Cardiac surgery has been described as a dying specialty with the astronomical growth of the field becoming overshadowed by its impending decline. The increasing use of less invasive methods is shifting the landscape away from open surgery toward the interventional techniques already dominated by other specialties. As with all good fiction, there is a foundation of fact. However this shift in practice signals not a slide into obsolescence but a new chapter in the history of a field still in its adolescence.

New technology has always driven the field of cardiac surgery. The advent of cardiopulmonary bypass in the 1950s revolutionized the field and allowed for progression beyond the management of pericardial pathology and basic penetrating trauma to open heart surgery in a bloodless, motionless field. The concomitant identification of a vast, untapped population of patients with atherosclerotic heart disease led to an explosion of cardiac surgery as a specialty, catapulted it to the forefront of medicine, and attracted the best and brightest to the field. This seemingly unending supply of patients, however, led to an innovative complacency and self-assurance that was shattered by the introduction of percutaneous coronary intervention, which led to a reduction in the volume of coronary artery bypass operations accompanied by a decline in the number of trainees entering the field.^1,2 However, this partially consumer-driven move towards less invasive intervention represents not a decline in cardiac surgery but an evolution in the way health care providers must approach the treatment of surgical disease. The increasingly rapid progression of new technology fosters an environment of innovation and change that must lead to a new paradigm of cardiac surgery.

Nowhere is this more evident than in the current management of functional mitral regurgitation (FMR). FMR occurs when dilated cardiomyopathy leads to mitral annular dilatation and papillary muscle displacement with leaflet tethering resulting in valvular insufficiency. The mitral regurgitation then contributes to further negative ventricular remodeling and progression of disease. With a five-year mortality approaching 50%,³ current guidelines recommend surgical correction of FMR; however, there is considerable debate about whether optimal management involves mitral valve repair or replacement, with long-term recurrence rates after mitral valve repair near 70%⁴ but increased operative morbidity and mortality with mitral valve replacement.⁵ With an ongoing randomized clinical trial,⁶ the debate continues; however, technological advancements into less invasive approaches may soon overshadow discussion of the merits of open surgical repair or replacement.

The development of telemanipulative instrumentation with robotic devices has led to mitral valve operations being performed with decreased pain, bleeding, functional limitation, and hospital length of stay, as well as improved cosmesis and quality of life,⁷ with outcomes similar to traditional approaches.⁸ Despite this success, and evidence that robotic mitral valve programs can be initiated without a prohibitive learning curve,⁹ adoption in the U.S. has been low.

The poor outcomes associated with surgical treatment of FMR have also led to the development of off-pump methods of addressing FMR. The Coapsys annuloplasty system is an external ventricular reshaping device to treat FMR. Consisting of two epicardial pads connected by a cord, Coapsys is implanted under echocardiographic guidance and compresses the left ventricle at both the level of the mitral annulus and papillary muscles to improve mitral leaflet coaptation and reduce left ventricular dimensions and wall stress. The Randomized Evaluation of a Surgical Treatment for Off-Pump Repair of the Mitral Valve (RESTOR-MV) trial¹⁰ identified a two-year survival advantage of Coapsys over mitral valve repair before the trial was prematurely terminated due to lack of funding.

Percutaneous methods of mitral valve repair are also under investigation. Coronary sinus mitral valve annuloplasty devices are inserted percutaneously into the coronary sinus to constrict the mitral annulus and, thus, improve leaflet coaptation. Initial studies have shown improvement in left ventricular and mitral annular dimensions, mitral regurgitation, left ventricular function, and patient functional status, with coronary compromise identified as a complication.^11,12 The Mitralign Bident system, which places sutured pledgets directly into the posterior annulus via a catheter across the aortic valve, plicating them together to achieve reduction annuloplasty, recently completed enrollment on a European Clinical trial. The Percutaneous Septal Sinus Shortening device (PS3 System), which anchors a cord between the coronary sinus and the atrial septum and is shortened to reduce mitral annular septolateral distance, demonstrated a 30-day reduction in mitral regurgitation severity and New York Heart Association functional class in phase I clinical trials. Percutaneous edge-to-edge repair of mitral regurgitation (MitraClip) has been shown to be noninferior to open mitral valve repair at four years¹³ and has gained popularity following the Endovascular Valve Edge-to-Edge Repair Study (EVEREST) II trial. However, the annular dilatation and leaflet tethering with the resultant reduction in coaptation area seen in FMR may limit its usefulness in some of these patients.

