| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
EDITORIAL |
United Kingdom
The Ross operation has many unique and intricate features, which need to be defined and understood if the operation is to achieve its potential. Although the operation was described nearly 35 years ago, it has continued to evolve through gradual understanding of the complex but elegant anatomic and physiological processes involved in execution of the operation as well as adaptation of the pulmonary valve to its new environment, coupled with the application of sophisticated methods of analysing the results of the operation. All of this has resulted in the accumulation of a large amount of knowledge, which strongly suggests that this operation could have an important, unique and wider role to play in the field of valve surgery provided that certain details are adhered to. Some of this knowledge is reviewed in this editorial.
Detailed studies of the form and function of the normal aortic valve have shown that this valve performs extremely sophisticated functions which depend largely on the biological properties of the valve at cellular and molecular level1–4 and are critically dependent on continued viability of the valve. The Ross operation is the only form of valve replacement which guarantees viability of the valve substitute both in the short and long term. We theorise that this should translate into clinical benefit both in terms of survival and quality of life. Recent studies using microsimulation to compare the pattern of survival of the Ross operation to the general population, have shown similar pattern of survival in the two groups which is significantly better than that observed after aortic valve replacement using other types of substitutes.5 Excellent postoperative survival after the Ross operation have been described by several authors6,7 including the article published in the "journal".8 Although it could be argued that these findings are due to patient selection, many of the reported series have included a significant number of high-risk patients such as those with active infective endocarditis or redo operations. Furthermore a prospective randomised trial to compare the Ross operation to homograft has shown enhanced survival after the Ross operation9 confirming the notion that continued viability of the valve can translate into major clinical benefit. Further larger prospective randomised trials, possibly multi centre are needed to confirm or refute these potentially important preliminary observations. Other aspects of the Ross operation which has evolved concern major technical modifications and refinements of the technique of explantation and insertion of the pulmonary autograft to minimise coronary and myocardial injury during explantation and attempt to eliminate the incidence of late dilatation of the autograft while avoiding the use of any foreign prosthetic material such as Teflon or Dacron strips which could defeat the purpose of the operation.
The original Ross operation involved insertion of the autologous pulmonary valve in the subcoronary position using two suture lines. This technique has the theoretical advantage of retaining normal aortic wall around the autograft which is thought to prevent progressive dilatation of the autograft root. This technique however has the potential of distorting the autograft. Although valves inserted by this technique can last for periods of up to 35 years,10 we have observed calcification in one of the cusps of the autograft which had to be due to abnormal movements of the cusps secondary to distortion. The technique of full aortic (or pulmonary) root replacement was originally introduced to maintain the exact relationship of the semilunar valve mechanism11 and have been shown to be an independent predictor of better survival and less degeneration following aortic homograft valve replacement.12 If that technique is used however, we believe that it is essential to use multiple interrupted sutures for the lower suture line with scalloping of the autograft to allow the hinge mechanism to be supported by the native aortic annulus. Another evolutionary point in the Ross operation is the inherent capacity to adapt to the new environment by altering its structure and physical properties.13 This however, does not occur immediately after the operation and therefore the newly implanted autograft root should not be subjected to pressure higher than 110/80 which could predispose to progressive root dilatation and/or chronic dissection of the arterial wall of the pulmonary autograft root.
Another aspect of the Ross operation which needs to evolve is development of stenosis of the pulmonary homograft in the right ventricular outflow. This process develops mainly during the first 18 months after operation14 and affects approximately 10% of patients. The exact cause of the process is unknown but appear to be due to an inflammatory process around the walls of the homograft rather than an immunological process affecting the homograft itself. At least two strategies have been proposed to prevent this complication, the first consists of the use of decellularized allografts15 while the second consists of the use of non steroidal anti-inflammatory drugs during the first three months. Neither of these methods have been shown to be effective. A definitive solution could be the use of a living tissue engineered pulmonary valve in the future.16 The Ross operation has evolved extensively and is probably the best form of valve replacement available today, however further evolution is required to perfect this operation and widen its application.
REFERENCES
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |
