Left ventricular assist device-associated driveline infections as a specific form of complicated skin and soft tissue infection/acute bacterial skin and skin structure infection - issues and therapeutic options

PURPOSE OF REVIEW

This review comments on the current guidelines for the treatment of wound infections under definition of acute bacterial skin and skin structure infections (ABSSSI). However, wound infections around a catheter, such as driveline infections of a left ventricular assist device (LVAD) are not specifically listed under this definition in any of the existing guidelines.

RECENT FINDINGS

Definitions and classification of LVAD infections may vary across countries, and the existing guidelines and recommendations may not be equally interpreted among physicians, making it unclear if these infections can be considered as ABSSSI. Consequently, the use of certain antibiotics that are approved for ABSSSI may be considered as 'off-label' for LVAD infections, leading to rejection of reimbursement applications in some countries, affecting treatment strategies, and hence, patients' outcomes. However, we believe driveline exit site infections related to LVAD can be included within the ABSSSI definition.

SUMMARY

We argue that driveline infections meet the criteria for ABSSSI which would enlarge the 'on-label' antibiotic armamentarium for treating these severe infections, thereby improving the patients' quality of life.

The Therapeutic Use of Impella Device in Cardiogenic Shock: A Systematic Review

Impella (Abiomed, Danvers, MA) devices nowadays have been linked to cardiogenic shock (CS) due to the importance of their use as therapeutic instruments. This study aims to review pathophysiologic mechanisms of cardiogenic shock and the implementation of Impella to overcome this condition. To investigate several different types of studies and analyze the use of Impella device in cardiogenic shock and the outcomes of heart malfunctioning and determine its positive and negative impacts as a therapeutic tool in cardiac ischemia and use as a resource in critical patients, we conducted a systematic review through different databases (PubMed, ScienceDirect, and Google Scholar) following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist and used the Medical Subjects Heading (MeSH) search strategy to obtain significant articles. We found 883 papers in total, and after removing duplicates, applying inclusion/exclusion criteria, and finding the most significant information, we ended up with 30 articles that were reviewed containing information about the impact of Impella device in cardiogenic shock in different locations. The study strongly concludes that Impella device in the setting of cardiogenic shock has more advantages than disadvantages in terms of outcomes and complications as a non-pharmacologic tool. Improvements in left ventricular ejection fraction and signs and symptoms of cardiogenic shock criteria were determinants. Nevertheless, complications during the implementation and use of the device were established; in this manner, the evaluation and treatment of each patient separately are imperative. Consequently, more studies on this relevant topic are needed.

Comparison of Hemodynamic Support by Impella vs. Peripheral Extra-Corporeal Membrane Oxygenation: A Porcine Model of Acute Myocardial Infarction

Objectives: Several mechanical circulatory assist devices are used to treat critically ill patients requiring hemodynamic support during post-myocardial infarction or cardiogenic shock. However, little guidance is available to choose an appropriate device to match a particular patient's needs. An increased understanding of hemodynamic effects of the pump systems and their impact on myocardial pre-/afterload might help to better understand their behavior in different clinical settings. Methods: This was an open-labeled, randomized acute animal experiment. A model of acute univentricular myocardial injury by temporary balloon occlusion was used. The experiment was carried out in 10 juveniles female Piétrain pigs. The animals were randomized to mechanical hemodynamic support either by peripheral veno-arterial (VA-)ECMO or Impella CP. Results: While both devices were able to provide flows above 3 L/min and maintain sufficient end-organ perfusion, support by Impella resulted in a significantly more pronounced immediate effect on myocardial unloading: At the onset of device support, the remaining native cardiac output was reduced by 23.5 ± 15.3% ECMO vs. 66.2 ± 36.2% (Impella, p = 0.021). Native stroke volume was significantly decreased by Impella support compared to ECMO, indicating less mechanical work being conducted by the Impella-supported hearts despite similar total assisted cardiac output. Conclusions: Peripheral VA-ECMO and the transaortic Impella pump resulted in contrasting hemodynamic fingerprints. Both devices provided sufficient hemodynamic support and reduce left ventricular end-diastolic pressure in the acute setting. Treatment with the Impella device resulted in a more effective volume unloading of the left ventricle. A significant reduction in myocardial oxygen consumption equivalent was achieved by both devices: The Impella device resulted in a left-shift of the pressure-volume loop and a decreased pressure-volume-area (PVA), while VA-ECMO increased PVA but decreased heart rate. These data highlight the importance of specifically targeting heart rate in the management of AMI patients on hemodynamic support.

