Thomas Schlöglhofer

Identification and Management of Pump Thrombus in the HeartWare Left Ventricular Assist Device System: A Novel Approach Using Log File Analysis.

OBJECTIVES The study sought to characterize patterns in the HeartWare (HeartWare Inc., Framingham, Massachusetts) ventricular assist device (HVAD) log files associated with successful medical treatment of device thrombosis. BACKGROUND Device thrombosis is a serious adverse event for mechanical circulatory support devices and is often preceded by increased power consumption. Log files of the pump power are easily accessible on the bedside monitor of HVAD patients and may allow early diagnosis of device thrombosis. Furthermore, analysis of the log files may be able to predict the success rate of thrombolysis or the need for pump exchange. METHODS The log files of 15 ADVANCE trial patients (algorithm derivation cohort) with 16 pump thrombus events treated with tissue plasminogen activator (tPA) were assessed for changes in the absolute and rate of increase in power consumption. Successful thrombolysis was defined as a clinical resolution of pump thrombus including normalization of power consumption and improvement in biochemical markers of hemolysis. Significant differences in log file patterns between successful and unsuccessful thrombolysis treatments were verified in 43 patients with 53 pump thrombus events implanted outside of clinical trials (validation cohort). RESULTS The overall success rate of tPA therapy was 57%. Successful treatments had significantly lower measures of percent of expected power (130.9% vs. 196.1%, p = 0.016) and rate of increase in power (0.61 vs. 2.87, p < 0.0001). Medical therapy was successful in 77.7% of the algorithm development cohort and 81.3% of the validation cohort when the rate of power increase and percent of expected power values were <1.25% and 200%, respectively. CONCLUSIONS Log file parameters can potentially predict the likelihood of successful tPA treatments and if validated prospectively, could substantially alter the approach to thrombus management.

Repair of Left Ventricular Assist Device Driveline Damage Directly at the Transcutaneous Exit Site

With increasing support duration of cardiac assist devices, transcutaneous drivelines remain a weak point of the therapy. First, they can be an entry point for infections, and second, cable lesions and even electrical failures due to material fatigue and eventual carelessness can occur. We report a case of a damaged outer sheath of a ventricular assist device driveline cable directly at the exit site, where the standard repair procedure with self-fusing tape may lead to biocompatibility problems and irritation of the entrance through the skin. Therefore, a new procedure was developed using a special sleeve expander tool and a highly expandable latex tubing to stabilize the defect in a flexible and biocompatible manner. A patient experienced a fracture of the outer sheath of a HeartWare HVAD driveline directly at the skin entrance (approximately 15 mm long, 5 mm distal from the skin). The metal strands and the electrical functionality were yet not affected, therefore, a pump exchange was not indicated. After considering several conventional solutions for repair as not applicable, a new approach was developed: a sleeve expander tool was applied, which allowed radial stretching of the latex tubing. After preparations of the tool and the cable site, the pump was briefly disconnected, the tubing was moved over the connector and was released at the site of fracture. The problem could be solved by keeping the cables flexibility and without additional risks to the skin. Within a still ongoing (5-month) follow-up, the skin entrance returned to perfect condition and no further intervention was necessary. In conclusion, this method allows a quick stabilization and repair of damaged driveline isolations even near the exit site, resulting in a biocompatible surface and consistent flexibility of the cable.

Increased Thromboembolic Events With Dabigatran Compared With Vitamin K Antagonism in Left Ventricular Assist Device PatientsCLINICAL PERSPECTIVE

Background— Left ventricular assist device–supported patients are usually anticoagulated with a combination of aspirin and vitamin K antagonists. Long-term vitamin K antagonist therapy can be complicated by unstable international normalized ratio values and patient-related compliance problems. Therefore, direct thrombin inhibitors may represent an alternative to vitamin K antagonists. Methods and Results— Thirty HeartWare ventricular assist device patients with stable renal function were planned for this prospective, randomized, open-label, single-center study. Patients were randomized to receive either phenprocoumon or dabigatran in addition to aspirin for long-term anticoagulation. Treatment duration was scheduled for 1 year and stopped after observation of a primary end point. Dabigatran dose was 110 and 75 mg BID in patients with normal or impaired renal function (glomerular filtration rate >80 mL/min or between 80 and 30 mL/min, respectively). The study was stopped prematurely for safety reasons after 16 patients (61±8 years, 1 female) were randomized. Thromboembolic events occurred in 4 subjects receiving dabigatran (50%) and in 1 receiving phenprocoumon (13%; P=0.28). No major bleeding was recorded, and no patient died during the study. Median time to treatment termination was significantly shorter in dabigatran patients (8.5 versus 12.0 months; P=0.015). Conclusions— Thromboembolic events on dabigatran led to early termination of a randomized controlled trial of dabigatran versus phenprocoumon in left ventricular assist device patients. Clinical Trial Registration— https://www.clinicaltrials.gov. Unique identifier: NCT02872649.

