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Department of Cardiac Surgery, University of Leicester, Glenfield Hospital, Groby Rd, Leicester, LE3 9QP United Kingdom
(Email: mg50{at}le.ac.uk).
The issue of what to do with a patent left internal thoracic artery (LITA) during cardiac reoperations is of paramount importance because it may affect the complexity of the surgical procedure to be carried out, the quality of the myocardial protection obtained, and as a result, the operative morbidity and mortality. Therefore, we have read with great interest the article by Smith and colleagues [1] in which they question whether a patent LITA needs to be clamped in reoperative cardiac surgery. This was a prospective, nonrandomized study, and although the authors tested the fitness of the statistical analysis performed, the choice of clamping the LITA graft or not was probably determined by the degree of adhesions and the difficulty of the dissection, thus introducing a selection bias that could be crucial for the interpretation of the results. By investigating the outcome on perioperative mortality only, this study is also limited in scope, and the crucial question on whether the clamping of the LITA affects myocardial protection remains unanswered. These shortcomings are recognized by the authors who then propose to undertake more elaborate and rigorously performed evaluations.
In our opinion, the dogma of the need for clamping the graft for better myocardial protection is unjustified and for more than 12 years we have adopted the policy of not dissecting and not clamping the LITA, as suggested by Lytle and colleagues [2], with excellent clinical results. Contrary to this dogma, greater myocardial ischemic injury would be expected if the LITA is clamped when most or all of the blood supply to the left anterior wall of the left ventricle completely relies on a patent LITA (eg, occlusion or severe obstruction on the proximal left anterior descending coronary artery) so that cardioplegia delivered through the aortic root cannot be homogenously distributed. In experimental animal studies we have demonstrated that the heterogeneous distribution of cardioplegia determined by the presence of severe coronary artery stenoses or occlusions results in reduced myocardial protection rendering the heart more susceptible to ischemic injury [3]. Also, the clinical experience with redo aortic and mitral valve surgery in the presence of a patent LITA supports the view that leaving the LITA undissected and unclamped is associated with good results [4, 5]. Furthermore, because the myocardium is constantly perfused by the opened LITA during aortic cross clamp, there will not be the need for additional protective interventions, such as deep hypothermia or retrograde coronary sinus infusion of cardioplegia. Based on the same principle, a similar approach can be used for other patent coronary bypass grafts. In summary, we advocate that patent LITA grafts should not be dissected and clamped during redo cardiac surgery, and that no special measures are needed to protect the myocardium that is adequately perfused. With the present evidence and knowledge, one wonders whether it is reasonable and justifiable to carry out more randomized studies subjecting patients to the potential risks of graft injury, inadequate myocardial protection, and greater mortality.
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  C. B. Park, R. M. Suri, H. M. Burkhart, K. L. Greason, J. A. Dearani, H. V. Schaff, and T. M. Sundt III What is the optimal myocardial preservation strategy at re-operation for aortic valve replacement in the presence of a patent internal thoracic artery? Eur J Cardiothorac Surg, June 1, 2011; 39(6): 861 - 865. [Abstract] [Full Text] [PDF]
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