Experimental Wall Shear Estimation as a Means of Predicting Thrombus Formation Within a 50cc Penn State Blood Pump

2010 ◽  
Author(s):  
Jason C. Nanna ◽  
Stephen R. Topper ◽  
Ning Yang ◽  
Breigh N. Roszelle ◽  
Steven Deutsch ◽  
...  
Keyword(s):  
Heart Function ◽  
Thrombus Formation ◽  
Flow Characteristics ◽  
Ventricular Assist Devices ◽  
Ventricular Assist ◽  
Shear Rates ◽  
Penn State ◽  
Wall Shear ◽  
The 1960S ◽  
Flow Stasis

The use of ventricular assist devices (VADs) as a means of cardiac support for patients with diminished heart function has been investigated since the 1960s [1]. While VAD therapy has had success in assisting the failing heart, thrombus formation within these devices is one of various complications that still limit its long term use. Research has shown that thrombus deposition in VADs is a function of the underlying fluid mechanics within these devices. Areas of flow stasis, high blood residence time, and wall shear rates under 500 s−1 are important flow characteristics driving thrombosis [2].

The 12cc Penn State Pulsatile Pediatric Ventricular Assist Device: Fluid Dynamics Associated With Valve Selection

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Benjamin T. Cooper ◽  
Breigh N. Roszelle ◽  
Tobias C. Long ◽  
Steven Deutsch ◽  
Keefe B. Manning
Keyword(s):  
Heart Valves ◽  
Flow Characteristics ◽  
Ventricular Assist Devices ◽  
Ventricular Assist ◽  
Bridge To Transplant ◽  
Recirculating Flow ◽  
Image Velocimetry ◽  
Penn State ◽  
Wall Shear ◽  
Pulsatile Vad

The mortality rate for infants awaiting a heart transplant is 40% because of the extremely limited number of donor organs. Ventricular assist devices (VADs), a common bridge-to-transplant solution in adults, are becoming a viable option for pediatric patients. A major obstacle faced by VAD designers is thromboembolism. Previous studies have shown that the interrelated flow characteristics necessary for the prevention of thrombosis in a pulsatile VAD are a strong inlet jet, a late diastolic recirculating flow, and a wall shear rate greater than 500s−1. Particle image velocimetry was used to compare the flow fields in the chamber of the 12cc Penn State pediatric pulsatile VAD using two mechanical heart valves: Björk–Shiley monostrut (BSM) tilting disk valves and CarboMedics (CM) bileaflet valves. In conjunction with the flow evaluation, wall shear data were calculated and analyzed to help quantify wall washing. The major orifice inlet jet of the device containing BSM valves was more intense, which led to better recirculation and wall washing than the three jets produced by the CM valves. Regurgitation through the CM valve served as a significant hindrance to the development of the rotational flow.

Impact of Outlet Valve Orientation on Fluid Dynamics of the 12 cc Penn State Pediatric Ventricular Assist Device

2008 ◽  
Author(s):  
Isabella E. Valenti ◽  
Breigh N. Roszelle ◽  
Michael V. Perone ◽  
Steven Deutsch ◽  
Keefe B. Manning
Keyword(s):  
Heart Valves ◽  
Thrombus Formation ◽  
Ventricular Assist Devices ◽  
Ventricular Assist ◽  
Bridge To Transplant ◽  
Penn State ◽  
Outlet Valve ◽  
Cardiovascular Defects ◽  
Interior Walls ◽  
Arteries And Veins

Congenital cardiovascular defects are the leading cause of death among live births [1]. These defects involve the interior walls of the heart, valves, arteries, and veins and change the normal flow of blood through the heart and into the systemic system. Fortunately, several options exist for the more than 35,000 children born with congenital heart disease. Ventricular assist devices (VADs) currently hold the most promise for bridge-to-transplant treatment; however, a major problem for these devices is thrombus formation and deposition.

