Intraoperative SVG flow was measured by the transit time principle in 68 connector-grafts (mean: 50.8 ± 27.8 mL/min) and 35 suture-grafts (mean: 42.0 ± 16.7 mL/min). None of the SVGs required revision on the basis of flow characteristics. There were no perioperative complications.
The mean follow-up period for these 80 patients was 182.2 ± 74.4 days (95% confidence interval [CI] 165.9–198.5). Two patients underwent early (predismissal) angiography that documented all connector-grafts occluded (1 connector-graft per patient) and were not submitted to additional follow-up. Both patients were asymptomatic at angiography, and both underwent balloon angioplasty/stent without complications. Nine patients were lost to follow-up (LTF), 3 after hospital dismissal (all with predismissal angiography documenting all connector-grafts being patent), and 4 before 6 months.
Of the 6 patients LTF at 6 months, 1 patient was LTF at 75 postoperative days after recurrence of symptoms due to an occluded left internal mammary graft (LIMA) receiving balloon angioplasty/stent (all vein grafts including 1 connector-graft were patent), 1 at 138 postoperative days after being intervened for an aortic valve endocarditis with angiographically documented patent grafts, 1 at 67 postoperative days after being referred to a different institution for management of a deep sternal wound infection, and 1 at 103 postoperative days after the angiogram documenting patent grafts was scheduled before the 6 months established by the protocol. Two patients refused early and late angiography.
The incidence of MACE (death, MI, stroke, TVR) was 10/80 (12.5%). One patient died on postoperative day 6 due to multiorgan failure, producing an operative mortality of 1/80 (1.25%). This patient was a 74-year-old woman with multiple comorbidities (hypertension, diabetes mellitus, pulmonary hypertension, prior MI, sick sinus node syndrome requiring a pacemaker) who underwent an isolated CABG with cardiopulmonary bypass requiring inotropic support and intraaortic balloon pump in the immediate postoperative period. Necropsy was performed showing all grafts patent and findings consistent with ischemic cardiomyopathy (non–device-related death).
Seven patients underwent TVR (8.8%), 6 on connector-grafts (all incidental findings in asymptomatic patients) and 1 on an arterial graft. The 6 patients undergoing TVR on a connector-graft were due to graft occlusion (4 patients), connector-anastomosis stenosis (1 patient), and distal anastomosis stenosis (1 patient). The patient undergoing TVR on an arterial graft was due to a LIMA graft occlusion. Two patients had a postoperative stroke (2.5%), 1 patient on postoperative day 6 and 1 patient 5 months after surgery secondary to aortic valve endocarditis. There were no postoperative MIs. Other complications were reoperation due to a deep sternal wound infection (1 patient), superficial sternal wound infection (1 patient), infective aortic endocarditis (1 patient), recurrence of symptoms (2 patients: 1 at 3 months after surgery due to an occluded LIMA graft, and 1 at 5 months after surgery with all grafts patent on angiography), and Dressler syndrome (1 patient).
Thirty-five patients (43.8%) underwent elective early angiography (mean 6 ± 2 days after surgery) for an early occlusion rate of 2/37 (5.4%) in connector-grafts, 0/35 (0%) in suture-grafts, and 0/27 (0%) in arterial-grafts. Sixty-eight patients (85%) underwent midterm angiography (mean 193 ± 36 days, 95% CI 184, 202) for an overall occlusion rate of 7/79 (8.9%) in connector-grafts, 3/40 (7.5%) in suture-grafts, and 2/63 (3.2%) in arterial-grafts. Occlusion rates according to the coronary artery territory being bypassed are illustrated in Table 1.
