182 Letters to the Editor coronary artery bypass grafting. We have not precluded obese, elderly, or diabetic patients from receiving bilateral IMA grafts because we believe that this procedure gives the best long-term result. We use diathermy only for pinpoint hemostasis on the presternal soft tissues and do not use bone wax; we believe strongly that these are important factors in our low rate of ster- nal infection. From January 1989 to December 1991, a total of 997 patients underwent coronary artery bypass grafting. Of these, 606 (60.8%) received bilateral IMA grafts, 373 (37.4%) received single IMA grafts, 16 (1.6%) received only vein grafts, and two received single right gastroepiploic artery grafts. Ster- nal infections occurred in only six patients (0.6%) overall, four in the bilateral IMA group (4/606), two in the single IMA group (2/373), and none in the vein graft group (0/16). Only two of these patients were diabetic, one in the single IMA group and one in the bilateral IMA group. The prevalence of diabetes was 12% overall. We do not believe that use of the IMA increases the risk of sternal wound infection. Preservation of the vitality of the presternal soft tissues is in our view the most important feature in preventing the dreaded complication of sternal infection. A. G. Jayakrishnan, MS, FRCSI A. Allan, FRCS A. T. Forsyth, FRACS J. B. Desai, FRCS, FRCS(Edin), C/Th Department of Cardiothoracic Surgery Kings College Hospital Denmark Hill London SE5 9RS United Kingdom REFERENCES I. Grossi EA, Esposito T, Harris LJ, et al. Sternal wound infections and use of internal mammary artery grafts. J THORAC CARDIOVASC SURG 1991;102:342-7. 2. Nishida H, Grooters RK, Soltanzadeh H, Thieman KC, Schneider RF, Kim W. Discriminate use of the electrocau- teryon the median sternotomy incision. J THORAC CARDIO- VASC SURG 1991;101:488-94. Reply to the Editor: We also read with interest the report by Grossi and his col- leagues' concerning sternal wound infections associated with the usage of the internal mammary artery (IMA) for grafting. We find their rates much higher than our experience, and we continue to insist that preserving viability of the presternal soft tissues is the way to prevent this dreaded complication after heart operations. As an update to our previous clinical article,' which reported our overall sternal wound infection rate of 0.15%, we summarize here the most recent figures on our infec- tion rate. From June 1989 to April 1992, we performed 1251 heart operations, of which 1045 were coronary artery bypass procedures. Of the coronary artery bypass graft procedures, 985 involved one or two IMA grafts. Sternotomy infection developed in five patients, for an overall rate of 0.32%. Three patients infected had an IMA graft, for a sternotomy infection rate of 0.3% in this group. It is our conclusion that infection rates well below I % can still be obtained with IMA grafts. We still find no differences in the infection rates in the diabetic and obese patient populations. We still believe that use of the cautery, whether in coagulation mode or cutting mode, on the presternal tissues is a violation of good surgical principles and that this technique should be abolished. The Journal of Thoracic and Cardiovascular Surgery July 1993 There is still nothing better than a cold steel knife, which leaves viable tissue on each side of the wound to cover the sternum. Ronald K. Grooters, M D Mid-Iowa Heart Institute Iowa Methodist Medical Center 1215 Pleasant, No. 308 Des Moines, IA 50309 REFERENCES I. Grossi EA, Esposito T, Harris LJ, et al. Sternal wound infections and use of internal mammary artery grafts. J THoRAc CARDIOVASC SURG 1991; I02:342-7. 2. Nishida H, Grooters RK, Soltanzadeh H, Thieman KC, Schneider RF, Kim W. Discriminate use of the electrocau- teryon the median sternotomy incision. J THoRAc CARDIO- VASC SURG 1991;101:448-94. Reply to the Editor: We agree with the preceding letter from Jayakrishnan and colleagues with regard to avoiding disruption of presternal soft tissue by minimizing both use of electrocautery and use of bone wax. However, other large patient series have demonstrated results similar to ours. Loop and coworkers' data I revealed a significant fivefold increase in infection in patients with diabe- tes and bilateral internal mammary artery (IMA) grafts and Kouchoukos and colleagues/ demonstrated significantly in- creased risk of 12.5% in patients with double IMA grafts and diabetes. Our experimental work! has led us to believe that the method of harvesting the IMA also has a large influence on the amount of devascularization of the sternum. We congratulate Jayakrishnan and coworkers for their admirably low rate of infection. However, their low overall rate of infection, small patient population, and low prevalence of diabetic patients make it impossible to perform any statistical analysis with significant power to test the interaction between bilateral IMA grafts and diabetes. Eugene A. Grossi, MD Rick A. Esposito, MD Aubrey Galloway, MD Gregory Baumann, PhD Department of Surgery New York University Medical Center New York, N. Y. REFERENCES I. Loop FD, Lytle BW, Cosgrove OM, et al. Sternal wound complications after isolated coronary artery bypass grafting; early and late mortality, morbidity, and cost of care. Ann Thorac Surg 1990;49:179-87. 2. Kouchoukos NT, Wareing TH, Murphy S, Pelate C, Mar- shall WG. Risks of bilateral mammary artery bypass graft- ing. Ann Thorac Surg 1990;49:210-9. 3. Asai T, Parish MA, Grossi EA, et al. Sternal ischemia is sig- nificantly greater with a pedicle IMA compared with a skel- etonized IMA. Current Surgery September, 1991;48:430-1. Dysfunction of the Duromedics heart valve in the tricuspid position: Report of three cases To the Editor: The Duromedics bileaflet mechanical heart valve prosthesis (Hemex Scientific, Inc., Austin, Tex.) has been used in clinical