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Ann Thorac Surg 2002;74:497-501
© 2002 The Society of Thoracic Surgeons

Original article: cardiovascular

Comparison of two stabilizer concepts for off-pump coronary artery bypass grafting

Christian Detter, MD*a, Tobias Deuse, MDa, Frank Christ, MDb, Dieter H. Boehm, MD, PhDa, Hermann Reichenspurner, MD, PhDa, Bruno Reichart, MDa

a Department of Cardiac Surgery, University Hospital Grosshadern, Ludwig-Maximilian-University, Munich, Germany
b Department of Anesthesiology, University Hospital Grosshadern, Ludwig-Maximilian-University, Munich, Germany

Accepted for publication April 25, 2002.

* Address reprint requests to Dr Detter, Department of Cardiovascular Surgery, University Hospital Eppendorf, Martinistrasse 52, D-20246 Hamburg, Germany
e-mail: detter{at}uke.uni-hamburg.de


   Abstract
Top
 Abstract
Introduction
 Material and methods
 Results
 Comment
 Acknowledgments
 References
 
Background. This study was designed to evaluate the efficacy of two different stabilizer concepts for off-pump coronary artery bypass grafting.

Methods. Between 2000 and 2001, 100 consecutive patients who underwent off-pump coronary artery bypass grafting were randomly assigned to two stabilization systems: the Medtronic Octopus 3 (n = 50) and the Genzyme Immobilizer (n = 50). During operation, two-dimensional cardiac surface motion was assessed by intravital microscopy using orthogonal polarization spectral imaging in 20 vessels at the anterior wall. Postoperative angiography of 47 vessels revealed anastomotic quality.

Results. Patient demographics were similar in both groups regarding age, sex, ejection fraction, and New York Heart Association functional class. In 7 patients the randomized Immobilizer was rejected by the surgeon for lateral or posterior wall revascularization and subsequently switched to the Octopus device. Patients received 1.8 ± 0.7 grafts in the Octopus and 1.6 ± 0.5 in the Immobilizer group (p = not significant). Two-dimensional cardiac surface motion was significantly less using the Immobilizer (109.7 ± 32.4 µm versus 423.5 ± 129.6 µm; p < 0.001). Time required for anastomosis was significantly shorter in the Immobilizer group (11.3 ± 3.5 versus 14.9 ± 2.4 minutes; p < 0.001). Postoperative angiography showed no vessel occlusions but two anastomotic stenoses in each group.

Conclusions. Both stabilizers have been shown useful for off-pump coronary artery bypass grafting. The Immobilizer system showed better epicardial immobilization of the anterior wall resulting in shorter anastomosis times. However, because the Octopus 3 handling is more flexible and allows easier access to all vessels, it is the device of choice for posterior wall revascularization in our institution.


   Introduction
Top
 Abstract
 Introduction
Material and methods
 Results
 Comment
 Acknowledgments
 References
 
Coronary artery revascularization on the beating heart without the use of cardiopulmonary bypass has emerged as a feasible and safe alternative to conventional coronary artery bypass grafting (CABG). Reduced oxidative stress, systemic inflammatory reaction, cerebral thromboembolism, and atheroembolism seem to be the major benefits of avoiding cardiopulmonary bypass, resulting in decreased patient morbidity and faster patient recovery [1, 2]. Recently, off-pump coronary artery bypass grafting (OPCABG) has shown to be suitable not only for selected patients, but also for redo operations, emergency revascularization, high-risk patients, and in the elderly [3–6]. Therefore, OPCABG is gaining popularity for a growing patient population.

Stabilizers are a major tool in OPCABG procedures, reducing the cardiac surface motion during suturing of the anastomosis. Local stabilization was achieved either by suction onto the heart surface with the Octopus 3 tissue stabilizer system (Medtronic GmbH, Düsseldorf, Germany) or by capturing the target vessel using vessel loops with the Immobilizer stabilization platform (Genzyme Surgical Products, Fall River, MA).

