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© 2004 European Association of Cardio-Thoracic Surgery
Late patency of the left internal thoracic artery graft in patients with and without previous successful percutaneous transluminal coronary angioplasty
a Department of Cardiovascular Surgery, Maizuru Mutual Hospital, Hama 1035, Maizuru, Japan 625-8585
* Corresponding author. Tel.: +81-773-62-2510; fax: +81-773-64-4301 Received July 28, 2003; received in revised form September 25, 2003; accepted October 4, 2003
The aim of this study was to compare early and late graft patency in patients with and without previous successful PTCA. Of the 70 patients who received both early and late follow-up angiography, 13 patients who had received successful PTCA at the left anterior descending coronary artery (LAD) before CABG (group I) and 31 patients who had not received preoperative PTCA in any vessel (group II) were retrospectively reviewed. There were no significant differences in patient characteristics including major coronary risk factors. The mean duration between the operation and control angiography was 35±23 months in group I and 36±19 months in group II (  ). Occlusions of the LITA graft were observed in four patients of group I and in four patients of group II. Cumulative patencies of the LITA graft were 54% in group I and 83% in group II ( ). The late patency rate of the LITA graft bypassed to the LAD in patients that received previous successful PTCA in the coronary artery tended to be lower than in patients without previous PTCA. This result should be confirmed by further prospective studies.
Key Words: Coronary artery bypass grafting; Percutaneous coronary angioplasty; Restenosis; Stent
At present, coronary artery bypass grafting (CABG) and percutaneous transluminal coronary angioplasty (PTCA) are both established procedures for coronary revascularization. The efficacy and outcomes for CABG and PTCA as primary treatments have been well documented [1,2], and PTCA in patients who received previous CABG have been also well investigated [3,4]. However, little data are available regarding the efficacy and risk of CABG after previous successful PTCA [5]. Barakate et al. reported that in a large retrospective study operative morbidity and mortality did not differ between patients who underwent CABG following initially successful PTCA and those underwent CABG as the primary intervention for coronary artery disease [6]. However, long term influence of previous successful PTCA followed by CABG is still unclear. The aim of this study was to compare early and late graft patency in patients with and without previous successful PTCA. To exclude influences of graft materials and bypassed vessels, only patients who received the left internal thoracic artery (LITA) grafting to the left anterior descending coronary artery (LAD) after previous PTCA for LAD lesion were retrospectively investigated.
2.1. Study population Between June 1994 and December 2001, 150 patients underwent coronary artery bypass with the LITA anastomosed to the LAD using cardiopulmonary bypass. Patients in whom a sequential or Y-LITA graft was used (  ) or those who underwent off-pump coronary artery bypass grafting ( ) were excluded. Of the remaining 134 patients who received a single LITA to the LAD, 121 underwent early follow-up coronary angiography within 1 month after operations, and 76 underwent late follow-up angiography at average of 36±20 months after CABG. Postoperative angiographic examination was performed in patients who gave consent for routine postoperative angiographic control (1 month, 1 year and 5-year after CABG). This also included evaluation for typical/atypical symptoms and newly developed ECG changes, or a cardiac assessment before a major surgical procedure (abdominal, vascular, etc.). Of the 70 patients who received both early and late follow-up angiography, 13 patients had received successful PTCA at the LAD before CABG (group I), 31 patients had not received preoperative PTCA in any vessel (group II), and the other 26 patients had received preoperative PTCA in the right coronary artery and/or circumflex artery (not included in this study). The ‘successful PTCA’ was defined as no occurrence of the restenosis 6 months after the PTCA. The CABG was performed for the patients with left main coronary stenosis more than 50% and/or three-vessel disease. The medical records of the patients of group I and II were retrospectively reviewed for this study. 2.2. Control angiograms A physician who was unaware of the aim of the study interpreted all angiograms. The results of postoperative angiography were obtained directly from the cardiac catheterization laboratory. Anastomotic failure was defined as occlusion or stenosis of 90% or greater. The presence of extensive conduit narrowing, ‘string sign’, was considered functionally occluded and recorded as non-patent. Graft patency rates included grafts without anastomotic failure.2.3. Statistical analysis Results were expressed as mean±standard deviation. All statistical analyses were performed using Statview version 5.0 (SAS Institute, USA). Survival analysis methods were based on the incidences of anastomotic failure that was confirmed to occur at the time of reangiography. Kaplan–Meier analysis was used for comparison of LITA patency between groups I and II. Student's t-test for continuous variables or 2 tests (Fisher's exact tests if  ) for categorical variables were performed. A P value less than 0.05 was considered significant.
3.1. Duration between the operation and control angiography The mean duration between the operation and control angiography was 35±23 months in group I and 36±19 months in group II ( ). 3.2. Patient characteristics Patient characteristics among the groups are shown in Table 1. There were no statistically significant differences between group I and II regard major coronary risk factors including diabetes, hypertension, hypercholesterolemia, smoking. The rate of patients with prior myocardial infarction tended to be higher in group I than that in group II, but it was not statistically significant ( ). Similarly, the rate of patients with left main coronary artery lesion greater than 50% stenosis and the mean number of diseased vessels were likely to be greater in group I than that in group II ( and 0.28, respectively).
