Abstract
Purpose: To compare the outcomes of left circumflex artery (LCx) revascularization using an internal thoracic artery (ITA) or radial artery (RA) as the second arterial graft.
Methods: Patients who underwent primary isolated coronary artery bypass grafting with left anterior descending artery revascularization using an ITA and LCx revascularization using another bilateral ITA (BITA group) or an RA (ITA-RA group) were included. All-cause mortality (primary endpoint), cardiac death, major adverse cardiac events, in-hospital death, and deep sternal wound infection (secondary endpoints) were evaluated.
Results: Among 790 patients (BITA, n = 548 (69%); ITA-RA, n = 242 (31%)), no significant difference in all-cause mortality between the groups was observed (hazard ratio (HR): 0.87; 95% confidence interval (CI): 0.67–1.12; p = 0.27) during follow-up (mean, 10 years). Multivariate analysis revealed that the BITA group exhibited significantly lower rates of long-term all-cause mortality (HR: 0.63; 95% CI: 0.48–0.84; p = 0.01). In the propensity-matched cohort (n = 480, 240 pairs), significantly fewer all-cause deaths occurred in the BITA group (HR: 0.66; 95% CI 0.47–0.93; p = 0.02). There were no significant differences in secondary outcomes.
Conclusions: When used as second grafts for LCx revascularization, ITA grafts may surpass RA grafts in reducing all-cause mortality 10 years postoperatively.
Keywords: coronary artery bypass grafting, arterial graft, internal thoracic artery, revascularization of left circumflex artery, long-term outcome
Introduction
Surgical revascularization with an internal thoracic artery (ITA) graft for anastomosis to the left anterior descending (LAD) artery in coronary artery bypass grafting (CABG) is the reference standard owing to its superior long-term patency.1,2) The optimal choice for a secondary graft, however, remains controversial. Although the 2021 American College of Cardiology/American Heart Association/Society for Cardiovascular Angiography and Intervention and the 2018 European Society of Cardiology/European Association for Cardio-Thoracic Surgery guidelines both recommend radial artery (RA) grafts over saphenous vein grafts (SVGs) and suggest bilateral ITA (BITA) grafting for specific patients,3,4) there is still debate about whether the ITA or RA serves as a preferable second graft.5–9) Recent research emphasizes a better long-term prognosis of arterial grafts than that of SVGs as secondary grafts.10–12) In light of this, the Japan Circulation Society’s 2018 guideline recommends the use of both the ITA and RA as class IIa secondary grafts. Notably, the guideline also endorses the use of the BITA for enhancing long-term cardiac outcomes and the in situ right ITA (RITA) graft anastomosis to LCx lesions, both as class Iia recommendations. However, the Japanese guidelines, largely based on Western research, may not fully align with the unique clinical presentation in the Japanese population. A notable study by Tsuneyoshi et al. is the only one that has evaluated the outcomes of CABG using the ITA or RA as a second arterial graft, specifically among Japanese patients.13) Their findings, based on a 5-year follow-up, indicated comparable long-term outcomes between the RA anastomosed to the aorta and the RITA used as a secondary graft. However, to effectively evaluate the superiority of the second graft, longer-term follow-up is essential. We aimed to evaluate the 10-year outcomes post-CABG when either the ITA or RA is used as the secondary arterial graft among Japanese patients.
Materials and Methods
Ethics statement
All study protocols were approved by the Research Ethics Committee of the Faculty of Medicine at Juntendo University on April 21, 2022 (approval no. E22-0096-H01). The need for informed consent was waived owing to the retrospective nature of this study. This study was performed in accordance with the principles of the Declaration of Helsinki.
Patient selection and study design
This was a single-center, retrospective, observational study. Patients who underwent primary isolated CABG between July 2002 and December 2012 at the Juntendo University Hospital were included in this study. Among them, patients who met the following inclusion criteria were further selected: (i) the ITA [right ITA (RITA) or left ITA (LITA)] was used for LAD revascularization and (ii) left circumflex artery (LCx) revascularization was conducted using an ITA [bilateral ITA (BITA) group] or RA (ITA-RA group).
All data were extracted from the institutional database in which data were prospectively collected following the definitions of the Society of Thoracic Surgeons National Adult Cardiac Database (https://www.sts.org/registries/sts-national-database/adult-cardiac-surgery-database).
