Clinical outcomes in patients with diabetes mellitus and multivessel disease (MVD) undergoing coronary revascularization have not been extensively evaluated, we sought to examine outcomes in a diabetic cohort of 195 consecutive patients with MVD characterized by SYNTAX scores (SSs) undergoing nonrandomized revascularization, 102 (52%) by percutaneous intervention (PCI) and 93 (48%) by coronary artery bypass grafting (CABG) at Liverpool Hospital (Sydney, Australia) from June 2006 to March 2010. Clinical outcomes were assessed at a median term of 14 months. The overall median SS was 44, with significantly higher SSs in CABG- than PCI-treated patients (48 vs 39, p <0.0001). There was a similar incidence of all-cause death, nonfatal myocardial infarction and stroke in PCI- and CABG-treated patients (6.1% vs 8.3%, p = 0.383; 12% vs 4.9%, p = 0.152; 3.1% vs 3.5%, p = 0.680 respectively). However, the rates of target vessel revascularization and major adverse coronary and cerebral event were significantly higher in PCI-treated patients than in those undergoing CABG (20% vs 1.2%, p <0.0001; 29% vs 15%, p = 0.034). Despite a much higher SS, patients who underwent PCI achieved comparable outcomes at 1 year to those with diabetes mellitus and a SS ≥33 as reported in the SYNTAX trial. In conclusion, in this single-center nonrandomized observational study, coronary revascularization by PCI is associated with increased major adverse coronary and cerebral events at 1-year follow-up, predominantly driven by a high rate of target vessel revascularization. Thus, CABG should remain the revascularization procedure of choice for diabetic patients with MVD and high SSs.
Diabetes mellitus (DM) is a powerful independent predictor of adverse cardiovascular events with an increased mortality regardless of the strategy used for coronary revascularization. Patients with DM account for ≥1/4 of all patients referred for revascularization. The pattern of coronary artery disease in diabetic patients is often complex with multiple lesions and widespread disease, making it difficult to achieve complete revascularization and adversely affecting the long-term prognosis. The Synergy Between Percutaneous Coronary Intervention With Taxus and Cardiac Surgery (SYNTAX) score (SS) quantifies angiographic disease complexity. Decisions about percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG) may be guided by the SS as patients with a high SS in whom PCI was the initial procedure often required further revascularization. The SS has a potential limitation, namely it does not account for clinical variables and patient co-morbidities. Risk stratification by SS in patients with multivessel disease (MVD) or left main coronary artery disease has been reported, CABG rather than PCI is recommended for diabetic patients without contraindications. Outcomes in diabetic patients with MVD and a high SS have been less well studied; therefore, we assessed clinical outcomes in a consecutive nonrandomized diabetic cohort undergoing revascularization.
Methods
This was a prospective nonrandomized single-center study at Liverpool Hospital in Sydney (June 2006 through March 2010) to determine clinical outcomes at 1 year in patients with DM and MVD who underwent revascularization by PCI or CABG. The study population comprised of consecutive diabetic patients with MVD screened for recruitment to the Future Revascularization Evaluation in Patients with Diabetes Mellitus: Optimal Management of Multivessel Disease (FREEDOM) trial but were not randomized because they did not meet eligibility criteria or declined randomization, as outlined in Figure 1 ; patients receiving medical treatment alone (n = 28) were excluded. All nonrandomized patients had DM and MVD with ≥70% stenosis in ≥2 major epicardial vessels (left anterior descending, left circumflex and right coronary arteries). In addition, patients with ≥50% stenosis in the left main coronary trunk and/or ≥1 chronic total occlusion were included. All patients were 18 years or older with confirmed DM (type 1: 3%, type 2: 97%) determined by increased fasting plasma glucose or abnormal oral glucose tolerance test result. Current therapy included oral hypoglycemic agents and/or insulin. The revascularization strategy was based on the location and severity of coronary artery disease, and discussions involved interventional/attending cardiologists and usually a cardiac surgeon. At our institution, selective criteria for the use of drug-eluting stent deployment were (1) left main coronary artery lesions; (2) ostial lesions in the left anterior descending, left circumflex or right coronary arteries (3) proximal left anterior descending coronary artery lesions; (4) vessels <3.0 mm with lesion >20 mm in length; (5) vessels ≤2.5 mm; (6) diabetics with vessels <3.0 mm; and (7) in-stent restenosis. Written informed consent was obtained from all patients before the revascularization procedure. Because the SS has been validated only in patients with native coronary artery disease, patients with previous CABG were excluded. This study was approved by the Liverpool Hospital ethics committee (QA2009/046 and QA2008/034).
