Fungal infections in ventricular assist devices

Etiology, pathology, and host-impaired immunity in medical implant-associated infections

Host impaired immunity and pathogens adhesion factors are the key elements in analyzing medical implant-associated infections (MIAI). The infection chances are further influenced by surface properties of implants. This review addresses the medical implant-associated pathogens and summarizes the etiology, pathology, and host-impaired immunity in MIAI. Several bacterial and fungal pathogens have been isolated from MIAI; together, they form cross-kingdom species biofilms and support each other in different ways. The adhesion factors initiate the pathogen's adherence on the implant's surface; however, implant-induced impaired immunity promotes the pathogen's colonization and biofilm formation. Depending on the implant's surface properties, immune cell functions get slow or get exaggerated and cause immunity-induced secondary complications resulting in resistant depression and immuno-incompetent fibro-inflammatory zone that compromise implant's performance. Such consequences lead to the unavoidable and straightforward conclusion for the downstream transformation of new ideas, such as the development of multifunctional implant coatings.

In Full Flow: Left Ventricular Assist Device Infections in the Modern Era

With the rising prevalence of heart disease in the United States, there is increasing reliance on durable mechanical circulatory support (MCS) to treat patients with end-stage heart failure. Left ventricular assist devices (LVADs), the most common form of durable MCS, are implanted mechanical pumps that connect to an external power source through a transcutaneous driveline. First-generation LVADs were bulky, pulsatile pumps that were frequently complicated by infection. Second-generation LVADs have an improved design, though infection remains a common and serious complication due to the inherent nature of implanted MCS. Infections can affect any component of the LVAD, with driveline infections being the most common. LVAD infections carry significant morbidity and mortality for LVAD patients. Therefore, it is paramount for the multidisciplinary team of clinicians caring for these patients to be familiar with this complication. We review the epidemiology, prevention, diagnosis, treatment, and outcomes of LVAD infections.

The Biocompatibility Challenges in the Total Artificial Heart Evolution

There are limited therapeutic options for final treatment of end-stage heart failure. Among them, implantation of a total artificial heart (TAH) is an acceptable strategy when suitable donors are not available. TAH development began in the 1930s, followed by a dramatic evolution of the actuation mechanisms operating the mechanical pumps. Nevertheless, the performance of TAHs has not yet been optimized, mainly because of the low biocompatibility of the blood-contacting surfaces. Low hemocompatibility, calcification, and sensitivity to infections seriously affect the success of TAHs. These unsolved issues have led to the withdrawal of many prototypes during preclinical phases of testing. This review offers a comprehensive analysis of the pathophysiological events that may occur in the materials that compose TAHs developed to date. In addition, this review illustrates bioengineering strategies to prevent these events and describes the most significant steps toward the achievement of a fully biocompatible TAH.

Variability in infection control measures for the percutaneous lead among programs implanting long-term ventricular assist devices in the United States

Ventricular assist devices (VADs) are a surgical treatment for heart failure. These devices may be implanted as a bridge to transplant or as destination therapy. After surgical recovery and education regarding device care, patients are discharged home. Meticulous care of the driveline must be taken to prevent infection and trauma of the site throughout the perioperative event and for the duration of support. Currently a standardized protocol for care of the driveline and exit site does not exist. VAD coordinators from across the country discussed the variability in care at different centers in the United States through a series of conference calls. A survey consisting of 16 questions was developed. The survey included questions on preoperative antibiotic recommendations, driveline placement and exit site suturing, frequency of dressing changes, and showering practices. VAD coordinators shared center-specific dressing protocols and any driveline success stories. This survey was sent to 73 centers; 38 centers (52%) responded. The purpose of the survey was to define current practice in order to move toward a standard of practice or protocol based on expert opinion for VAD driveline care and to assess the need for future studies.

Antifungal prophylaxis for invasive mycoses in high risk patients

PURPOSE OF REVIEW

New broader spectrum antifungal agents with favorable safety profiles have been available for the last 15 years making prophylaxis feasible. The purpose of this article is to review recent studies in patient populations at high risk for invasive fungal infections.

