univariate and multivariate sensitivity analyses on patients with a history of CABG to assess the effect of PCI procedures on clinical outcomes compared with those who received medical management only.
      All statistical analyses were undertaken by using Stata 14.2 (College Station, Texas). All statistical analyses were two-tailed, and an alpha of 5% was used throughout.

      Results

      Baseline and Comorbidity Profile

      A total of 7,250,768 patients were admitted with a diagnosis of acute MI between January 2004 and September 2015, of which 449,548 (6.2%) had history of CABG. The process of patients’ inclusion and exclusion is presented in Supplemental Figure 1. The proportion of patients with an acute MI and a history of CABG increased during the study period from 5.5% in 2004–2009 to approximately 7% in 2011–2015 (Supplemental Figure 2, available online at http://www.mayoclinicproceedings.org). Patients with prior CABG were significantly older and more likely to be male, White, and to present with NSTEMI. Furthermore, patients with prior CABG had a higher prevalence of comorbid conditions such as AF, previous MI and PCI, anemia, diabetes mellitus, peripheral vascular diseases, renal failure, and lower prevalence of STEMI presentation, shock, VT, VF, and cardiac arrest during admission (Table 1).
      Table 1Clinical Characteristics
      ACS = acute coronary syndrome; CABG = coronary artery bypass graft; CAD = coronary artery disease; CVA = cerebrovascular accident (stroke or transient ischemic attack); IQR = interquartile range; MI = myocardial infarction; NSTEMI = non–ST-segment elevation myocardial infarction; PCI = percutaneous coronary intervention; STEMI = ST-segment elevation myocardial infarction.
      ,
      Values are shown as percentages unless otherwise stated.
      Variable/group (%)TotalCABG naivePrior CABGP value
      n7,250,7686,801,220449,548
      Age, median (IQR), y68 (57-79)67 (56-79)73 (64-82)<.001
      Male606069<.001
      Ethnicity
       White777780<.001
       Black10107
       Hispanic777
       Asian/Pacific Islander222
       Native American111
       Other333
      Clinical syndrome
       NSTEMI ACS656987<.001
       STEMI293113<.001
       Weekend admission262627<.001
       Shock, % during admission553<.001
       Cardiac arrest332<.001
       Paroxysmal ventricular tachycardia665<.001
       Ventricular fibrillation/flutter2.72.81.5<.001
      Comorbidities
       Hypercholesterolemia494955<.001
       Thrombocytopenia33.23.2.58
       Smoking353530<.001
       Atrial fibrillation/flutter171721<.001
       Previous MI9817<.001
       Previous PCI10916<.001
       Previous CVA335<.001
       Family history of CAD774<.001
       Alcohol abuse331.5<.001
       Anemia151418<.001
       Rheumatoid arthritis/collagen vascular diseases2.22.21.8<.001
       Congestive heart failure0.870.880.80<.001
       Chronic pulmonary disease212122<.001
       Coagulopathy4.444.4<.001
       Depression667<.001
       Diabetes282838<.001
       Drug abuse221<.001
       Hypertension677566<.001
       Hypothyroidism101011<.001
       Liver disease1.21.21<.001
       Lymphomas0.490.490.48.63
       Fluid and electrolyte disturbances191917<.001
       Metastatic cancer0.860.870.74<.001
       Other neurologic disorders5.85.76<.001
       Obesity121210<.001
       Paralysis1.61.71.6.13
       Peripheral vascular disease111018<.001
       Psychoses21.72.1<.001
       Pulmonary circulation disorder0.10.10.1.14
       Renal failure (chronic)171627<.001
       Solid tumor without metastases1.41.41.7<.001
       Valvular heart disease0.250.250.27.17
       Weight loss2.12.21.5<.001
       Dementia1.91.92.1<.001
      Hospital bed size
       Small111112<.001
       Medium252526
       Large646462
      Hospital region
       Northeast191920<.001
       Midwest232321
       South414041
       West171818
      Location/teaching status
       Rural101012<.001
       Urban non-teaching414143
       Urban teaching494945
      Primary expected payer
       Medicare575675<.001
       Medicaid664
       Private insurance272816
       Self-pay662
       No charge0.560.590.2
       Other332
      Median household income (percentile)
       0-25th292930<.001
       26-50th272728
       51-75th242423
       76-100th202019
      a ACS = acute coronary syndrome; CABG = coronary artery bypass graft; CAD = coronary artery disease; CVA = cerebrovascular accident (stroke or transient ischemic attack); IQR = interquartile range; MI = myocardial infarction; NSTEMI = non–ST-segment elevation myocardial infarction; PCI = percutaneous coronary intervention; STEMI = ST-segment elevation myocardial infarction.
      b Values are shown as percentages unless otherwise stated.