This study was designed to evaluate the efficacy of two different stabilizer concepts comparing the Octopus 3 and the Immobilizer device during OPCABG.


   Material and methods
Top
 Abstract
 Introduction
 Material and methods
Results
 Comment
 Acknowledgments
 References
 
From April 2000 to September 2001, 100 consecutive patients who underwent OPCABG at the University of Munich were included in a prospective study. During the same time period, a total of 880 patients underwent isolated CABG with cardiopulmonary bypass. Thus, 11.4% of CABG was performed off-pump in our institution. The patient selection was carried out according to specific anatomic criteria, coronary artery morphology, and the severity of comorbidities. Thus, indications for OPCABG at our institution were: (1) single or double vessel revascularization; (2) multivessel revascularization in high-risk multimorbid patients with several comorbidities; (3) coronary artery disease with no heavily calcified arteries or diffusely atheromatous coronary vessels; and (4) the patient asked for a minimally invasive surgical procedure.

Four surgeons were participating in this study with all of them being familiar with both stabilization devices. Patients were randomly assigned to either the Octopus 3 (n = 50) or the Immobilizer (n = 50) stabilization system before the beginning of the operation.

The preoperative demographics of the patients showed no significant difference between the two groups regarding age, sex, previous bypass procedure, comorbidities, and left ventricular ejection fraction. Table 1 summarizes the demographics of these patients. The majority of patients were in Canadian Cardiovascular Society classes II and III.


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  		Table 1. Preoperative Demographics

 
All patients received anesthesia under a standardized protocol and were continuously monitored by electrocardiography with ST-segment analysis, hemodynamic monitoring with Swan-Ganz catheters, and transesophageal echocardiography for detection of regional wall motion deterioration during the entire surgical procedure. Continuous mixed venous saturation measurements were obtained in all patients. The patient was positioned on a water-heated mattress in the operation room. Heparin was given with a dose of 100 IU/kg body weight before the division of the internal mammary artery to accomplish an activated coagulation time of more than 250 seconds. Half of the amount of heparin was reversed by the use of protamine after completion of the anastomoses.

Off-pump surgical technique
The technique used has already been described in detail [7]. In brief, all patients were approached through a total median sternotomy. Pericardial traction sutures were placed between the left pulmonary veins and the inferior vena cava for exposure of the different coronary vessels, avoiding hemodynamic compromise and rhythm disturbances. Since August 2001 the Starfish Heart Positioner (Medtronic GmbH) was used instead of pericardial traction sutures in the Octopus group (n = 9) for cardiac positioning. The Starfish Heart Positioner was attached to the apex to enhance lateral or posterior wall exposure. The randomized stabilizer was adjusted to reduce epicardial movement at the target vessel. Using the Octopus stabilizer (Fig 1A), the coronary arteries were surrounded proximally to the region of the anastomosis with 4-0 or 5-0 polypropylene sutures (Ethicon, Somerville, NJ) that were snared over a pledget for temporary interruption of blood flow. Suction (400 mm Hg) was then applied for stabilization of the corresponding vessels. With the Immobilizer device (Fig 1B), two-vessel loops were used proximally and distally to the anastomotic site to provide atraumatic, anterior-posterior compression and to achieve hemostasis.



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  		Fig 1. Two different stabilizer concepts: (A) the Octopus tissue stabilizer system (Medtronic GmbH, Düsseldorf, Germany) achieving local stabilization by suction onto the heart surface and (B) the Immobilizer stabilization platform (Genzyme Surgical Products, Fall River, MA) achieving stabilization by capturing the target vessel using vessel loops.

 
Usually, the left anterior descending coronary artery territory was revascularized first to minimize the effect of heart manipulation. The distal coronary anastomoses were performed using 7-0 or 8-0 polypropylene suture for the internal mammary artery and 7-0 polypropylene for the saphenous vein grafts. Preconditioning was not routinely performed. An intracoronary shunt was inserted only if necessary due to electrocardiographic changes or arrhythmias. A humidified carbon dioxide blower was used in each group for improved visibility. The proximal anastomoses were made with running 6-0 polypropylene sutures during single partial clamping of the aorta.

