Introduction The profession of cardiothoracic surgery is facing many challenges. The forces affecting cardiac surgeons today are similar to those that affected vascular surgeons 5 to 7 years ago. Cardiologists and vascular surgeons have developed catheter-based skill sets that are being used to treat cardiovascular disease with less invasive approaches. Cardiac surgeons are now at a crossroads and many are learning these minimally invasive techniques. The future of cardiothoracic surgery will be determined by the net result of five unique forces: (1) a decrease in referrals for coronary revascularization with an increase in referrals for valvular disease; (2) an aging population with cardiovascular disease remaining the most common cause of death; (3) a decline in interest in the field of cardiothoracic surgery by general surgery residents and medical students; (4) a predicted shortage of cardiac surgeons; and (5) the development of new minimally invasive techniques by cardiac surgeons and cardiologists. Each of these influences will be further investigated.
Decrease in Coronary Revascularization/ Increase in Valve Procedures
Data from the American College of Cardiology National Cardiovascular Data Registry (ACC NCDR) indicate a decrease in the number of diagnostic catheterizations and percutaneous coronary interventions (PCI) per institution from 2004 to 2006. Diagnostic catheterizations decreased from 1600 cases/institution in 2004 to 1440 cases/institution in 2006. Similarly, PCI decreased from 800 cases/institution in 2004 to 710 cases/institution in 2006.1 Thus, there is strong evidence for a decline in the number of cardiac catheterizations performed in the United States. Potential explanations for this include improved medical treatment with beta-blockers, statin therapy, and ACE-inhibitors, as well as improvements in PCI with the advent of drug-eluting stents (DES) in 2003. Over the last 5 years, the number of patients being referred for coronary artery bypass grafting (CABG) has also decreased, likely as a result of less catheterizations, improvements in stent technology, and aggressive percutaneous interventions including stenting of triple-vessel disease, left main disease, and bifurcating lesions. These improvements in medical therapies have resulted in a decrease in the number of CABG operations by 28% from 1997 to 2004.2,3 In contrast, data from the National Inpatient Sample have documented an increase in the number of valve operations by 28% and an increase in the number of “other” open-heart operations by 24% over the last 10 years.4 Data collected by the Society of Thoracic Surgeons (STS) also support a change in the type of cardiac operations performed in the United States. In 1997, isolated CABG comprised 76% of all cardiac operations, but by 2006, this number had declined to 60%5 (Figure 1). The proportion of aortic and mitral valve operations increased from 14% to 19% from 1997 to 2006. Moreover, the proportion of other cardiac operations including ventricular assist devices, aortic aneurysm repair, and arrhythmia surgery increased from 10% to 20% during the same time period. General thoracic operations, including lobectomies and pneumonectomies have increased by more than 10% compared to the previous decade.4 These data collectively indicate a change in the case mix in cardiac surgery, with a shift from CABG to valve and other operations. There have previously been concerns that CABG will be eliminated by the continued improvements in PCI. To date, no stent has even approached the long-term patency rates the internal mammary artery provides. On the contrary, there have been suggestions of an increase in the need for CABG in the near future, as there appears to be natural progression of disease in stented patients. Moreover, the use of DES may decline due to several recent reports of in-stent thrombosis with off-label use.6 With more than 50% of DES inserted for off-label use, the U.S. Food & Drug Administration has issued a warning that DES may cause death in these patients.7
The National Center for Health Statistics and the U.S. Census Bureau have projected a significant increase in the American population, with the highest population growth among the elderly (Figure 2). The U.S. population > or = 65 years of age is 37 million persons and is increasing by > 2% yearly.8 Furthermore, the aging Baby Boom population (born 1946 to 1964, post World War II) comprises 30% of the population. In 2011, the first of the “Baby-Boom” generation will turn 65.9 By 2029, all of the members of the Baby-Boom generation will be at least 65 years old.9 The population of 65–74-year-old is projected to increase from 6% of the population in 2005 to 10% of the population in 20308 (Figure 3). The population of those 75 years or older will increase from 6% in 2005 to 9% in 2030 to 12% in 2050.8 In summary, the elderly population (> or = 65 years) is expected to increase 100% by 2030.8,9 Not only is a large proportion of the population aging, but the life expectancy is also continuing to rise. The average life expectancy for a 65-year-old in the United States has increased from 17.4 years in 1995 to 18.4 years in 2003.10 Similarly, the average life expectancy for an 85-year-old has increased from 6.0 years in 1995 to 6.8 years in 2003.10 Cardiac disease remains the leading cause of death in the United States among all different race and sex groups.11 More than two-thirds of Americans over the age of 65 have cardiovascular disease.11 In 2003, heart disease accounted for more than 563,000 deaths or 31% of all cause mortality.8 Over the last two decades, there has been a decrease in the death rate for heart disease. From 1979 to 1997, the death rate from cardiac diseases has decreased by 20% in blacks and by 37% in whites.11 Improvements in treatment and access to health care have been proposed as explanations for the decrease in cardiac mortality.