      Management Strategy and Crude Clinical Outcomes

      Almost half of prior CABG patients (48%) and two-thirds of the CABG-naive group (68%) underwent an invasive coronary angiogram during admission. The proportion of patients who received PCI (26% vs 44%) and CABG (1% vs 9%) were significantly lower in patients with a history of CABG as opposed to those with no prior CABG (Table 2).
      Table 2Management Approach and Crude Clinical Outcomes
      CABG = coronary artery bypass grafting; FFR = fractional flow reserve; IABP = intra-aortic balloon pump; IQR = interquartile range; MACCE = major acute cardiovascular and cerebrovascular events (composite of death, stroke and cardiac complications); PCI = percutaneous coronary intervention.
      ,
      Values are percentages unless otherwise stated.
      Variable groupTotalCABG naivePrior CABGP value
      n7,250,7686,801,220449,548
      Medical management (no CABG/PCI)494773<.001
      Angiogram676848<.001
      CABG991<.001
      PCI
       Performed434426<.001
       With bare metal stent12126<.001
       With drug-eluting stent303018<.001
      Number of stents
       1212212<.001
       2895<.001
       3331.6<.001
       4+1.11.10.7<.001
       Unknown1097<.001
      Number of vessels stented
       1282817<.001
       2553<.001
       30.740.750.57<.001
       4+0.140.140.14.54
       Bifurcating PCI0.820.830.44<.001
       FFR assessment0.460.470.26<.001
       Intracoronary imaging1.81.90.96<.001
       Use of mechanical circulatory support (IABP or other assisted devices)552<.001
      Crude outcomes
       MACCE, %7.787<.001
       All-cause mortality, %5.85.85.5<.001
       Acute ischemic stroke, %1.661.681.3<.001
       Major bleeding, %3.63.633.12<.001
       Cardiac complications
      Cardiac complication is composite of “cardiac tamponade, hemopericardium, coronary artery dissection, pericardial effusion and Pericardiocentesis.”
      , %
      0.690.720.21<.001
       Length of stay, median (IQR), days3 (2-6)3 (2-6)3 (2-5)<.001
       Total charge (US dollars), median (IQR)43,992 (22,884-76,729)44,906 (23,610-78,042)30,700 (15,454-56,526)<.001
      a CABG = coronary artery bypass grafting; FFR = fractional flow reserve; IABP = intra-aortic balloon pump; IQR = interquartile range; MACCE = major acute cardiovascular and cerebrovascular events (composite of death, stroke and cardiac complications); PCI = percutaneous coronary intervention.
      b Values are percentages unless otherwise stated.
      c Cardiac complication is composite of “cardiac tamponade, hemopericardium, coronary artery dissection, pericardial effusion and Pericardiocentesis.”

      Temporal Changes

      In a temporal analysis to assess management strategy during the study period, we observed an increase in the invasive management (received either PCI or CABG) over time in both CABG-naive (P for trend <.001) and prior CABG cohorts (P for trend <.001) (Supplemental Figure 3, available online at http://www.mayoclinicproceedings.org).

