Left ventricular assist devices (LVAD) have been demonstrated to be effective in bridging patients with end-stage heart failure to transplantation. 1,2 However, development of a device related infection can be a source of significant morbidity and mortality. 3–5 Furthermore, there is some degree of uncertainty as to whether the presence of infection while on support adversely impacts successful bridging to transplant or survival after transplant. 6 The focus of this study was to ascertain whether development of a device related infection while on mechanical support adversely impacted the rate of successful bridging to transplant or posttransplant survival.
Patients and Methods
We retrospectively reviewed our experience at Columbia Presbyterian Medical Center with bridge to transplant patients from June 1996 through January 2003, focusing on patients who developed device related infections. During this time period, 174 patients with end-stage heart failure underwent LVAD implantation as a bridge to transplant. LVAD support was provided by the Heartmate single lead vented electric (SLVE) device (Thoratec, Pleasanton, CA). Device related infections were defined by the presence of a positive culture from device inflow, outflow, diaphragm, pocket, or drive line during support or at the time of device removal along with leukocytosis and management of infection with the administration of antibiotics. LVAD endocarditis referred specifically to the colonization of the blood contacting the device surfaces leading to sepsis. The rate of successful bridging to transplant and posttransplant survival at 1, 3, and 5 years was evaluated for patients with and without device related infections.
Data were represented as frequency distributions and percentages. Continuous variables were expressed as a mean ± standard deviation (SD) and were compared using independent sample t-tests. Categorical variables were compared by means of chi-square analysis. For all analyses, p < 0.05 was considered statistically significant. Kaplan-Meier analysis was used to calculate survival along with a log-rank p value when comparing groups. Actuarial posttransplant survival at 1, 3, and 5 years was calculated for patients with and without device related infections by constructing life tables. Development of a device related infection was also evaluated using multivariate Cox proportional hazard models to ascertain whether it was a significant, independent predictor of mortality. All data were analyzed using SPSS 11.5 (SPSS Inc., Chicago, IL).
Incidence of Device Related Infections
Of the 174 patients with end-stage heart failure who underwent implantation of a Heartmate LVAD as a bridge to transplant, 32 (18.4%) developed device related infections while on support. This included 12 patients with drive line infections, 14 with pocket infections, 4 with pump infections, and 2 with device endocarditis.
Clinical demographics are outlined in Table 1. Age, sex, and race distribution were similar for patients with and without infection (p = NS). In addition, etiology of heart failure was similar for both groups, with coronary artery disease (n = 98, 56.3%) the most frequent etiology (p = NS). LVAD implantation scores, derived from five clinical variables including ventilatory status, reoperation, previous LVAD, central venous pressure (CVP), and prothrombin time (PT), with an inverse relationship between score and clinical stability, were similar for both groups (p = NS). 7
Bridging to Transplant
There was no significant difference in the rate of successful bridging to transplant in 23 (71.9%) patients with infections versus 103 (72.5%) patients without infection (p = 0.406).
Actuarial survival at 1, 3, and 5 years posttransplant was 95.6%, 86.2%, and 79.3% for the infection group, versus 90.9%, 88.1%, and 82.2% for the group without infection (p = 0.986) (Figure 1).
Evaluation of Infection Using Multivariate Cox Proportional Hazard Models
LVAD infection was not a statistically significant risk factor for posttransplant mortality using multivariate Cox proportional hazard models (odds ratio 0.642, 95% confidence interval 0.416–0.872, standard error 0.162, p = 0.980).
In this study, we demonstrated that patients who developed device related infections had similar rates of successful bridging to transplant and posttransplant survival as compared with patients without device related infections. This supports proceeding with transplantation in patients who develop a device related infection while on mechanical support. However, the precise timing of transplantation in the setting of a device related infection remains an issue that requires further analysis. 8,9 Our challenge remains to continue to decrease device related infections. 10 This is particularly important in patients who are being considered for LVADs as destination therapy. 11
Limitations of this study include those related to a retrospectively performed analysis. Identification of clinical variables were obtained by chart review, which has inherent limitations, such as access and accuracy of the data. In addition, as a retrospective observational study, the study is subject to selection bias and incomplete data collection. Finally, although we analyzed our experience with 174 patients over the last 7 years, the number of patients in the infection group was relatively low, thus limiting statistical power. Although we demonstrated no statistically significant difference in successful bridging to transplant or posttransplant survival between patients with and without device related infections, it is possible that, had a larger cohort of patients with device related infections been studied by conducting a multi-institutional analysis, a statistically significant difference in survival might have been observed.
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