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Ann Thorac Surg 2003;76:S2240-S2245
© 2003 The Society of Thoracic Surgeons
a Cardiopulmonary Research Science and Technology Institute and Medical City Dallas Hospital, Dallas, Texas, USA
* Address reprint requests to Dr Mack, 7777 Forest Lane, Suite A323, Dallas, TX 75230, USA.
e-mail: mjmack{at}earthlink.net
Presented at the symposium, "Gibbon & His Heart-Lung Machine: 50 Years & Beyond," Philadelphia, PA, May 2, 2003.
Abstract
Initial pioneering efforts of direct coronary artery bypass were all performed on a beating heart. Although originally introduced into cardiac surgery for the repair of intracardiac defects, the ability of John Gibbon's heart-lung machine to create a motionless, bloodless operative field catalyzed coronary artery bypass surgery. During the ensuing decades tens of millions of patients benefited from coronary revascularization on cardiopulmonary bypass. As we celebrate the 50th anniversary of the invention of the heart-lung machine the landscape of interventional treatment of coronary artery disease has shifted dramatically. Although instrumental in the genesis of the field of coronary revascularization, the role of the heart-lung machine has now diminished. Two thirds of all coronary revascularization is now performed by percutaneous approaches and one fourth of all coronary artery bypass grafting procedures are performed without the heart-lung machine. However owing to the complexity of patients now requiring revascularization as well as recently introduced incremental improvements to cardiopulmonary bypass including coated, low prime circuits, closed integrated systems, and pharmacologic adjuncts Gibbon's heart-lung machine will continue to play an integral role in this field.
At this 50th anniversary of the invention of the heart-lung machine it is fitting to acknowledge the central role that the invention and its development has played in the management of coronary artery disease. There is probably no medical device that has had a greater impact on patient's lives and influenced the management of a disease more than John Gibbon's heart-lung machine. I am humbled by the opportunity to place in perspective the central role of Dr Gibbon and his magnificent machine at this symposium of the true giants of cardiac surgery. The ensuing 50 years since the successful introduction of the heart-lung machine in clinical practice have seen dramatic paradigm shifts in the management of coronary artery disease. From the risk factor modification by diet, lipid-lowering agents, smoking cessation, exercise, and medical therapy to the introduction in the 1970s of catheter-based intervention, to the rediscovery of "pumpless" coronary artery bypass grafting in the late 1990s, disease management of ischemic heart disease has shifted dramatically. Before addressing the central role of the heart-lung machine in surgery for coronary artery disease I will first address the antecedent events that set the stage for the introduction of cardiopulmonary bypass into the treatment of coronary artery disease.
The first 50 years
Early surgical treatment of coronary artery disease
The surgical treatment of coronary artery disease began in the early part of the 20th century. It had been recognized in the mid-19th century that there was an association between coronary artery obstruction and the clinical syndrome of angina pectoris. The initial human surgical attempts to relieve angina were by a thoracocervical sympathectomy to denervate the heart in 1913. Subsequent surgical attempts included thyroidectomy to lower the metabolic demands placed upon the heart [1]. However it was actually about this time that the father of vascular surgery, Alexis Carrel, began investigation into the field of improving blood supply to the heart. He anastomosed an innominate artery of a dog to the coronary artery of a second dog on a beating heart in 1910 [2]. He also made the assessment at that time that it would be optimal to develop a heart-lung machine to stop the heart and protect the brain while performing the anastomosis.
Attempts in humans to more directly address coronary artery disease would wait a number of decades however. In 1935 Claude Beck devised a procedure in which he abraded the pericardium and grafted pectoralis muscle or omentum as a method of stimulating additional myocardial blood supply [3]. Beck subsequently developed two other procedures, the Beck I operation in which he added a partial occlusion of the coronary sinus and the Beck II operation in which the brachial artery was interposed between the aorta and coronary sinus to retrograde perfuse the myocardium along with partial ligation of the coronary sinus [4, 5].
Subsequently other attempts to increase myocardial blood flow were stimulated by the work of Vineberg who in 1946 implanted the cut end of an internal mammary artery directly into the myocardium and performed this operation in hundreds of patients during the next 15 years [6]. Direct coronary artery bypass grafting was first demonstrated experimentally by Demikhov in 1952 using an internal mammary artery graft experimentally in dogs [7]. In 1957 Bailey reported coronary endarterectomy in humans and in the following year Longmire also reported successful coronary endarterectomy [8, 9].