Finally, in addition to less invasive mitral repair techniques, clinical investigation into transcatheter mitral valve implantation has begun with preliminary perioperative data suggesting feasibility in high-risk patients.¹⁴ As such, despite the advancements in less invasive technology for the treatment of mitral regurgitation the debate over whether to repair or replace in FMR is likely to continue as the durability of repair with these new technologies will be largely unknown and transcatheter valve replacement may reduce the morbidity and mortality associated with open mitral replacement.

Cardiac surgery is not dying but is in fact a specialty in its adolescence adapting to the evolution of modern medicine. New and evolving technology has always guided cardiac surgeons. The development of new technology has always shaped and driven the field of cardiac surgery, from the initial development of cardiopulmonary bypass to advancements in cardioplegia, to the development of mechanical and bioprosthetic valves, or to current technological advancements aimed at minimizing the invasiveness of surgical intervention. As patients continue to grow older and sicker, they will require progressively more complex procedures and will simultaneously demand less invasive treatments of their disease, leading to an increase in the number of combined procedures performed and the number of reinterventions necessary. As such, future cardiac surgeons will require both surgical and interventional skills as the application of endovascular and minimally invasive techniques expand.

It is the ability to adapt to and embrace new technology that has enabled the incredible growth of cardiac surgery as a specialty. However this may not be enough. Cardiac surgeons must not simply adapt to change but partner with industry, participate in prospective clinical trials, and lead with innovation to guide the future of cardiac surgery instead of simply reacting to it. Technological advancements will always be two steps ahead of proven therapies because of the time it takes to evaluate long-term clinical outcomes. For this reason, the cardiac surgeon's job will be to ensure that suboptimal treatments are not allowed to be justified by their less invasive methods. As cardiac surgery becomes isolated from the diagnostic process, the line between what is necessary and what is available becomes blurred, as exemplified by the fact that up to 30% of ad hoc percutaneous coronary interventions are performed in patients who would have benefitted from coronary artery bypass.¹⁵ Thus, surgeons must both maintain relationships with the diagnostic practitioners and stay at the forefront of technologic advances to ensure that patients receive optimal care and the most appropriate therapies. The advancement of transcatheter aortic valve replacement (TAVR) is a prime example of the need for continued close collaboration as colleagues and partners. Physicians will soon use transcatheter techniques to manage more than half of aortic stenosis cases. While current Centers for Medicare & Medicaid Services regulations require cardiac surgeon involvement in all TAVR cases, it is not enough to be a passive observer waiting for a complication – the surgeon must be an active participant in the multidisciplinary heart team helping to lead these cases.

The future of cardiac surgery hinges on the surgeon's ability to improve techniques, innovate in therapies, and diversify practice. However, personal development and education often slow or cease altogether after completion of training with reluctance of some experienced practitioners to learn new techniques. Cardiac surgeons must challenge this archetype by improving cardiac surgical residency through expansion of training techniques and clinical skill sets to include open, minimally invasive, and percutaneous techniques, improvement in simulation training, and recruitment of the best and brightest young practitioners. Cardiac surgeons must retrain, stay at the forefront of technological advancement, actively participate in prospective research, and maintain the ability to evolve with the ever-changing field of cardiac surgery. As TA English stated in an article in Thorax published in 1979, "These are difficult matters but [...] I believe they are best approached by preserving a flexible training programme that can be adjusted to meet the needs of the subspecialisation as these arise."¹⁶