Operative procedure
Under general anesthesia, all patients underwent a median sternotomy in the frog-leg position. Almost all patients underwent off-pump CABG, performed according to internationally established techniques. All arterial grafts, including the ITA and RA, were harvested using a skeletonized technique with an ultrasound coagulation incision device (HARMONIC; ETHICON, Johnson & Johnson, New Brunswick, NJ, USA). The basic strategy for graft selection in CABG was to perform the LITA-LAD anastomosis first. The decision to use either the RA or RITA as the secondary graft depended on the surgeon’s preference. The RA graft was avoided in patients with diabetes mellitus (DM) and chronic kidney disease (CKD, Stage 4 or 5) owing to the potential future need for a forearm arteriovenous fistula. An aortic no-touch strategy was selected when the ascending aorta exhibited plaque or calcification, which was assumed to indicate a high risk of stroke.
The following methods were employed to prevent deep sternal wound infection (DSWI): (i) ITA harvesting using the skeletonized technique, (ii) placement of a subcutaneous drain, (iii) avoidance of bone wax, (iv) adequate saline flushing before chest closure, and (v) administration of prophylactic antibiotics until after the postoperative 48 hours. Patients routinely began taking aspirin, statins, and β-blockers on the first day after surgery and continued unless contraindicated. For cases in which RA grafts were used, oral diltiazem was administered for 3 months postoperatively to prevent spasms in the RA graft.
Outcomes
The primary endpoint was all-cause death. Secondary endpoints were cardiac death, major adverse cardiac events (MACEs), in-hospital death, and DSWI. MACEs were defined as the composite endpoints of heart failure admissions, ischemic cardiac events, and all-cause death. Cardiac death was defined as death due to heart failure, acute myocardial infarction, lethal arrhythmia, or nontraumatic sudden death. Sudden death was defined as unexpected natural death occurring within 24 hours of onset. DSWI was defined as a sternal infection necessitating refixation of the sternum or omentoplasty.
Follow-up
Patients underwent regular follow-up at Juntendo University Hospital. Physicians assessed a patient’s overall condition and reviewed the results of chest radiographs, electrocardiography, and echocardiography. Additionally, each patient completed a questionnaire on symptoms, cardiac and cerebrovascular events, cardiac-related readmissions, and cardiac interventions. Patients unable to visit the hospital were contacted by phone to inquire about their physical condition, symptoms, and any adverse events. Some patients were lost to follow-up due to relocation or non-adherence to hospital visits. The follow-up duration was defined as the period from the operation date to the date of death or the last contact. The mean follow-up period was 9.7 years.
Statistical analysis
In comparing patient characteristics, categorical data are presented as frequencies and percentages, whereas continuous variables are depicted using mean ± standard deviation (SD) or median (interquartile range). For univariable comparisons between the groups, t-tests were used for normally distributed variables and two-sample proportion tests for binary variables. Chi-squared tests were used to evaluate relationships among multivalued categorical variables. Kaplan–Meier analysis and log-rank tests were used to evaluate postoperative survival in both the entire and the propensity score-matched populations. Cox proportional hazard regression modeling was used to estimate the treatment effect and its statistical significance for cumulative survival and MACE-free survival between the BITA and ITA-RA groups. The following variables were included as covariates in multivariable models: age, sex, DM, CKD (Stages 4 and 5), cerebrovascular disease, peripheral artery disease, left ventricular ejection fraction, and the use of ITA graft.
Propensity score matching was used to reduce selection bias in assigning patients to specific grafts when comparing second arterial graft outcomes in the BITA and ITA-RA groups (Supplementary File: available online). Covariates in the logistic regression for calculating propensity scores included age, sex, CKD, cerebrovascular diseases, peripheral artery disease, DM, and left ventricular function. Statistical significance was established at p <0.05, with all analyses conducted using JMP software (JMP Pro version 16; SAS Institute, Cary, NC, USA). C-statistics were used to assess the ability to accurately differentiate between the two groups, indicated by an area under the receiver operating characteristic curve of 0.613, signifying satisfactory discrimination. Standardized differences were used to assess covariate balance post-propensity score matching, considering a difference of ≤10% as ideal.14)
Results
This study included 1722 patients who underwent isolated primary CABG between 2002 and 2012. Among them, 1676 patients underwent LITA-LAD anastomosis, including 1310 who underwent LCx revascularization. Furthermore, 520 patients who underwent LCx revascularization with an SVG or the gastroepiploic artery were excluded. In total, 790 patients fulfilled the inclusion criteria, with 548 and 242 patients in the BITA and ITA-RA groups, respectively (Fig. 1). The mean age was 66 (±10) years, and 18% of patients were female. The BITA group included significantly more patients with DM and patients with Stage 4 or higher CKD. A total of 240 pairs (n = 480) from the BITA and ITA-RA groups were identified by propensity score matching. After propensity score matching, the two groups were effectively balanced (Fig. 2). A comparison of baseline characteristics, surgical technique, and postoperative course for the entire cohort and the propensity score-matched cohort is shown in Tables 1–3. Details regarding graft combinations and utilization are found in Table 4.
