Increased Risk of Sternal Complications in Patients with Plasma Cell Dyscrasias (PCDs) Undergoing Coronary Artery Bypass Graft (CABG)

Introduction: Skeletal events, including fractures, form an important part of the clinical spectrum of PCDs. Skeletal surveys, even though less sensitive than MRI, remain the usual method of screening for lytic lesions and fractures in these patients but may miss subtle abnormalities. Patients undergoing a CABG normally require a midline sternal incision, which may increase the risk of a skeletal event. Patients with PCDs also have an increased risk of infection, thrombosis, and renal failure. To our knowledge, there is no published data about complications of cardiothoracic surgery in these patients. We hypothesized that patients with PCDs will have a higher risk of complications when compared to those without such history.

Methods: Data on patients who underwent non-urgent coronary artery bypass graft (CABG) surgery from 2007 to 2011 was obtained by querying the Healthcare Cost and Utilization State Inpatient Databases for Florida and California. Information was available only for the inpatient stay plus a 30-day follow-up period. Diagnoses of multiple myeloma and monoclonal gammopathy of unknown significance (MGUS) were identified using ICD-9-CM codes. Mixed-effects logistic models were used to measure the association between PCDs and postoperative sternal complications controlling for demographics and comorbidity. Secondary outcomes of study in bivariate analysis included postoperative complications and 30-day readmission rates.

Results: A total of 54,422 patients who underwent non-urgent CABG were identified. Of those patients, 500 were known to have a PCD. Ninety two percent of those patients (462 out of 500) had a diagnosis of MGUS. Median age was 66.6 years for the control group and 65.4 years in the PCDs group, and the male to female ratio was equal in both cohorts. In the PCD group, there was a statistically significant higher incidence of anemia, obesity, and renal failure prior to surgical intervention. Sternal infections occurred in 519 (1%) of the patients in the control group versus 18 (3.6%) of the patients in PCDs group (p<0.001). The 30-day all cause readmission rate was similar between the two groups but the 30-day sternal complication rate was significantly higher in the PCDs group (6.8% vs 3.7%; p<0.001). The odds ratio of sternal infection was 3.84 (CI 2.38-6.20) and the odds ratio of sternal dehiscence was 3.87 (CI 1.98-7.57) in the PCDs group when compared to the control group, both of which are statistically significant. Similarly, the odds ratio of sternal complications at 30-days was 1.92 (CI 1.35-2.73) in the PCDs group when compared to the control group. There were no statistically significant differences in the rates of postoperative myocardial infarctions, strokes, urinary tract infections, acute kidney injury, pneumonias, deep venous thrombosis, and gastrointestinal complications between the two cohorts.

Conclusions: Our data shows that patients with PCDs have a lower hemoglobin level, renal insufficiency, and are obese at the time of coronary bypass surgery. It is important to note that the majority of the subjects in our study population had MGUS, a condition usually associated with little morbidity. Nonetheless, our cohort of patients with PCDs had a significantly increased risk of sternal wound infection and dehiscence. The treating physicians should be aware of these risks and patients should be informed. Prospective studies will be necessary to confirm and extend these findings.