      Clinical Outcomes in CABG-Naive Versus Prior-CABG Patients

      In-hospital MACCE, rates of all-cause mortality, acute ischemic stroke, major bleeding, and cardiac complications were higher in CABG-naive patients compared with those with prior CABG (Table 2). After adjustment of baseline clinical differences, odds of in-hospital MACCE (OR, 0.98; 95% CI, 0.95 to 1.005; P=.11), all-cause mortality (OR, 1; 95% CI, 0.98 to 1.04; P=.6), and major bleeding (OR, 0.99; 95% CI, 0.94 to 1.03; P=.54) were similar between the two groups. However, adjusted risk of acute ischemic stroke was slightly lower in prior CABG patients (OR, 0.89; 95% CI, 0.84 to 0.95; P<.001) compared with the CABG-naive cohort (Table 3).
      Table 3Adjusted In-Hospital Clinical Outcomes in CABG Naive Versus Prior CABG
      CABG = coronary artery bypass grafting; MACCE = major acute cardiovascular and cerebrovascular events (composite of death, stroke and cardiac complications).
      ,
      CABG naive is the reference group.
      Variable/group (%)Odds ratio95% CIP value
      MACCE0.980.95-1.005.11
      All-cause mortality10.98-1.04.6
      Acute ischemic stroke0.890.84-0.95<.001
      Major bleeding0.990.94-1.03.54
      a CABG = coronary artery bypass grafting; MACCE = major acute cardiovascular and cerebrovascular events (composite of death, stroke and cardiac complications).
      b CABG naive is the reference group.

      PCI Versus Medical Management in Prior CABG

      We performed a sensitivity analysis in prior-CABG patients to compare and contrast clinical and demographical characteristics and adverse outcomes in those who received PCI compared with those who received medical management only. Clinical characteristics of both cohorts are described in Supplemental Table 2 (available online at http://www.mayoclinicproceedings.org). In crude analysis, unadjusted MACCE (3.5% vs 8%, P<.001), in-hospital mortality (2% vs 7%, P<.001), ischemic stroke (0.85% vs 1.45%, P<.001), and major bleeding (2.3% vs 3.4%, P<.001) were significantly lower in those prior-CABG patients who received PCI compared with those who received medical management only (Supplemental Table 3, available online at http://www.mayoclinicproceedings.org). However, the frequency of cardiac complications (composite of “cardiac tamponade, hemopericardium, coronary artery dissection, pericardial effusion, and Pericardiocentesis”) was significantly higher in PCI cohort (0.63% vs 0.04%, P<.001). The median total charge (US dollars) was higher in the PCI group ($59,242; IQR, $42,106 to $87,595) compared with those who received medical management only ($21,930; IQR, $12,269 to $38,770).
      After adjustment of all baseline factors in the multivariable analyses, odds of in-hospital MACCE (OR, 0.64; 95% CI, 0.57 to 0.72; P<.001), all-cause mortality (OR, 0.45; 95% CI, 0.38 to 0.53; P<.001), and acute ischemic stroke (OR, 0.71; 95% CI, 0.59 to 0.86; P<.001) were significantly lower in those who received PCI compared with medical management (Table 4). However, risk of all-cause bleeding was similar (OR, 1.08; 95% CI, 0.94 to 1.23; P=.26) between the two groups. We observed reduced MACCE and in-hospital mortality in patients who received PCI compared with those who received medical management only, irrespective of history of CABG (Supplemental Figure 4, available online at http://www.mayoclinicproceedings.org). An overview of our findings is presented in the Figure.
      Table 4Adjusted In-Hospital Clinical Outcomes in Prior CABG Patients Who Received PCI Versus Medical Management
      CABG = coronary artery bypass grafting; MACCE = major acute cardiovascular and cerebrovascular events (composite of death, stroke, and cardiac complications in PCI and CABG in addition to thoracic complications in CABG); PCI = percutaneous coronary intervention.
      Values shown are percentages unless otherwise stated.
      After exclusion of CABG-naive patients and those who have prior CABG but received redo CABG during index admission.
      Medical management is reference group.
      Variable/groupOdds ratio95% CIP value
      MACCE0.640.57-0.72<.001
      All-cause mortality0.450.38-0.53<.001
      Acute ischemic stroke0.710.59-0.86<.001
      All-cause bleeding1.080.94-1.23.26
      a CABG = coronary artery bypass grafting; MACCE = major acute cardiovascular and cerebrovascular events (composite of death, stroke, and cardiac complications in PCI and CABG in addition to thoracic complications in CABG); PCI = percutaneous coronary intervention.
      b Values shown are percentages unless otherwise stated.
      c After exclusion of CABG-naive patients and those who have prior CABG but received redo CABG during index admission.
      d Medical management is reference group.
      Figure thumbnail gr1
      FigureOverview of important study findings. CABG = coronary artery bypass grafting; MACCE = major adverse cardiovascular and cerebrovascular events; MI = myocardial infarction; NSTEMI = non–ST-segment elevation myocardial infarction; PCI = percutaneous coronary intervention; STEMI = ST-segment elevation myocardial infarction; VF = ventricular fibrillation; VT = ventricular tachycardia.
      In multivariate analyses, history of CABG in acute MI was independently associated with lower odds of receipt of an in-hospital coronary angiogram (OR, 0.37; 95% CI, 0.36 to 0.38; P<.001) and PCI (OR, 0.49; 95% CI, 0.48 to 0.50; P <0.001) (Supplemental Tables 4-5, available online at http://www.mayoclinicproceedings.org).

