Minimally invasive coronary artery bypass grafting: an experimental perspective.

Abstract

HomeCirculationVol. 99, No. 11Minimally Invasive Coronary Artery Bypass Grafting Free AccessEditorialPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyRedditDiggEmail Jump toFree AccessEditorialPDF/EPUBMinimally Invasive Coronary Artery Bypass Grafting An Experimental Perspective Cornelius Borst and Paul F. Gründeman Cornelius BorstCornelius Borst From the Department of Cardiology, Heart Lung Institute, Utrecht University Hospital, Utrecht, Netherlands. Search for more papers by this author and Paul F. GründemanPaul F. Gründeman From the Department of Cardiology, Heart Lung Institute, Utrecht University Hospital, Utrecht, Netherlands. Search for more papers by this author Originally published23 Mar 1999https://doi.org/10.1161/01.CIR.99.11.1400Circulation. 1999;99:1400–1403In their recent editorial “Minimally Invasive Coronary Bypass: A Dissenting Opinion,” Bonchek and Ullyot1 express concerns about ill-guided attempts to deviate from the conventional revascularization procedure that is “safe, effective, durable, reproducible, complete, versatile, and teachable.” In the present editorial, an experimental perspective on the search for less invasive surgical strategies is provided that will convey an opposite opinion. First, a brief reappraisal is warranted of the safety of coronary artery bypass graft surgery (CABG) during cardiac arrest supported by cardiopulmonary bypass (CPB).Safety of Conventional CABGThe great majority of CABG patients benefit greatly from coronary revascularization, but the surgical procedure is not without adverse effects. The Society of Thoracic Surgeons (STS) National Cardiac Surgery Database (January 1998) lists complications of 170 895 CABG-only operations, including 13 736 reoperations, performed in the United States in 1996. Operative mortality was 2.9% (2.5% in men, 4.0% in women). Operative mortality increases with age, from 1.1% at age 20 to 50 years to 7.2% at 81 to 90 years. In only 65.4% of procedures were no complications reported. Most complications are listed in the Table.Another way to assess the clinical outcome of conventional CABG is to analyze hospital discharge data from health insurance records.2 Of 101 812 patients ≥65 years old operated on in January through October 1993 in the United States, 4.3% died in hospital. Of particular concern are patients (3.6%) who were discharged to a non–acute-care facility.3 Owing to complications, 10.2% were discharged late (>14 days) to home. Thus, 81.9% were discharged to home in ≤14 days. In the first 2 months after discharge to home, 0.7% died and 9.9% were readmitted for cardiovascular, respiratory, or cerebrovascular reasons.Although each of these numbers needs to be carefully interpreted in its context, the Table and the health insurance data,2 taken together, would seem to fall short of the “excellent outcomes” attributed to conventional CABG by Bonchek and Ullyot.1Mechanisms of Adverse EffectsThe adverse effects of conventional CABG have been recognized from the beginning and are well documented.4 After 30 years of technical and surgical evolution, however, the approach to coronary surgery has remained basically unaltered.4 Worldwide, virtually all 800 000 patients per year are exposed to median sternotomy, full heparinization, CPB with aortic cross-clamping, global ischemic cardiac arrest with or without cooling, saphenous vein harvest and aortic side-clamping, and an anesthetic regimen specific to CPB-supported CABG.There are solid reasons to perform coronary surgery on an arrested heart. The surgeon is provided with a still field, absence of blood in the anastomotic area, and an empty, flaccid heart that can be manipulated easily to expose all coronary branches. As enumerated above, however, these technical advantages to the surgeon do not come with a free ride to the patient, in particular the elderly patient.234The adverse cerebral effects, including neurocognitive impairment, are attributed to a combination of particulate emboli generated by manipulation of the ascending aorta, microthrombi due to platelet activation, and gaseous emboli, as well as cerebral sequelae of the extracorporeal circulation–induced whole-body inflammatory response. The latter is manifested by fever, activation of leukocytes, complement, C-reactive protein and a host of other factors, arrhythmias, endothelial dysfunction, interstitial fluid accumulation, pulmonary dysfunction, renal dysfunction, and organ failure in severe cases. Emboli may contribute to organ dysfunction. Prolonged ischemic cardiac arrest and extracorporeal circulation may cause hemodynamic disorders and bleeding disorders necessitating administration of blood products.The mortality