Innovations: Technology & Techniques in Cardiothoracic & Vascular Surgery:
The Results of the Enclose II Proximal Anastomotic Device in 178 Off-Pump Coronary Artery Bypass Surgeries
Seto, Yuki MD, PhD*; Yokoyama, Hitoshi MD, PhD*; Takase, Shinya MD*; Tanji, Masahiro MD†; Takahashi, Koki MD†; Takahashi, Shoichi MD‡; Hirota, Jun MD§; Kondo, Shunichi MD, PhD∥; Hagiwara, Kenichi MD∥; Watanabe, Masaaki MD¶
From the *Department of Cardiovascular Surgery, Fukushima Medical University School of Medicine; †Ota Nishinouchi Hospital; ‡Hoshi General Hospital; §Iwaki Kyoritsu General Hospital; ∥Ohara Medical Center; and ¶Aizu Chuo Hospital, Fukushima, Japan.
Accepted for publication July 1, 2012.
Disclosure: The authors declare no conflict of interest.
Address correspondence and reprint requests to Yuki Seto, MD, Department of Cardiovascular Surgery, Fukushima Medical University, School of Medicine, 1 Hikarigaoka, Fukushima 960-1295, Japan. E-mail: firstname.lastname@example.org.
Objective: Enclose II is a new device for proximal coronary artery bypass anastomoses. We evaluated the safety and effectiveness of Enclose II in patients who underwent off-pump coronary artery bypass grafting (CABG).
Methods: Enclose II was used for isolated off-pump CABG in 178 patients at six heart centers between October 2005 and December 2009. The preoperative characteristics of the patients, complications related to Enclose II, and early graft patency rates were examined.
Results: A total of 222 proximal anastomoses were performed in 178 patients using Enclose II. Forty-four of these patients had two proximal anastomoses using this device. New cerebral infarction that arose in two patients (1.1%) was not related to Enclose II. No aortic injury occurred. The graft patency rate was 96.4% at 1 year after surgery.
Conclusions: Enclose II is a safe and useful assist device for proximal anastomoses in patients undergoing off-pump CABG.
Cerebral infarction remains a fatal complication of coronary artery bypass grafting (CABG).1 Off-pump CABG (OPCAB) has recently been introduced as an alternative to on-pump CABG because OPCAB can reduce cerebral infarctions caused by cardiopulmonary bypass in high-risk patients.2 An aorta no-touch technique, or avoiding a partial aortic clamp during OPCAB, can also prevent strokes.3,4 Instead of a partial aortic clamp, some devices for proximal anastomosis can reduce the incidence of cerebral infarction by avoiding microembolisms caused by aortic side-biting clamps. The Symmetry Bypass connector (St. Jude Medical, St. Paul, MN USA) and the PAS-Port proximal connector device (Cardia Inc, Redwood City, CA USA) are automated systems for clampless proximal vein anastomosis.5–10 The Heartstring proximal anastomotic system (Guidant, Indianapolis, IN USA) is a device that allows proximal hand-sewn anastomoses in a bloodless surgical view.11,12
Enclose II (Novare Surgical Systems, Cupertino, CA USA) was introduced as an assist device for hand-sewn proximal anastomoses to enable graft anastomosis to the aorta without a partial clamp and provide a better bloodless view than the Heartstring. Relatively few patients have been enrolled in studies evaluating the safety and usefulness of Enclose II13–15 (Fig. 1). The present study examines the safety and effectiveness of Enclose II in 178 patients who underwent OPCAB at several heart centers.
The Novare Enclose II proximal anastomotic device was used for isolated OPCAB in 178 patients at six centers between October 2005 and December 2009. Patients who were converted to on-pump CABG were excluded from this series. The ethics committee at our hospital approved the study, and all patients signed informed consent forms before undergoing OPCAB using Enclose II. The ascending aorta was preoperatively evaluated by enhanced computed tomography (CT) to identify calcifications and intramural thrombus that might pose risks for thromboembolisms during the procedure. Intraoperatively, the internal medial thickness (IMT) of the ascending aorta was measured longitudinally and tangentially using epiaortic ultrasonography. Patients with IMTs of 4 mm or more or severe aortic calcifications were excluded. We applied the “aorta nontouch technique” and anastomosed a free graft to the in situ graft in a Y shape for such patients. Enclose II was applied when at least the insertion and anastomosis site were free of atherosclerotic diseases.
The graft design policy at our institution has been described,16 whereas anastomosing the left internal thoracic artery (LITA) to the left anterior descending artery was standard policy for all surgeons. Whether intra-aortic balloon pumping (IABP) was introduced was essentially decided by each surgeon. Patients with circulatory collapse or continuous preoperative chest pain had probably already received an IABP. We introduced IABP before general anesthesia when patients had a left ejection fraction of less than 30% or with left main trunk diseases. When the circulation was unstable for any reason or ST elevated changes on electrocardiography were found during OPCAB, IABP was also introduced via a femoral artery in the surgical field.