      Discussion

      This is the first national analysis to examine clinical characteristics, management, temporal trends, and clinical outcomes of patients presenting with an acute MI, with or without a history of CABG. After adjustment, we observed similar odds of MACCE, all-cause mortality, and major bleeding between the two groups. However, sensitivity analysis of the prior-CABG patients who received PCI showed that they had better clinical outcomes in the form of in-hospital MACCE and all-cause mortality compared with those who received medical management despite the fact that patients with prior-CABG were less likely to receive invasive management.
      The European Society of Cardiology and American College of Cardiology/American Heart Association guidelines recommend an early invasive approach along with medical therapy in patients who present with acute MI and have a high risk of adverse clinical outcomes.
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      • et al.
      2017 ESC guidelines for the management of acute myocardial infarction in patients presenting with ST-segment elevation: the task force for the management of acute myocardial infarction in patients presenting with ST-segment elevation of the European Society of Cardiology (ESC).
      Patients with prior CABG are recognized as a high-risk cohort; therefore, an early invasive approach with a possibility of revascularization is favored in this group. However, these recommendations are based on limited data. Patients with prior CABG have been excluded from many important clinical trials including VINO
      • Wallentin L.
      • Lindhagen L.
      • Arnstrom E.
      • et al.
      Early invasive versus non-invasive treatment in patients with non-ST-elevation acute coronary syndrome (FRISC-II): 15 year follow-up of a prospective, randomised, multicentre study.
      and RITA3
      • Fox K.A.A.
      • Poole-Wilson P.
      • Clayton T.C.
      • et al.
      5-year outcome of an interventional strategy in non-ST-elevation acute coronary syndrome: the British Heart Foundation RITA 3 randomised trial.
      ,
      • Peterson E.D.
      • Roe M.T.
      • Rumsfeld J.S.
      • et al.
      A call to ACTION (acute coronary treatment and intervention outcomes network): a national effort to promote timely clinical feedback and support continuous quality improvement for acute myocardial infarction.
      • Subherwal S.
      • Bach R.G.
      • Chen A.Y.
      • et al.
      Baseline risk of major bleeding in non-ST-segment-elevation myocardial infarction: the CRUSADE (Can Rapid risk stratification of Unstable angina patients Suppress ADverse outcomes with Early implementation of the ACC/AHA Guidelines) Bleeding Score.
      • Cannon C.P.
      • Weintraub W.S.
      • Demopoulos L.A.
      • Robertson D.H.
      • Gormley G.J.
      • Braunwald E.
      Invasive versus conservative strategies in unstable angina and non-Q-wave myocardial infarction following treatment with tirofiban: rationale and study design of the international TACTICS-TIMI 18 Trial. Treat Angina with Aggrastat and determine Cost of Therapy with an Invasive or Conservative Strategy. Thrombolysis In Myocardial Infarction.
      • Damman P.
      • Wallentin L.
      • Fox K.A.A.
      • et al.
      Long-term cardiovascular mortality after procedure-related or spontaneous myocardial infarction in patients with non-ST-segment elevation acute coronary syndrome: a collaborative analysis of individual patient data from the FRISC II, ICTUS, and RITA-3 trials (FIR).
      and only contributed to small numbers of patients in other ACS clinical trials (in OASIS-5: 1643 of 20,078 patients, in LIPSIA-NSTEMI: 41 of 600 patients, in Italian elderly ACS: 29 of 313, and in After Eighty Study: 76 of 457 patients).
      • Jolly S.S.
      • Faxon D.P.
      • Fox K.A.
      • et al.
      Efficacy and safety of fondaparinux versus enoxaparin in patients with acute coronary syndromes treated with glycoprotein IIb/IIIa inhibitors or thienopyridines: results from the OASIS 5 (Fifth Organization to Assess Strategies in Ischemic Syndromes) trial.
      • Thiele H.
      • Rach J.
      • Klein N.
      • et al.
      Optimal timing of invasive angiography in stable non-ST-elevation myocardial infarction: the Leipzig Immediate versus early and late PercutaneouS coronary Intervention triAl in NSTEMI (LIPSIA-NSTEMI Trial).
      • Savonitto S.
      • Cavallini C.
      • Petronio A.S.
      • et al.
      Early aggressive versus initially conservative treatment in elderly patients with non-ST-segment elevation acute coronary syndrome: a randomized controlled trial.
      • Lee M.M.
      • Petrie M.C.
      • Rocchiccioli P.
      • et al.
      Non-invasive versus invasive management in patients with prior coronary artery bypass surgery with a non-ST segment elevation acute coronary syndrome: study design of the pilot randomised controlled trial and registry (CABG-ACS).
      • Tegn N.
      • Abdelnoor M.