The field of coronary revascularization was given a significant unexpected boost by the inadvertent discovery of direct coronary angiography by Mason Sones at the Cleveland Clinic in 1959 during performance of aortography [10, 11]. This technique of directly demonstrating the sites of coronary obstruction radiographically significantly catalyzed the whole field. The first internal mammary artery graft in humans was performed by Kolesov on a beating heart in Leningrad in 1964 [12]. With a recent resurgence of interest in beating heart surgery these initial historical chapters have recently been eloquently retold by Dr Kolesov's son, Evengenii, in many beating heart surgery symposiums.
Introduction of the Heart-Lung machine
Inventions usually occur to address an unmet need. Frequently however the ultimate, most impactful application of an invention is not the one for which it was designed or intended but one that was never envisioned by its inventor. There are a plethora of examples of this throughout history from portable telecommunications to personal computers to spin-offs from the space program. Gibbons original intent in inventing the heart-lung machine was of course to be able to surgically repair intracardiac defects. Doctor Gibbon began developing an artificial device for bypassing the heart and lungs in 1931 [12]. By 1935 he had successfully used a prototype heart-lung bypass machine to keep a cat alive for 26 minutes. After the interruption of World War II a series of new experiments in dogs in the 1950s commenced using IBM-built machines and culminated in the first successful use of the heart-lung machine in humans (Figs 1 and 2).
On May 6, 1953, an 18-year-old woman became the first human to successfully undergo open heart surgery with a machine totally supporting her heart and lung function [13].
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By 1971 Favoloro and Effler at the Cleveland Clinic reported on 741 cases of coronary artery bypass grafting performed with saphenous vein grafts and cardiopulmonary bypass on an arrested heart [16].
The ultimate value of a disruptive technology such as cardiopulmonary bypass is due not necessarily to the original invention alone but to the subsequent incremental improvements. Indeed many incremental improvements in cardiopulmonary bypass surgery have been made in the last 40 years that have enhanced both early and late outcomes by decreasing procedural morbidity and enhancing user friendliness. Such incremental improvements include replacing roller pumps with centrifugal pumps, bubble oxygenators with membrane oxygenators, and new cannula designs and circuit coating. Perioperative morbidity and mortality have been further reduced by improvements in myocardial protection by the introduction of crystalloid cardioplegia and subsequently blood cardioplegia and retrograde myocardial preservation techniques [17]. The long-term results of the operation were significantly improved by the widespread use of arterial grafting [18–20]. Despite the significant incremental improvements made, significant adverse events still occur owing to the use of cardiopulmonary bypass. The inflammatory response generated by the exposure to nonendothelial cell surfaces of blood during cardiopulmonary bypass incites a powerful inflammatory response that causes the release of a host of microembolic, vasoactive, cytotoxic substances that affect every organ and tissue within the body [21].
The next 50 years
Percutaneous coronary intervention
The enduring nature of coronary artery bypass grafting bespeaks of its long history, safety, and efficacy. It is a proven operation that can be reproducibly performed by a wide variety of surgeons with varying degrees of skill and acumen with generally good results. However there are significant complications of this procedure that may negate an otherwise successful result. History is replete with examples of the introduction of new technology that has significantly impacted the status quo. The examples of such disruptive technology include the replacement of silver film photography with digital techniques; the disruptive technology of cellular telecommunications has forever impacted the wire line telephone, digital printing has totally replaced offset printing, and closer to home the introduction of such disruptive technology as percutaneous coronary intervention by Greunitzig in 1979 and its subsequent iterative improvements has significantly affected the role of coronary artery bypass grafting in the management of coronary artery disease [22]. Although the number of coronary artery bypass graft procedures performed has doubled in the 24 years between 1979 and 2003 to approximately 800,000 procedures worldwide, the growth in percutaneous coronary intervention (PCI) has increased even more dramatically and eclipsed by a wide margin the number of interventions performed by a surgical approach. Reasons for this include the less invasive nature of the revascularization procedure with less procedural mortality and morbidity. It is estimated that there will be more than 1.5 million catheter-based procedures performed worldwide this year. In the United States the margin is even greater. In a recent review of experience in the HCA, Inc hospital system, 65.5% of all coronary revascularization was performed by PCI with only one third now being performed by coronary artery bypass grafting [23]. Furthermore although the total rate of coronary revascularization is increasing by 3.3% annually, this growth is totally due to the increase in percutaneous techniques, which have been increasing at a rate of 6.8% annually with a 2% annual decrement in the number of CABG procedures performed annually. With the introduction of drug-eluting stents occurring this year the Achilles heel of PCI, restenosis, is addressed. It has been further speculated that the role of surgical coronary revascularization will continue to decrease as a proportionate share of total revascularization procedures.