Fig. 1. Flow diagram of patient selection. CABG: coronary artery bypass grafting; LAD: left anterior descending artery; LCx: left circumflex artery; SVG: saphenous vein graft; GEA: gastroepiploic artery; ITA: internal thoracic artery; RA: radial artery; BITA: bilateral internal thoracic artery.
Fig. 2. Primary outcome. Kaplan–Meier survival curves were plotted for all-cause death in the entire cohort (left) and in the propensity score-matched cohort (right). The shaded areas represent the 95% confidence intervals. BITA: bilateral internal thoracic artery; ITA: internal thoracic artery; RA: radial artery.
Table 1. Baseline characteristics of study participants.
| Entire cohort (n = 790) | Propensity score-matched cohort (n = 480) | ||||||
|---|---|---|---|---|---|---|---|
| BITA(n = 548) | ITA-RA(n = 242) | P-value | SMD | BITA(n = 240) | ITA-RA(n = 240) | SMD | |
| Age (years) | 66 ± 10 | 66 ± 9.5 | 0.98 | <0.01 | 67 ± 10 | 66 ± 9.6 | 0.11 |
| Male sex | 459 (83%) | 191 (79%) | 0.11 | 0.12 | 194 (81%) | 189 (80%) | 0.05 |
| BMI (kg/m2) | 24 ± 3.1 | 24 ± 2.9 | 0.46 | 0.06 | 24 ± 3.1 | 24 ± 2.9 | 0.04 |
| Hypertension | 403 (74%) | 178 (74%) | 0.93 | 0.02 | 170 (71%) | 177 (74%) | 0.08 |
| Smoking history | 334 (61%) | 135 (57%) | 0.27 | 0.09 | 144 (60%) | 134 (57%) | 0.07 |
| Family history | 136 (25%) | 43 (18%) | 0.04 | 0.17 | 53 (22%) | 43 (18%) | 0.10 |
| Cerebrovascular disease | 80 (15%) | 40 (17%) | 0.52 | 0.05 | 32 (13%) | 40 (17%) | 0.10 |
| Peripheral artery disease | 75 (14%) | 28 (12%) | 0.49 | 0.06 | 32 (13%) | 28 (12%) | 0.05 |
| Diabetes | 315 (58%) | 116 (48%) | 0.01 | 0.19 | 126 (53%) | 115 (48%) | 0.09 |
| HbA1c (%) | 6.2 ± 1.2 | 6.1 ± 1.3 | 0.52 | 0.05 | 6.1 ± 1.2 | 6.1 ± 1.3 | <0.01 |
| eGFR (mL/min/1.73 m2) | 62 ± 27 | 71 ± 21 | <0.01 | 0.29 | 68 ± 28 | 73 ± 37 | 0.10 |
| CKD Stage 1 | 312 (57%) | 164 (69%) | <0.01 | 0.23 | 151 (63%) | 162 (68%) | 0.09 |
| CKD Stages 2 and 3 | 170 (31%) | 74 (31%) | 0.93 | <0.01 | 84 (35%) | 74 (31%) | 0.09 |
| CKD Stages 4 and 5 | 66 (12%) | 4 (1.7%) | <0.01 | 0.42 | 5 (2.1%) | 3 (1.3%) | 0.06 |
| LDL-C ≥140 (mg/dL) | 64 (12%) | 31 (13%) | 0.64 | 0.03 | 28 (12%) | 31 (13%) | 0.04 |
| BNP (pg/mL) | 66 (28–161) | 56 (25–143) | 0.22 | 0.15 | 57 (25–109) | 57 (25–143) | 0.04 |
| LVEF (%) | 56 ± 14 | 58 ± 14 | 0.05 | 0.15 | 58 ± 13 | 58 ± 14 | 0.04 |
| LVEF <50% | 175 (32%) | 67 (28%) | 0.24 | 0.09 | 39 (16%) | 41 (17%) | 0.02 |
| Number of diseased vessels | 3.3 ± 0.7 | 3.2 ± 0.7 | 0.12 | 0.12 | 3.3 ± 0.7 | 3.2 ± 0.7 | 0.12 |
| 2-vessel disease | 64 (12%) | 32 (13%) | 0.55 | 0.05 | 34 (14%) | 32 (13%) | 0.03 |
| 3-vessel disease | 262 (48%) | 128 (53%) | 0.19 | 0.10 | 103 (43%) | 126 (53%) | 0.19 |
