Initial experience with sutureless proximal anastomoses performed with a mechanical connector leading to clampless off-pump coronary artery bypass surgery

Experimental Model for Sutureless Proximal Anastomosis by the Viabahn Open Revascularization TEChnique (VORTEC)

Introduction

In the treatment of complex aneurysms, debranching is an extra-anatomical revascularization of visceral arteries followed by endograft coverage of the thoracoabdominal aorta. It eliminates the need for a thoracotomy and aortic clamping, but requires the performance of several technically demanding visceral anastomosis. In 2008, Lachat described visceral revascularization with the use of a sutureless distal anastomosis, performed by the telescoping of an endograft in the visceral branch, named VORTEC (Viabahn Open Revascularization TEChnique).

Objective

An experimental model was created to test the feasibility and short term results of performing a telescoped proximal anastomosis to the abdominal aorta.

Methods

Swine model. The abdominal aorta was dissected and ligated between the renal arteries and the iliac vessels. Three centimeters bellow the renal arteries a Viabahn endograft was telescoped for 2 cm into the proximal aorta. The other extremity was conventionally anastomosed to the distal aorta. Patency, sealing and tensile strength of the anastomosis were tested.

Results

Time for performing the telescoped anastomosis was shorter (5.4±2.8 min versus 10.3±3.4 min, P<0.05). All grafts were patent and both types of anastomosis presented no bleeding. Immediate tensile strength showed a higher strength of the conventional suture (22.7 x 14.3 N, P<0.09). After 30 days there was no pseudo-aneurysms and the strength of the conventional and VORTEC anastomosis were similar (37.3 x 40.8 N, respectively, P=0.17).

Conclusion

Telescoped proximal anastomosis by the technique of VORTEC is feasible. After 30 days the tensile strength of the both anastomosis were similar.

Anastomotic devices for coronary artery bypass grafting

With the advent of off-pump and minimally invasive coronary artery bypass grafting, efforts to facilitate construction of the graft to coronary anastomosis have increased. As a result, a number of anastomotic devices have been developed. While the ideal anastomotic device should be easy to use, produce a geometrically optimal anastomosis with minimal endothelial damage and minimal blood-exposed nonintimal surface, a number of design constraints apply. This review collects the available preclinical and clinical data for some of the devices, with special regard as to surgical outcome, patency rate and the need for additional perioperative anticoagulation treatment.

Study of coronary artery bypass using the PAS-Port device: assessment by multidetector computed tomography

OBJECTIVE

The use of automatic anastomotic devices in coronary artery bypass grafting surgery is associated with lower patency rates in comparison to conventional anastomosis methods. This is thought to be caused by graft curvature occurring after closing of the chest wall.

METHODS

We evaluated 39 grafts in 28 patients who underwent off-pump coronary artery bypass surgery using the PAS-Port. After surgery, the proximal anastomotic angle of each stent, graft morphology, and patency were evaluated with axial and sagittal views.

RESULTS

The angle for the left anterior descending coronary artery segment was relatively obtuse on the left side of the ascending aorta, and the graft loop formation was not necessary. The angle for the left circumflex coronary artery segment was significantly acute for anastomosis from the upper left side of the ascending aorta. Because grafts are under the constraints of a large loop, graft length tended to become easily excessive or deficient. The angle for the right coronary artery segment was relatively obtuse. The space on the right side of the heart was so narrow that in some cases we had difficulty setting out the appropriate graft location to prevent graft curvature. No bending or stenosis was present in any graft, showing a patency rate of 100%.

CONCLUSION

The short-term results of coronary bypass grafting using PAS-Port are satisfactory.

Forty-one-month follow-up of the Symmetry aortic connector system for proximal venous anastomosis

OBJECTIVE

Results of short- and midterm follow-up studies of the patency rate of the Symmetry aortic connector systems (St Jude Medical, Inc, Minneapolis, Minn) are controversial. Long-term follow-up studies are still lacking (so far, the longest mean follow-up period was 19 months). The aim of our study was (1) to evaluate the patency rate of this device over a longer time-period and (2) to analyze risk factors for graft occlusion.

METHODS

Between November 2000 and July 2003, 76 Symmetry aortic connector systems were implanted in 42 patients. At follow-up, 24 patients with 44 mechanical connectors were studied with 64-slice cardiac computed tomography. Eight patients had died previously, 6 patients refused to undergo a computed tomographic scan, and 4 patients had to be excluded because of impaired renal function.