Clinical and In Vitro Evidence That Left Ventricular Assist Device-Induced von Willebrand Factor Degradation Alters Angiogenesis

Background Gastrointestinal bleeding from angiodysplasia is a major problem in continuous-flow left ventricular assist device (LVAD) patients. LVAD shear stress causes pathologic degradation of VWF (von Willebrand factor). A mechanistic relationship between VWF degradation and angiodysplasia has not been explored. We tested 2 novel hypotheses: (1) clinical hypothesis: VWF fragments are elevated in LVAD patients that develop angiodysplasia and (2) in vitro hypothesis: VWF fragments generated during LVAD support alter angiogenesis, which may contribute to angiodysplasia. Methods and Results Clinical study: Paired blood samples were collected from continuous-flow LVAD patients (n=35). VWF was quantified with immunoblotting. In vitro experiments: (1) To investigate whether LVAD support alters angiogenesis, human endothelial cells were cultured with LVAD patient plasma (n=11). To investigate mechanism, endothelial cells were cultured with VWF fragments produced by exposing human VWF and ADAMTS-13 (VWF protease) to LVAD-like shear stress (175 dyne/cm², n=8). Clinical study results: in all patients (n=35, mean support 666±430 days), LVAD support degraded high-molecular-weight VWF multimers ( P<0.0001) into low-molecular-weight VWF multimers ( P<0.0001) and VWF fragments ( P<0.0001). In patients with gastrointestinal bleeding from angiodysplasia (n=7), VWF fragments were elevated ( P=0.02) versus nonbleeders. In contrast, in patients with gastrointestinal bleeding without angiodysplasia, VWF fragments were not elevated versus nonbleeders ( P=0.96). In vitro experiments results: LVAD patient plasma caused abnormal angiogenesis with reduced tubule length ( P=0.04) and migration ( P=0.05). Similarly, endothelial cells grown with VWF degradation fragments exhibited reduced tubule length ( P<0.001) and migration ( P=0.01). Conclusions LVAD patients who bled from angiodysplasia had higher levels of VWF fragments than nonbleeders and gastrointestinal bleeders without angiodysplasia. VWF fragments caused abnormal angiogenesis in vitro. These findings suggest that VWF fragments may be a mechanistic link between LVAD support, abnormal angiogenesis, angiodysplasia, and gastrointestinal bleeding.

Left Ventricular Assist Device Inflow Cannula Angle and Thrombosis Risk

BACKGROUND

As heart failure prevalence continues to increase in the setting of a static donor supply, left ventricular assist device (LVAD) therapy for end-stage heart failure continues to grow. Anecdotal evidence suggests that malalignment of the LVAD inflow cannula may increase thrombosis risk, but this effect has not been explored mechanistically or quantified statistically. Our objective is to elucidate the impact of surgical angulation of the inflow cannula on thrombogenicity.

METHODS AND RESULTS

Unsteady computational fluid dynamics is used in conjunction with computational modeling and virtual surgery to model flow through the left ventricle for 5 different inflow cannula angulations. We use a holistic approach to evaluate thrombogenicity: platelet-based (Lagrangian) metrics to evaluate the platelet mechanical environment, combined with flow-based (Eulerian) metrics to investigate intraventricular hemodynamics. The thrombogenic potential of each LVAD inflow cannula angulation is quantitatively evaluated based on platelet shear stress history and residence time. Intraventricular hemodynamics are strongly influenced by LVAD inflow cannula angulation. Platelet behavior indicates elevated thrombogenic potential for certain inflow cannula angles, potentially leading to platelet activation. Our analysis demonstrates that the optimal range of inflow angulation is within 0±7° of the left ventricular apical axis.

CONCLUSIONS

Angulation of the inflow cannula >7° from the apical axis (axis connecting mitral valve and ventricular apex) leads to markedly unfavorable hemodynamics as determined by computational fluid dynamics. Computational hemodynamic simulations incorporating Lagrangian and Eulerian metrics are a powerful tool for studying optimization of LVAD implantation strategies, with the long-term potential of improving outcomes.

Coronary Artery Remodeling and Fibrosis With Continuous-Flow Left Ventricular Assist Device Support

BACKGROUND

Coronary artery fluid dynamics may be altered because of the nonphysiological flow seen in continuous-flow left ventricular assist devices (CF-LVADs). Our aim was to study the structure and composition of coronary vessels after CF-LVAD.

