Obesity and left ventricular assist device driveline exit site infection

Interaction of obesity and infections

There is evidence that certain infections may induce obesity. Obese persons may also have more severe infections and have compromised response to therapies. The objective of this study is to review the available literature identifying infections that potentially contribute to greater body mass index (BMI) and differential responses of overweight and obese persons to infections. A systematic literature review of human studies examining associations between infections and weight gain, differential susceptibility, severity, and response to prevention and treatment of infection according to BMI status (January 1980-July 2014) was conducted. Three hundred and forty-three studies were eligible for inclusion. Evidence indicated that viral infection by human adenovirus Ad36 and antibiotic eradication of Helicobacter pylori were followed by weight gain. People who were overweight or obese had higher susceptibility to developing post-surgical infections, H1N1 influenza and periodontal disease. More severe infections tended to be present in people with a larger BMI. People with a higher BMI had a reduced response to vaccinations and antimicrobial drugs. Higher doses of antibiotics were more effective in obese patients. Infections may influence BMI, and BMI status may influence response to certain infections, as well as to preventive and treatment measures. These observations have potential clinical implications.

Readmission due to driveline infection can be predicted by new score by using serum albumin and body mass index during long-term left ventricular assist device support

Survival in patients with continuous flow left ventricular assist device (CF LVAD) had been increased owing to improved perioperative management procedures. The second target for successful long-term LVAD treatment was to reduce readmission especially due to device-specific infection, which was one of the major unsolved complications. Among 57 enrolled patients who had received CF LVAD and been followed for 530 days on median at our institute between 2008 and 2014, 21 patients experienced readmission due to driveline infection (DLI) at 190 days after the surgery on median. Considering the result of Uni/Multivariate Cox regression analyses demonstrating lower serum albumin concentration (S-ALB) (hazard ratio 0.144) and body mass index (BMI) (hazard ratio 0.843) both obtained at discharge were independent predictors of readmission due to DLI, we constructed a New Score "7 × [S-ALB (g/dL)] + [BMI]", which significantly stratified readmission-free rate into 3 groups [low (>50 Pt), intermediate (44-50 Pt), and high risk group (<44 Pt)] during 2-year study period (p = 0.008). Survival remained unchanged irrespective of DLI, whereas those with DLI needed longer in-hospital treatment (p < 0.05). In conclusion, readmission due to DLI could be predicted by using two simple nutrition parameters at discharge. Early nutrition assessment and intervention may reduce readmission and improve patients' quality of life during long-term LVAD support.

Ventricular assist device implantation improves skeletal muscle function, oxidative capacity, and growth hormone/insulin-like growth factor-1 axis signaling in patients with advanced heart failure

BACKGROUND

Skeletal muscle dysfunction in patients with heart failure (HF) has been linked to impaired growth hormone (GH)/insulin-like growth factor (IGF)-1 signaling. We hypothesized that ventricular assist device (VAD) implantation reverses GH/IGF-1 axis dysfunction and improves muscle metabolism in HF.

METHODS

Blood and rectus abdominis muscle samples were collected during VAD implantation and explantation from patients with HF and controls. Clinical data were obtained from medical records, biomarkers measured by enzyme-linked immunosorbent assay (ELISA), and gene expression analyzed by reverse transcription and real-time polymerase chain reaction (RT-PCR). Grip strength was assessed by dynamometry. Oxidative capacity was measured using oleate oxidation rates. Muscle fiber type and size were assessed by histology.