RESULTS

From a total of 44 mechanical connectors studied, 24 (55%) were occluded, 20 (45%; confidence intervals 31%-61%) were patent, and 7 of these grafts showed stenosis in the area of the connector. Mean follow-up was 41 +/- 10 months (18-52 months). Sex, age, left main stenosis, hyperlipidemia, hypertension, renal failure, target vessel, stenosis of the target vessel, diameter of the target vessel, type of surgical intervention, diabetes, ejection fraction, postoperative anticoagulation regimen, and the connector size showed no significant influence on the bypass graft patency (P > .05). The bypass graft flow was recognized to be the only risk factor for bypass graft occlusion (P = .0256).

CONCLUSION

Midterm follow-up data show a high number of occluded Symmetry aortic connector system vein grafts. On the basis of these observations, the use of the connector was abandoned at our institution.

Gaseous and solid cerebral microembolization during proximal aortic anastomoses in off-pump coronary surgery: the effect of an aortic side-biting clamp and two clampless devices

OBJECTIVES

Intraoperative cerebral microembolism is a cause of cerebral dysfunction after cardiac surgery, and particulate microemboli are the most damaging. Using a new-generation transcranial Doppler ultrasound, we compared the number and nature of microemboli in patients undergoing off-pump coronary artery bypass grafting during performance of proximal anastomoses with three techniques: an aortic side-biting clamp and two clampless devices (the Enclose II device [Novare Surgical Systems, Inc, Cupertino, Calif] and the Heartstring II device [Guidant Corporation, Santa Clara, Calif]) developed to obviate the need for an aortic side-biting clamp, thereby reducing the number of cerebral microemboli.

METHODS

Bilateral continuous monitoring of the middle cerebral arteries was performed with a multirange, multifrequency transcranial Doppler device that both automatically rejects artifacts online and discriminates between solid and gaseous microemboli. Recordings were continuously undertaken during performance of 66 proximal aortic anastomoses in 42 patients. Thirty-five anastomoses were performed with an aortic side-biting clamp, 20 with the Enclose device, and 11 the Hearstring device.

RESULTS

Most microemboli occurred during application/insertion and removal of each device from the ascending aorta. The median number (interquartile range) of total microemboli was 11 (6-32) during side clamping, 11 (6-15) with the Enclose device, 40 (31-48) with the Heartstring device (P < .01). The proportion of solid microemboli was significantly higher in the side-clamp group (23%) compared with 6% and 1% in the Enclose and Heartstring groups, respectively (P < .01).

CONCLUSIONS

Avoidance of aortic side clamping results in a significant reduction in the proportion of solid microemboli detected with transcranial Doppler. As solid microemboli are probably the most damaging, use of the Enclose and Heartstring devices may represent an important strategy for minimizing cerebral injury during proximal aortic anastomoses.

Conventional surgery with aortic cross-clamping

This article provides a brief description of how to perform proximal and distal anastomosis on the arrested empty heart along with the grafting strategy and utilisation of different conduits in coronary artery revascularisation. Sequential grafting and indications of coronary artery revascularisation has also been described.

Cerebral microembolization during off-pump coronary artery bypass surgery with the Symmetry aortic connector device

OBJECTIVE

The use of aortic connector systems for proximal vein grafts in off-pump coronary artery bypass grafting might minimize aortic manipulation by eliminating the need for partial aortic clamping. The objective of this study was to asses whether use of a Symmetry connector (St Jude Medical, Inc, St Paul, Minn) reduced intraoperative cerebral embolization.

METHODS

Thirty-two consecutive patients underwent off-pump coronary artery bypass grafting. Sixteen patients received at least one mechanical proximal vein graft anastomosis with a Symmetry aortic connector system. Sixteen patients representing the control group underwent operations with standard suturing techniques using partial aortic clamping. During surgical intervention, all patients were monitored continuously with multifrequency transcranial Doppler scanning, which detected and differentiated cerebral emboli.

RESULTS

There were significantly more cerebral emboli in the Symmetry group (median, 36) compared with the control group (median, 11; P = .027). This was due to a higher number of gaseous emboli in the Symmetry group than in the control group (median, 27 vs 8; P = .014), whereas there was no significant difference regarding the number of solid emboli (median, 7 vs 3; P = .139).

CONCLUSION

Use of a Symmetry connector system during proximal vein graft anastomosis increased the number of emboli to the brain compared with a standard technique in coronary bypass surgery without cardiopulmonary bypass.