METHODS AND RESULTS

Coronary arteries were collected from patients with heart failure (HF) at the time of transplantation, of whom 15 were supported with a CF-LVAD before transplant (HF+LVAD group) and 9 were not (HF non-LVAD group). In addition, coronary samples were obtained from 5 nonfailing age-matched donors (nonfailing group). Histological analysis was performed to quantify coronary morphology, composition, vascular fibrosis, and vasa vasorum density. The age and sex mix of the 3 groups were similar, and the mean duration of LVAD support was 213 days. Compared with patients with HF and nonfailing donors, the arteries from patients with HF+LVAD had expansion of the adventitia, breakdown of the internal elastic lamina, and increased adventitial collagen deposition and density of vasa vasorum.

CONCLUSIONS

Among patients supported with CF-LVADs, the coronary arteries develop marked remodeling with increased adventitial fibrosis. The physiological consequences of these structural changes are unknown, but it is possible that arterial contractility may be impaired, thus limiting coronary flow reserve and promoting myocardial ischemia. This may contribute to CF-LVAD complications, such as ventricular arrhythmias and right ventricular failure. As more patients receive CF-LVADs and new pump technology attempts to modulate flow profiles and pulsatility, further research is needed to understand the mechanisms and long-term sequela of these changes in coronary arteries and other vascular beds.

Living Without a Pulse: The Vascular Implications of Continuous-Flow Left Ventricular Assist Devices

Pulsatility seems to have a teleological role because evolutionary hierarchy favors higher ordered animals with more complex, multichamber circulatory systems that generate higher pulse pressure compared with lower ordered animals. Yet despite years of such natural selection, the modern generation of continuous-flow left ventricular assist devices (CF-LVADs) that have been increasingly used for the last decade have created a unique physiology characterized by a nonpulsatile, nonlaminar blood flow profile with the absence of the usual large elastic artery Windkessel effect during diastole. Although outcomes and durability have improved with CF-LVADs, patients supported with CF-LVADs have a high rate of complications that were not as frequently observed with older pulsatile devices, including gastrointestinal bleeding from arteriovenous malformations, pump thrombosis, and stroke. Given the apparent fundamental biological role of the pulse, the purpose of this review is to describe the normal physiology of ventricular-arterial coupling from pulsatile flow, the effects of heart failure on this physiology and the vasculature, and to examine the effects of nonpulsatile blood flow on the vascular system and potential role in complications seen with CF-LVAD therapy. Understanding these concomitant vascular changes with CF-LVADs may be a key step in improving patient outcomes as modulation of pulsatility and flow characteristics may serve as a novel, yet simple, therapy for reducing complications.

Performance Improvement to Decrease Readmission Rates for Patients With a Left Ventricular Assist Device

BACKGROUND

The 30-day readmission rate for patients with a left ventricular assist device implantation at a large, urban, Midwest hospital system (from October 2013 to September 2014) was estimated at 32.1%.

PROBLEM STATEMENT

Readmission rates were a concern at this facility. Review of the readmissions, change in practice, and home expectations of patients and families have identified an opportunity to improve the transitions of care for this left ventricular assist device (LVAD) program. Therefore, the purpose of this project was to evaluate the effectiveness and feasibility of a transitional care model (TCM) for care of patients with left ventricular devices.

METHODS

Ten patients were enrolled in the pilot that was implemented in June 2015. A transitional care nurse trained to support patients with ventricular assist devices was used to facilitate patient flow. The goal was to create an individualized plan for the development or improvement of self-management skills to decrease readmission rates. The transitional care nurse collaborated with the ventricular device team.

OUTCOMES

The 30-day readmission rate during the pilot was 14.3% compared to the previous annual overall rate of 42.6%.

IMPLICATIONS FOR PRACTICE

Based on these results, further research is recommended into interventions consistent with the TCM to advance care coordination and to facilitate care transition in the this fragile patient population.