Enclose II was applied as follows. We initially anastomosed the proximal ends of free grafts to the aorta and then the distal ends to target coronary arteries. To reduce motion of the ascending aorta caused by heartbeats during anastomosis, we cushioned the right side of the ascending aorta using layers of folded gauze (Fig. 2). Motion of the anastomosis site was also minimized using an Octopus (Medtronic Inc, Minneapolis, MN USA) attached to the proximal ascending aorta. A 14-gauge needle was introduced into the ascending aorta through a 3-0 polypropylene purse-string suture. We inserted the lower jaw of Enclose II into the aorta via a created hole. After the diaphragmatic membrane of Enclose II was opened in the aorta, the upper jaw was clamped onto the aortic surface until bleeding from the drainage tube stopped. We cut the aorta inside the upper jaw using a BD beaver mini-blade to create a hole for the anastomosis and trimmed it using an aortic punch. The view during the anastomosis was bloodless when the diaphragmatic membrane tightly fit the inner aortic wall. All proximal anastomoses were manually constructed using continuous 6-0 polypropylene suture attached to a semicircular needle. The same device was used if more than one proximal anastomosis was required. The lower jaw was pivoted into the aorta, and Enclose II was repositioned. One device was used for up to three proximal anastomoses according to the manufacturer’s instructions. After the proximal anastomosis was completed, Enclose II was removed from the aorta and hemostasis was achieved by tightening the purse-string suture.
We examined the preoperative characteristics of the patients, early graft patency rates, and complications at each center. Graft patency was evaluated by 64-slice multidetector enhanced CT or angiography. Patients were administered an oral β-blocker and sublingual nitroglycerin at 1.5 hours and immediately before CT scanning, respectively. Cardiologists or radiologists reconstructed the images with volume rendering and evaluated graft patency.
Continuous variables are expressed as means ± SDs, and categorical variables are expressed as absolute numbers (percentages). Graft patency curves were constructed using the Kaplan-Meier method.
Table 1 shows the preoperative characteristics of the patients (mean age, 69.1 years; range, 44–93 years). More than 35% of them had hypertension, 44% had diabetes mellitus, and 26% had hyperlipidemia. Cerebral infarction was found in 14% of patients and atrial fibrillation in 2.5%. Enclose II was not suitable for the ascending aorta in three (1.5%) patients because of severe atherosclerosis. Five (2.5%) patients with a partially calcified ascending aorta underwent proximal anastomosis with Enclose II.
A total of 222 proximal anastomoses were constructed in 178 patients using Enclose II. Forty-four (24%) of them underwent two anastomoses (Table 2). None of the patients required more than two proximal anastomoses. The mean number of distal anastomoses was 2.7 ± 0.8. The bypass conduits were saphenous veins (n = 158) and radial arteries (n = 62) in this series.
Two patients (1.1%) developed new cerebral infarctions (Table 3). One was from a thromboembolism caused by a new atrial fibrillation on postoperative day 10. The other was caused by temporary cerebral hypotension on postoperative day 2. Aortic injury and aortic dissection were not evident. Inadvertent rupture of the diaphragmatic membrane was caused by the suture needles in three patients (1.6%), requiring the introduction of another Enclose II. Figure 3 shows the graft patency rates. The patients were followed up after OPCAB for an average of 638 days (range, 30–1584 days). Graft patency in 23 of 178 patients was evaluated by angiography, and the remainder, except for four who died in the hospital, were evaluated by 64-multislice CT. The graft patency rate of the anastomoses using Enclose II was 96.4% after 1 year.
The findings of this multicenter study of 178 patients showed that Enclose II is a safe and useful assist device for hand-sewn proximal anastomoses during OPCAB. Neither aortic dissection nor new cerebral infarction was associated with this device in any of the patients. Enclose II enables proximal anastomosis without aortic partial clamping. Thus, the Enclose II–related procedure is characterized as gentle enough to prevent the detachment of atherosclerotic plaque or damage to the aorta. The early graft patency rates were similar to those of recent reports using partial aortic side-biting clamps.4,17
Several experiences with Enclose II have been reported.4,13,14,17,18 Aranki and colleagues13 performed 76 proximal anastomoses using Enclose II in 50 patients who underwent either OPCAB or on-pump CABG and reported the relatively short duration for proximal anastomosis of 8 minutes. Akpinar and colleagues reported that Enclose II is less traumatic and that clamp-associated complications are reduced compared with those using partial clamps.14
This study demonstrated that Enclose II was safe and useful for proximal anastomosis during OPCAB in 178 patients at six centers. More patients underwent OPCAB in the present study than in previous reports. The fact that this series proceeded at six centers is significant because several operators participated under different surgical policies.
The incidence of a loose fit for the ascending aorta in our experience is 1.6%. The reason for this remains obscure, but we speculate that some devices did not follow the curve of the vessel, especially when they were repositioned and pivoted for the second proximal anastomosis. We surmounted this problem using the partial clamp alternative to Enclose II during anastomosis.