RESULTS

Elevated GH (0.27 ± 0.27 versus 3.6 ± 7.7 ng/ml in HF; p = 0.0002) and lower IGF-1 and insulin-like growth factor binding protein (IGFBP)-3 were found in HF (IGF-1, 144 ± 41 versus 74 ± 45 ng/ml in HF, p < 0.05; and IGFBP-3, 3,880 ± 934 versus 1,935 ± 862 ng/ml in HF, p = 0.05). The GH/IGF-1 ratio, a marker of GH resistance, was elevated in HF (0.002 ± 0.002 versus 0.048 ± 0.1 pre-VAD; p < 0.0039). After VAD support, skeletal muscle expression of IGF-1 and IGFBP-3 increased (10-fold and 5-fold, respectively; p < 0.05) accompanied by enhanced oxidative gene expression (CD36, CPT1, and PGC1α) and increased oxidation rates (+1.37-fold; p < 0.05). Further, VAD implantation increased the oxidative muscle fiber proportion (38 versus 54 %, p = 0.031), fiber cross-sectional area (CSA) (1,005 ± 668 versus 1,240 ± 670 μm(2), p < 0.001), and Akt phosphorylation state in skeletal muscle. Finally, hand grip strength increased 26.5 ± 27.5 % at 180 days on-VAD (p < 0.05 versus baseline).

CONCLUSION

Our data demonstrate that VAD implantation corrects GH/IGF-1 signaling, improves muscle structure and function, and enhances oxidative muscle metabolism in patients with advanced HF.

Innovative Free-range Resonant Electrical Energy Delivery system (FREE-D System) for a ventricular assist device using wireless power

Technological innovation of a smaller, single moving part has an advantage over earlier large pulsatile ventricular assist devices (VADs) prone to mechanical failure. Drivelines limit the potential for extended patient survival durations with newer pumps and act as source for infection, increased morbidity, rehospitalizations, and reduced quality of life. The Free-range Resonant Electrical Energy Delivery (FREE-D) wireless power system uses magnetically coupled resonators to efficiently transfer power. We demonstrate the efficiency over distance of this system. The experimental setup consists of an radiofrequency amplifier and control board which drives the transmit resonator coil, and a receiver unit consisting of a resonant coil attached to a radiofrequency rectifier and power management module. The power management module supplies power to the axial pump, which was set at 9,600 rpm. To achieve a seamless wireless delivery in any room size, we introduced a third relay coil. This relay coil can be installed throughout a room, whereas a single relay coil could be built into a jacket worn by the patient, which would always be within range of the receive coil implanted in the patient's body. The power was delivered over a meter distance without interruptions or fluctuations with coil, rectifier, and regulator efficiency more than 80% and overall system efficiency of 61%. The axial pump worked well throughout the 8 hours of continuous operation. Having same setup on the opposite side can double the distance. A tether-free operation of a VAD can be achieved by FREE-D system in room-size distances. It has the potential to make the VAD therapy more acceptable from the patient perspective.

Prevention of percutaneous driveline infection after left ventricular assist device implantation: prophylactic antibiotics are not necessary

Infection is a major source of morbidity and mortality after ventricular assist device (VAD) implantation. The percutaneous driveline is the most common site of infection in these patients and often serves as a portal to deeper pump infections. There are no data defining the role of prophylactic antibiotics in preventing these infections. We compared all patients who underwent primary HeartMate II VAD implantation at two different institutions employing two different driveline infection prevention strategies between February 2007 and September 2011. While all patients received perioperative antibiotics, driveline maintenance strategies included sterile dressing changes with Hibiclens application without continued prophylactic antibiotics (Abx) (Mayo Clinic, n = 141, No Abx) and sterile dressing changes with continued prophylactic antibiotics (University of Michigan Hospital, n = 144, Abx). Although gender was similar between cohorts (Abx: 79% male vs. No Abx: 84% male, p = 0.25), median age at implant (Abx: 59 vs. No Abx: 64, p = 0.001) and destination therapy as indication for VAD (Abx: 22% vs. No Abx: 60%, p < 0.001) were significantly different. Follow-up was available in all late survivors (Abx: 140 patients, No Abx: 127 patients). Median duration of support was similar between groups (Abx: 12.3 months vs. No Abx: 11 months, p = 0.44). Total patient-years of device support were 172 years for 140 patients in the Abx cohort and 146 years for 127 patients in the No Abx cohort. Driveline drainage/infection was observed in 25 of 140 patients (18%) in the Abx group and 16 of 127 (13%) in the No Abx group (p = 0.15). Device exchange for major driveline infection was performed in seven patients in the Abx group and 0 patients in the No Abx group. Total driveline infection events per patient-years of support were 0.15 for the Abx group and 0.11 in the No Abx group (p = 0.43). There was no significant difference in the raw incidence of major driveline infections or driveline infections per patient-years of support in patients who were maintained on prophylactic antibiotics compared with those who were not. These data suggest that other factors may be more important than prophylactic antibiotics in preventing driveline infections.