Myocardial Recovery in Peripartum Cardiomyopathy After Hyperprolactinemia Treatment on BIVAD.

Peripartum cardiomyopathy (PPCMP) requiring mechanical circulatory support is rare; however, it is a life-threatening disease with recovery rates poorer than expected. Herein, we describe a case of successful recovery of a patient with PPCMP. Implantation of a biventricular ventricular assist device was performed; additionally, the patients hyperprolactinemia was treated with cabergoline, resulting in a fast complete restoration of ventricular function.

Daily life activity in patients with left ventricular assist devices.

Purpose Exercise capacity is usually evaluated by peak oxygen consumption (peak-VO2). However, assessment of peak-VO2 in patients with a left ventricular assist device (LVAD) might not be the best method to provide insight into their daily life activity. The aim of this study was to assess the postoperative activity of LVAD patients using actigraphy and to compare these patients to a healthy and a heart-transplanted (HTx) population. Methods Activity was continuously monitored using wrist-accelerometers in LVAD patients after implantation, during 4 weeks of rehabilitation following hospital discharge, and at 2 follow-up assessments. Peak-VO2 values measured during rehabilitation were correlated with activity. Additionally, actigraphy data from LVAD recipients were compared with data measured in healthy and HTx subjects. Results After hospital discharge a significant increase in physical activity of LVAD recipients was observed (55 ± 28 vs. 102 ± 23 Activity Scores, n = 11, p = 0.002). During rehabilitation as well as at the follow-ups (140 ± 43 and 253 ± 33 days post-implantation) no significant increase in activity was observed. Peak-VO2 values correlated to daily activity both in LVAD and HTx patients (r > 0.5). Average daily activity was significantly lower in LVAD and HTx patients than in the healthy population (130 ± 30 and 148 ± 60 vs. 245 ± 63 Activity Score; n = 18 in each group, p < 0.001). Conclusions Activity in LVAD recipients increased substantially after hospital discharge with no further significant improvement observed during a period of 8.5 months. Similarly to the peak-VO2, also the daily activity of LVAD recipients was 53% compared to healthy subjects. These results highlight the need for an optimized physical therapy in this patient cohort.

Importance of linguistic details in alarm messages of ventricular assist devices

Purpose In the daily use of ventricular assist devices (VAD), and especially in emergency situations, an easy, self-explanatory handling of the peripheral components is essential to solving life-threatening situations, for non-experienced bystanders as well as professional staff members. It has been proven that displaying messages can significantly improve proper reactions. However, in the case we report, an accidental pump cable disconnection could not be solved without the assistance of the VAD coordinator. Case Report A long-term HeartWare® HVAD patient inadvertently disconnected himself from the pump, most probably due to a metabolically caused mental disorder, for which he had been readmitted to the hospital. Unluckily, the pump cable slipped beneath the bed sheet and the ward staff was not able to solve the problem. The staff who were involved claimed that the messages on the controller did not help them to resolve the difficulty. A comparison between the German and English texts revealed some ambivalence in the German wordings. Results Laypersons were asked to respond to this situation in a simulated scenario, starting with the original alarm messages “VAD stopped”-“VAD gestoppt” and “Connect Driveline”-“Verb-Kabel anschl.” If they were unable to solve the problem within 3 minutes, another translation was offered orally: “Pumpe steht” and “Pumpenkabel anschließen”. None of the 5 test persons were able to respond correctly to the emergency situation with the original translation, but when provided with a modified translation, everybody solved the problem within 30 seconds. Conclusions Even small linguistic differences can lead to critical differences in the usability and, thus, the safety of VAD peripherals. Detailed discussions with professional translators and/or practical tests of failure scenarios may optimize usability.

An alternative method to create highly transparent hollow models for flow visualization.