RECENT FINDINGS

Itraconazole, lipid formulations of amphotericin B, posaconazole, caspofungin and micafungin have been utilized for prophylaxis in different immunocompromised host settings. Itraconazole and caspofungin remain an option especially in patients with hematological diseases. Low dose liposomal amphotericin B shows a lower morbidity rate in patients treated for acute myeloid leukemia. Posaconazole demonstrated survival benefits in this setting although data have only been presented at an international meeting. In the transplantation setting, micafungin was superior to fluconazole during the early neutropenic phase and posaconazole was superior to fluconazole in preventing invasive aspergillosis in hematopoietic transplant recipients treated for graft-versus-host disease. Results from the latter study have thus far only been presented in abstract form.

SUMMARY

Prophylaxis should only be given to a high-risk population. Results of studies should demonstrate morbidity and mortality advantages. The new generation of azoles and echinocandins have a favorable safety and drug interaction profile and appear advantageous in specific settings of immunosuppression. Pending full publication, posaconazole appears to be an appropriate agent for prophylaxis in acute myeloid leukemia patients or patients treated for graft-versus-host disease. Micafungin is superior to fluconazole in the neutropenic phase of hematopoietic transplantation.

Candidemia in Patients with Ventricular Assist Devices

During the period 1998-2004, candidemia developed in 7 of 117 ventricular assist device recipients at our hospital, and the associated mortality rate was 71%. Five cases of candidemia were due to Candida parapsilosis, and 2 were due to Candida albicans. Three of the 7 patients with ventricular assist device-associated Candida bloodstream infections were cured, and the device was retained in 2 of the 3 patients.

Intravascular Device Infections

Intravascular devices such as pacemakers, implantable cardioverter-defibrillators (ICDs), left ventricular assist devices (LVADs), and prosthetic vascular grafts are life-saving therapies for patients with malignant arrhythmias, heart failure, and various vascular diseases. As indications for their use have increased, so has the prevalence of infectious complications associated with these devices. We present a review of the clinical literature on the epidemiology, diagnosis, and management of infectious complications of these intravascular devices. Most intravascular device infections are thought to result from skin flora contamination during implantation. Infection of the subcutaneous portion of the device can subsequently track to deeper intravascular tissues. Infection that involves the intravascular or intracardiac portion of these devices carries a high morbidity and mortality. Despite appropriate antibiotic therapy, cure of infection is frequently possible only with device removal. Well-designed placebo-controlled, randomized studies evaluating antimicrobial therapy for treatment of intravascular device infections are lacking. In the absence of better information, authorities recommend antibiotics targeted toward cultured organisms for approximately 4 to 6 weeks and device removal.

Candida infections of medical devices

The number of indwelling medical devices is escalating, and an increasing proportion of device-related infections are being caused by Candida spp. Candida spp. produce biofilms on synthetic materials, which facilitates adhesion of the organisms to devices and renders them relatively refractory to medical therapy. Management of device-related Candida infections can be challenging. Removal of the infected device is generally needed to establish cure of Candida infections of medical devices. However, since the pathogenesis of Candida bloodstream infection is complicated, more studies are necessary to determine the role of catheter exchange in patients with both gastrointestinal tract mucositis and indwelling catheters. The medical and economic impact of these infections is enormous.

What price support? Ventricular assist device induced systemic response

Use of ventricular support systems has been associated with myriad systemic complications. Engendered by the blood-biomaterial interface of a unique host/device relationship, these complications include diverse humoral dyscrasias that frequently culminate in episodes of bleeding, hemolysis and thrombogenicity, heightened susceptibility to inflammation and infection, and transient immunal compromise. Recent endeavor in biocompatibility research has served to illustrate the critical role played by cellular, humoral, and neurohormonal components in regulating cytokine expression and has provided insight into the complexities involved in such biomechanical juxtapositions. The following is intended as a review of current literature attempting to address the many aspects of this host/device interaction and their consequences for the supported patient.

Infection in ventricular assist devices: prevention and treatment

Infection is one of the most important challenges to the use of implanted mechanical circulatory support systems (MCSS), particularly as we enter the era of permanent device use in patients who are not candidates for cardiac transplantation. This paper describes the pathogenesis of MCSS infection, with particular attention to the role of biofilm-forming bacteria. Suggestions are presented for the prevention and treatment of infections in implanted MCSS.