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Ann Thorac Surg 1999;68:1478-1481
© 1999 The Society of Thoracic Surgeons

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Supplement: Minimally Invasive Cardiac Surgery

A two-year, three institution experience with the Medtronic Octopus: systematic off-pump surgery

^a Park Nicollet Clinic, HealthSystem Minnesota, Minneapolis, Minnesota, USA
^b Pinnacle Health, Harrisburg, Pennsylvania, USA
^c Queens University, Kingston, Ontario, Canada

Address reprint requests to Dr Spooner, Park Nicollet Clinic, 6490 Excelsior Blvd, Suite 200W, St. Louis Park, MN 55426
e-mail: tspooner{at}aol.com

Presented at Evolving Techniques and Technologies in Minimally Invasive Cardiac Surgery, San Antonio, TX, Jan 22–23, 1999.

Abstract

Background. The popularity of beating heart coronary artery bypass (CAB) has grown with the development of mechanical stabilizers. Multicenter study offers an opportunity to examine methods and risk relating to this practice.

Methods. The experience since March 1997, utilizing both the original Medtronic Octopus system and the second-generation, retractor-mounted, Octopus II for beating heart CAB (Medtronic, Inc, Minneapolis, MN), was retrospectively reviewed at three institutions.

Results. Four hundred fifty-six patients completed Octopus CAB (Medtronic, Inc), performed through left thoracotomy (54), partial (33), or full (374) sternotomy, and epigastric (3) incisions with an average of 1.9 grafts/patient. Morbidities were reviewed: transfusion (20.6%), reoperation for bleeding (1.0%), atrial fibrillation (13.3%), completed stroke (0.2%), perioperative myocardial infarction (0.8%), and new intraaortic balloon pump (IABP) (0.4%), without episodes of deep sternal infection or renal failure. The mortality rate (0.32%), when compared to the Society of Thoracic Surgeons’ (STS)-predicted mortality (1.37% and 2.36%) at two institutions, was significantly less (p < 0.05). Twelve nonurgent and one urgent conversion to cardiopulmonary bypass occurred. Six patients have required reintervention on bypassed vessels.

Conclusions. To facilitate lateral and inferior wall grafting, a variety of techniques were utilized, including positioning, sternal and pericardial mobilization, and a new pericardial-based sling retractor, all designed to improve exposure while maintaining hemodynamic stability. The Octopus devices were safely applied with low morbidity and mortality utilizing varied operative approaches at three institutions.

Early attempts at beating heart coronary artery bypass (CAB) were hindered by poor local cardiac immobilization. Enthusiasm was further diminished by the attraction of cardiac standstill with cardiopulmonary bypass (CPB). Work performed in 1964, by Kolessov [1], with left thoracotomy beating heart CAB has had increased recent interest relating to alternate surgical approaches to coronary artery disease. To facilitate these techniques, hand-held instruments have now evolved into devices such as the Medtronic-Utrecht Octopus system (Medtronic, Inc) [2], that utilizes a table-mounted mechanical stabilizer combined with suction for epicardial fixation. Success requires the systematic practice of specific techniques such as those designed to improve exposure of the circumflex marginal branches, including the Janke net [3], an oblique sinus gauze sponge [4], and a vaginal tape technique (Calafiore, personal communication). This study serves to retrospectively review the experience at three institutions using the original and new second-generation Octopus systems. These institutions had prior beating heart surgical experience and began efforts, in earnest, to expand programs with these new devices. Periodic contacts were made between the institutions to identify specific problems for process improvement.