      • Aaberge L.
      • et al.
      Invasive versus conservative strategy in patients aged 80 years or older with non-ST-elevation myocardial infarction or unstable angina pectoris (After Eighty study): an open-label randomised controlled trial.
      • Sanchis J.
      • Nunez E.
      • Barrabes J.A.
      • et al.
      Randomized comparison between the invasive and conservative strategies in comorbid elderly patients with non-ST elevation myocardial infarction.
      Apart from a recently published pilot study where Lee et al
      • Lee M.M.Y.
      • Petrie M.C.
      • Rocchiccioli P.
      • et al.
      Invasive versus medical management in patients with prior coronary artery bypass surgery with a non-ST segment elevation acute coronary syndrome.
      reported 12-month outcome data from 60 prior-CABG patients (invasive group, n=31; medical group, n=29), no major clinical trials exclusively examined clinical outcomes of an invasive versus medical approach in patients who presented with acute MI and had prior CABG.
      • Lee M.M.
      • Petrie M.C.
      • Rocchiccioli P.
      • et al.
      Non-invasive versus invasive management in patients with prior coronary artery bypass surgery with a non-ST segment elevation acute coronary syndrome: study design of the pilot randomised controlled trial and registry (CABG-ACS).
      In our study, only half of prior CABG patients underwent invasive coronary angiography. There are many logistic and clinical factors which affect the selection of a management approach for prior-CABG patients presenting with acute MI. For instance, patients with a previous CABG surgery often have more comorbid conditions and more extensive CAD that may potentially bias clinicians to adopt either conservative approach or selective invasive management strategy.
      • Kim M.S.
      • Wang T.Y.
      • Ou F.S.
      • et al.
      Association of prior coronary artery bypass graft surgery with quality of care of patients with non-ST-segment elevation myocardial infarction: a report from the National Cardiovascular Data Registry Acute Coronary Treatment and Intervention Outcomes Network Registry-Get With the Guidelines.
      These findings are consistent with CRUSADE Quality Improvement Initiative, showing that higher-risk patients are less likely to receive invasive therapies despite a greater possible benefit from a more aggressive management approach.
      • Bhatt D.L.
      • Roe M.T.
      • Peterson E.D.
      • et al.
      Utilization of early invasive management strategies for high-risk patients with non-ST-segment elevation acute coronary syndromes: results from the CRUSADE Quality Improvement Initiative.
      However, it is possible that some of the prior-CABG patients underwent computed tomography coronary angiogram before invasive coronary angiography and were therefore not offered an invasive approach.
      In the present study, revascularization, which was primarily in the form of PCI, was performed in one-quarter of prior-CABG patients and half of those who underwent coronary angiography. There are many possible explanations of this observation. Comorbid conditions and frailty may limit the potential for revascularization to improve patients’ quality of life. There might be a subset of the patients who underwent assessment of viable myocardium, with or without computed tomography coronary angiogram /invasive coronary angiogram, and were not offered revascularization because of the absence of viability. Despite using modern drug-eluting stent platforms and techniques, long-term outcomes of SVG PCIs are suboptimal. Lesions within SVGs are often thrombus laden and degenerate, and predispose distal embolization. The risk of no-reflow and peri-procedural MI are reported to be higher in SVG-PCI compared with native-vessel PCI in many studies.
      • Brilakis E.S.
      • O'Donnell C.I.
      • Penny W.
      • et al.
      Percutaneous coronary intervention in native coronary arteries versus bypass grafts in patients with prior coronary artery bypass graft surgery: insights from the Veterans Affairs Clinical Assessment, Reporting, and Tracking Program.
      ,
      • Varghese I.
      • Samuel J.
      • Banerjee S.
      • Brilakis E.S.
      Comparison of percutaneous coronary intervention in native coronary arteries vs. bypass grafts in patients with prior coronary artery bypass graft surgery.
      Furthermore, bypass grafts enhance the progression of atherosclerosis and calcification in native coronary arteries with up to 43% of the bypassed native vessels developing chronic total occlusions after 1 year of surgery.
      • Pereg D.
      • Fefer P.
      • Samuel M.
      • et al.
      Native coronary artery patency after coronary artery bypass surgery.
      Percutaneous coronary intervention to either SVGs or in native coronary arteries in prior-CABG patients are technically more challenging compared with those in CABG-naive patients. This may reveal uncertainties about performing complex PCI when the procedural risk may be believed to be higher than potential benefits.