Extent of angiographic disease was scored according to the SS algorithm, the details of which have been previously reported. In brief, the SS is composed of individual scores for each lesion with stenosis of ≥50% in a vessel with diameter ≥1.5 mm by visual assessment. The SS was calculated independently by 2 experienced interventional cardiologists; an average of the 2 scores was calculated. In cases with 15% discrepancy between the 2 scores, a third SS was determined by another interventional cardiologist, and the average of all 3 scores was taken. All scorers had completed a Web-based tutorial for SS evaluation ( http://www.syntaxscore.com ). Scorers were blinded to patient history, method of revascularization, and clinical outcome.
Baseline patient characteristics were obtained by research personnel from departmental and hospital electronic databases. Follow-up information was recorded from a review of hospital records or by telephone follow-up with patients, their family members, or primary care physicians. Clinical outcomes after PCI or CABG were assessed at 1 year. Clinical end points were all-cause death, nonfatal myocardial infarction, stroke, target vessel revascularization. Combined end points included a composite of death/myocardial infarction/stroke and major adverse coronary and cerebral events (composite of death, myocardial infarction, stroke, or any coronary revascularization). Myocardial infarction was identified according to the definition in the Arterial Revascularization Therapy Study (ARTS). Cerebrovascular accident was defined as a focal neurologic deficit lasting >24 hours and with imaging evidence of cerebral infarction or hemorrhage. Target vessel revascularization was defined as treatment by PCI or CABG caused by restenosis or thrombosis of the targeted vessel(s).
All analyses were conducted using SPSS 19 (SPSS, Inc., Chicago, Illinois). All statistical tests were 2-tailed and p values <0.05 were considered statistically significant. Odds ratio and 95% confidence interval were calculated for comparisons of categorical variables between groups. Continuous variables were expressed as median and interquartile range unless otherwise indicated. Student’s unpaired t test or Mann–Whitney nonparametric test was used to evaluate differences in continuous variables. Categorical variables were presented as number and percentage, and compared using chi-square test or Fisher’s exact test where appropriate. Levene homogeneity-of-variance test was used to test for equal variance. Clinical outcomes were determined using Kaplan–Meier analysis and groups were compared using log-rank test.
Results
A total of 195 patients with DM and MVD who underwent nonrandomized revascularization by PCI or CABG were included in this analysis: 102 (52%) in the PCI group and 93 (48%) in the CABG group. Baseline demographics, clinical characteristics, and indications for revascularization for the groups are listed in Table 1 . Compared to patients who underwent CABG, those who underwent PCI were older (69 vs 64 years, p = 0.048). Gender was similarly distributed in the two groups, with approximately 70% being men. Prevalence rates of hypertension, dyslipidemia, cerebral vascular disease, peripheral vascular disease, family history of coronary heart disease, previous myocardial infarction, and current smoking were similar between the 2 groups. In addition, there was no significant difference in body mass index and duration of DM. Clinical indications for revascularization in the 2 groups such as stable coronary heart disease, ST-segment elevation myocardial infarction, non–ST-segment elevation myocardial infarction, and unstable angina pectoris also were comparable between the PCI and CABG groups.
