Ann Thorac Surg 2007;83:S832-S834
© 2007 The Society of Thoracic Surgeons
Supplement
Fifty Years of Thoracic Aortic Surgery: Lessons Learned and Future Directions
Stephen Westaby, PhD, FETCS*,
Gabriele B. Bertoni, MD
Department of Cardiac Surgery, John Radcliffe Hospital, Oxford, United Kingdom
* Address correspondence to Dr Westaby, Oxford Heart Centre, John Radcliffe Hospital, Department of Cardiac Surgery, Headley Way, Headington, Oxford OX3 9DU, UK (Email: stephen.westaby{at}orh.nhs.uk).
Presented at Aortic Surgery Symposium X, New York, NY, April 27–28, 2006.
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Abstract
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During the past 50 years, the genetic basis and natural history of aortic disease has been defined. Surgical methods evolved to reduce mortality and morbidity from bleeding, renal impairment, cerebral injury, and paraplegia. Aortic surgery is now a specialty in itself. Experienced groups achieve a mortality rate of less than 2% for root operations and less than 15% for arch surgery and aortic dissection. The introduction of stent grafts has changed the approach to vascular pathology. These are less intimidating for the patient but have unsolved risks with uncertain long-term outcome. In the future, an evidence-based balance between conventional surgical procedures versus interventional strategies is required.
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Introduction
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The year 2006 marks the 50th anniversary of the first thoracoabdominal replacement and the first ascending aortic operation using the pump oxygenator [1, 2]. These were performed by the doyens of aortic surgery, Drs DeBakey and Cooley, using aortic homografts to replace the aneurysms. As for other branches of cardiovascular surgery, the pioneering days have passed. Surgical strategies have evolved, undergone refinement, and sometimes disappeared. Endovascular stent grafting has been the last major development in aortic disease and, whilst evolving rapidly, major safety issues remain [3].
What then are the enduring lessons from the last half-century, and where will the specialty progress from here?
The aorta is a large tube. As such, it is easy to replace using the durable synthetic vascular grafts that emerged from Houston in the 1960s [4]. Major landmarks in aortic surgery are annotated in Appendix [5]. The frenetic activity occurred in the beginning; afterwards came the fine-tuning. Many major contributions were not in the technicalities of an individual operation but in decision-making or supportive management.
Aneurysm rupture and aortic dissection are catastrophic events that can be avoided by elective surgery. The timing of operation has been finely balanced between the probability of acute events versus the risk of operative mortality. In 2000, the UK Cardiac Surgical Register reported mortality rates of 14.6% for aortic root, 28% for aortic arch, and 31.5% for descending aorta replacements [6]. This created a dilemma for cardiologists who wished to refer young Marfan patients for surgery. The solution is to concentrate the patients with a smaller number of aortic enthusiasts who achieve mortality rates of less than 2% for elective root surgery and less than 10% for arch and descending operations. The simple step of creating dedicated aortic surgery centers is now as relevant as the specialist cardiac pediatric practice.
The definition of the genetic origins and natural history of aortic disease, notably by the Johns Hopkins and Yale groups, forms the basis for decision-making and cardiovascular risk screening [7, 8]. Current guidelines support intervention when the ascending aorta reaches 5.0 cm in Marfan syndrome or 5.5 cm in others (6.0 cm and 6.5 cm for the descending aorta). Svensson and colleagues [9] logically suggest that size should be related to body habitus and family history. Supporting this approach are recent findings from 591 patients in the International Registry of Aortic Dissection, of whom 40% dissected with an aortic diameter of less than 5 cm, and 59% were less than 5.5 cm [10]. Size is clearly not a sufficient marker for risk of dissection, and better predictors are required. These may be biomarkers, genetic studies, or measures of aortic function such as wall stiffness. Although leading centers supplied the data, their overall dissection mortality was 27%, leaving room for improvement.
Life expectancy in Marfan syndrome is transformed by elective aortic root surgery. The gold standard was established by Gott and colleagues using the Bentall procedure [11]. Nevertheless, the long-term morbidity from a prosthetic valve and anticoagulation is substantial for these young patients. This was the stimulus for David and Feindel [12] and others to develop native valve-sparing operations for aortic root disease. With gradual refinement, these provide excellent long-term durability with freedom from prosthetic valve complications, and as a consequence, far fewer Bentall operations are now performed. As is the case for the Ross procedure, these valve-sparing operations should not be undertaken on an occasional basis.
In surgery of the arch, descending, and thoracoabdominal aorta, specialized techniques have evolved for brain, spinal cord, and visceral protection. The outcome is determined by the propensity for ischemic injury and embolic events. All organs need oxygen, and it is probably safer to provide it. Careful studies from the Mount Sinai and Johns Hopkins groups have defined the safe duration of hypothermic circulatory arrest to be about 40 minutes at 16°C [13]; however, in many cases, this time will prove insufficient to perform an extensive resection.