| 4-vessel disease | 222 (41%) | 82 (34%) | 0.08 | 0.14 | 103 (43%) | 82 (34%) | 0.18 |
| LCx lesion | |||||||
| 75% | 82 (15%) | 49 (20%) | 0.07 | 0.14 | 38 (16%) | 49 (20%) | 0.12 |
| 90% | 237 (43%) | 92 (38%) | 0.18 | 0.11 | 107 (45%) | 92 (38%) | 0.13 |
| 99% | 66 (12%) | 29 (12%) | 1.00 | <0.01 | 26 (11%) | 29 (12%) | 0.04 |
| 100% | 91 (17%) | 41 (17%) | 0.91 | 0.01 | 35 (15%) | 40 (17%) | 0.06 |
| LMT lesion | 221 (40%) | 81 (33%) | 0.07 | 0.14 | 103 (43%) | 80 (38%) | 0.20 |
| LAD >75% | 492 (90%) | 217 (90%) | 1.00 | <0.01 | 223 (93%) | 216 (90%) | 0.10 |
| Dx >75% | 190 (35%) | 92 (38%) | 0.38 | 0.07 | 73 (30%) | 92 (38%) | 0.94 |
| RCA >75% | 426 (78%) | 191 (79%) | 0.71 | 0.04 | 171 (71%) | 190 (79%) | 0.18 |
| Euro SCORE (%) | 1.5 (1.0–2.6) | 1.3 (0.8–2.0) | 0.57 | 0.07 | 1.4 (0.9–2.3) | 1.4 (0.8–2.0) | 0.02 |
| Japan Score (%) | 0.9 (0.6–1.5) | 0.8 (0.5–1.2) | 0.31 | 0.12 | 0.9 (0.6–1.2) | 0.8 (0.5–1.2) | 0.10 |
Unless indicated otherwise, data are presented as the mean ± standard deviation, median (interquartile range), or n (%).
BITA: bilateral internal thoracic artery; ITA: internal thoracic artery; RA: radial artery; SMD: standardized mean difference; BMI: body mass index; HbA1c: hemoglobin A1c; LDL-C: low-density lipoprotein cholesterol; eGFR: estimated glomerular filtration rate; BNP: brain natriuretic peptide; LVEF: left ventricular ejection fraction; LMT: left main trunk; RCA: right coronary artery; LCx: left circumflex artery
Table 2. Operative outcomes.
| Entire cohort (n = 790) | Propensity score-matched cohort (n = 480) | ||||||
|---|---|---|---|---|---|---|---|
| BITA(n = 548) | ITA-RA(n = 242) | p-value | SMD | BITA(n = 240) | ITA-RA(n = 240) | SMD | |
| OPCAB | 542 (99%) | 234 (96%) | <0.01 | 0.21 | 239 (99.6%) | 229 (97.5%) | 0.27 |
| Operative time (min) | 311 ± 78 | 332 ± 86 | <0.01 | 0.26 | 306 ± 77 | 333 ± 85 | 0.33 |
| Preoperative IABP | 18 (3.3%) | 15 (6.2%) | 0.08 | 0.14 | 8 (3.3%) | 15 (6.3%) | 0.14 |
| Emergency | 28 (5.1%) | 26 (11%) | <0.01 | 0.21 | 15 (6.3%) | 26 (11%) | 0.16 |
| RITA-LAD | 67 (12%) | 8 (3.3%) | <0.01 | 0.34 | 30 (13%) | 8 (3.3%) | 0.34 |
| Other graft selection | |||||||
| Gastroepiploic artery | 195 (36%) | 124 (51%) | <0.01 | 0.31 | 80 (33%) | 123 (51%) | 0.37 |
| Saphenous vein | 197 (36%) | 54 (22%) | <0.01 | 0.30 | 78 (33%) | 54 (23%) | 0.23 |
| Central anastomosis | 242 (44%) | 176 (73%) | <0.01 | 0.60 | 100 (42%) | 175 (73%) | 0.67 |
| Composite graft | 144 (26%) | 80 (33%) | 0.06 | 0.15 | 61 (25%) | 79 (33%) | 0.17 |
| I-graft | 26 (4.7%) | 16 (6.6%) | 0.30 | 0.08 | 15 (6.3%) | 14 (5.8%) | 0.02 |
| Y-graft | 118 (22%) | 65 (27%) | 0.12 | 0.12 | 46 (19%) | 65 (27%) | 0.19 |
Unless indicated otherwise, data are presented as the mean ± SD or n (%).