| Baseline Characteristics | PCI | CABG | p Value |
|---|---|---|---|
| (n = 102) | (n = 93) | (n = 195) | |
| Age (years) | 69 (59–74) | 64 (58–71) | 0.048 |
| Men | 72 (70%) | 66 (71%) | 0.954 |
| Body mass index (kg/m 2 ) | 30 (26–34) | 30.8 (27–34) | 0.812 |
| Hypertension ⁎ | 93 (92%) | 90 (98%) | 0.072 |
| Dyslipidemia † | 88 (88%) | 79 (88%) | 0.963 |
| Previous myocardial infarction | 35 (35%) | 29 (33%) | 0.811 |
| Cardiovascular disease | 11 (11%) | 10 (11%) | 0.956 |
| Peripheral vascular disease | 13 (13%) | 11 (12%) | 0.893 |
| Current smoking | 21 (22%) | 18 (20%) | 0.781 |
| Family history of coronary heart disease | 28 (28%) | 36 (40%) | 0.071 |
| Duration of diabetes mellitus (months) | 120 (60–207) | 120 (72–207) | 0.734 |
| Stable coronary heart disease | 31 (30%) | 32 (34%) | 0.549 |
| Acute coronary syndrome | 71 (70%) | 61 (66%) | |
| ST-segment elevation myocardial infarction | 5 (7%) | 2 (3%) | |
| Non–ST-segment elevation myocardial infarction | 32 (45%) | 33 (54%) | |
| Unstable angina pectoris | 34 (48%) | 26 (43%) |
⁎ Arterial pressure >130/85 mm Hg or on antihypertensive treatment.
† Total cholesterol level ≥4.0 mmol/L or on lipid-lowering treatment.
The SS and angiographic characteristics of the 2 groups are shown in Figures 2 and 3 , respectively. The overall SS of all patients was 44 (35 to 52). Patients who underwent CABG had a higher SS than those who underwent PCI (48 vs 39, p <0.0001). With respect to angiographic characteristics, the CABG group was associated with a two-fold larger proportion of 3-vessel disease compared to the PCI group (61% vs 30%, p <0.0001). Patients with ≥1 chronic total occlusion and/or left main coronary artery stenosis >50% predominantly underwent revascularization with CABG rather than PCI (48% vs 32%, p = 0.028; 37% vs 2.9%, p <0.0001, respectively).
The clinical follow-up period was 14 months (10 to 20), and follow-up details were successfully obtained in 94% of patients. Clinical outcomes ( Table 2 ) and Kaplan–Meier curves for all-cause death, nonfatal myocardial infarction, stroke, composite of death/stroke/myocardial infarction, target vessel revascularization, and major adverse coronary and cerebral events after revascularization are shown in Figure 4 . There was no significant difference in all-cause death (6.1% vs 8.3%, p = 0.383), nonfatal myocardial infarction (12% vs 4.9%, p = 0.152), stroke (3.1% vs 3.5%, p = 0.680), and composite of death/stroke/myocardial infarction (18% vs 14%, p = 0.600) within the study follow-up period between the PCI and CABG groups. However, incidences of target vessel revascularization (19% vs 1.2%, p <0.0001) and major adverse coronary and cerebral events (29% vs 15%, p = 0.034) were, as expected, higher in the PCI than in the CABG group. In PCI-treated patients, there were similar rates in all-cause death, nonfatal myocardial infarction, stroke, and target vessel revascularization irrespective of bare-metal stent or drug-eluting stent deployment ( Table 3 ).
| Characteristic | Number of Events | p Value | |
|---|---|---|---|
| PCI | CABG | ||
| (n = 102) | (n = 93) | ||
| All-cause death | 6 (6%) | 7 (8%) | 0.613 |
| Nonfatal myocardial infarction | 11 (11%) | 4 (4%) | 0.094 |
| Nonfatal stroke | 3 (3%) | 3 (3%) | 0.896 |
| Death/stroke/myocardial infarction | 18 (18%) | 12 (14%) | 0.457 |
| Target vessel revascularization | 19 (19%) | 1 (1%) | <0.0001 |
| Major adverse coronary and cerebral events | 29 (29%) | 13 (14%) | 0.016 |
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