Predicted Shortage of Cardiac Surgeons
Despite improved survival from cardiac diseases, there is expected to be a shortage of cardiovascular specialists, relative to the aging population. A recent study has been performed by the Association of American Medical Colleges (AAMC) in conjunction with STS and the American Association for Thoracic Surgery (AATS) to project future workforce needs in cardiothoracic surgery. The American Medical Association (AMA) Masterfile identified 4,700 physicians who reported their primary specialty as cardiothoracic surgery. According to the AMA, over 50% of active cardiothoracic surgeons are over the age of 55 (compared to 33% of all physicians) and 15% are over the age of 65. The data are consistent with surveys of members of the STS and AATS.12 Due to an aging workforce in cardiothoracic surgery, an estimated 54% of the current workforce is expected to retire in the next 12 years. The report by the AAMC was based on estimates including the aging cardiac surgery workforce, an aging population, and made the assumption that open revascularization for coronary artery disease (CABG) would be completely replaced by PCI. CABG accounts for nearly 40% of the relative value units for practicing cardiothoracic surgeons. The AAMC modeled different potential scenarios for the number of finishing cardiothoracic residents. Even with assumptions that every available training program is filled (130 positions/year), the AAMC has projected a shortage of 1,500 cardiothoracic surgeons, or 25% of the workforce, by 2025. These are conservative estimates, with the assumption that CABG will be eliminated. In reality, most consider complete elimination of CABG to be unlikely.
Decline in Interest in Cardiac Surgery
Interest in general surgery has been relatively stable over the last several years. With the institution of the 80-hour work week and focus on resident education, applications in general surgery rebounded from a fall in applications in 2002. From 2003–2007, over 99% of the approximately 1,050 available PGY-1 general surgery slots were filled through the NRMP match program.13 The proportion of U.S. medical school graduates has decreased from 85% in 2004 to 78% in 2007,13 indicating that more positions are being filled by foreign medical school graduates. While there appears to be relatively stable interest in general surgery, interest in cardiothoracic surgery has declined. The NRMP match in thoracic surgery (includes both general thoracic and cardiothoracic tracks) show a decline in the number of applicants in thoracic surgery residency over the last several years (Figure 4). Data from the 2007 match indicate that nearly 40% of the 92 programs and 33% of the 130 positions were not filled14 (Figure 5). Furthermore, only 70 applicants in 2007 were U.S. graduates. Reasons for this lack of interest in cardiothoracic surgery likely include significant work hours, lack of compensation, and poor job prospects. Surveys of physicians indicate that cardiothoracic surgeons work more than 60 hours per week on average. In fact, younger cardiothoracic surgeons may work as many as 84 hours per week.15 Medicare reimbursement for cardiac surgery has seen dramatic reductions since the 1980s. As a result of Medicare reform in the early 1990s, reimbursement for CABG fell by more than 50% compared to reimbursement in the 1980s.16 In 2002, CABG reimbursement by Medicare had decreased by 38% compared to the 1990s,17 a trend that has continued over the last 5 years. Residents in cardiothoracic surgery cite dwindling reimbursement rates and limited job selection as the two biggest concerns with the field. A recent poll of graduates from approved cardiothoracic surgery programs in the U.S. identified significant difficulties in finding suitable job placement.18 In this report, 16% of those polled did not receive a single job interview, and 80% of those who sought additional training did so as a result of an inability to find a suitable job. Over 80% reported difficulty in finding a job. Importantly, almost one-fourth of those polled would not choose a career in cardiothoracic surgery again, and more than half would not recommend the field to potential trainees. Finally, training in all surgical subspecialties, including cardiothoracic surgery, is exceedingly long with our current training system. The mean number of years required to complete training in cardiothoracic surgery is 8.6 years.18 Due to concerns that length of training has deterred applicants from the field, the ACGME has recently approved a 6-year training paradigm upon completion of medical school for cardiothoracic surgery. The aforementioned factors have resulted in a decline in interest in the field of cardiothoracic surgery.
