ROLE OF EPICARDIAL PACING WIRE CULTURES IN THE DIAGNOSIS OF POSTSTERNOTOMY MEDIASTINITIS

wires used after surgery are placed in the mediastinum, so the culture of these wires could be useful for the diagnosis of this disease. To test this hypothesis, we routinely cultured the epicardial pacing wire s of 565 patients undergoing extracorporeal circulation. Wires were re moved on the 7th to 9th postoperative day under sterile conditions and were cultured with routine techniques used for the culture of venous catheters. Mediastinitis developed in 16 patients, and Staphylococcus aureus was the most common pathogen (81.25%). We had 103 positive and 462 negative cultures. There were 458 true-negative, 12 true-positive, 91 false-positive and 4 false-negative results. For mediastinitis in general, epicardial pacing wire culture has a sensitivity of 75%, spec ificity of 83.4%, positive predictive value of 11.6%, and negative pre dictive value of 99.1%. For Staphylococcus aureus mediastinitis, epica rdial pacing wire culture has a sensitivity of 84.6%, specificity of 9 5.8%, positive predictive value of 32.3%, and negative predictive valu e of 99.6%. We conclude that a sterile culture of the epicardial pacin g wires strongly contradicts a diagnosis of postsurgical mediastinitis .