Methods

We reviewed the records of patients with previous CABG who underwent PCI at 2 institutions from November 2006 to October 2014. The local Ethics Committee approved the use of the clinical data for this investigation. The indications for PCI were symptomatic myocardial ischemia or evidence of a positive stress test with either electrocardiogram or nuclear imaging. PCI strategies were determined by the operator for each case. Postprocedural administration of antiplatelet therapy has been described elsewhere. All patients were informed about the risks of the procedure and each patient provided written informed consent.

Left ventricular ejection fraction (EF) was obtained from transthoracic echocardiography or diagnostic left ventriculography. Renal function was expressed as the estimated glomerular filtration rate, calculated using the Modification of Diet in Renal Disease formula, as modified for Japanese patients. Peripheral arterial disease was defined as the presence of lower extremity peripheral artery disease, carotid artery stenosis, or abdominal aortic aneurysm. Lower extremity peripheral artery disease was defined as an ankle-brachial index <0.9 or a history of endovascular or surgical revascularization. The presence of ≥50% carotid stenosis recorded by ultrasonography or a history of endovascular or surgical revascularization was defined as carotid artery stenosis. Abdominal aortic aneurysm was defined as aortic diameter >30 mm or a history of endovascular or surgical repair. The CABG-SYNTAX score was calculated by determining the SYNTAX score of the native coronary and deducting points based on the importance of the diseased coronary segment with a functioning bypass graft anastomosed distally, as proposed previously.

The primary end point of this study was cardiovascular mortality. Clinical information was obtained from a review of the hospital record or by telephone. Death was regarded as being of cardiac origin, unless obvious noncardiac causes could be identified. Myocardial infarction was defined as an increase in serum creatine kinase level to more than twice the upper limit of normal value with an elevated creatine kinase-MB level. Target lesion revascularization (TLR) was defined as either PCI or CABG for restenosis of the target lesions that included the proximal and distal edge segments, as well as the ostium of the side branches associated with symptoms or objective signs of ischemia. Stroke was defined as ischemic or hemorrhagic stroke requiring hospitalization with symptoms lasting >24 hours. Stent thrombosis was assessed according to the Academic Research Consortium definition.

Continuous variables were expressed as the mean ± SD, and categorical variables as counts and/or percentage. Categorical variables were compared using the chi-square test. Multivariate analyses of independent predictors of cardiovascular mortality and TLR were performed using the Cox-proportional hazard regression model. Variables with p <0.05 on univariate analysis were selected for the multivariate analysis in consideration of potential confounding variables. Receiver-operating characteristic analysis was used to estimate the predictive performance of each score. The area under the receiver-operating characteristic curves was compared according to the method of DeLong et al. Time-to-event variables are presented as Kaplan–Meier estimates and compared using the log-rank test. A probability of p <0.05 was considered statistically significant. All statistical analyses were performed using JMP Pro, Version 12 (SAS Institute, Cary, North Carolina) and R statistical software.

Results

During the study period, 279 consecutive patients with previous CABG underwent PCI. Among these, 7 patients without diagnostic angiogram available or with poor imaging quality were excluded. Thus, 272 patients (217 men, mean age: 70.4 ± 9.7 years) were included for further analysis. The baseline characteristics of the study population are presented in Table 1 . The overall baseline distribution of the CABG-SYNTAX score is presented in Figure 1 . In the index procedures, PCI for the native coronary accounted for nearly all patients (88%; Table 2 ).

The distribution of CABG-SYNTAX scores is illustrated. The median CABG-SYNTAX score was 25 (interquartile range: 18 to 33.5).

The median duration of follow-up for the survivors was 4.1 years (interquartile range: 1.6 to 6.4 years). Complete 1-, 2-, and 4-year follow-up information was obtained for 86%, 76%, and 60% of all patients, respectively. Cardiovascular deaths occurred in 40 patients, including 15 with congestive heart failure, 13 with sudden death, one with cerebrovascular disease, one with ruptured aortic aneurysm, and 10 that were unknown. When the patients were divided into 2 groups according to the median of CABG-SYNTAX score, the frequency of all-cause death, cardiovascular death, and myocardial infarction was significantly greater in the higher CABG-SYNTAX score group than in the lower CABG-SYNTAX score group ( Table 3 ). In the multivariate analysis, age >75 years, left ventricular EF <40%, end-stage renal disease on hemodialysis, peripheral artery disease, and CABG-SYNTAX score >25 were independent predictors of cardiovascular mortality ( Table 4 ). Baseline CABG-SYNTAX score was one of the significant factors for TLR in univariate analysis.

Table 4

Predictors of adverse outcome

	Cardiovascular Mortality				Target Lesion Revascularization
	Univariate		Multivariate		Univariate		Multivariate
	HR (95% CI)	p Value	HR (95% CI)	p Value	HR (95% CI)	p Value	HR (95% CI)	p Value
Age (>75 years)	2.87 (1.53–5.46)	0.001	2.82 (1.45–5.52)	0.002	1.21 (0.67–2.12)	0.52
Men	1.99 (0.79–6.66)	0.19			0.61 (0.34–1.16)	0.13
Diabetes mellitus	1.03 (0.55–1.96)	0.93			1.14 (0.66–2.01)	0.65
Acute myocardial infarction	2.55 (0.87–5.97)	0.08			0.32 (0.02–1.46)	0.17
Left ventricular ejection fraction <40%	3.45 (1.68–6.67)	0.001	2.99 (1.39–6.07)	0.006	0.99 (0.38–2.14)	0.98
End-stage renal disease on hemodialysis	4.43 (1.96–9.09)	<0.001	2.90 (1.15–6.75)	0.02	3.70 (1.67–7.35)	0.002	2.93 (1.27–6.00)	0.01
Peripheral artery disease	2.99 (1.55–6.13)	<0.001	2.20 (1.10–4.64)	0.03	1.75 (1.01–3.05)	0.046	1.32 (0.73–2.39)	0.36
Absence of statin therapy	2.72 (1.45–5.13)	0.002	1.76 (0.88–3.48)	0.11	1.65 (0.93–2.86)	0.09
Absence of beta blockers	0.88 (0.47–1.73)	0.71			0.83 (0.48–1.45)	0.50
Absence of angiotensin converting enzyme inhibitor/angiotensin receptor blocker	1.60 (0.86–3.00)	0.14			1.03 (0.58–1.78)	0.93
CABG-SNYTAX score >25	3.02 (1.55–6.33)	<0.001	2.37 (1.19–5.05)	0.01	1.74 (1.01–3.07)	0.047	1.20 (0.65–2.24)	0.56
PCI for left main	1.35 (0.68–2.55)	0.38			2.11 (1.20–3.64)	0.01	1.81 (0.99–3.28)	0.05
PCI for graft vessel	1.15 (0.39–2.69)	0.78			0.99 (0.38–2.14)	0.98
Rotational atherectomy	1.14 (0.33–2.95)	0.80			3.61 (1.76–6.79)	0.001	2.63 (1.23–5.24)	0.01
Angiographic success	0.38 (0.15–1.26)	0.10			0.69 (0.25–2.84)	0.56

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