Minimally Invasive Techniques and Future Directions
For more than three decades, cardiothoracic surgeons primarily performed one operation: CABG. Improvements have been made in this operation, including choice of conduit, cardioplegia techniques, and improvements in cardiopulmonary bypass, allowing critically ill patients to undergo this operation safely. During the same time period, cardiothoracic surgeons have reduced their involvement in vascular surgery and have given up pacemaker implantations. Until recently, there has been little innovation or widespread acceptance of new approaches in cardiac surgery. Interventional cardiologists have made PCI safe with good mid-term results. As a result of changes in the management of patients with coronary disease, cardiothoracic surgeons have had to develop alternative, less invasive approaches.
Coronary Artery Revascularization
It has been suggested that vein graft patency may not be superior to PCI, with up to a 28% graft failure rate at 18 months.19 However, the long-term patency for arterial grafts, specifically the left internal mammary artery (LIMA), has not been matched with current stents. This has led to the promotion of “hybrid” approaches to coronary revascularization.20,21 In patients with multivessel disease, the LIMA is harvested and anastomosed to the left anterior descending artery off-pump via a mini-sternotomy or small thoracotomy.20 This surgical revascularization can also be performed entirely endoscopically with robotic assistance.21 In the same setting, PCI of the other significant lesions is performed. Whether this approach will be superior to complete surgical revascularization is not yet clear; however, it is evident that many patients seek this less invasive approach.
Valve surgery has benefited from improvements in valve prostheses and more aggressive and successful valve repair. Importantly, catheter-based technology is evolving to treat valvular disease. A device to treat mitral leaflet pathology in patients with mitral regurgitation has been developed. The E-valve® device (E-valve, Menlo Park, California) can secure both leaflets of the mitral valve together to treat regurgitation and has been used with acceptable term results in clinical trials. Percutaneous or transapical aortic valve replacement has been performed with relative short-term success in high-risk patients. Limitations in the past have been related to the approach to deliver the device as well as identifying the optimal imaging technique, since the valve needs to be placed below the coronary arteries. In Vancouver, percutaneous transfemoral aortic valves were placed in 50 high-risk patients, with an 86% success rate, and a 12% 30-day mortality rate.22 In those patients who survived, the valve remained functional for 1 year. Transapical, beating-heart aortic valve replacement may allow for more control during delivery and offers similar results of 14% 30-day mortality and 43% 6-month mortality in high-risk surgical candidates.23 Current first-generation devices are clearly inferior to open-surgical valve replacement. As technology improves, second- and third- generation devices are expected to become safer and more durable. The long-term success of these devices compared to conventional open-valve replacement will need to be determined. Cardiac surgeons will need to continue to be involved in this evolving technology.
The treatment of aortic aneurysms has evolved with cardiac surgeons learning to treat these using less invasive approaches. Endovascular repair of thoracic aortic aneurysms has proven to have a lower complication rate, while offering equivalent mid-term results to conventional open repair. Endovascular repair may be the preferred treatment in elderly patients (? 75 years of age), with a 5% mortality rate and 11% stroke rate.24 At the University of Virginia since 2002, more than 50% of all descending thoracic aortic disease (aneurysms, dissections, and traumatic aortic injuries) have been treated with an endovascular approach. Although technically more challenging, the ascending aorta has also been treated successfully with endovascular repair.25 Limitations include the narrow margin for error between the coronary and innominate arteries, the length of the delivery device, and the left ventricular ejection fraction during deployment.25 Cardiac surgeons have been slower than our vascular surgery colleagues to embrace endovascular approaches due to limited training centers. As more cardiac surgeons acquire these skill sets, it is anticipated that more training centers will become available. At present, there are still technical limitations to the endovascular treatment of the aortic arch due to the great-vessel branches.
