Original article
Adult cardiac
Mediastinitis After Coronary Artery Bypass Grafting Risk Factors and Long-Term Survival

https://doi.org/10.1016/j.athoracsur.2010.02.038Get rights and content

Background

Mediastinitis is a severe complication of coronary artery bypass grafting. The aim of the present study was to determine incidence of mediastinitis, its risk factors, and its effect on early and long-term survival.

Methods

The study has a dual design, a case-control, and a retrospective cohort, using a source population of 18,532 consecutive patients who underwent coronary artery bypass grafting from January 1989 to December 2000. The closing date was February 1, 2008. Median follow-up was 10.3 (range 8.1 to 18.9) years. Patients with mediastinitis were compared with a random control group without mediastinitis issued from the same source population in a ratio 1:4. The crude effect of mediastinitis was estimated using rate ratio and 95% confidence limits. Adjustment for multiconfounders was done with the Cox model. A logistic model was used to pinpoint risk factors of mediastinitis. Calibration and discrimination of a prognostic model was done.

Results

One hundred seven patients (0.6%) developed mediastinitis. Diagnosis was made 12 (9 to 19) days postoperatively. Independent risk factors of mediastinitis using the logistic model were advanced age, male gender, left main stenosis, body mass index 30 kg/m2 or greater, chronic obstructive pulmonary disease, diabetes, and increased amount of blood transfusion. There was no increased risk of early mortality (odds ratio = 0.58; 95% confidence interval 0.13 to 2.61) (p = 0.48) but there was increased risk of morbidity (intraaortic balloon pump, ventricular and supraventricular arrhythmia, stroke, inotrope, and myocardial infarction). Follow-up had a median observation time of 10.3 years. Survival for patients with mediastinitis was 49.5 ± 5.0% versus 71.0 ± 2.2% for controls (p < 0.01). Analysis of specific death causes documented that cardiac deaths were significantly more frequent in mediastinitis patients than in control patients. When controlling for the confounding effect of the other variables (age, cardiopulmonary bypass time, body mass index, chronic obstructive pulmonary disease), the hazard ratio associated with mediastinitis on long-term mortality was 1.59, 95% confidence limits (1.16 and 2.70) (p = 0.003).

Conclusions

The incidence of mediastinitis in 18,532 patients undergoing coronary artery bypass grafting surgery was low. The major preventable risk factor of mediastinitis was amount of blood transfusion. Mediastinitis had an excess risk of early morbidity and was associated with a significant reduced long-term survival. Most deaths were considered to be cardiac.

Section snippets

Source Population

The study was approved by the Regional Medical Ethics Committee and represents a multicenter collaboration between Rikshospitalet University Hospital, The Feiring Heart Clinic, and Oslo Heart Center. The institutions maintain the same diagnostic criteria and treatment with active and prospective epidemiologic surveillance of hospital infections. Between January 1989 and December 2000, a total of 18,532 adult patients undergoing CABG surgery were considered in our analysis. The diagnosis of

Risk Factors of Mediastinitis Using the Case-Control Design

The two groups of patients were comparable with respect to preoperative, intraoperative, and postoperative variables (Table 1). Mediastinitis occurred in 107 (0.6%) of 18,532 patients. The time between surgery and onset of symptoms was 12 (9 to 19) days. Irrigation time was 7 (1 to 24) days.

Independent risk factors of mediastinitis were pinpointed using the logistic model. Our results are summarized in Table 2. Age over 70 years had a 74% increased risk compared with younger patients, and male

Risk Factors of Mediastinitis

Multivariate analysis identified six preoperative variables as highly significant independent predictors for the development of mediastinitis. Four of these risk factors (diabetes, obesity BMI ≥ 30 kg/m2, COPD, and age) have often been associated with occurrence of mediastinitis [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]. In addition we found male gender and LMS to be significantly associated with mediastinitis.

Diabetes mellitus turned out to be one of the most important predictors of mediastinitis. This

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