BITA: bilateral internal thoracic artery; ITA: internal thoracic artery; RA: radial artery; SMD: standardized mean difference; OPCAB: off-pump coronary artery bypass grafting; RITA: right internal thoracic artery; LAD: left anterior descending artery; IABP: intra-aortic balloon pumping
Table 3. Postoperative outcomes.
| Entire cohort (n = 790) | Propensity score-matched cohort (n = 480) | ||||||
|---|---|---|---|---|---|---|---|
| BITA(n = 548) | ITA-RA(n = 242) | p-value | SMD | BITA(n = 240) | ITA-RA(n = 240) | SMD | |
| Hospital stay (days) | 11 ± 8.7 | 12 ± 7.3 | 0.47 | 0.06 | 11 ± 6.6 | 12 ± 7.3 | 0.11 |
| ICU stay (days) | 1.6 ± 1.6 | 2.5 ± 5.4 | <0.01 | 0.24 | 1.5 ± 1.6 | 2.5 ± 5.3 | 0.25 |
| Postoperative stroke | 8 (1.5%) | 6 (2.5%) | 0.38 | 0.14 | 5 (2.1%) | 5 (2.1%) | <0.01 |
| Respiratory failure | 7 (1.3%) | 4 (1.7%) | 0.74 | 0.03 | 3 (1.3%) | 4 (1.7%) | 0.03 |
| Acute kidney injury | 29 (5.3%) | 6 (2.5%) | 0.09 | 0.15 | 11 (4.6%) | 6 (2.5%) | 0.11 |
| POAF | 143 (26%) | 50 (21%) | 0.11 | 0.13 | 49 (20%) | 34 (14%) | 0.13 |
Unless indicated otherwise, data are presented as the mean ± SD or n (%).
BITA: bilateral internal thoracic artery; ITA: internal thoracic artery; RA: radial artery; SMD: standardized mean difference; ICU: intensive care unit; POAF: postoperative atrial fibrillation
Table 4. Internal thoracic artery (ITA) and radial artery (RA) arrangement.
| Entire cohort (n = 790) | Propensity score-matched cohort (n = 480) | ||
|---|---|---|---|
| RITA (n = 548) | |||
| In situ | 427 (78%) | 193 (80%) | |
| In situ | RITA-LCx | 401 (73%) | 178 (74%) |
| In situ I composite | RITA-I composite graft—LCx | 26 (4.7%) | 15 (6.2%) |
| Y composite | LITA-LAD – free RITA (Y composite graft)—LCx | 118 (22%) | 46 (19%) |
| Others | 3 (0.5%) | 1 (0.4%) | |
| RA (n = 242) | |||
| Ao-RA | Ao-RA | 162 (67%) | 161 (67%) |
| LITA Y composite | LITA-LAD – RA (Y composite graft)—LCx | 61 (25%) | 60 (25%) |
| GEA Y composite | GEA-RCA – RA (Y composite graft)—LCx | 4 (1.7%) | 4 (1.7%) |
| Others | 15 (6%) | 15 (6%) |
Unless indicated otherwise, data are presented as n (%).