      Once baseline differences were adjusted for, we observed that the odds of in-hospital mortality, MACCE, and major bleeding were similar between prior-CABG and CABG-naive cohorts. Our findings are consistent with previously reported observational studies data by Teixeira et al
      • Teixeira R.
      • Lourenco C.
      • Antonio N.
      • et al.
      Can we improve outcomes in patients with previous coronary artery bypass surgery admitted for acute coronary syndrome?.
      and Kim et al.
      • Kim M.S.
      • Wang T.Y.
      • Ou F.S.
      • et al.
      Association of prior coronary artery bypass graft surgery with quality of care of patients with non-ST-segment elevation myocardial infarction: a report from the National Cardiovascular Data Registry Acute Coronary Treatment and Intervention Outcomes Network Registry-Get With the Guidelines.
      In an analysis of 1495 consecutive patients (prior CABG: 73 patients), Teixeira et al
      • Teixeira R.
      • Lourenco C.
      • Antonio N.
      • et al.
      Can we improve outcomes in patients with previous coronary artery bypass surgery admitted for acute coronary syndrome?.
      reported no significant differences in in-hospital mortality (9.5% vs 5.9%; P=0.2), or mortality at 1 year (9.8% vs 9.1; P=0.84), MACCE at 1 year (22% vs 17%; P=0.37), and almost 50% of patients underwent invasive coronary angiogram during hospital admission. However, relatively small numbers, single-center data, and lack of robust adjustments for differences in baseline clinical characteristics were the main limitations of this study. In an analysis of 47,557 NSTEMI patients (prior-CABG: 8790 patients), Kim et al
      • Kim M.S.
      • Wang T.Y.
      • Ou F.S.
      • et al.
      Association of prior coronary artery bypass graft surgery with quality of care of patients with non-ST-segment elevation myocardial infarction: a report from the National Cardiovascular Data Registry Acute Coronary Treatment and Intervention Outcomes Network Registry-Get With the Guidelines.
      observed similar adjusted odds of bleeding (OR, 1; 95% CI, 0.92 to 1.11) and in-hospital mortality (OR, 0.99; 95% CI, 0.87 to 1.11). However, in contrast to our study, neither of these studies analyzed the effect of PCI on clinical outcomes in prior CABG patients. There are many possible explanations of these observations. It has been previously reported that acute MI patients who had prior CABG presented with smaller sized infarcts as measured by peak creatinine kinase levels or with subsequent formation of Q waves on electrocardiogram (ECG).
      • Grines C.L.
      • Booth D.C.
      • Nissen S.E.
      • et al.
      Mechanism of acute myocardial infarction in patients with prior coronary artery bypass grafting and therapeutic implications.
      ,
      • Wiseman A.
      • Waters D.D.
      • Walling A.
      • Pelletier G.B.
      • Roy D.
      • Theroux P.
      Long-term prognosis after myocardial infarction in patients with previous coronary artery bypass surgery.
      Prior CABG patients develop collateral circulations, which reduced infarct size.
      • Grines C.L.
      • Booth D.C.
      • Nissen S.E.
      • et al.
      Mechanism of acute myocardial infarction in patients with prior coronary artery bypass grafting and therapeutic implications.
      ,
      • Charney R.
      • Cohen M.
      The role of the coronary collateral circulation in limiting myocardial ischemia and infarct size.
      In addition, these patients may have obstruction of a segment that is distal to the graft anastomosis, resulting in small area MI. Moreover, prior CABG patients may have an MI due to occlusion of small branch, wherein the native coronary artery is protected by a patent graft.
      • Crean P.A.
      • Waters D.D.
      • Bosch X.
      • Pelletier G.B.
      • Roy D.
      • Theroux P.
      Angiographic findings after myocardial infarction in patients with previous bypass surgery: explanations for smaller infarcts in this group compared with control patients.
      Alternatively, if the graft occluded during an MI, the downstream myocardium may still be perfused through the native coronary vessel.
      Our analysis indicates lower adjusted odds of in-hospital mortality, acute ischemic stroke, and MACCE in those prior-CABG patients who received PCI compared with medical management without any additional risk of major bleeding. This is an important finding in this study as PCI was under-used as the revascularization strategy of choice in acute MI patients who had prior CABG, even though it was associated with better clinical outcomes compared with medical management. These findings may provide insight to physicians regarding the utility of an invasive management strategy in this patient group. Prospective, randomized controlled clinical data are needed to validate these observational findings.