Early and midterm patency of the proximal anastomoses of saphenous vein grafts made with a Symmetry Aortic Connector System

OBJECTIVE

The purpose of this study was to investigate (1) the early and midterm patency rates in saphenous vein grafts that were anastomosed with the Symmetry Aortic Connector System (St Jude Medical, Inc, St Paul, Minn) and (2) risk factors for graft occlusion.

METHODS

Thirty-one patients underwent off-pump coronary artery bypass grafting for proximal saphenous vein graft anastomoses with the aortic connector system. Intraoperative graft flow was studied with transit time flowmetry, and angiography was performed before discharge in 29 cases. Midterm (at least 1 year after the operation) saphenous vein graft patency was assessed by coronary angiography or 3-dimensional coronary computed tomography in 27 cases.

RESULTS

Postoperative angiography demonstrated a 100% patency rate and no significant stenosis at the connector-anastomosed sites. The 1-year patency rate of the saphenous vein grafts with the aortic connector system was 92.6%, with 2 cases of saphenous vein graft occlusion. Both of these cases had low graft flow and poor left ventricular function documented during the operation.

CONCLUSION

Once surgical errors had been ruled out, the 1-year patency rate of proximal saphenous vein grafts anastomosed with the aortic connector system was favorable. Poor left ventricular function and low graft flow during the operation were risk factors for midterm graft occlusion. Selection of the target vessel and its runoff may also be an important determinant of long-term patency.

Evaluation of the Enclose Proximal Anastomosis Device in Coronary Artery Bypass Grafting

PURPOSE

Minimal manipulation of the ascending aorta during coronary artery bypass grafting may reduce the incidence of adverse perioperative events related to atheroembolic events. The objective of this study was to evaluate a new proximal anastomotic device (Novare Enclose device [Novare Surgical Systems, Cupertino, CA]).

DESCRIPTION

Over a 23-month period, a total of 76 proximal anastomoses were performed in 50 patients (40 males and 10 females; mean age, 74.36 years). In 45 patients, the proximal anastomosis was constructed before the distal (25 off-pump and 20 on-pump), and in 5 patients the proximal anastomosis was constructed on cardiopulmonary bypass because of diseased ascending aortas.

EVALUATION

The average time per anastomosis was <8 minutes. There were no device related complications. There were no atheroembolic complications in this cohort of patients. One patient underwent cardiac catheterization postoperatively, and the proximal vein anastomosis in this patient was widely patent.

CONCLUSIONS

The Novare Enclose proximal anastomotic device (Novare Surgical Systems) appears to be safe and effective as a tool for proximal anastomosis within a reasonable time period and is comparable with accepted techniques.

Bypassing the Pump

Improvements in techniques in coronary revascularization over the past decade have led to a revival of interest in off-pump coronary artery surgery. A fifth of coronary revascularization procedures are now performed off-pump. Randomized trials comparing off-pump surgery with conventional coronary artery bypass grafting using cardiopulmonary bypass (CPB) mainly included low-risk patients and were therefore underpowered to detect a difference in mortality. Current evidence, however, suggests a significant reduction in morbidity with off-pump surgery. The avoidance of CPB and the elimination of any aortic manipulation may significantly reduce the risk of stroke. Those benefits are likely to be most marked in older, sicker patients, who represent an increasing proportion of the surgical population.

Atherosclerosis of the ascending aorta as a major determinant of the outcome of cardiac surgery

Epiaortic ultrasonography has high sensitivity for the detection of atherosclerosis. In several studies, the technique has identified atherosclerosis of the ascending aorta as the major risk factor for stroke after cardiac surgery. The level of risk depends on the presence, location and extent of disease when the ascending aorta is surgically manipulated. This knowledge enables clinicians to focus on the diagnostic and surgical technique and to consider the various options. Routine use of intraoperative epiaortic ultrasonography should be applied so that surgical manipulation of the ascending aorta can be reduced or, if possible, avoided in patients with atherosclerosis of the ascending aorta. Alternatively, if major manipulation such as clamping must be performed in the presence of severe atherosclerosis, the use of intra-aortic filters could be considered.

No-touch aorta off-pump coronary surgery: the effect on stroke

OBJECTIVE

Studies examining the neuroprotective effects of off-pump coronary artery bypass grafting have shown inconsistent results. Most studies, however, have not differentiated between clampless and clamp off-pump techniques. The aim of this study was to evaluate the effect of avoiding aortic manipulation on major neurologic outcomes after off-pump coronary artery bypass grafting.