Minimally invasive coronary artery bypass surgery
Beginning in the mid-1990s two new surgical revascularization strategies were introduced in attempts at reducing the invasiveness of the standard coronary artery bypass grafting (CABG) procedure performed on cardiopulmonary bypass with ischemic arrest. Revascularization either on an arrested heart with peripheral cannulation through a small access incision (port access) or on a beating heart with a limited access approach (MIDCABG) was introduced [24, 25]. The lack of demonstrated benefit and the significant technical challenge associated with the port access approach have until now limited the application of that approach for coronary revascularization [26]. In a similar manner the technical challenges associated with the MIDCABG procedure as well as the ability to perform only a single vessel bypass and the rarity of single vessel disease at the present day has served to limit this approach [27]. However the recognition of improved outcomes in selected patients by the elimination of cardiopulmonary bypass served as an impetus to develop off-pump coronary artery bypass (OPCAB) as a treatment option for patients with multivessel disease. Although the initial coronary artery bypass procedures were performed on a beating heart in the 1960s before utilization of Gibbon's heart-lung machine, the creation of a motionless, bloodless field made further attempts at developing these techniques moot. Despite significant improvements made and the introduction of suction stabilization techniques to maintain a local rather than global, relatively motionless, bloodless field the awareness of the side effects associated with the systemic inflammatory response from cardiopulmonary bypass has led to renewed interest in the beating heart technique [28]. Since its introduction by Benetti and Subramanian in 1996 off-pump surgery has continued to grow so that currently it comprises approximately 25% of all CABG procedures performed in the United States [23]. Growth has been catalyzed by the introduction of suction stabilizer and suction exposure devices as well as technique advancements (Fig 3).
There have now been more than a thousand peer review publications in the past 7 years that generally show equivalency or superiority of off-pump surgery compared with the gold standard arrested heart (on-pump) surgery. These have now been summarized in two recent reviews [29, 30]. However there are only three prospective, randomized studies comparing the two techniques [31–33]. A meta-analysis of these three trials, which comprised a total of 879 patients, reveals an off-pump mortality rate of 0.2% compared with an on-pump mortality rate of 0.9% (Table 1).
Even the meta-analyses are underpowered to show a significant difference however. In addition the incidence of stroke is less off pump compared with on pump, although again the results do not reach statistical significance (Table 2).
The percent of patients requiring transfusion is approximately 50% off-pump compared with on-pump surgery (Table 3).
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Despite the challenges posed by less invasive coronary revascularization techniques however, including drug-eluting stents, the significant incremental improvements to CABG continue to occur. Endoscopic positioners and stabilizers to facilitate limited access CABG hold the promise of truly allowing limited access beating heart multivessel coronary revascularization. The role of robotics and anastomotic devices to facilitate or eliminate sutured limited access anastomosis are also promising (Fig 6). Despite the proven benefit of long-term results with arterial grafting, saphenous vein grafts still remain the predominant conduit employed. Recently introduced have been intraoperative saphenous vein graft treatment with blockers (E2F decoy) to limit upregulation of gene expression in the vessel endothelium to prevent neointimal hyperplasia and graft arteriosclerosis and to prolong graft patency. The current Prevent IV trial is a 3,000-patient multicenter randomized trial at more than 100 STS national database sites in the United States. If results of this trial are positive as the early small pilot studies have been the long-term results of coronary artery bypass grafting could be significantly improved.
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In conclusion cardiac surgery is currently in the midst of a major paradigm shift. Coronary artery bypass grafting using current iterations of Gibbon's heart-lung machine will continue to remain a major technique for coronary artery bypass operations in the foreseeable future. However with the success of competitive revascularization techniques including off-pump CABG surgery and percutaneous techniques, the predominant role of the Gibbon heart-lung machine in coronary revascularization will continue to decrease. The road to limited access multivessel CABG surgery will continue to be a difficult one; however progress is being made. The complexity of patients undergoing surgical revascularization will continue to increase and the diversification of the procedures within cardiac surgery will continue to grow. The contribution of Gibbon's heart-lung machine will only increase in historical stature even though the future role for on-pump CABG will diminish.
References
This article has been cited by other articles:
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  G. Cipriano Jr., A. C. Camargo Carvalho, G. F. Bernardelli, and P. A. Tayar Peres Short-term transcutaneous electrical nerve stimulation after cardiac surgery: effect on pain, pulmonary function and electrical muscle activity Interactive CardioVascular and Thoracic Surgery, August 1, 2008; 7(4): 539 - 543. [Abstract] [Full Text] [PDF]
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 S. Beholz, L. Zheng, M. Rusche, M. Kessler, and W. Konertz Low-Prime System Minimizes Transfusions and Hemodilution in Coronary Bypass Asian Cardiovasc Thorac Ann, February 1, 2006; 14(1): 10 - 13. [Abstract] [Full Text] [PDF]
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