Obesity in heart failure: impact on survival and treatment modalities

Heart failure (HF) and obesity are commonly seen in the USA. Although obesity is associated with traditional cardiovascular disease, its relationship with HF is complex. Obesity is an accepted risk factor for incident HF. However, in patients with established HF, there exists a paradoxical correlation, with escalating BMI incrementally protective against adverse outcomes. Despite this relationship, patients with HF may desire to lose weight to reduce comorbidities or to improve quality of life. Thus far, studies have shown that intentional weight loss in obese patients with HF does not increase risk, with strategies including dietary modification, physical activity, pharmacotherapy, and/or surgical intervention.

Impact of adverse events on ventricular assist device outcomes

Left ventricular assist devices have been proven to be superior to medical therapy for advanced heart failure patients awaiting heart transplantation and viable alternatives to transplantation for destination therapy patients. Improvements in the design of ventricular assist devices have been rewarded by a decrease in adverse events and an increase in survival. Despite significant progress, even the latest generation left ventricular assist devices are burdened by a significant long-term adverse events profile that will increasingly challenge physicians as patients survive longer on implantable mechanical circulatory support. In this review, we analyze the impact of long-term adverse events on clinical outcomes in the major trials of continuous flow left ventricular assist devices. We discuss several of the more pertinent and interesting adverse events, examine their potential causes, and explore their future implications.

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.

The pharmacotherapy implications of ventricular assist device in the patient with end-stage heart failure

Advances in mechanical circulatory support, such as the use of ventricular assist devices (VADs), have become a means for prolonging survival in end-stage heart failure (HF). VADs decrease the symptoms of HF and improve quality of life by replacing some of the work of a failing heart. They unload the ventricle to provide improved cardiac output and end-organ perfusion, resulting in improvement in cardiorenal syndromes and New York Heart Association functional class rating. VADs are currently used asa bridge to heart transplantation, a bridge to recovery of cardiac function, or as destination therapy. Complications of VAD include bleeding, infections, arrhythmias, multiple organ failure, right ventricular failure, and neurological dysfunction. Patients with VAD have unique pharmacotherapeutic requirements in terms of anticoagulation, appropriate antibiotic selection, and continuation of HF medications. Pharmacists in acute care and community settings are well prepared to care for the patient with VAD. These patients require thorough counseling and follow-up with regard to prevention and treatment of infections, appropriate levels of anticoagulation, and maintenance of fluid balance. A basic understanding of this unique therapy can assist pharmacists in attending to the needs of patients with VAD.

Continuous-flow devices and percutaneous site infections: clinical outcomes

BACKGROUND

Although continuous-flow left ventricular assist device (LVAD) support has become standard therapy, the complexities of device and patient management remain a challenge. In particular, percutaneous site infections (PSI) are a serious complication during the post-implant course. We sought to study the incidence, risk factors, and clinical effect of PSI.

METHODS

Data were obtained from the Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) Registry. All adult patients who received a primary intracorporeal continuous flow LVAD between June 2006 and September 2010 were included. Descriptive statistics, Kaplan-Meier depictions, and multivariable analysis in the parametric hazard domain were used for statistical analysis.

RESULTS

A total of 239 PSIs were documented in 197 of 2,006 recipients (9.8%) of a continuous-flow LVAD. Mean follow-up was 8.1 months. Mean time to development of a PSI was 6.6 months. At 1 year after implant, nearly 19% of continuous-flow LVAD recipients developed a PSI. Multivariate analysis showed younger age (hazard ratio, 1.20; p < 0.0001) was the only factor predicting a PSI. Continuous-flow LVAD recipients who did not develop a PSI had improved survival (p = 0.004). Twenty-three patients died after development of a PSI. Sepsis was the most common cause of death (26.1%).