      Study Strengths and Limitations

      This study has several strengths. This is the largest ever study to assess management strategies, temporal trends, and clinical outcomes of patients with a history of CABG surgery who present with acute MI. Large sample size of this study gives us adequate statistical power to capture differences in clinical outcomes between the patient groups studied. Moreover, because patients with prior CABG are often excluded or under-represented in landmark PCI trials, our data represents the best available current evidence in this cohort.
      This study has several limitations. First, the NIS is an administrative database that may be vulnerable to coding inaccuracies, although the use of ICD-9-CM codes has been validated in many previous publications.
      • Birman-Deych E.
      • Waterman A.D.
      • Yan Y.
      • Nilasena D.S.
      • Radford M.J.
      • Gage B.F.
      Accuracy of ICD-9-CM codes for identifying cardiovascular and stroke risk factors.
      ,
      • DeShazo J.P.
      • Hoffman M.A.
      A comparison of a multistate inpatient EHR database to the HCUP Nationwide Inpatient Sample.
      Second, although the NIS dataset included many variables of interest, additional information such as blood investigations, imaging details, antiplatelets, and antithrombotic regimens, procedural details, operator experience, information about culprit vessels, infarct size, pharmacotherapy, and lesion characteristics are not routinely collected and may provide additional information for risk stratification, case complexity, and procedural outcomes. Third, NIS only records in-hospital clinical outcomes and it is possible that long-term follow-up data may show even greater differences in clinical outcomes between PCI and medical management in prior CABG patients. Fourth, it is possible that type 2 MIs were also coded as acute MIs and hence included in the study. If so, it is possible that there were more type 2 MIs (eg, sepsis, etc) in patients who had prior CABG because they tended to be older and had more comorbidities. This may contribute to a less invasive approach, and many of these patients would not even undergo coronary angiography. Finally, it is not clear from the NIS dataset whether the ACS event was due to a ruptured plaque in either the graft or native vessel, which may impact on clinical outcomes differently.

      Conclusion

      Our study shows that invasive coronary angiography was offered in less than half of patients with prior CABG who presented with acute MI with only one-quarter of patients receiving PCI. The odds of receiving invasive management remained low in the prior-CABG patients even after adjustment of baseline differences. We did not observe any significant difference in in-hospital MACCE, mortality, and major bleeding between prior-CABG and CABG-naive patients who presented with acute MI. Lower odds of in-hospital MACCE and mortality were observed in prior-CABG patients who underwent PCI compared with medical management without any increased odds of major bleeding. A randomized control clinical trial is needed to assess differences between contemporary invasive and medical therapies in prior CABG patients who presented with acute MI.

      Supplemental Online Material

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