Aim Transparent hollow models are needed to visualize and quantify flow in various applications. To obtain the final transparent model, an intermediate molding of the fluid space with an easily removable material is required. Currently used materials to produce this intermediate molding have limitations: toxicity, cost, and a tendency to penetrate the final model, thereby degrading its transparency. In this work an alternative method is presented using chocolate as the fluid-space molding material. Methods Starting from a three-dimensional computer aided design (CAD) geometry, a fluid space model of a human aorta was produced out of chocolate. The replica was coated and cast in a block of highly transparent silicone (Sylgard184; Dow-Corning, Midland, MI, USA). After the silicone was cured, the chocolate was removed using hot water. The geometric accuracy of the fluid-space mold and the transparency of the final model were investigated. Results The mean divergence of the chocolate fluid-space mold from the original geometry was 5.7%. The silicone casting had no defects and perfect transparency for particle tracking. Fluid boundaries were invisible when tested with a fluid whose refractive index matched silicone. Conclusions The process we describe is a cheap and effective way to create transparent models that have excellent optical quality.

International coordinator survey results on the outpatient management of patients with the HeartWare® ventricular assist system

Purpose While the HeartWare® Ventricular Assist System (HVAS) is a successful therapy for end-stage heart failure, outpatient management methods can vary significantly and require further investigation. Methods A survey to assess the long-term HVAS patient management and monitoring strategies was completed by 36 international heart centers that currently have over 1,450 patients on VAD support either at home or in the hospital. Multiple choice questions examined VAD program characteristics, anticoagulation management, driveline exit-site dressing and showering recommendations, blood pressure and pump parameter monitoring, and patient discharge protocols. Results Outpatient international normalized ratio (INR) was most frequently measured every 3–4 days (28.6%), and the most frequent schedule for changing driveline exit site dressings was 3 times per week (30.6%). Only 25.7% of centers required their patients to measure blood pressure at home. A subgroup analysis was performed to assess the influence of center experience and larger centers generally had more frequent monitoring compared to smaller centers. Conclusions This survey showed specific differences in outpatient management strategies that were previously unreported. However, further studies with correlations to patient outcomes are necessary to determine optimal patient management recommendations.

Chapter 22 – Wearable systems

A multitude of wearable ventricular assist devices (VADs) currently provide circulatory support to heart failure patients worldwide. An important aspect of VAD development is the usability of a device, which is beyond the performance of bench tests to show proper functioning. User-friendly alarms, pump flow monitoring, adequate product design including sufficient battery lifetime, and safe power supply, as well as pump-to-controller connectors, are mandatory in this lifesaving technology. Despite existing human factor engineering guidelines and standards, several usability studies are indicating potential design limitations of currently used VADs, thus leading to restrictions in daily life and to emotional distress and caregiver burden. This chapter aims to summarize the history, development, and current status of wearable VAD components; it will also summarize the necessary future steps for refinement to minimize technical complications and to improve patient safety and user satisfaction.

A Standardized Telephone Intervention Algorithm Improves the Survival of Ventricular Assist Device Outpatients: VAD TELEPHONE INTERVENTION ALGORITHM

Abstract Ventricular assist devices (VADs) are an established therapeutic option for patients with chronic heart failure. Continuous monitoring of VAD parameters and their adherence to guidelines are crucial to detect problems in an early stage to optimize outcomes. A telephone intervention algorithm for VAD outpatients was developed, clinically implemented and evaluated. During the phone calls, a structured inquiry of pump parameters, alarms, blood pressure, INR, body weight and temperature, exit‐site status and heart failure symptoms was performed and electronically categorized by an algorithm into 5 levels of severity. VAD outpatient outcomes without (n = 71) and with bi‐weekly telephone interviews in their usual care (n = 25) were conducted using proportional hazard Cox regression, with risk adjustment based on a propensity score model computed from demographics and risk factors. From February 2015 through October 2017, 25 patients (n = 3 HeartMate II, n = 4 HeartMate 3 and n = 18 HeartWare HVAD) underwent 637 telephone interventions. In 57.5% of the calls no problems were identified, 3.9% were recalled on the next day because of alarms. In 26.5% (n = 169), the VAD Coordinator had to refer to the physician due to elevated blood pressure (n = 125, >85 mm Hg), INR < 2.0 or > 4.0 (n = 24) or edema (n = 10), 11.9% of the calls led to a follow‐up because of equipment or exit‐site problems. Propensity‐adjusted 2‐year survival (89% vs. 57%, P = 0.027) was significantly higher for the telephone intervention group. Continuous, standardized communication with VAD outpatients is important for early detection of upcoming problems and leads to significantly improved survival.