We enrolled 8,176 consecutive patients with ACS, of which 461 patients (5.6%) had prior CABG. Patients with prior CABG had significantly more adverse baseline characteristics than those without CABG (Table ). When compared with non-CABG ACS patients, ACS patients with prior CABG were older [63 vs 55 years, p<0.0001], and significantly more likely to have had a prior history of angina, myocardial infarction (MI) and percutanous coronary intervention (PCI) [86.6 vs 37.7%; 66.8 vs 21.8%; 32.5 vs 10.5%, respectively, p<0.0001]. They were more likely to be type 2 diabetic, hypertensive and dyslipidemic [62.3 vs 37.6%; 75.7 vs 47.8%; 70.3 vs 29.5%, respectively, p< 0.0001]. Comorbidities including previous stroke and peripheral arterial disease were more prevalent in the CABG group compared with the non-CABG group [9.5 vs 4.3%; 9.5 vs 2.0% respectively, p<0.0001]. CABG patients had also more chronic obstructive pulmonary disease (COPD) [8.9 vs 5.1%, p=0.001] and were more likely to have been on dialysis [2.0 vs 0.9%, p=0.046].
Baseline Patient Characteristics and Comorbidities of the Study Cohort
Table summarizes the data on clinical presentation and investigations. ACS patients with prior CABG were more likely to present with advanced Killip class II-IV (33.1 vs 21.1%, P < 0.0001) compared to ACS without prior CABG. Compared to the non-CABG patients, the CABG patients were more likely to present with UA and NSTEMI (46.6 vs 27.6%; 41.4 vs 31.6% respectively, p<0.0001). In addition, ACS patients with prior CABG were more likely to have left ventricular dysfunction (LVEF ≤ 40%: 49.4 vs 29.8%, P < 0.0001). On initial laboratory testing, the CABG patients tested with significantly lower levels of total and low-density lipoprotein (LDL) cholesterol and higher serum creatinine levels (P < 0.05).
Baseline Clinical Presentations, Investigations and Discharge Diagnosis of Study Cohort
Treatment patterns are presented in Table . For STEMI patients, approximately half of those with prior CABG received thrombolytic therapy (48.7%) with no significant difference between the CABG and non-CABG groups (P > 0.05). During the first 24 h following admission, CABG patients were more likely to be treated with angiotensin converting enzyme inhibitors/angiotensin receptor blockers (ACEI/ARB) (75.1 vs 67.3%, P< 0.05); diuretics (45.5 vs 24.2%, P < 0.0001) and nitrates (89.3 vs 80.8%, P < 0.0001) than patients without prior CABG, and slightly less likely to be treated with aspirin, beta-blockers and heparin. At the time of discharge, patients with prior CABG were less likely to be discharged on aspirin and beta-blockers, but more likely to be discharged on statins, nitrates and diuretics. Prior CABG patients compared with non-CABG patients underwent fewer coronary angiograms during the index hospitalization (15.9 vs 12.1%, P > 0.05) (Table ).
Treatment Patterns for ACS Patients with and without Prior CABG
ACS patients with CABG suffered more episodes of recurrent ischemia (Table ) (13.9 vs 9.3%, P < 0.05), heart failure (24.1 vs 15.7%, P < 0.0001), and requiring ventilator support (8.3 vs 4.6%, P < 0.05). They received more inotropic support (11.5 vs 7.4%, P < 0.001), had higher rates of major bleeds (2.2 vs 0.6%, P < 0.05), strokes (2.2 vs 0.6%, P < 0.0001) and in-hospital mortality rate (5.6 vs 3.5%, P < 0.05) than the non-CABG patients.
In-Hospital Course and outcomes for ACS Patients with and without Prior CABG
In univariate analyses, patients with prior CABG were significantly more likely to have adverse events during their admission for ACS with significantly higher rates of recurrent ischemia, heart failure, requirement for mechanical ventilation and inotropic support, major bleeding, stroke and death (Table ). After adjusting for differences in baseline characteristics and ACS type (Table ), prior CABG was associated with about a 4-fold increased risk of recurrent ischemia and more than 2-fold increased risk of cardiogenic shock among patients with STEMI but not in patients NSTE-ACS (P for interaction <0.0001 and 0.0087, respectively). There was a trend for significant association between history of CABG and increased risk of death (OR 1.55, 95%CI 0.95-2.54, P=0.08).
Adjusted in-Hospital outcomes in Patients with Acute Coronary Syndrome and Prior CABG Compared with those without Prior CABG