3.3. Surgical characteristics Mean number of distal anastomoses was 2.69±0.75 in group I and 2.70±0.65 in group II (  ). Radial artery was used as an additional arterial graft in four patients in group I, and in 11 patients in group II ( ). 3.4. PTCA characteristics prior to CABG In group I, mean duration between previous successful PTCA and CABG was 17±30 months, and mean number of preoperative PTCA was 2.07±1.6. Eight patients received stent implantation, and three underwent rotablator.3.5. LITA graft patency Occlusions of the LITA graft were observed in four patients in group I; two within 1 month after CABG, one at 22 months after CABG, and one at 37 months after CABG. Likely, occlusions were observed in four patients in group II; two within 1 month after CABG, one at 7 months after CABG, and one at 42 months after CABG. Cumulative patencies of the LITA graft were 54% in group I and 83% in group II (; Fig. 1).
3.6. Comment The present study demonstrated that the late patency rate of the LITA graft bypassed to the left anterior descending coronary artery in patients that received previous successful PTCA in the coronary artery tended to be lower than in patients without previous PTCA, although coronary risk factors and the stenosis rate of the LAD did not differ between group I and II. The LITA graft bypassed to the LAD has been considered to be the most reliable graft with excellent long-term patency from 80 to 98% [7]. In this study, the cumulative patency of the LITA in patients without previous PTCA was within this range, however, that in patients with previous PTCA was clearly lower although the difference between the two groups was not significant. There are several possible reasons that might explain this result. The first is that a stent implantation attached in previous PTCA procedures may adversely affect the long-term patency of grafts bypassed to a coronary artery where previous PTCA was performed. Among patients that received previous PTCA, a stent implantation was performed for three of four patients who suffered from the LITA graft occlusion. Farb et al. described that chronic inflammatory cells (lymphocytes and macrophages) around stent strut were commonly seen even 30 days after stent implantation [8]. There is a possibility that stent implantation causes prolonged inflammation response and it adversely affects an anastomosis site of the LITA graft which is always performed at the downstream of a stent implantation site and hence is likely to be sensitive to such inflammatory cytokine [9]. This may cause an anastomosis failure in patients who received previous stenting followed by CABG. The second is that there is a possibility that a patient who suffers from restenosis of a PTCA site may also be likely to suffer from graft failure when they undergo CABG because of constitutional problem. An institutional condition and/or a disease which was not evaluated in this study might have accelerated atherosclerotic change or neointimal proliferation. For instance, recently it has been noticed that membrane glycoprotein IIb/IIIa plays a major role in platelet function, and glycoprotein IIIa polymorphism is one of the coronary risk factors which affect both restenosis after PTCA and graft occlusion after CABG [10]. There is a possibility that factors which were not evaluated in this study influenced our result. The third is the problem of the study design itself. The present study was a retrospective observational study involving a very small study population, and existence of several biases can not be denied. From the present study, it is not possible to confirm whether poor LITA graft patency in patients with previous PTCA is a general tendency, let alone to demonstrate the mechanism of this result. To confirm the result of this study and to clarify the mechanism, a further prospective study should be performed comparing long-term patency and clinical outcome of patients that underwent CABG following previous successful PTCA. In conclusion, the late patency rate of the LITA graft bypassed to the LAD in patients that received previous successful PTCA in the coronary artery tended to be lower than in patients without previous PTCA in the present retrospective observational study. This result should be confirmed by further prospective studies.
ICVTS on-line discussion Author: Dr. Hitoshi Hirose, Cleveland Clinic Foundation, Cardiovascular Surgery, 2300 Overlook Rd #312, Cleveland, OH 44106, USA Date: 10-Dec-2003 Message: The results of the graft patency rate of the left internal thoracic artery (LITA) was inferior in the patients who had previous successful percutaneous transluminal coronary angioplasty (PTCA) to those in the patients who had not received PTCA therapy at all prior to the surgery. There was a study showing that less extensive stenosis in the left anterior descending artery (LAD) provides lower patency rates in the LITA graft. The group of patients with "successful PTCA" might have had a less stenotic LAD, and that is why the patency of the LITA was not as great as the patients without history of PTCA. I would like the author to clarify whether less stenosis in vessels grafted after PTCA could explain the less favorable patency? Response Author: Dr. Hiroyuki Kamiya, Maizuru Kyosai Hospital, Department of Cardiovascular Surgery, Hama 1035, Maizuru 625-8585, Japan Date: 01-Jan-2004 Message: The stenosis rate of the anastomosed LAD was not significantly different between two groups as shown in Table 1. We performed the study because we had the impression that the graft patency rate was not good in patients after repeated PTCA. A statistical conclusion was not reached from our results, however we would like to present these results in order to stimulate such studies in other institutes with large patient volume. We think the issue is very important in the era of aggressive PTCA. doi:10.1016/S1569-9293(03)00229-9
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Abstract
1. Introduction