Orthogonal polarization spectral imaging
Two-dimensional cardiac surface motion of the beating heart was assessed with intravital microscopy using orthogonal polarization spectral imaging, a new technology for imaging of the microcirculation using reflected light [8]. The tissue was illuminated with linearly polarized light and imaged through a polarizer oriented orthogonal to the plane of the illuminating light, which produced high contrast microvascular images with a resolution of approximately 1 µm.

After a sufficient stabilization was achieved, the orthogonal polarization spectral imaging device Cytoscan E-II (Cytometrics, Inc., Philadelphia, PA) was fixed at the immobilized area to visualize the epicardial microvessels. The tip of the lens was brought in contact with the epicardial surface and the focus was adjusted. Small epicardial vessels were used as markers on the heart surface (Fig 2). The two-dimensional cardiac surface motion was recorded and assessed by computer-aided measurement of the distance of the maximum deviation of the small vessels in both directions. In total, 20 vessels (n = 12 in the Octopus group; n = 8 in the Immobilizer group) were evaluated. Because only target vessels at the anterior wall (left anterior descending coronary artery or diagonal branch) could be reached by the intravital microscope, no objective statement about stabilization properties at the lateral or posterior wall could be made. Three sequences were measured for each target vessel and means were built.



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  		Fig 2. A typical image of the surface myocardial microcirculation taken by means of the orthogonal polarization spectral imaging device (Cytoscan E-II). Epicardial microvessels were visualized and used as markers on the heart surface. The two-dimensional cardiac surface motion was assessed by computer-aided measurement of the maximum deviation of the microvessels in both directions.

 
Quality control and assessment criteria
Intraoperative quality assessment was performed by ultrasound-based flowmeters in all patients. Postoperative electrocardiographic studies were performed and serial samples of creatine kinase (CK), CK-MB, and cardiac troponin I were determined every 6 hours up to 48 hours in any patient. Myocardial infarction was defined as either an increase in CK-MB enzyme levels of more than 50 U/L or Q-wave in the postoperative electrocardiogram. An early postoperative control angiography was generally recommended, except for patients with renal insufficiency, and was always performed in patients with postoperative angina or increased CK-MB enzyme levels. However, the majority of the patients declined to undergo elective subsequent angiography. Furthermore, excellent graft patency could be demonstrated after OPCABG by different institutions [7, 9]. Therefore, postoperative catheterization was abandoned from routine protocol step-by-step. Thus, postoperative angiography was only assessed in 24 vessels (26.7%) in the Octopus group and 23 vessels (34.3%) in the Immobilizer group.

Statistical analysis
Continuous data were analyzed using the unpaired Student’s t test or the analysis of variance test for multiple groups, categorical data using the {chi}2 test. Values were expressed as mean ± standard deviation. Probability values of less than 0.05 were considered significant. Statistical analysis was performed using the SPSS statistical software package 10.0 for Windows (SPSS, Inc, Chicago, IL).


   Results
Top
 Abstract
 Introduction
 Material and methods
 Results
Comment
 Acknowledgments
 References
 
The average number of grafts per patient was 1.8 ± 0.7 in the Octopus group, compared to 1.6 ± 0.5 in the Immobilizer group (p = 0.08). In the Octopus group, 18 patients (36.0%) had single, 26 (52.0%) double, 4 (8.0%) triple graft revascularization, and 2 (4%) patients received four grafts compared to 19 patients (44.2%) with single and 24 (55.8%) with double graft revascularization in the Immobilizer group (p = 0.13).