and morbidity of conventional CABG invite exploration of surgical revascularization strategies with fewer adverse effects. In addition, the current expansion of coronary angioplasty by stenting is a potent stimulus to search for coronary surgery procedures with substantially reduced mortality, morbidity, and reconvalescence period.Minimally Invasive CABG: A Minimal-Adverse-Effects ApproachThe terminology for less invasive CABG is utterly confusing. “Minimally invasive” refers to procedures that range from thoracoscopic CABG with CPB (peripheral cannulation) to median sternotomy CABG on the beating heart. In between, MIDCAB refers to direct-vision left internal thoracic artery (LITA) grafting to the left anterior descending coronary artery (LAD) on the beating heart through a 5- to 10-cm left anterolateral thoracotomy (also referred to as LAST operation).5 OPCAB refers to off-pump CABG, whatever the access. ECAB refers to endoscopic CABG, whether off-pump or on-pump.The Babylonian confusion in terminology originates from the 2 diverging starting points in the search for less invasive methods. The approach developed at Stanford was inspired by the advent of video-assisted thoracic surgery, but it retained CPB with peripheral cannulation.6 The beating-heart approach,789 in contrast, was inspired by the recognition that the major adverse events are due to CPB rather than to median sternotomy.1011 A third approach combined beating-heart surgery and limited access,5812 sometimes including thoracoscopic LITA takedown.13In our view, a “minimally invasive” approach to coronary surgery is to be regarded as a “minimal adverse effects” approach that starts by omitting CPB and cardiac arrest. In the assessment of minimally invasive CABG results, the distinction between off-pump and on-pump procedures is crucial.Without CPBOmitting CPB and cardiac arrest gives rise to alternative problems. First, beating-heart coronary motion hampers anastomosis suturing. Second, interruption of recipient artery flow may induce regional ischemia, arrhythmias, and hemodynamic deterioration. Third, perforating branches in the vicinity of the arteriotomy may produce torrential retrograde blood flow in the arteriotomy that obscures its edges and hampers suturing. Fourth, anterior displacement of the beating heart to expose posterior branches interferes with normal pump function and causes a drop in cardiac output. Fifth, in contrast to the arrested, decompressed heart, the (enlarged) beating heart may leave limited space in the thorax for the surgeon to work in comfortably. Sixth, identification of the target vessel may be more difficult. Seventh, to date, an intramyocardial course of the coronary artery and diffuse disease are relative contraindications. Thus, by avoiding a host of adverse effects of CPB and cardiac arrest, a host of new problems is generated. Most of these issues, however, are being dealt with.Anesthetic and Postoperative RegimenWithout CPB, a modified anesthetic perioperative and postoperative regimen is required to deal with the different surgery and to allow extubation in the operating room, to limit or obviate intensive care stay, and to allow early discharge.Coronary MotionMicrosurgery seems to be incompatible with a moving target. In some centers, however, the distal anastomosis has been accomplished in >1000 patients by means of traction sutures and instruments held by the assistant.91011 The introduction of mechanical stabilizers in 199558141516 greatly facilitated local epicardial motion restraint to ≈1×1 mm in the epicardial plane when the target site is immobilized by means of a tissue stabilizer attached to the operating table14 or to the rib retractor.15 Mechanical stabilizers cause negligible injury1415 and hardly affect stroke volume1516 unless the heart is displaced.16 An alternative, still experimental approach is the brief, drug-induced ventricular asystole that allows placing 1 stitch.17 Once that is done, ventricular pacing is resumed.Angiographic PatencyThere is little consensus on the precise “gold standard” for angiographic patency.18 One recent gold standard is based on 645 patients from an international multicenter randomized trial.19 At a mean follow-up of 11 days, a widely patent LITA-to-LAD graft (stenosis <50%) was found in 584 patients (91.0%). After CABG without CPB using a mechanical stabilizer, similar patency rates of ≥90% are reported in single- and multiple-vessel cases, both at early512182021 and at 6-month follow-up.822 A mechanical stabilizer significantly improves early angiographic results and event-free survival in the first 1.5 years.20Interruption of Coronary FlowOwing to the presence of well-developed collateral circulation in patients with coronary artery disease, 10- to 20-minute