MIAVS has evolved over an 18-year experience at the Cleveland Clinic in terms of the preferred incision, cannulation strategy and method of myocardial protection. A significant driver of this gradual evolution has been the overarching concern that safety be maintained with the introduction of any new surgical technique. It is notable that the initial series of parasternal aortic valve procedures reported by Cosgrove and Sabik in 1996 were performed with zero mortality. Mortality in the current era for isolated AVR continues to be low and well under the expected mortality for similar patients in the Society for Thoracic Surgery (STS) database. It is in light of this difference that Cleveland Clinic surgeons have been slow to adopt right thoracotomy approaches for aortic valve surgery despite a large experience at some other institutions. Until recently, most large series of anterior thoracotomy AVRs have reported mortality in the range of 2–3%, which is in line with STS averages but higher than would be expected for large aortic valve centers. Glauber and colleagues have shown over several recent publications a declining mortality for the thoracotomy approach, which likely reflects increasing experience and the use of central aortic cannulation.[8,10] Our small evolving experience with this approach suggests that it is a valuable tool in the MIAVS armamentarium in selected patients without need for a concomitant aortic procedure and with favorable anatomy on preoperative imaging. Our own data would suggest that upper hemisternotomy is a safe, reproducible operation that has demonstrable benefits in terms of earlier discharge, less blood utilization, decreased pain, and improved pulmonary outcomes. It may be considered the standard of care for isolated aortic valve operations and a reasonable option for concomitant procedures on the ascending aorta and root. Routine use of MIAVS combined with early conversion when necessary, and careful consideration of patients with potential contraindications results in excellent early and late outcomes that are at least comparable to sternotomy and possibly better.
The fact that MIAVS is safe and beneficial is certainly not as controversial as it once was, with a number of authors reporting large series with excellent mortality outcomes.[10–13] In contrast to many other centers, we do not select this approach routinely for reoperations. In this cohort of patients in particular, we believe the reduction of operative risk and complications to be paramount. Safe sternal re-entry, adequate exposure, identification and isolation of patent internal thoracic artery grafts and meticulous myocardial protection are considered hallmarks of the Cleveland Clinic technique for cardiac reoperations. With this approach, the morbidity and mortality of reoperation approaches that of primary operation. As increased flexibility is often needed to deal safely with the pitfalls of a reoperative field, sternotomy remains the preferred approach for these cases. For upper hemisternotomy MIAVS, we have not seen the need for routine percutaneous femoral venous cannulation, as exposure for central venous cannulation is almost always possible.
This review of the Cleveland Clinic experience in MIAVS leaves a number of unanswered questions. One significant potential benefit of MIAVS is improved patient perceptions of quality of life and post-hospital outcomes such as return to work and functional capacity. Longitudinal follow-up in these patients is limited to metrics obtained by in-patients who return to the Cleveland Clinic for evaluation and by our routine telephone screening. Anecdotal evidence would suggest that patients perceive their operation to be smaller and less impactful to their lives when performed minimally invasively. However, long-term satisfaction and patient reported outcome data are lacking in our institution. In the current era where MIAVS is preferred for most surgeons for isolated aortic valve cases, we do not have the data to suggest why sternotomy was chosen in that subset. At this point there is not sufficient evidence to explain the recent sharp increase in concomitant procedures.
In light of the overwhelming evidence that aortic valve disease remains undertreated even in patients with well established diagnoses by echocardiography, the ability to offer MIAVS is an important tool for surgeons and cardiologists to increase acceptance of aortic valve surgery. It is clear that patients do not want sternotomy when it can be avoided. Many will seek to delay surgery if sternotomy is necessary even if the benefits of surgery are clear. If a safe, reproducible minimally invasive operation can be provided, including concomitant procedures when necessary and reasonable, this artificial barrier to surgery can be reduced. The Cleveland Clinic experience represents vast numbers (over 3,000) of minimally invasive aortic valve surgeries over 18 years, with proven safety and demonstrable benefits. Surgical technique has evolved to standardize the upper hemisternotomy approach as the most flexible, allowing most cases to be conducted with central arterial and venous cannulation, and single dose cardioplegia, in addition to allowing for ascending aortic and root repair with minimal modification in technique. The standardized approach outlined here is generalizable to any experienced valve surgeon who wishes to bring the benefits of MIAVS to affected patients.
It is as yet unclear whether mini-thoracotomy MIAVS will bring additional benefits without additional morbidity. Small series from other institutions suggest a benefit over upper hemisternotomy, and this approach is attractive to many patients. We postulate that routine central cannulation will be essential to avoid an increase in stroke rate with these approaches, as may be reflected in the higher mortality of some series. Our early experience suggests that these operations can be performed with aortic cannulation and a reasonable learning curve. Future propensity matched analysis will need to determine the risk/benefit ratio of mini-thoracotomy MIAVS compared with upper hemisternotomy. In addition, short and long-term patient reported quality of life data are still lacking. Several software and mobile tools are in development at the Cleveland Clinic that may allow surgeons to better track patients' progress in terms of pain, return to work, activity level, and satisfaction once they leave the hospital.
Ann Cardiothorac Surg. 2015;4(2):140-147. © 2015 AME Publishing Company