Infection remains a feared complication after cardiac device implantation. Whether early postprocedural leukocytosis, a recognized marker of infection, is an indicator of impending infection is unclear and was the focus of this study. A retrospective chart review of consecutive patients who underwent implantable cardioverter defibrillator or pacemaker implantation was performed. The association between change in white blood cell (WBC) count and development of infection after device implantation was assessed. Infection was defined as pocket or lead infection or as bacteremia or sepsis <60 days after implantation. Pre- and postprocedural WBC counts were obtained within 48 hours of the procedure. Significant leukocytosis was defined as a ≥50% increase in WBC count; 1,245 device implantations met inclusion criteria. Device-related infections occurred in 8 cases (0.6%). A modest 17.6 ± 30.2% increase in WBC count was observed for the entire cohort. Cases resulting in infection demonstrated minimal change in WBC count (mean +5.5 ± 26.5%). No infections occurred in patients with ≥50% increases in WBC count or postprocedural WBC counts >15,000/μl. Subjects with significant leukocytosis were younger (mean age 61.9 ± 16.5 vs 65.6 ± 15.1 years, p <0.01), had longer procedure times (mean 198 ± 97 vs 170 ± 77 minutes, p <0.001), and received biventricular implantable cardioverter-defibrillators (25% vs 13.9%, p <0.001). In conclusion, after device implantation, a ≥50% increase in WBC count occurred in about 10% to 15% of patients. Age, race, type of device, and procedure time influenced the development of significant leukocytosis. Elevation in WBC count after cardiac device implantation was not associated with an increased risk for early infection.
Recent epidemiologic studies have reported an increase in hospital admissions for cardiac device-related infections. Specifically, Voigt et al reported a 49% increase in the number of cardiac device implantations from 1996 to 2003 (from 159,585 to 237,720). This increase was driven predominantly by implantable cardioverter-defibrillator (ICD) implantations (an increase of 160% for ICDs vs 31% for pacemakers). Over that same time period, however, the number of admissions attributed to cardiac device–related infections increased threefold (2.8-fold for pacemakers and sixfold for ICDs). Increasing age and renal failure were identified as independent predictors of in-hospital mortality in patients with device-related infections. An absolute increase in the white blood cell (WBC) count is often observed 24 to 48 hours after cardiac device implantation. A systemic inflammatory response has been described after open and minimally invasive surgical procedures. Whether a similar response occurs after cardiac device implantation is unknown. The focus of this study was to examine the prevalence and clinical significance of postimplantation leukocytosis.
Methods
We performed a retrospective medical record review of procedure-related complications in patients who underwent ICD or pacemaker implantation from August 2004 to August 2007. Early infection was defined as definite infection of the pocket or lead system or development of systemic infection (i.e., bacteremia) identified <60 days after implantation. Bleeding complications, defined as hematoma formation, need for blood transfusion, or development of cardiac tamponade, were also recorded as secondary end points.
Patients were excluded if they had 1 of the following: age <18 years, absence of necessary demographic data or WBC count within 48 hours before and after cardiac device implantation, known coagulation or bleeding disorders, or thrombocytopenia (defined as platelet count <50,000/mm 3 ).
Patients were grouped according to percentage change in WBC count. Demographic information, including age, gender, and weight, was obtained at the time of procedure. Hospital records were reviewed to determine patients’ medical histories at the time of device implantation. Records from the index hospitalization and clinic notes within 60 days of the procedure were reviewed for documentation of procedure-related complications.
All devices were placed by 1 of 12 board-certified or board-eligible electrophysiologists at the Johns Hopkins Hospital and Johns Hopkins Bayview Medical Center. Leads were placed using an axillary approach. Rarely, a cut-down procedure was performed to access the cephalic vein, on the basis of physician preference. All patients received intravenous antibiotics immediately before skin incision that were continued for the next 24 hours. The choice of intravenous antibiotics was left to the discretion of the attending surgeon. In general, cefazolin was used in all patients, with 2 notable exceptions. Clindamycin was substituted in patients with known penicillin allergy and vancomycin in those with a documented histories of methicillin-resistant Staphylococcus aureus colonization or bacteremia. A 5-day course of oral antibiotics (cephalexin or clindamycin) was subsequently administered upon completion of intravenous antibiotics. The pocket was irrigated with an antibiotic solution containing neomycin and polymyxin B sulfates in all patients before placement of the generator.
Continuous variables were compared with values in controls using paired Student’s t tests and are expressed as mean ± SD. Differences in proportional variables were determined using chi-square statistics and are expressed as frequency counts or percentages. A p value <0.05 was considered statistically significant. Given the small number of end points of the study, multivariate analysis was not possible. The study was approved by the Internal Review Board Committee for the Johns Hopkins Medical Institutions.
Results
A total of 1,512 medical records were reviewed. Of these, 1,245 patients met study entry criteria and were included. Table 1 lists the baseline characteristics for the entire cohort. There were a total of 8 infection-related complications (0.6%) identified within the follow-up period ( Table 2 ). The mean percentage change in WBC count for patients who did not experience any procedure-related complications was not significantly different from those who developed infections after cardiac device implantation (16.6 ± 29.5% vs 5.5 ± 26.5%, p = NS). There was no correlation between postprocedural WBC count and risk for infection ( Figure 1 ).
| Variable | Percentage Change in WBC Count | p Value | |||||
|---|---|---|---|---|---|---|---|
| Cohort (n = 1,245) | <−30% (n = 25) | −0% to −30% (n = 335) | 0% to 30% (n = 555) | 30.0% to 50% (n = 176) | >50% (n = 154) | ||
| A | B | C | D | E | |||
| Age (yrs) | 65 ± 15 | 66 ± 16 | 65 ± 15 | 66 ± 15 | 67 ± 15 | 62 ± 17 | <0.01 ∗ |
| Men | 66% | 52% | 62% | 66% | 69% | 70% | NS |
| Caucasian | 72% | 68% | 74% | 74% | 71% | 65% | <0.03 † |
| Weight (kg) | 83 ± 21 | 75 ± 18 | 84 ± 21 | 83 ± 21 | 82 ± 22 | 82 ± 20 | <0.05 ‡ |
| Procedure time (minutes) | 174 ± 80 | 151 ± 59 | 162 ± 66 | 171 ± 74 | 185 ± 99 | 198 ± 97 | <0.02 § |
| Creatinine (mg/dl) | 1.3 ± 1.1 | 1.3 ± 0.9 | 1.4 ± 1.3 | 1.3 ± 1.2 | 1.3 ± 1.0 | 1.2 ± 0.8 | NS |
| Mean percentage change in WBC count | 18 ± 30 | −39 ± 8 | −10 ± 7 | 14 ± 8 | 38 ± 6 | 76 ± 28 | NA |
| Hemoglobin (g/dl) | 12.6 ± 2.1 | 11.8 ± 2.2 | 12.3 ± 2.0 | 12.6 ± 2.0 | 12.9 ± 2.0 | 12.8 ± 2.0 | <0.02 || |
| International normalized ratio | 1.1 ± 0.3 | 1.0 ± 0.3 | 1.1 ± 0.3 | 1.1 ± 0.3 | 1.1 ± 0.2 | 1.1 ± 0.3 | NS |
| Pacemaker | 41% | 52% | 43% | 41% | 44% | 25% | <0.02 ¶ |
| ICD | 44% | 44% | 44% | 45% | 38% | 49% | <0.02 # |
| Biventricular ICD | 15% | 4% | 13% | 14% | 18% | 24% | <0.04 § |
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