References

1. Riley RF, Don CW, Powell W, Maynard C, Dean LS. Trends in coronary revascularization in the United States from 2001 to 2009: recent declines in percutaneous coronary intervention volumes. Circ Cardiovasc Qual Outcomes 2011;4:193-7.
2. Salazar JD, Ermis P, Laudito A, et al. Cardiothoracic surgery resident education: update on resident recruitment and job placement. Ann Thorac Surg 2006;82:1160-5.
3. Gillinov AM, Wierup PN, Blackstone EH, et al. Is repair preferable to replacement for ischemic mitral regurgitation? J Thorac Cardiovasc Surg 2001;122:1125-41.
4. Hung J, Papakostas L, Tahta SA, et al. Mechanism of recurrent ischemic mitral regurgitation after annuloplasty: continued LV remodeling as a moving target. Circulation 2004;110:II85-90.
5. Grossi EA, Goldberg JD, LaPietra A, et al. Ischemic mitral valve reconstruction and replacement: comparison of long-term survival and complications. J Thorac Cardiovasc Surg 2001;122:1107-24.
6. Perrault LP, Moskowitz AJ, Kron IL, et al. Optimal surgical management of severe ischemic mitral regurgitation: to repair or to replace? J Thorac Cardiovasc Surg 2012;143:1396-403.
7. Suri RM, Antiel RM, Burkhart HM, et al. Quality of life after early mitral valve repair using conventional and robotic approaches. Ann Thorac Surg 2012;93:761-9.
8. Chitwood WR, Jr., et al. Robotic mitral valve repairs in 300 patients: a single-center experience. J Thorac Cardiovasc Surg 2008;136:436-41.
9. Yaffee DW, Loulmet DF, Kelly LA, et al. Can the learning curve of totally endoscopic robotic mitral valve repair be short-circuited? Innovations (Phila) 2014;9:43-8.
10. Grossi EA, Woo YJ, Patel N, et al. Outcomes of coronary artery bypass grafting and reduction annuloplasty for functional ischemic mitral regurgitation: a prospective multicenter study (Randomized Evaluation of a Surgical Treatment for Off-Pump Repair of the Mitral Valve). J Thorac Cardiovasc Surg 2011;141:91-7.
11. Harnek J, Webb JG, Kuck KH, et al. Transcatheter implantation of the MONARC coronary sinus device for mitral regurgitation: 1-year results from the EVOLUTION phase I study (Clinical Evaluation of the Edwards Lifesciences Percutaneous Mitral Annuloplasty System for the Treatment of Mitral Regurgitation). JACC Cardiovasc Interv 2011;4:115-22.
12. Siminiak T, Wu JC, Haude M, et al. Treatment of functional mitral regurgitation by percutaneous annuloplasty: results of the TITAN Trial. Eur J Heart Fail 2012;14:931-8.
13. Mauri L, Foster E, Glower DD, et al. 4-year results of a randomized controlled trial of percutaneous repair versus surgery for mitral regurgitation. J Am Coll Cardiol 2013;62:317-28.
14. Sondergaard L, Brooks M, Ihlemann N, et al. Transcatheter mitral valve implantation via transapical approach: an early experiencedagger. Eur J Cardiothorac Surg 2015 Feb 3. [Epub ahead of print]
15. Hannan EL, et al. Predictors and outcomes of ad hoc versus non-ad hoc percutaneous coronary interventions. JACC Cardiovasc Interv 2009;2:350-6.
16. English TA. Future of cardiothoracic surgery. Thorax 1979;34:443-6.

Keywords: Adolescent, Aortic Valve, Aortic Valve Stenosis, Atrial Septum, Cardiac Surgical Procedures, Cardiomyopathy, Dilated, Cardiopulmonary Bypass, Clinical Competence, Cooperative Behavior, Coronary Artery Bypass, Coronary Sinus, Dilatation, Heart Arrest, Induced, Heart Valve Diseases, Heart Ventricles, Mitral Valve, Mitral Valve Annuloplasty, Mitral Valve Insufficiency, Pain, Papillary Muscles, Percutaneous Coronary Intervention, Prospective Studies, Quality of Life, Robotics, Surgeons, Transcatheter Aortic Valve Replacement, Ventricular Function, Left, Ventricular Remodeling

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