Material and methods

After review of angiograms, 469 patients were entered as candidates for beating heart CAB operations performed utilizing the Octopus system. The average age was 62.8 years (range 26–89) and 77% were male. The average ejection fraction was 55.7%, and 6.6% of patients underwent reoperations. Generally, a minimum size of 1.5-mm diameter target artery was desired with discrete, as opposed to diffuse, stenosis. Poor ejection fraction and/or cardiomegaly were an impedance if posterior or lateral wall (but not anterior wall) grafting were proposed and cardiac decompression by CPB was preferred. Once the heart was exposed, cardiac manipulation and arterial target inspection finally determined the applicability of beating heart techniques. Standard anesthetic techniques were used with electrocardiogram (EKG), arterial line, and Swan-Ganz catheter (Baxter-Healthcare Corp, Irvine, CA). Body temperature was maintained above 35°C. To double the activated clotting time, 1.5–2 mg/kg heparin was administered. Proximal silicone elastomer figure-of-eight snares alone, or combined with a distal silicone elastomer harness, or 4-0 Prolene sutures (Ethicon, Somerville NJ) with Teflon buttresses (Impra Inc, Tempe, AZ) combined with an intracoronary Flo-Restor (Bio-Vascular, St. Paul, MN) were used to control bleeding at the anastomotic site. Rivetti-Levinson intracoronary shunts (Integra Life Sciences, Plainsboro, NJ) were inserted if EKG changes developed after arterial occlusion at two institutions but not used at one. Visualization was improved with the Medtronic Clearview blower/mister (Medtronic, Inc). Anastomoses were sewn using running 7-0 or 8-0 Prolene sutures. Patients requiring CPB after beating heart CAB techniques failed were considered conversions. During the postoperative follow-up interval, interventions required for recurrent angina, either angiography, angioplasty with or without stenting, or reoperation were reviewed.

The first-generation Medtronic Octopus system was utilized beginning in March 1997. This is an operating room, side-rail, table-mounted device, utilizing separate reusable articulating arms and disposable tissue stabilizers. The second-generation device had its first clinical use in November 1998. The Octopus II is a less bulky, disposable, universal retractor-mounted device with dual-spreading tissue stabilizers.

Single-vessel coronary artery bypass
Single-vessel CAB operations were performed on 177 patients using some type of arterial conduit in 99% of cases. Early in this experience, most single-vessel left anterior descending coronary artery (LAD) bypasses were performed through the small anterior thoracotomy approach [5]. Due to issues relating to mammary artery exposure for direct dissection, concerns about expeditious exposure in the event of cardiovascular collapse, and problems with postoperative pain, surgeons at two of the institutions preferred to perform operations, in the later half of the study period, through the lower partial sternotomy incision [6]. Redo anterior-wall grafting, though, continued to be performed through an anterior thoracotomy incision. In the markedly obese patient, a median sternotomy was preferred.

Five operations (two reoperations) were performed to bypass critical obtuse marginal (OM) stenoses through a lateral thoracotomy incision. Saphenous vein or radial artery were used to bypass from the descending thoracic aorta to the OM with local Octopus stabilization. One patient, with a severe ischemic cardiomyopathy with preoperative hypotension requiring inotropic support and intraaortic balloon pump, underwent successful CAB with peripheral cardiopulmonary support and local Octopus stabilization.

Four patients underwent CAB to a posterior descending artery (PDA) using the right gastroepiploic artery. The approach was through an epigastric incision in three cases and through a lower partial sternotomy incision in 1 patient.

Multiple vessel coronary artery bypass
The median sternotomy incision was used most commonly for multiple-vessel CAB; however, 1 two-vessel CAB was performed through a partial sternotomy, and 2 two-vessel and 1 three-vessel bypasses were performed through anterolateral thoracotomy incisions in this series. Two bypass grafts were performed in 154 patients (33.8%), three grafts in 102 (22.4%), and four grafts in 23 patients (5.0%). At least one arterial graft was used in 99% of patients, while the frequency of total arterial grafting varied at each institution (100%, Pym; 11%, Spooner; 4.4%, Hart).