interruption of coronary flow is remarkably well tolerated under the conditions of the operation. In rare cases, mostly when the right coronary artery is occluded, hemodynamic instability may arise from arrhythmia or ischemia. A temporary luminal shunt,23 arteriotomy seal,24 or distal perfusion cannula may prevent this complication.BloodThe temporary luminal shunt23 or 200-μm-thick arteriotomy seal24 may also be used to advantage in preventing blood from obscuring the arteriotomy edges. Another way to fight blood in the arteriotomy is by saline spray combined with a blower.Hemodynamic DeteriorationOff-pump CABG has remained mainly limited to the LAD and a diagonal branch, the right coronary artery, and the posterior descending artery. Together with the lack of space and unfavorable angle of attack, grafting of circumflex branches is still a major challenge owing to hemodynamic deterioration when the beating heart is retracted anteriorly to expose posterior branches in a median sternotomy approach. In the porcine model,16 the 40% drop in stroke volume is attributed to deformation of primarily the right ventricle. At the expense of augmented preloads, the Trendelenburg maneuver is capable of restoring arterial pressure. In selected patients with multivessel disease, beating-heart revascularization of posterior branches through median sternotomy is feasible but demanding.8 Inotropic support is sometimes needed.8Beating-Heart Coronary SurgeryAccording to industry estimates, >30 000 CABG operations worldwide have been performed on the beating heart by use of a commercially available mechanical stabilizer, through both full and limited access. Current indications include favorable coronary anatomy and high-risk cases. Coronary surgery on the beating heart is more demanding than conventional surgery. The first part of the learning curve, however, can be shortened by training in an animal laboratory. In centers that have initiated a program for CABG on the beating heart using a mechanical stabilizer, soon 10% to 15% of cases are being performed without CPB. This percentage will rise substantially when grafting of circumflex branches becomes more generally feasible.Arterial ConduitsWithout cross-clamping and puncturing of the ascending aorta, only the side-biting clamp for the proximal anastomosis of the saphenous vein graft remains as a source of plaque embolization. Arterial grafts, if used exclusively,25 will abolish this last cause of cerebral embolization from manipulation of the aorta. Avoiding the long wound from vein harvesting in the leg will further contribute to reduction in postoperative pain and morbidity. If no adequate arterial conduits are available, less invasive, endoscopic methods to harvest the saphenous vein are now available that are associated with less pain and fewer wound complications.26 In addition, novel devices are being developed to construct the proximal anastomosis on the aorta without a side-biting clamp.Access ReductionA limited-access approach58121315182021 is attractive in cases that require limited revascularization, eg, a small anterolateral thoracotomy for LITA grafting to the LAD territory or subxyphoidal laparotomy for gastroepiploic artery grafting to the distal right coronary artery or proximal posterior descending artery. As long as revascularization on the beating heart of posterior branches remains too great a challenge, a hybrid approach to multivessel disease may be considered in which only the LAD territory is revascularized by LITA grafting through minithoracotomy, and other lesions are treated by percutaneous angioplasty.27Randomized TrialsThe first randomized study (62 patients) on isolated LITA-to-LAD grafting on the beating heart28 reports significant reductions in systemic inflammatory response, postoperative morbidity, and hospital stay compared with conventional coronary surgery. Based on promising results in the first 100 patients in Utrecht,8 the Netherlands National Health Insurance Council has funded a multicenter study that started in March 1998. This study involves 2 randomized trials in which it is intended to revascularize by arterial grafts only. One trial compares multivessel CABG without CPB using a mechanical tissue stabilizer versus conventional CABG with CPB. The second trial compares multivessel CABG without CPB using a stabilizer versus stenting. Both trials include angiographic follow-up at 1 year in a randomized subset of the 560 patients.Closed-Chest Thoracoscopic CABGThe thoracoscopic coronary surgery approach developed originally at Stanford6 uses peripheral cannulation for CPB and global cardiac arrest. On top of augmented complexity, surgery time, and costs, this adds the risks of aortic dissection and other peripheral complications21 to the