Successful Placement of Nasointestinal Feeding Tubes Using an Electromagnetic Sensor-Guided Enteral Access System in Patients With Left Ventricular Assist Devices

Technology advances have made it possible to prolong life for patients with heart failure who are not transplant candidates or while awaiting transplant. Many different cardiac devices are available that can be used as a bridge to transplant (temporary support) or as a destination therapy (permanent support). Placement of these devices can cause complications that, if not addressed, could negatively impact the nutrition status of patients. Placement of nasointestinal feeding tubes using an electromagnetic sensor-guided enteral access system (EMS-EAS) has been difficult in patients with implantable devices because of the potential for interference with the EMS-EAS and the left ventricular assist device (LVAD). The purpose of this paper was to report the results using a modified method to place nasointestinal tubes in patients with LVADs by elevating the receiver off the xiphoid process. There were 42 feeding tube placements in 25 patients. Results showed a 69% success rate of placement into the small bowel, 13 unsuccessful placements, and no adverse or sentinel events associated with tube placement using this method. Results indicated the modified method is a safe approach to help expedite feeding tube placement in a nutritionally compromised patient. The success rate is comparable with non-LVAD patient populations requiring nasointestinal tube placement via EMS-EAS. To our knowledge, this is the first published case series addressing a modified method for nasointestinal tube placement in patients with LVAD. More research is needed to determine ideal separation distances or other techniques to improve the success rate in this patient population.

Ventricular Assist Device in Acute Myocardial Infarction

BACKGROUND

Patients with acute myocardial infarction (AMI) complicated by acute heart failure or cardiogenic shock have high mortality with conventional management.

OBJECTIVES

This study evaluated outcomes of patients with AMI who received durable ventricular assist devices (VAD).

METHODS

Patients in the INTERMACS (Interagency Registry for Mechanically Assisted Circulatory Support) registry who underwent VAD placement in the setting of AMI were included and compared with patients who received VAD for non-AMI indications.

RESULTS

VAD were implanted in 502 patients with AMI: 443 left ventricular assist devices; 33 biventricular assist devices; and 26 total artificial hearts. Median age was 58.3 years, and 77.1% were male. At implantation, 66% were INTERMACS profile 1. A higher proportion of AMI than non-AMI patients had pre-operative intra-aortic balloon pumps (57.6% vs. 25.3%; p < 0.01), intubation (58% vs. 8.3%; p < 0.01), extracorporeal membrane oxygenation (17.9% vs. 1.7%, p < 0.01), cardiac arrest (33.5% vs. 3.3%, p < 0.01), and higher-acuity INTERMACS profiles. At 1 month post-VAD, 91.8% of AMI patients were alive with ongoing device support, 7.2% had died on device, and 1% had been transplanted. At 1-year post-VAD, 52% of AMI patients were alive with ongoing device support, 25.7% had been transplanted, 1.6% had left VAD explanted for recovery, and 20.7% had died on device. The AMI group had higher unadjusted early phase hazard (hazard ratio [HR]: 1.24; p = 0.04) and reduced late-phase hazard of death (HR: 0.57; p = 0.04) than the non-AMI group did. After accounting for established risk factors, the AMI group no longer had higher early mortality hazard (HR: 0.89; p = 0.30), but it had lower late mortality hazard (HR: 0.55; p = 0.02).

CONCLUSIONS

Patients with AMI who receive VAD have outcomes similar to other VAD populations, despite being more critically ill pre-implantation. VAD therapy is an effective strategy for patients with AMI and acute heart failure or shock in whom medical therapy is failing.

Tunneling a Pulmonary Artery Graft: A Simplified Way to Insert and Remove a Temporary Right Ventricular Assist Device

Right ventricular failure can occur early or late after left ventricular assist device implantation. Support with a right ventricular assist device is needed in patients whose right ventricular failure does not respond to conservative management. The use of a temporary right ventricular assist device can enable the recovery of right ventricular function and avoid the use of a more permanent biventricular assist device, which is associated with complications and higher costs. We present our technique of instituting temporary right ventricular assist device support in patients who have undergone left ventricular assist device implantation.

Left Ventricular Assist Devices: A Rapidly Evolving Alternative to Transplant

Left ventricular assist devices are becoming an increasingly prevalent therapy for patients with Stage D heart failure with reduced ejection fraction. Technological advances have improved the durability of these devices and have significantly lengthened survival in these patients. Quality of life is also improved, although adverse events related to device therapy remain common. Nevertheless, with the continuing organ donor shortage for cardiac transplantation, left ventricular assist devices are frequently serving as a substitute for transplant, particularly in the elderly patient.