The technical challenge surrounding proper presentation of the beating heart and exposure of target coronary arteries were critical for successful grafting and was especially difficult for marginal arteries. Limited local cardiac surface motion must be combined with minimal hemodynamic compromise. Integral steps are described including sternal and pericardial mobilization, positioning, and ancillary cardiac mass support.

Following sternotomy and chest-wall retractor placement, an effort is made to create a space in which the heart may be easily displaced with minimal compression by surrounding tissues. To accomplish this, the right-sided attachments from the posterior sternal table to the pericardium are widely divided and a deep cut is made in the right diaphragmatic pericardial corner. The retractor blades on the right side of the sternum are elevated. An unrestricted space is now formed for the heart beneath the right sternum as it is retracted to the right for lateral-wall exposure of marginal arteries. Proper positioning allows the natural effect of gravity to aid in rolling the heart while an OM or PDA is exposed. To maximize the rotation of the operating room table to the patient’s right, the left side of the patient’s chest is elevated 20 degrees prior to sterile draping on a bolster. When exposing a marginal artery, the patient may then be extremely rotated to the right and in the Trendeleburg position. This combination optimizes visualization by causing the heart to be weighted in a rightward and cranial direction, while at the same time, fluid-loading to maintain blood pressure.

Another challenge for difficult lateral wall grafting is efficient positioning of the Octopus system after rightward displacement of the heart from the pericardial well. Though there are a variety of methods to achieve the desired displacement, the primary author’s preference is a new pericardial-based sling retractor. To fashion this, the heart is manually retracted to the right, exposing the posterior pericardium. The needle on a 36 inch long 3-0 Tevdec suture (Deknatel, Fall River, MA) is passed through the pericardium at a point located just behind the coronary sinus and directly beneath the origin of the most distal marginal artery (usually halfway between the inferior pulmonary vein and inferior vena cava). This same needle is then passed through the midpoint of a 2-cm wide stockinette gauze that has been cut to 30 cm in length. As an assistant gently retracts the inferior surface of the heart, the suture is tied, drawing the stockinette gauze deep into the pericardium. The sling, now securely anchored centrally to the posterior pericardium, forms a "V" with the two gauze arms lying freely outside of the chest. As the surgeon applies traction to the free "arms" of the stockinette gauze, the point of pericardial fixation is drawn in an anterior direction gently elevating the heart from the mediastinum. The "arms" abut the epicardium in an atraumatic fashion to allow optimum positioning. "Arms" oriented in the pericardial sac to the left side of the heart can be pulled toward the right side of the incision and expose the marginal artery territory (Fig 1). Orienting one of the free "arms" along the distal lateral surface of the left ventricle, with the second "arm" to the right side of the diaphragmatic surface, will expose the PDA as the "arms" are drawn tight. Clamps are used to secure the gauze "arms" to the drapes. The Octopus system is positioned and used for fine local myocardial stabilization and not support of the cardiac mass.

View larger version (158K): [in this window] [in a new window]   Fig 1. Pericardial sling shown as it is used to expose a distal marginal artery.

Results

Beating heart CAB was attempted on 469 patients in this study period (Table 1). Conversion to CPB occurred in 13 of the 469 patients (2.8%) with 1 urgent. Reasons for conversion were most often related to difficulty exposing a marginal artery (7/13). Conversions for LAD grafts were secondary to severe EKG changes with mild hypotension (1/13), ventricular tachycardia upon occlusion (1/13), and an artery buried in the interventricular septal fat (1/13). Intolerance of right coronary artery occlusion also occurred (2/13). The single mortality was attributed to irreparable injury of a mildly stenosed marginal artery. This patient required urgent (1/13) CPB for assessment and died 2 weeks following surgery. The frequency of conversions decreased in the second year of observation (10 versus 3). Postoperative morbidities included transfusion in 20.6%, reoperation for bleeding in 1.0%, atrial fibrillation in 13.3% (partial data, 331 patients), completed stroke in 0.2%, perioperative myocardial infarction in 0.8% (region of infarct was not grafted in 2 cases), and requirement for a new intraaortic balloon pump in 0.4%. There were no instances of deep-wound infection or new renal failure. The 30-day mortality rate was 0.2% with the STS average predicted mortality at two centers 1.37 ± 2.20% (range for 149 patients: 0.17–20.17) and 2.36 ± 3.11% (range for 182 patients: 0.14–22.27). There was a statistically significant difference in observed (0.32%) and expected (1.91%) 30-day mortality rates (p < 0.05) when results were compared at the two institutes that utilized the STS database (331 patients). The mean postoperative length of stay for all patients was 5.3 days.