adverse effects of CPB and prolonged myocardial ischemia. Currently, the “port-access” approach is performed under direct vision through a 5- to 8-cm thoracotomy port.21Since May of 1998, in at least 3 European centers, thoracoscopic attempts at coronary surgery on the arrested heart have been resumed with the aid of recently developed 3D visualization and master-slave robotic surgery systems. The latter systems will soon open the way to thoracoscopic bypass grafting on the beating heart using a stabilizer suited to closed-chest application.14 Ultimately, however, a facilitated coronary anastomosis technique, as for example a stapling device,29 once modified for thoracoscopic application, may allow closed-chest beating-heart coronary surgery by relatively simple and inexpensive means.ConclusionsEarly reports begin to provide support for the postulated benefits of coronary surgery on the beating heart (whether through full or limited access): less mortality and morbidity, earlier return to normal activities, lower costs, and equivalent angiographic quality of the bypasses and event-free survival in the first year. In most hands, optimal coronary immobilization by a mechanical stabilizer remains a prerequisite to construct a technically satisfactory distal anastomosis.20The major obstacle to beating-heart coronary surgery is hemodynamic deterioration when, in a median sternotomy approach, the posterior side of the beating heart is exposed. There are no fundamental reasons, however, to assume that this obstacle cannot be largely surmounted in the near future. In addition, the issue of “completeness” in revascularization deserves reconsideration. In some instances, the cardiac surgeon and the interventional cardiologist may join therapeutic hands.Reduction in access in combination with maintaining direct vision is likely to contribute in selected cases to a further reduction in adverse effects. Closed-chest coronary stabilization methods, 3D visualization, and thoracoscopic master-slave robotic surgery systems will allow closed-chest CABG without CPB in the near future. Facilitated anastomosis techniques may accelerate this development at lower costs.It is conceivable that 5 years hence >50% of coronary surgery will be performed on the beating heart, mainly with arterial conduits, in part through limited access and, depending on costs, in part through the closed-chest approach. These formidable changes in surgical strategy and methods require careful exploration in small incremental steps. One ought not to be deterred from searching for solutions to great technical and surgical challenges,1 if so much is ultimately to be gained for so many patients.The opinions expressed in this editorial are not necessarily those of the editors or of the American Heart Association. Table 1. Complications CABG-Only Patients in the United States, 1996First Operation (n=157 159)Reoperation (n=13 736)OperativeMortality all CABG-only2.67.3First operation, elective1.85.4Perioperative myocardial infarction1.13.4Reoperation4.67.4For bleeding2.23.1NeurologicalStroke2.43.1Permanent1.72.2Transient0.70.8Delirium2.22.9Continuous coma >24 h0.40.9PulmonaryEndotracheal ventilation >24 h5.310.2Pneumonia2.23.8Pulmonary edema1.93.4Acute respiratory distress syndrome1.01.8RenalRenal failure2.95.2Dialysis required0.81.7GastrointestinalGastointestinal complication2.33.0VascularAcute limb ischemia0.40.8MultiorganMultisystem failure0.61.4OtherAtrial fibrillation18.217.5Cardiac arrest1.43.8Heart block requiring permanent pacemaker0.71.0Anticoagulant complication0.50.6Tamponade0.40.5InfectionSternal infection1.31.5Leg infection1.31.5Urinary tract infection1.41.4Septicemia0.91.6No complication listed65.959.4Readmission ≤30 days4.54.9Values are percentages. Source: STS National Cardiac Surgery Database (January 1998), pp 108 and 149.FootnotesCorrespondence to Cornelius Borst, MD, PhD, Professor of Experimental Cardiology, Heart Lung Institute, Utrecht University Hospital (Room G02.523), PO Box 85500, 3508 GA Utrecht, Netherlands. E-mail [email protected] References 1 Bonchek LI, Ullyot DJ. Minimally invasive coronary bypass: a dissenting opinion. Circulation.1998; 98:495–497.CrossrefMedlineGoogle Scholar2 Cowper PA, Peterson ED, DeLong ER, Jollis JG, Muhlbaier LH, Mark DB. Impact of early discharge after coronary artery bypass graft surgery on rates of hospital readmission and death. J Am Coll Cardiol.1997; 30:908–913.CrossrefMedlineGoogle Scholar3 Roach GW, Kanchuger M, Mangano CM, Newman M, Nussmeier N, Wolman R, Aggarwal A, Marschall K, Graham SH, Ley C, Ozanne G, Mangano DT. Adverse cerebral outcomes after coronary bypass surgery. N Engl J Med.1996; 335:1857–1863.CrossrefMedlineGoogle Scholar4 Favaloro RG. 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