RITA: right internal thoracic artery; LCx: left circumflex artery; LAD: left anterior descending artery; RA: radial artery; Ao: aorta; LITA: left internal thoracic artery; GEA: gastroepiploic artery; RCA: right coronary artery
Primary outcomes
Kaplan–Meier survival curves showed that the BITA group had a significantly lower mortality rate in the propensity-matched cohort (log-rank p = 0.02). In the multivariable analysis, using the Cox proportional hazards model, of the propensity-matched cohort, the BITA group exhibited a substantially lower mortality rate (hazard ratio (HR): 0.54; 95% confidence interval (CI): 0.38–0.76; p = 0.01) than the ITA-RA group. In the multivariate analysis, using the Cox proportional hazards model, of the entire cohort, the BITA group exhibited significantly lower rates of long-term all-cause mortality than the ITA-RA group (HR: 0.63; 95% CI: 0.48–0.84; p = 0.01) (Fig. 2, Table 5).
Table 5. Study outcomes.
| Entire cohort (n = 790) | Propensity score-matched cohort (n = 480) | |||||||
|---|---|---|---|---|---|---|---|---|
| BITA(n = 548) | ITA-RA(n = 242) | Adjusted RR (95% CI) | p-value | BITA(n = 240) | ITA-RA(n = 240) | Adjusted RR (95% CI) | p-value | |
| Primary outcome | ||||||||
| All-cause death | 151 (29%) | 94 (40%) | 0.63 (0.48–0.84)A | 0.01 | 53 (23%) | 94 (41%) | 0.54 (0.38–0.76)A | 0.01 |
| Secondary outcomes | ||||||||
| MACEs | 96 (18%) | 52 (22%) | 0.72 (0.55–0.93)A | 0.01 | 42 (18%) | 53 (23%) | 0.73 (0.53–0.99)A | 0.04 |
| Cardiac death | 29 (5.3%) | 17 (7.0%) | 0.66 (0.34–1.28)A | 0.22 | 11 (4.6%) | 17 (7.1%) | 0.60 (0.27–1.31)A | 0.20 |
| In-hospital death | 7 (1.3%) | 2 (0.8%) | 0.64 (0.13–3.12)B | 0.73 | 1 (0.4%) | 2 (0.8%) | 2.01 (0.18–22.3)B | 1.00 |
| DSWI | 7 (1.3%) | 1 (0.4%) | 0.32 (0.04–2.62)B | 0.45 | 3 (1.3%) | 1 (0.4%) | 0.33 (0.03–3.20)B | 0.62 |
Unless indicated otherwise, data are presented as n (%).
AHazard ratio (95% CI).
BOdds ratio (95% CI).
BITA: bilateral internal thoracic artery; ITA: internal thoracic artery; RA: radial artery; RR: relative risk; CI: confidence interval; MACEs: major adverse cardiac events; DSWI: deep sternal wound infection
Secondary outcomes
The multivariate analysis, employing the Cox proportional hazards model, revealed a significantly lower cumulative incidence of MACEs in the BITA group than in the ITA-RA group (HR: 0.72; 95% CI: 0.55–0.93; p = 0.01). In the propensity-matched cohort, the BITA group exhibited significantly lower cumulative incidences of MACEs than the ITA-RA group (HR: 0.73; 95% CI: 0.53–0.99; p = 0.04). No significant differences in the incidences of in-hospital death and DSWI were observed between the two groups in both cohorts (Fig. 3, Table 5).
Fig. 3. Secondary outcomes. Kaplan–Meier survival curves were plotted for MACEs and cardiac death in the entire cohort (left) and in the propensity score-matched cohort (right). The shaded areas represent the 95% confidence intervals. BITA: bilateral internal thoracic artery; ITA: internal thoracic artery; RA: radial artery; MACEs: major adverse cardiac events.
Discussion
The main finding of this study was that the ITA graft was superior to the RA graft when used as a second graft for LCx revascularization in terms of all-cause mortality over approximately 10 years in a propensity score-matched cohort. Additionally, multivariable analysis of the entire cohort revealed that the use of the BITA resulted in fewer MACEs and improved long-term mortality.
In the entire cohort, DM and CKD, known as risk factors for poor outcomes following CABG,15,16) were more prevalent in the BITA group than in the ITA-RA group. The propensity score matching likely standardized the patient backgrounds, potentially leading to improved mortality rates in the BITA group.