Angiographic assessment for recurrent angina occurred in 6/456 cases. One graft was occluded in each of 2 patients (1 of three, and 1 of two grafts) who were then treated medically. Two patients developed new stenoses in ungrafted vessels and were treated with angioplasty. One patient developed stenotic lesions in a vein-graft body, eventually requiring a beating heart reoperation. One patient developed native LAD stenosis distal to the left internal mammary artery graft insertion in an uninstrumented area and was treated successfully with angioplasty.

Comment

In this retrospective multi-institutional review, the Octopus system was used in a wide variety of CAB operations through an array of incisions. Its use allowed maximal use of arterial grafts if desired. In fact, one institution used arterial grafts in all patients. Morbidity and mortality rates were low. The frequency of conversion to CPB was low and decreased with the surgeon’s experience both with the Octopus system and with beating heart surgical techniques. The frequency of use of the Octopus system increased with added experience. The percentage of CAB operations performed by each author grew respectively in the first 3 months (41%, 63%, and 40%) compared to the last 3 months (76%, 90%, and 70%).

Efficiency with smooth flow of the operation and adequate target stabilization remain primary challenges (and frustrations) for surgeons, particularly for multiple-graft operations. Improvement requires proper preoperative case selection, as well as practiced intraoperative techniques that result in expeditious exposure, hemodynamic stability, and adequate target artery immobilization. The use of an ancillary stabilization device, in particular, is of significant value. The pericardial-based sling as described is simple and low-profile, and removes most of the weight of the heart from the Octopus system. Reducing this weight demand allows the primary function of the Octopus system to be fine local immobilization.

The second-generation Octopus II device was intuitive to use with a versatile, retractor mounting system. It lacked the bulk and complicated set-up problems that have been seen with the earlier design. It was utilized through a variety of incisions to graft anterior, lateral, and posterior-wall vessels with early postoperative results similar to those of the first-generation device.[7]

Footnotes

All of the authors of this paper have educational consulting agreements regarding beating heart surgery with Medtronic, Inc.

References

1. Kolessov V.I. Mammary artery-coronary artery anastomosis as method of treatment for angina pectoris. J Thorac Cardiovasc Surg 1967;54:535-544.[Medline]
2. Borst C., Jansen E.W.L., Grundeman P.F., et al. 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]
3. Janke W.H. Heart support for coronary artery bypass surgery involving the circumflex artery system. J Thorac Cardiovasc Surg 1974;67:883-884.[Medline]
4. Galvin I.F., Newman D.C. Circumflex exposure using a cardiac sling. Ann Thorac Surg 1990;49:833-834.[Medline]
5. Calafiore A.M., Di Giammarco G., Teodori G., et al. Left anterior descending coronary artery grafting through left anterior small thoracotomy without cardiopulmonary bypass. Ann Thorac Surg 1996;61:1658-1665.[Abstract/Free Full Text]
6. Doty D.B., Dirusso G.B., Doty J.R. Full-spectrum cardiac surgery through a minimal incision. Ann Thorac Surg 1998;65:573-577.[Abstract/Free Full Text]
7. Cheung D., Flemma R.J., Mullen D.C., Lepley D. An alternative approach to isolated circumflex coronary artery bypass reoperations. Ann Thorac Surg 1982;33:302-303.[Medline]

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