By Core-Laboratory analysis (Perfuse Core Laboratories, Boston, MA) performed on connector-grafts at midterm follow-up, mean TIMI flow grade was 2.97 ± 0.17 (95% CI 2.9–3.0) (65 grafts analyzed), mean corrected TIMI frame count was 20.0 ± 8.4 (95% CI 17.5–22.4) (46 grafts technically suitable for analysis), and mean TMPG was 2.4 ± 1.0 (95% CI 2.2–2.7) (56 grafts technically suitable for analysis). By quantitative coronary angiography, worst stenosis in the area of the connector-anastomosis was a mean of 17.9 ± 15.9% (95% CI 14.2–21.7) with 69 grafts technically suitable for analysis. When calculating the stenosis grade with reference to the target coronary artery, the mean stenosis was –24.5% ± 38.2% (95% CI –33.4 to –15.6) (71 grafts technically suitable for analysis).
This study was the first clinical experience with the second-generation Symmetry G2 connector. It was conducted to evaluate the new device as compared with conventional suture technique. The 89.2% successful deployment rate for the connector could have been influenced by the learning curve. There were no adverse events associated with the removal of connectors. Intraoperative graft patency as measured with flow rates did not differ between connector and suture SVG (50.8 ± 27 mL/min and 42.0 ± 16.7 mL/min, respectively).
Two patients experienced recurrence of symptoms during the follow-up period, both unrelated to the Symmetry G2 device. A 10/80 (12.5%) incidence of MACE (death, MI, stroke, TVR) and a mortality of 1/80 (1.25%) for this study is within expected limits when compared to reports in the literature.9 On a meta-analysis of randomized trials of percutaneous transluminal coronary angioplasty (PTCA) versus CABG, Gruberg et al. found a 1 year composite MACE rate (death, nonfatal MI, stroke, repeat revascularization) of 13% and a mortality rate of 2.8% for the CABG group (1533 patients).10 All the occlusion/stenoses responsible for the TVR events were incidental angiographic findings (nonclinical events) at the time of the scheduled coronary angiography on asymptomatic patients. A TVR rate of 8.8% appears higher than reported rates in the literature. Gruberg in the same publication reported a rate of repeat revascularization at 1 year of 4.4% for the CABG group. Of the 7 patients undergoing TVR, 6 were on connector-grafts, 4 were due to graft occlusions, 1 was due to a proximal anastomosis stenosis, and 1 was due to a distal anastomosis stenosis. It is worth mentioning that the 2 occlusions for connector-grafts going to the left anterior descending territory were grafts performed to diagonal branches. Overall midterm occlusion rates for connector-grafts did not statistically differ significantly from the ones on suture grafts (overall midterm of 11.1% vs. 7.5%, respectively) and are within reported historical controls.11,12
Unfortunately, 9 patients were lost to follow-up, although primary consent was given preoperatively. This is a crucial impairment of the follow-up studies bearing some invasiveness. Incidentally, 6 of the patients lost to follow-up had angiograms for different reasons and showed patent connector-grafts.
Much of the criticism regarding the first-generation Symmetry G2 connecting system was the 90-degree takeoff of the vein graft out of the aorta leading to possible kinking. This problem was solved by St. Jude Medical, as the second generation took off at an angle of approximately of 45 degrees.
The aim of the prospective nonrandomized study was to evaluate not only the clinical midterm follow-up,13 but also the patency rate of the grafts as documented with angiography. This could explain the high rate of TVR (8.8%), because all patients were asymptomatic on follow-up, but re-intervention was initiated as soon as an occlusion or stenosis was detected.
The anticipated reduction of incidence of MACE (death, MI, stroke, TVR) as a result of decreased manipulation of the aorta cannot be confirmed, but is comparable with the results of historical populations from literature.
In conclusion, this study demonstrated that the second generation of connecting systems has a midterm patency rate that is comparable with conventional sutured anastomoses. It offers a valuable alternative in cases of severe atheromatous or heavily calcified aortas and in off-pump bypass surgery to avoid the use of an aortic side-biting clamp. Further development of connectors might significantly decrease invasiveness.
The statistical power of the 6-month follow-up was weakened by the high number of patients lost to follow-up. The difference between the connector and the hand-sewn technique has some uncertainty, although mathematically it showed no significance.
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Keywords:© 2005 Lippincott Williams & Wilkins, Inc.
Cardiovascular disease; Bypass grafting; Mechanical anastomosis