There are several past studies5–9) that have compared the BITA and ITA-RA. The Arterial Revascularization Trial was the first randomized controlled study to compare 10-year survival between using a single ITA and BITA. This was a landmark study that could eliminate selection bias; however, in many patients, grafts different from the assigned grafts were used. While there was no significant difference in long-term survival between the two groups, in the intention-to-treat group, the long-term outcome of the BITA group was superior to that of the as-treated group.17,18) The Radial Artery Patency and Clinical Outcomes trial, a prospective randomized controlled trial, compared the use of the RA and the ITA anastomosed to the aorta as inflow conduits.19) In this trial, the RA graft was associated with better 10-year estimated survival; however, the LCx revascularization rate using the RA graft was only 70%, the graft was also anastomosed to the RCA, and ITA grafts were used in all aortocoronary bypass grafts. Owing to the differences in target vessels and the fact that all ITAs were anastomosed to the aorta as free grafts, the results of this study are entirely distinct and not comparable.
Tsuneyoshi et al. reported that the RA anastomosed to the aorta is comparable to the RITA as the second arterial graft in a 5-year follow-up in Japanese participants.13) Three potential reasons for these differing results include the following: (i) inclusion of patients with CKD, (ii) use of composite grafts, and (iii) RA grafts harvested using the skeletonized technique. Composite grafts compete for blood flow based on the target vessel’s stenosis rate, potentially influencing patency. In this study, composite grafts tended to be used more in the ITA-RA group than the BITA group, which may have affected the long-term outcome of the RA graft.
When comparing the RA and the ITA, the biophysiological differences could not be ignored. There are some differences in the arterial wall structure and muscular tonus between elastic arteries and muscular arteries. In contrast to the ITA, which is an elastic artery and less prone to late degeneration, muscular arteries, known to be susceptible to late degeneration, might not show a significant difference in mortality rates between the RA and ITA unless the follow-up period exceeds 10 years, rather than being just a few years. Bakaeen et al. reported that using the BITA improved long-term survival by maximizing the area of the myocardium supplied by the ITA20); this finding is consistent with the results of the present study. It is conceivable that a skeletonized RA is associated with poorer long-term outcomes, and the maximized revascularization area of an ITA might lead to a significant survival difference between the BITA and ITA-RA; however, further research is required.
When using the BITA, concerns remain regarding the increased risk of DSWI due to reduced blood flow to the sternum. However, the safety of BITA skeletonization was previously reported in a meta-analysis by Gaudino et al.,12) who concluded that the risk of DSWI is not significantly increased by harvesting the ITA using the skeletonizing technique. In a sub-analysis of the Arterial Revascularization Trial, the risk of DSWI was similar between using a skeletonized BITA or a non-skeletonized SITA, and a skeletonized BITA was relatively safe.21) In this study, there was no significant difference between the BITA and ITA-RA groups in the development of DSWI; the five steps used to prevent DSWI in this study may have contributed to this result.
Limitations
Bias in graft selection cannot be ruled out owing to the retrospective nature of this study. Although the propensity score matching analysis resulted in comparable groups, the study was not randomized; therefore, additional effects from missing covariates cannot be excluded. In observational studies of CABG, limitations, including the inability to eliminate surgeon’s preferences and third graft mismatches, often exist, even with the use of propensity score matching. Given that this was a retrospective study with 10 years of follow-up, there were interruptions in the follow-up, and the incidence of cardiovascular events may not be all-inclusive. In general, the prognosis after CABG is probably attributable to graft patency. However, graft patency assessment was impossible in this study because we did not perform routine coronary computed tomography angiography or follow-up coronary angiography. Therefore, the prognostic value of graft patency could not be determined, and the reason for the significant difference in this hard endpoint could not be determined. Consequently, further investigations are necessary.
Conclusions
This study suggests that CABG using the ITA as the secondary arterial graft for LCx revascularization significantly reduces all-cause mortality over approximately 10 years compared to that using the RA without increasing the risk of in-hospital mortality or DSWI. Consequently, the use of the ITA as a second arterial graft for LCx revascularization may provide superior outcomes compared to the use of RA.
Declarations
Ethics approval and consent to participate
All study protocols were approved by the Research Ethics Committee of the Faculty of Medicine at Juntendo University on April 21, 2022 (approval no. E22-0096-H01). The need for informed consent was waived owing to the retrospective nature of this study.
Funding
None.
Data availability statement
The deidentified participant data will not be shared.
Disclosure statement
The authors declare that there are no conflicts of interest.
Supplementary File
References
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The deidentified participant data will not be shared.