The Status of Failure and Reliability Testing of Artificial Blood Pumps

Usability of ventricular assist devices in daily experience: a multicenter study

In daily life, the safe, intuitive use of ventricular assist devices (VADs) and especially their peripheral components is not only a question of life quality, but also sometimes crucial for survival. To investigate the advantages and disadvantages of different systems and to get patient feedback on preferred features, a multicenter study was initiated. Based on previous single-center studies, a questionnaire was developed to ascertain patients' experiences, difficulties with, and desires concerning use of the system. This questionnaire was provided both to ongoing patients and to new VAD patients after a minimum hospital discharge time of 6 weeks, at a regular checkup. Additionally, the patients completed a standardized questionnaire on life quality (Kansas City Cardiomyopathy Questionnaire). The centers that contributed to this study were Bad Oeynhausen, Berlin, Hannover, and Vienna. Three hundred fifty-two completed questionnaires on eight different pump types were obtained. An important result is that 42% of those questioned dropped their controller bag at least once. Depending on the device, between 2 and 55% disconnected it unintentionally. Confidence in safe use of the system decreased significantly with age, from 80% at age 20-30 years to 33% at 70-80 years. In devices with an LCD display, 94% considered the readability sufficient. Ninety-four percent considered the training adequate. Between 22 and 88% of the patients called the emergency telephone hotline, depending on the device, and 23-46% depending on the center. This first multicenter study on VAD usability reveals considerable differences among devices and centers. The comparative assessment aims to help optimize device design, patient management, and training.

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.

A durability study of a paracorporeal pulsatile electro-mechanical pneumatic biventricular assist device

In 2002, the paracorporeal pulsatile electro-mechanical pneumatic ventricular assist device (VAD) began to be developed by the Korea Artificial Organ Center at Korea University under a Health & Medical Technology Research and Development program which finished in 2008. In vitro durability testing was conducted on the paracorporeal pulsatile pneumatic VAD to determine device durability and to evaluate device failures. The 1- and 2-year reliability of the paracorporeal pulsatile pneumatic VAD was shown to be 91.2% and 54.9%, respectively, with an 80% confidence level. Failure modes were analyzed using fault tree analysis, with customized software continuously acquiring data during the test period. After this period, 21 in vivo animal tests were done, with 14 cases of left atrium to left ventricle (LV) inflow cannulation (36Fr)/outflow grafting to descending aorta, and seven cases of apex cannulation of LV to descending aorta (12 mm). The longest postoperative day (182 days) in Korea was recently recorded in in vivo animal testing (bovine, 90 kg, male, 3.5-4.0 L/min flow rate, and 55 bpm).

New strategies for surgical management of ischemic cardiomyopathy

Ischemic cardiomyopathy affects an estimated 3 million people in the USA and is the most common cause of heart failure. Traditional operations have included heart transplantation, myocardial revascularization, mitral valve repair, left ventricular reconstruction, first-generation left ventricular assist devices and cardiac resynchronization therapy. These operations have become safer in recent times, due to improved technologies. Current technologies and surgical approaches can benefit a significant number of patients. However, there remains a large group of patients in whom traditional approaches can not be offered. Newer generation ventricular assist devices, passive ventricular restraint devices and cellular-based therapies (including skeletal- and bone marrow-derived stem cells) have the potential to be more universal in their applications. Ongoing investigations with each of these modalities will allow surgeons to offer treatment to patients who are not considered surgical candidates at this time.

Effects of mechanical valve orifice direction on the flow pattern in a ventricular assist device

We have been developing a pneumatic ventricular assist device (PVAD) system consisting of a diaphragm-type blood pump. The objective of the present study was to evaluate the flow pattern inside the PVAD, which may greatly affect thrombus formation, with respect to the inflow valve-mount orientation. To analyze the change of flow behavior caused by the orifice direction (OD) of the valve, the flow pattern in this pump was visualized. Particle image velocimetry was used as a measurement technique to visualize the flow dynamics. A monoleaflet mechanical valve was mounted in the inlet and outlet ports of the PVAD, which was connected to a mock circulatory loop tester. The OD of the inlet valve was set at six different angles (OD = 0 degrees, 45 degrees, 90 degrees, 135 degrees, 180 degrees, and 270 degrees, where the OD opening toward the diaphragm was defined as 0 degrees ) and the pump rate was fixed at 80 bpm to create a 5.0 l/min flow rate. The main circular flow in the blood pump was affected by the OD of the inlet valve. The observed regional flow velocity was relatively low in the area between the inlet and outlet port roots, and was lowest at an OD of 90 degrees. In contrast, the regional flow velocity in this area was highest at an OD of 135 degrees. The OD is an important factor in optimizing the flow condition in our PVAD in terms of preventing flow stagnation, and the best flow behavior was realized at an OD of 135 degrees.