CONCLUSIONS

PSIs occur in approximately 19% of continuous-flow LVAD recipients by 12 months after implant. Young age is the only predictor of PSI. Importantly, development of a PSI adversely affects survival. Efforts to enhance driveline integration and to develop future totally implantable systems are warranted.

Left ventricular assist device-related infections: past, present and future

Over the last decade, left ventricular assist device (LVAD) implantation has emerged as an alternative treatment strategy in patients with advanced heart failure irrespective of their transplant eligibility. However, success and applicability of this therapy is largely limited by high complication rates associated with these devices. Although superior outcomes have been achieved with the second-generation continuous-flow LVADs, device-related infections continue to be a prevalent complication in this patient population and contribute significantly to the financial burden of this therapy due to an increased need for hospitalizations and surgical interventions. Patient selection, device design and LVAD-induced immune system dysfunction appear to be major risk factors for the development of device-related infections. Improvements in device design and better patient selection strategies, particularly with respect to identifying individuals with genetic susceptibility to device-related infections, may further reduce this prevalent complication and improve outcomes in patients with advanced heart failure.

Toward total implantability using free-range resonant electrical energy delivery system: achieving untethered ventricular assist device operation over large distances

Heart failure is a terminal disease with a very poor prognosis. Although the gold standard of treatment remains heart transplant, only a minority of patients can benefit from transplants. Another promising alternative is mechanical circulatory assistance using ventricular assist devices. The authors envision a completely implantable cardiac assist system affording tether-free mobility in an unrestricted space powered wirelessly by the innovative Free-Range Resonant Electrical Energy Device (FREE-D) system. Patients will have no power drivelines traversing the skin, and this system will allow power to be delivered over room distances and will eliminate trouble-prone wirings, bulky consoles, and replaceable batteries.

Infectious complications in patients with left ventricular assist device: etiology and outcomes in the continuous-flow era

BACKGROUND

Continuous-flow left ventricular assist devices (LVAD) are increasingly being used in patients with end-stage heart failure and have largely replaced older generation pulsatile devices. While significant rates of infection have been reported in patients with pulsatile device support, incidence and outcomes of this complication for the continuous-flow device patients remain unknown.

METHODS

Between June 2005 and August 2009, 81 patients were implanted with continuous-flow LVADs at Washington University School of Medicine either as bridge to transplantation or as destination therapy. Outcomes of this study included incidence of postimplantation infection, types of infection, microbiologic profile, and association of postimplantation infections with clinical endpoints.

RESULTS

Forty-two patients (51.9%) had at least one type of infection on continuous-flow LVAD support with a mean follow-up period of 9.2 ± 9.2 months. Patients who had an infection on LVAD support had a significantly prolonged hospital stay (37.9 ± 32.0 versus 20.7 ± 23.0 days, p = 0.008) and a trend toward increased mortality (33.1% versus 18.7% at 2 years, respectively, log rank p = 0.102) compared with patients who did not. Subgroup analysis revealed that postimplantation sepsis was significantly associated with increased mortality in the continuous-flow LVAD cohort (61.9% versus 18.0% at 2 years, respectively, in septic and nonseptic patients, log rank p = 0.001). The majority of the sepsis cases occurred before hospital discharge, whereas most of the device related infections occurred after discharge. Resistant Staphylococcus and Pseudomonas species were the most common pathogens leading to device- and nondevice-related local infections. Development of driveline or pocket infection had no effect on survival in patients with continuous-flow assist device support (p = 0.193).

CONCLUSIONS

Even though better clinical outcomes have been achieved with the newer generation continuous-flow devices, infection complications-in particular sepsis-are still a major risk for patients with continuous-flow LVAD implantation. Prevention strategies with aggressive medical and surgical management of infections may increase survival and decrease morbidity among continuous-flow LVAD patients.