Percutaneous ventricular assist device placement during active cardiopulmonary resuscitation for severe refractory cardiogenic shock after acute myocardial infarction

Cardiogenic shock after acute myocardial infarction is associated with a high mortality rate despite modern reperfusion methods and intra-aortic balloon pump support. For myocardial infarction patients in cardiogenic shock that is refractory to intra-aortic ballon pump counterpulsation and pressors (severe refractory cardiogenic shock), there are limited means to rapidly provide additional hemodynamic support. We present the case of a 49-year-old man who presented with an anterior wall acute myocardial infarction complicated by cardiogenic shock. After resuscitation and stabilization with intra-aortic balloon pump and pressor support, the patient underwent successful emergent percutaneous transluminal coronary angioplasty and stenting of the left anterior descending coronary artery. Forty-eight hours later, the patient again went into severe refractory cardiogenic shock; pulseless electrical activity arrest followed. Cardiopulmonary resuscitation was started, and the patient underwent urgent placement of a TandemHeart percutaneous ventricular assist device. The device enabled the reversal of terminal hemodynamic collapse during active cardiopulmonary resuscitation, subsequent stabilization of the patient, and discharge of the patient from the hospital after device removal. In this patient, the percutaneous ventricular assist device was successful in the treatment of severe refractory cardiogenic shock after acute myocardial infarction.

Use of a percutaneous ventricular assist device for treatment of cardiogenic shock due to critical aortic stenosis

We present the case of a 72-year-old woman who was transferred to our institution in cardiogenic shock and with multiple-organ failure, due to critical aortic stenosis. She was considered too high-risk to undergo aortic valve replacement. A TandemHeart percutaneous ventricular assist device was used to stabilize the patient's condition before surgery, and she subsequently underwent successful aortic valve replacement. To our knowledge, this is the 1st report in the literature of this particular application of the TandemHeart device.

Saphenous vein graft flow during left ventricular assistance with an axial-flow pump

The effects of continuous-flow support on bypass graft flow have not been quantified clinically. Continuous-flow left ventricular assist devices unload the left ventricle throughout the cardiac cycle, which narrows pulse pressure and converts passive left ventricular filling during diastole to active flow throughout the cardiac cycle. We report the case of a 63-year-old man with severe congestive heart failure who underwent coronary artery bypass grafting and was supported with an axial-flow pump. In this patient, saphenous vein graft flow during left ventricular assistance provided adequate coronary perfusion.

Hemodynamic support with a percutaneous left ventricular assist device during stenting of an unprotected left main coronary artery

Coronary artery bypass grafting prolongs survival in patients with left main coronary artery stenosis. However, this benefit is denied to patients who refuse the procedure or who are poor surgical candidates due to comorbid conditions. We describe a novel technique for the percutaneous revascularization of stenosis in an unprotected left main coronary artery in high-risk patients. The TandemHeart, a percutaneously inserted left ventricular assist device, was used to provide periprocedural hemodynamic support during angioplasty and stenting of an unprotected left main coronary artery for stenosis in a 70-year-old woman. The device was removed immediately after the procedure, and the patient was discharged from the hospital on the 2nd postprocedural day. The potential advantages of angioplasty with the support of percutaneous left ventricular assist devices in high-risk patients are discussed.

Congenital absence of anterior pericardium at left ventricular assist device implantation

We report a case of congenital absence of the anterior pericardium in a 41-year-old man who was undergoing implantation of a left ventricular assist device for treatment of congestive heart failure.

First clinical use of the redesigned HeartMate II left ventricular assist system in the United States: a case report

Axial flow ventricular assist devices show great promise as a potential treatment for patients with end-stage heart failure. The HeartMate II system, redesigned on the basis of initial clinical experiences in Europe, is now in clinical trials in the United States. We report on the 1st use of the newly redesigned HeartMate II in the United States. The system has unique features, which include an accurate flow estimator and the ability to automatically detect and correct excessive left ventricular unloading. The new design also incorporates changes in the texturing of the blood-contacting surfaces to prevent thrombosis. The implantation technique and configuration are similar to those of the HeartMate XVE LVAS and require a median sternotomy for access. The 1st patient to receive the device in the United States has had an uncomplicated perioperative course and now awaits transplantation.

Management of patients supported on the Hemopump cardiac assist system

The Hemopump Cardiac Assist System is a relatively new intraarterial, axial-flow circulatory assist device that offers temporary left ventricular support to patients in refractory cardiogenic shock, without requiring major surgery for insertion. Use of the Hemopump is associated with a low complication rate. Device-related morbidity is extremely rare. Because the Hemopump is safe for use in community hospitals, the number of patients supported by this device is expected to increase. In this report, we present general guidelines for the care of patients supported by the Hemopump. We describe techniques for the management of afterload reduction, supravalvular dislodgement, device malfunction, ventricular ectopy, intracardiac shunting, and inflow cannula obstruction.