In 7 patients, the randomized Immobilizer system was rejected by the surgeon due to impracticable device handling, because sufficient stabilization was not possible in the posterior wall region. In all 7 patients (one single, two double, and four triple graft revascularizations), grafting of the lateral or the posterior wall was necessary. The drop-outs were not taken into further account, reducing the number of patients in the Immobilizer group to 43 patients.

Mean time of operation did not differ significantly among groups and was 193 ± 62 minutes and 179 ± 61 minutes in the Octopus and Immobilizer groups, respectively (p = 0.21). Time required for anastomosis was significantly lower in the Immobilizer group (11.3 ± 3.5 minutes) than in the Octopus group (14.9 ± 2.4 minutes; p < 0.001).

Maximum two-dimensional cardiac surface motion was significantly less using the Immobilizer device (109.7 ± 32.4 µm) in comparison to the Octopus system (423.5 ± 129.6 µm) in the left anterior descending coronary artery region (p < 0.001) (Fig 3).



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  		Fig 3. Two-dimensional cardiac surface motion using the two stabilization systems. Maximum two-dimensional cardiac surface motion was significantly less using the Immobilizer device (109.7 ± 32.4 µm) in comparison to the Octopus stabilizer (423.5 ± 129.6 µm).

 
There were three conversions to cardiopulmonary bypass in the Octopus group due to an intramyocardial, severe calcified coronary vessel, hemodynamic instability during exposure of the target vessel, and a low bypass flow. In this patient, the distal bypass anastomosis was revised with cardiopulmonary bypass. An intramyocardial left anterior descending coronary artery led to conversion to cardiopulmonary bypass in 1 patient in the Immobilizer group. All anastomoses were performed safely with the arrested heart without further complications. There was no myocardial infarction and no cerebrovascular accident in either group. All intra- and postoperative data are listed in Table 2.


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  		Table 2. Intraoperative and Postoperative Data

 
Intraoperative bypass flow rates were satisfactory with no differences among groups (61.7 ± 18.1 mL/min versus 58.4 ± 16.1 mL/min; p = 0.53). Early postoperative angiography was performed in 24 grafts (26.7%) in the Octopus group and 23 grafts (34.3%) in the Immobilizer group. The graft patency rate was 100% in both groups. No graft occlusions except for two anastomotic stenoses more than 50% were found in each group (p = not significant). Two catheter interventions with percutaneous transluminal coronary angioplasty and stent implantation were necessary in each group. All postoperative angiographic results are listed in Table 3.


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  		Table 3. Postoperative Angiography

 

   Comment
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
Acknowledgments
 References
 
Both stabilizers used in our institution have been shown to be useful in OPCABG. However, these stabilizers represent different strategies of cardiac stabilization and vessel occlusion. With the Immobilizer Stabilization System, vessel occlusion and immobilization is achieved by capturing the target vessel with gentle epicardial herniation through the anastomotic window of the Cohn platform. Vessel loops are used to provide atraumatic, anterior-posterior compression and to achieve hemostasis. The Octopus is a suction device, stabilizing the heart surface by applying suction to the epicardium with suction cups without exerting pressure. The purpose of this study was to evaluate the efficacy of two different stabilizer concepts comparing the Octopus and Immobilizer device during OPCABG.

Anastomosis time was significantly shorter in the Immobilizer group than in the Octopus group (11.3 ± 3.5 minutes versus 14.9 ± 2.4 minutes). The shorter anastomosis times with the Immobilizer may directly correlate with the better stabilizing properties. In fact, this was confirmed by intravital microscopy using orthogonal polarization spectral imaging [8], which showed less two-dimensional cardiac surface motion with the Immobilizer compared to the Octopus device in the left anterior descending coronary artery region (p < 0.001). Borst and colleagues [10] showed a wall motion reduction to 1 by 1 mm with the Octopus 1 stabilizer. In this study, further motion reduction with the new generation of the Octopus 3 could be demonstrated and was even better with the Immobilizer. Capturing the anastomotic site with the Immobilizer platform seems superior to epicardial suction alone. However, excellent intraoperative bypass flow rates and angiographic results could be achieved with a patency rate of 100% with both stabilization systems.

