Left Ventricular Assist Device Outflow Cannula Obstruction by the Rare Environmental Fungus Myceliophthora thermophila

LVAD Outflow Graft Role in Pump Thrombosis

Left ventricular assist devices are (LVAD) used for circulatory support in patients with end-stage heart failure. Hemolysis/pump dysfunction is a well-known complication of this therapy with various etiologic causes. A small proportion of these complications are caused by outflow graft obstructions; this complication has received little attention in the scientific literature. Herein, we provide a comprehensive overview of the role of the LVAD outflow graft obstruction and its treatment options.

Postoperative Management for Patients With Durable Mechanical Circulatory Support Devices

Mechanical circulatory support devices have been approved as bridge to transplantation, as bridge to recovery, or as destination therapy to treat end-stage heart failure. The perioperative challenges for the anesthesiologist and the intensivist caring for these patients include device-related complications, hemodynamic instability, arrhythmias, right ventricular failure, and coagulopathy. Perioperative management in this high-risk population has a significant impact on patient outcomes. This review focuses immediate postoperative intensive care unit management of device-related complications.

Screening for Outflow Cannula Malfunction of Left Ventricular Assist Devices (LVADs) With the Use of Doppler Echocardiography: New LVAD-Specific Reference Values for Contemporary Devices

BACKGROUND

Echocardiographic assessment of left ventricular assist devices (LVADs) is used as a screening tool to evaluate the integrity and mechanics of the pump and circuit. We aimed to 1) establish the normal range and upper reference limit of peak velocity of the outflow cannula for the modern era of LVADs and 2) assess the clinical performance of the currently cited and newly proposed reference limits in patients with continuous-flow LVADs as a screening tool for cannula malfunction.

METHODS

LVAD outflow peak CW velocities were measured with the use of Doppler transthoracic echocardiography (TTE) in 57 patients with LVADs (44 with Heartmate II (HM2), 13 with Heartware (HW)). The average velocity and the upper and lower normal reference limits (defined as ±2 standard deviations from the mean) for each LVAD type was calculated. The upper reference limit was then used as a screening threshold for cannula malfunction.

RESULTS

The average outflow cannula peak velocity for the normal HM2 cohort was 1.86 ± 0.44 m/s with upper and lower reference limits of 2.73 m/s and 0.98 m/s, respectively. The average outflow cannula peak velocity for the normal HW cohort was 2.36 ± 0.53 m/s with upper and lower reference limits of 3.42 m/s and 1.3 m/s, respectively, which was significantly higher than the HM2 cohort (P = .004).

CONCLUSIONS

In both HM2 and HW LVADs, the average peak outflow velocity and reference limit for the normal population, as measured by Doppler TTE, was markedly higher than the currently used LVAD reference limits of 2 m/s and are significantly different between devices. Patients with peak outflow velocities above our upper reference limits should be evaluated for LVAD outflow cannula malfunction.

Case report: atypical fungal obstruction of the left ventricular assist device outflow cannula

We describe a very rare case of outflow cannula obstruction with fungal infectious thrombus formation. Discussion includes the etiology, diagnosis, and management of fungal infection complications related with long-term mechanical circulatory support. Left ventricular assist devices (LVADs) are increasingly used as bridge to transplant and permanent long-term therapy in the population with end-stage heart failure. Even though better clinical outcomes have been achieved with the newer-generation continuous-flow devices, infection complications are still a major risk for patients with continuous-flow LVAD implantation in long-term follow-up [Ann Thorac Surg 90:1270-1277, 2010]. Device-related infections can be categorized as driveline infections, pump-pocket infections, and LVAD-associated endocarditis [Expert Rev Med Devices 8: 627-634, 2011]. The microbiological profile is very heterogeneous; the most common pathogens are Staphylococcus, Pseudomonas, Streptococcus species, and Candida. Severe fungal infection may lead to dysfunction of the LVAD due to obstructive mass formation within the device. Due to the only anecdotal reports in the current literature, we present a very rare case of outflow fungal infectious thrombus formation leading to outflow cannula obstruction in patient with LVAD.

Intraoperative transesophageal echocardiography and ventricular assist device insertion

A decade after cardiac surgery was established, transesophageal echocardiography (TEE) was developed and used to evaluate perioperative cardiac performance. It has become an invaluable tool to provide real-time information in the cardiac operating room. TEE provides practical and useful information prior to insertion as well as after placement of the device. Additionally, during episodes of device malfunction or hemodynamic instability, TEE can be extremely useful in defining the etiology of the problem. As ventricular assist devices (VADs) have undergone evolution in design and as more VADs are being implanted, the development of specific indications for TEE use during device placement is a relevant issue. Formal guidelines for use of TEE during VAD insertion are yet to be adopted or implemented, but for now TEE remains an essential tool for managing this patient population.

Invasive Myceliophthora thermophila infection mimicking invasive aspergillosis in a neutropenic patient: a new cause of cross-reactivity with the Aspergillus galactomannan serum antigen assay

Myceliophthora thermophila is a thermophilic mould widely found in the environment but rarely responsible for human infections. We describe a case of invasive Myceliophthora thermophila infection mimicking invasive aspergillosis in a neutropenic patient with haematological malignancy. Cross-reactivity with Aspergillus galactomannan assay (GM) was demonstrated by repeated positive results and confirmed by cross-reaction between the fungal isolate and the GM assay. The patient was successfully treated with voriconazole. Potential GM cross-reactivity must be considered in future studies including patients categorized as having probable invasive aspergillosis using the GM as the only mycological criterion.

HeartMate II ventricular assist device thrombosis-an echocardiographic approach to diagnosis: can Doppler evaluation of flow be useful?

A 68-year-old man was admitted to the hospital 4 months after HeartMate II ventricular assist device implantation, because his clinical status had deteriorated and his levels of lactate dehydrogenase and free hemoglobin had increased. Transthoracic echocardiography performed at admission revealed decreased basic diastolic continuous flow velocity with a pulsatile increase in flow velocity during ventricular contraction in both inflow and outflow cannulas. Twelve hours after beginning lytic therapy, basal diastolic continuous flow velocity had increased, and the amplitude between diastolic and systolic flow velocity had decreased. The clinical status of the patient improved, and his lactate dehydrogenase decreased. A decrease in basal diastolic flow may be a valuable marker of flow disturbance in continuous flow ventricular assist devices.