There has been significant growth in surgical treatment of arrhythmias. Atrial fibrillation (AF) affects nearly 2.5 million Americans and is increasing. Estimates suggest a 25% lifetime risk of AF for patients > 40 years of age.26 AF carries a six-fold increase in the risk of stroke.27 Percutaneous treatment of AF is challenging and time-consuming, as most electrophysiologists attempt to isolate pulmonary veins with full -thickness lesions. A traditional cut-and-sew Cox-Maze eliminates AF in more than 95% of patients, with long-term follow up, but often exposes these patients to long cross-clamp and cardiopulmonary bypass times.28 Importantly, the drivers for AF have been identified epicardial surface of the pulmonary veins.29 These challenges in the treatment of AF have resulted in the development of new surgical treatments primarily involving anatomic lesions similar to a traditional Cox-Maze operation, but using energy sources to create these full-thickness lesions. Industry has responded with the development of multiple energy sources to create these lesion sets including radiofrequency, microwave, cryoablation, and ultrasound. Treatment of AF is still commonly performed during concomitant cardiac operations such as mitral valve surgery. The treatment of lone AF is becoming more common using minimally invasive approaches without cardiopulmonary bypass. These techniques range from single to bilateral mini-thoracotomies, to unilateral or bilateral thoracoscopic ablation and removal of the left atrial appendage. The results of these approaches vary from 60–90% success.30,31 Reasons for such discrepancy in the literature are due to different patient populations (permanent vs. paroxysmal AF), differing monitoring techniques to detect AF (electrocardiogram vs. Holter monitor), and varying length of follow up. As this is an active area of industry research and development, future technologies including intraoperative mapping and better energy sources will improve current results.
Heart Failure Surgery
An area of potential significant growth in cardiac surgery is in the treatment of heart failure. More than 5 million Americans carry a diagnosis of heart failure and 500,000 patients are diagnosed yearly.32 In the United States, the diagnosis of heart failure is the most common cause of hospital admission in elderly patients.33 The number of patients undergoing heart transplantation has only modestly increased due to a shortage of organ donors. Currently, approximately 2,000–2,500 heart transplants are performed yearly compared to 14,000 eligible patients each year.34 Left ventricular assist devices (LVAD) were initially devised as a “bridge-to-transplant” to allow patients time until a suitable donor became available. Multiple devices have been developed for this indication. Only one device has Food & Drug Administration approval for use as “destination therapy” in patients who are not candidates for heart transplantation. Newer devices are smaller and easier to insert than older, bulkier devices which have narrow patient size limitations. As the population in the United States ages, surgery for heart failure is expected to become more common.
Robotic Cardiac Surgery
Robotic cardiac surgery has created significant excitement in the field and the public eye. Many of the operations currently performed via a traditional median sternotomy have been successfully performed using the da Vinci robot (Intuitive Surgical, Mountain View, California), including: mitral valve repair, atrial septal defect closure, CABG, left ventricular lead insertion, and aortic valve replacement.35 Recent improvements in this technology include three-dimensional vision, a wider choice of instruments, and superior range of motion.35 Benefits over conventional approaches include improved visualization, less pain, and improved patient satisfaction compared to traditional approaches. There are several limitations to this technology at present, including specific patient selection (based on body size and habitus), difficulty in training surgeons, and long cardiopulmonary bypass and cross-clamp times. Nevertheless, this remains an exciting aspect of cardiothoracic surgery that is anticipated to evolve with further improvements in technology.
Cardiothoracic surgery is under the influence of several unique forces. It is anticipated that there will be a significant workforce shortage given the aging population and decline in interest in the field. Reimbursement may shift in response to supply-demand economics. In the past, cardiac surgeons have been viewed primarily as technicians, far different from our vascular and general thoracic surgery colleagues who have become specialists in disease management. In a similar manner, cardiac surgeons need to become masters of specific disease processes such as coronary artery disease, valve diseases, aneurysmal diseases, and arrhythmias. Our training will continue to evolve with dedicated time to learn catheter-based skills and imaging skills. Cardiothoracic surgery still remains a rewarding and fulfilling field that continues to evolve based on the needs of the population. Technology has embraced new avenues of development in cardiac surgery. The future of cardiothoracic surgery, though it will be significantly different from the past, is bright.