As a result, antegrade perfusion of the carotid arteries, as promoted by Bachet and colleagues [14], Kazui, and others, and visceral artery perfusion popularized by Coselli and colleagues [15] in thoracoabdominal surgery, are combined with profound or moderate hypothermia. Organ perfusion reduces the risk of reperfusion injury and multiorgan failure but not paraplegia. Retrograde cerebral perfusion through the venous system has proven to be a less-than-reliable diversion.
Release from the time constraints of hypothermic circulatory arrest has important benefits. Not least is the opportunity for meticulous suturing to prevent bleeding and the deleterious effects of blood transfusion. Detailed perioperative care by using cell-saving devices, hemofiltration, and catheter interventions for postoperative malperfusion have made important contributions to reduction in hospital mortality. Antifibrinolytic agents cannot substitute for Prolene (Ethicon, Somerville, NJ) deficiency, and remain controversial particularly in the hypothermic patient [16].
Borst and colleagues [17] cleverly linked arch with descending aortic resection with the elephant trunk method, a particularly useful strategy in chronic type A dissection. Although an enduring technique, the interim and combined mortality rate of separate arch and descending aortic resections has promoted the use of extensive one-stage resections, notably by Svensson and colleagues [18] and Kouchoukos and colleagues [19]. These operations use combined sternotomy and thoracoabdominal incisions or the "bucket handle" bilateral thoracotomy method. Although resection from valve to bifurcation is feasible, it remains a daunting prospect for both patient and surgeon.
Before Dotter performed his first endovascular procedure in 1964, he commented "the angiographic catheter can be more than a tool for diagnostic observation; used with imagination it can be an important surgical instrument." Thirty years later (1994), the Stanford group introduced stent graft treatment for descending aortic aneurysms [3]. This provides the potential to link with the elephant trunk technique, thus eliminating the second open operation. Since then, catheter based coronary stents, endovascular stent grafts, and closure devices have revolutionized the treatment of cardiovascular disease, and some predict that almost all cardiovascular pathology will be managed by endovascular techniques.
Current practice requires refinement to reduce the considerable complication rate of 7% to 10% for stroke, 3% to 13% for paraplegia, and a 45% event rate in the first year [20]. Even so, leading units use stent grafts for most distal arch, descending, and abdominal aneurysms as well as traumatic aortic rupture and coarctation. More extensive high-risk aneurysms and complications of endovascular treatment are left for the surgeon. This situation has implications for training in the same way that closure of atrial and ventricular septal defects and patent ductus arteriosus have been lost from congenital heart surgery.
Where does the surgeons’ future lie in a results-orientated risk adverse environment? Salerno, at the 2006 Annual Meeting of The Society of Thoracic Surgeons, advocated training in catheter interventional skills to incorporate endovascular stenting into cardiothoracic practice. Established open operations will still improve through refinement in technique. Other advances will occur in three areas: prevention of disease, improved systems of care, and advances in technology (Table 1). As for coronary disease, antismoking campaigns, statins, blood pressure control, and genetic screening programs will reduce the surgical workload, although advanced age has the opposite effect.
Improved systems of care will develop in specialist units with close cooperation between interventionalists and surgeons. Operating rooms should be equipped for combined procedures. As outcomes improve, the threshold for intervention will fall even further. Emerging technology can be expected to play an important role in improving results, particularly for endovascular procedures where neurological injury limits success.
Although some developments are predictable, the future would not be the future if we could see it now. We must remain confident that surgery will continue to play an important role in the management of aortic disease. In the words of Winston Churchill during World War II, "Never, never, never, give up."
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Appendix
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Landmarks in Thoracic Aortic Surgery
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References
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- The Society of Cardiothoracic Surgeons of Great Britain and Ireland. National adult cardiac surgical database report 2000–001. Available at: http://www.scts.org/sections/audit/Cardiac/index.html. Accessed June 1, 2006.
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- Svensson LG, Crawford ES, Coselli JS, Safi HJ, Hess KR. Impact of cardiovascular operation on survival in the Marfan patient Circulation 1989;80:I233-I242.[Medline]
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- O’Connor JV, Wilding T, Farmer P, Sher J, Ergin MA, Griepp RB. The protective effect of profound hypothermia on the canine central nervous system during one hour of circulatory arrest Ann Thorac Surg 1986;41:255-259.[Abstract]
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- Coselli JS, Conklin LD, LeMaire SA. Thoracoabdominal aortic aneurysm repair: review and update of current strategies Ann Thorac Surg 2002;74S188–4.
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- Borst HG, Walterbusch G, Schaps D. Extensive aortic replacement using "elephant trunk" prosthesis Thorac Cardiovasc Surg 1983;31:37-40.[Medline]
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- Kouchoukos NT, Mauney MC, Masetti P, Castner CF. Single-stage repair of extensive thoracic aortic aneurysms: experience with the arch-first technique and bilateral anterior thoracotomy J Thorac Cardiovasc Surg 2004;128:669-676.[Abstract/Free Full Text]
- Svensson LG. Device discordancy: lost cords, quick-fix seekers, quality, and ethics J Thorac Cardiovasc Surg 2006;131:261-263.[Free Full Text]
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Abstract
Introduction