One major advantage of the Octopus was the ability of easy readjustment at the anastomotic site by switching off the suction and repositioning the device. Thus, the vessel can easily be dissected over a longer distance for detection of the optimal target area for coronary anastomosis. After fixation of the vessel loops, the Immobilizer is less flexible and readjustment is uncomfortable. Because the Starfish Heart Positioner is available and combined with the Octopus stabilizer, cardiac positioning is even more simplified, which facilitates the access and exposure of coronary arteries. This minimizes the associated hemodynamic deterioration, especially for lateral and posterior wall revascularization. Therefore, we prefer the suction stabilization system, consisting of the Octopus 3 and Starfish, whenever revascularization to the lateral or posterior wall is indicated.


   Acknowledgments
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
 Acknowledgments
References
 
Funding for this project was provided by Medtronic GmbH, Düsseldorf, Germany.


   References
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
 Acknowledgments
 References
 

  1. Matata B.M., Sosnowski A.W., Galinanes M. Off-pump bypass graft operation significantly reduces oxidative stress and inflammation. Ann Thorac Surg 2000;69:785-791.[Abstract/Free Full Text]
  2. Bowles B.J., Lee J.D., Dang C.R., Taoka S.N., Nekomoto K. Coronary artery bypass performed without the use of cardiopulmonary bypass is associated with reduced cerebral microemboli and improved clinical results. Chest 2001;119:25-30.[Abstract/Free Full Text]
  3. Stamou S.C., Pfister A.J., Dangas G., Corso P.J. Beating heart versus conventional single-vessel reoperative coronary artery bypass. Ann Thorac Surg 2000;69:1383-1387.[Abstract/Free Full Text]
  4. Locker C., Shapira I., Paz Y., Kramer A., Gurevitch J., Mohr R. Emergency myocardial revascularization for acute myocardial infaction: survival benefits of avoiding cardiopulmonary bypass. Eur J Cardiothorac Surg 2000;17:234-238.[Abstract/Free Full Text]
  5. Stamou S.C., Corso P.J. Coronary revascularization without cardiopulmonary bypass in high-risk patients: a route to the future. Ann Thorac Surg 2001;71:1056-1061.[Abstract/Free Full Text]
  6. Koutlas T.C., Elbeery J.R., Williams J.M., Moran J.F., Francalancia N.A., Chitwood W.R., Jr Myocardial revascularization in the elderly using beating heart coronary artery bypass surgery. Ann Thorac Surg 2000;69:1042-1047.[Abstract/Free Full Text]
  7. Detter C., Reichenspurner H., Boehm D.H., Thalhammer M., Schutz A., Reichart B. Single vessel revascularization with beating heart techniques—minithoracotomy or sternotomy?. Eur J Cardiothorac Surg 2001;19:464-470.[Abstract/Free Full Text]
  8. Groner W., Winkelman J.W., Harris A.G., Ince C., Bouma G.J., Messmer K., Nadeau R.G. Orthogonal polarization spectral imaging: a new method for study of the microcirculation. Nat Med 1999;5:1209-1212.[Medline]
  9. Mack M.J., Magovern J.A., Acuff T.A., Landreneau R.J., Tennison D.M., Tinnerman E.J., Osborne J.A. Results of graft patency by immediate angiography in minimally invasive coronary artery surgery. Ann Thorac Surg 1999;68:383-390.[Abstract/Free Full Text]
  10. Borst C., Jansen E.W., Tulleken C.A., Gründeman P.F., Mansvelt Beck H.J., van Dongen J.W., Hodde K.C., Bredee J.J. Coronary artery bypass grafting without cardiopulmonary bypass and without interruption of native coronary flow using a novel anastomosis site restraining device ("Octopus"). J Am Coll Cardiol 1996;27:1356-1364.[Abstract]



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