Saphenous vein grafts were selected as conduits for relatively younger patients (Table 2). Our series included 61 patients who were older than 75 years and 41 critical or emergency patients for whom a saphenous vein would be preferable as a conduit because it is easier to harvest and 29 patients with more than three coronary branches that were each targeted for revascularization. Saphenous veins have a greater diameter than radial arteries and thus were a better match to form sequential bypasses for this group.
Enclose II has several advantages. Venous and arterial grafts can be used, and various anastomotic shapes can be easily designed, which cannot be achieved using an automated system for proximal anastomosis such as the St. Jude Symmetry device and Cardiac Passport device. Fit with the aorta can be easily assessed by monitoring blood leakage from the drainage tube. Repositioning Enclose II is easy, and it provides a clear bloodless area. Even if a bloodless area cannot be arranged despite correct use of Enclose II, it can be created by suctioning blood from the attached drainage tube. Enclose II offers a clearer bloodless view than the Heartstring system.
One disadvantage of Enclose II is the requirement for two nonatherosclerotic areas on the aorta. One is needed to insert the lower jaw of Enclose II, and the other is needed to create a hole for the anastomosis. On the other hand, Enclose II can be applied when two narrow points are free of atherosclerosis, even if the rest of the aorta is sclerotic. We performed proximal anastomoses using several techniques during OPCAB.
We intraoperatively applied epiaortic ultrasonography to investigate atherosclerotic diseases at the ascending aorta and prevent Enclose II from causing cerebral embolisms. Patients with IMTs of more than 4 mm at the ascending aorta were excluded from application of Enclose II in our series, which is supported by previous reports.19 Wareing and colleagues19 classified patients based on the presence of mild, moderate, or severe atherosclerotic diseases. Our patients with IMTs of 3 mm or less were equivalent to their mild group, which was considered appropriate to undergo standard cardiac surgical procedures to prevent cerebral embolisms. Classically, Mills and Everson1 classified ascending aortic atherosclerosis into three types. We excluded patients with ascending aortic atherosclerosis equivalent to their types I and II if preoperatively determined by CT. Patients with type III atherosclerotic aortae were also excluded based on the findings of intraoperative epiaortic ultrasonography. These protocols did not clinically detect any cerebral infarction caused by Enclose II. Of course, microembolisms might have occurred that were imperceptible on CT images but detectable by magnetic resonance imaging. However, magnetic resonance imaging is usually applied in our hospital only when clinical neurological impairment arises. As a result, the stroke rate in our series was 1.1%, which was equivalent to the 1.2% in the 2012 STS database.
To reduce movement of the ascending aorta, we usually cushion the side of it with layers of folded gauze and attach an Octopus to the basal side. Introducing these two strategies might reduce the rate of membrane rupture caused by sutures and blades. The incidence of membrane damage in the present study was 1.6% compared with reports of 2.5% to 3.0%.14–16 We recommend these simple techniques for all coronary surgeons. The simple attachment and bloodless view of anastomosis sites not only help less experienced surgeons to easily complete the technique but also might prevent cerebral infarctions.
A key limitation of this study is that it was not a randomized controlled trial. Basically, we intend to use Enclose II for all patients who undergo OPCAB and require proximal anastomosis. Therefore, a randomized controlled trial regarding Enclose II is impossible in our hospitals.
We are also unable to describe the sensitivity of the anastomotic stenoses because CT scanning and reconstruction protocols differed among institutions.
The overall safety and value of Enclose II could not be precisely determined in only 178 patients. A study of a larger patient cohort is required to produce concrete conclusions.
Enclose II was safe and useful for proximal anastomosis during OPCAB in 178 patients. However, long-term graft patency remains unknown, and further follow-up is required.
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This is an interesting report on 178 patients in which the Enclose II proximal coronary artery bypass anastomotic device was used for isolated off-pump coronary artery bypass grafting. A total of 222 proximal anastomoses were performed in these patients. Graft patency was evaluated by 64-multislice computed tomography (n = 151) or angiography (n = 23) in all patients who survived surgery between 30 and 1584 days after the procedure. The graft patency was 96.4% after 1 year.
Because this is a relatively small cohort of patients, the safety and efficacy of this device could not be precisely determined; however, the results are encouraging. A major weakness of this analysis was the small number of patients who underwent angiography. The use of computed tomographic scanning does not allow for a detailed look at the quality of the proximal anastomosis. Moreover, there were two neurological events in this series, and it is impossible to completely exclude the contribution of the Enclose II device to these complications. Long-term patency, safety, and efficacy will require a larger experience with a longer follow-up.
The authors are to be congratulated for the careful follow-up and evaluation of their results with the Enclose II proximal anastomotic device.
Aortic manipulation; Perioperative stroke; Cerebral infarction; Off-pump coronary artery bypass surgery
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