METHODS

A total of 700 consecutive patients undergoing multiple-vessel off-pump coronary artery bypass grafting between 2000 and 2003 were included. The 429 patients undergoing aortic no-touch technique were compared with 271 patients in whom partial aortic clamps were applied. The aorta was screened by manual palpation, and epiaortic ultrasonography was used selectively.

RESULTS

The frequency of detected atherosclerotic aortic disease was higher in the no-touch group (17.4% vs 5.1%, P < .0001). No-touch revascularization was achieved with arterial conduits, arranged in T-graft or in situ configurations (50%). The respective graft/patient ratios were 2.5 +/- 0.6 and 2.6 +/- 0.6 in the side-clamp and no-touch groups ( P = .009); however, revascularization of the posterolateral myocardial territory was comparable (87% vs 90%, difference not significant). The incidence of stroke (0.2% vs 2.2%, P = .01) was significantly lower in the no-touch group (1/429). Logistic regression identified partial aortic clamping as the only independent predictor of stroke (odds ratio 28.5, confidence interval 0.22-333, P = .009), increasing this risk 28-fold. Peripheral vascular disease ( P = .068), diabetes ( P = .072), and history of stroke ( P = .074) trended toward stroke.

CONCLUSIONS

Avoiding partial aortic clamping during off-pump coronary artery bypass grafting provides superior neurologic outcome. The results are reproducible and irrespective of the severity of aortic disease or the method of aortic screening. This technique is recommended whenever technically feasible.

Intraoperative and intermediate-term angiographic results of coronary artery bypass surgery with Symmetry proximal anastomotic device

OBJECTIVE

The objective of this study was to investigate the patency in saphenous vein coronary bypass grafts in which the proximal anastomoses were performed with automatic connector devices or with a traditional suture technique.

METHODS

Forty-six patients underwent coronary artery bypass grafting without cardiopulmonary bypass by using one thoracic graft and one or more saphenous vein grafts. Grafts were attached to the aorta with a Symmetry connector (St Jude Medical, Inc, St Paul, Minn) in 23 patients, and partial occlusion of the aorta and sutured anastomoses were used in 23 other patients. Grafts were studied intraoperatively with transit time flowmetry and angiography and revised if necessary. Angiography was repeated after 3 to 5 months.

RESULTS

Intraoperative graft patency did not differ between the 2 groups. Follow-up angiography demonstrated excellent thoracic graft patency. Vein graft patency decreased to 50% in the Symmetry group, whereas it was 90% in the suture group ( P = .01). Twenty-five percent of the Symmetry grafts had significant stenosis in the connector.

CONCLUSION

Saphenous vein grafts anastomosed to aorta with the Symmetry proximal connector have low intermediate patency compared with those with traditionally sutured anastomoses. We do not recommend the routine use of this device in coronary artery bypass operations.

The Right Internal Thoracic Artery and Right Gastroepiploic Artery: Alternative Sites for Proximal Anastomosis in Patients with Atherosclerotic Calcified Aorta

BACKGROUND

Atherosclerotic or calcified ascending aorta is an important predictor of adverse cerebrovascular events. Using off-pump coronary artery bypass (OPCAB) with composite and in situ arterial grafting to avoid aortic manipulation and clamping may reduce the risk of stroke related to aortic atheroembolism. When the aorta is calcified and cannot serve as a safe site for proximal anastomosis, this anastomosis can be performed on the proximal segment of the right internal thoracic artery (ITA) and right gastroepiploic artery (RGEA). Four such cases are described.

METHODS

In 2 patients, the proximal right ITA was used as the site for proximal saphenous vein graft (SVG) anastomosis. Chronic obstructive lung disease in one patient and insulin-dependent diabetes in the other precluded performance of OPCAB with bilateral ITA. In addition, positive Allen test precluded performance of composite T-graft with radial artery (RA) on ITA. Both SVGs were anastomosed distally to the posterior descending artery. In 2 other patients, RA was connected end-to-side to the proximal segment of the RGEA. Both of these patients had repeat operations. The distal end of the RGEA was too small, and concerns regarding the future flow to a very large coronary bed precluded its use as an in situ graft.

RESULTS

All patients underwent the operative procedures without any neurological or cardiovascular adverse effects, and all are midterm, symptom-free survivors. Postoperative graft patency was confirmed intraoperatively with flow measurements and postoperatively with control angiography or coronary imaging computed tomography.

CONCLUSIONS

The RITA and proximal RGEA can serve safely as sites for proximal anastomosis in patients with atherosclerotic calcified aorta undergoing OPCAB.