A Fluid Dynamics Study Focusing on Wall Shear Rates Within the Penn State 12 cc Pulsatile Pediatric Ventricular Assist Device: A Comparison of Mechanical Heart Valve Types

2007 ◽  
Author(s):  
Benjamin T. Cooper ◽  
Breigh N. Roszelle ◽  
Tobias C. Long ◽  
Steven Deutsch ◽  
Keefe B. Manning
Keyword(s):  
Ventricular Assist Device ◽  
Mechanical Heart Valve ◽  
Flow Characteristics ◽  
Assist Device ◽  
Ventricular Assist ◽  
Recirculating Flow ◽  
Image Velocimetry ◽  
Penn State ◽  
Wall Shear ◽  
Pulsatile Vad

Previous studies have shown that the interrelated flow characteristics necessary for the prevention of thrombosis in a pulsatile ventricular assist device (VAD) are a strong inlet jet, a late diastolic recirculating flow, and adequate wall washing (greater than 500 s−1). Particle image velocimetry was used to compare the flow fields in the chamber of the 12 cc Penn State pediatric pulsatile VAD using two valves: Björk-Shiley Monostrut (BSM) tilting-disc valves at the inlet and outlet and Carbomedics (CM) bi-leaflet valves at the inlet and outlet. In conjunction with the flow evaluation, wall shear data were calculated and analyzed to help to quantify wall washing. The major orifice inlet jet of the device containing BSM valves was more intense which led to better circulation and wall washing than the three jets produced by the CM valves Regurgitation through the CM valve was observed and served as a significant hindrance to the development of the rotational flow.

A Particle Image Velocimetry Study of the Penn State 50cc Left Ventricular Assist Device: The Impact of Varying Heart Rate

2011 ◽  
Author(s):  
Michael A. Navitsky ◽  
Jason C. Nanna ◽  
Stephen R. Topper ◽  
Steven Deutsch ◽  
Keefe B. Manning
Keyword(s):  
Heart Failure ◽  
Thrombus Formation ◽  
Left Ventricular ◽  
Ventricular Assist Devices ◽  
Left Ventricular Assist Devices ◽  
Ventricular Assist ◽  
Bridge To Transplant ◽  
Left Ventricular Assist ◽  
Penn State ◽  
The Impact

Approximately 5.7 million Americans are afflicted with heart failure, with a reported 670,000 new diagnoses each year [1]. Left ventricular assist devices (LVADs) function as a bridge to transplant therapy for advanced staged heart failure patients awaiting a donor heart. A pulsatile 50cc LVAD, Figure 1, is currently under development for cardiac support of patients with limited chest cavity size. Although the 50cc LVAD is functional in assisting a failing ventricle, complications such as thrombus formation may limit long term usage.

A Correlative Study of Fluid Mechanics and Evidence of Thrombus Formation Within the Penn State 50 CC Left Ventricular Assist Device

2012 ◽  
Author(s):  
Stephen R. Topper ◽  
Michael A. Navitsky ◽  
Christopher A. Siedlecki ◽  
Steven Deutsch ◽  
Gerson Rosenberg ◽  
...  
Keyword(s):  
Thrombus Formation ◽  
Major Complication ◽  
The United States ◽  
Left Ventricular ◽  
Ventricular Assist Devices ◽  
Heart Transplants ◽  
Ventricular Assist ◽  
Bridge To Transplant ◽  
Left Ventricular Assist ◽  
Penn State

An estimated 82.6 million American adults live with one or more forms of cardiovascular disease and in past years, it was the cause of over 55% of all deaths in the United States, more than any other type of major disease [1]. With a limited number of available donors, heart transplants are seldom an option. As a result, ventricular assist devices (VADs) have become a viable alternative to immediate transplant. Today, VADs are widely used as bridge-to-recovery, bridge-to-transplant and destination therapy devices. Despite past improvements in VAD design, a major complication that continues to arise is thrombus formation within the pump.

scholarly journals A Fluid Dynamics Study in a 50 cc Pulsatile Ventricular Assist Device: Influence of Heart Rate Variability

2011 ◽  
Vol 133 (10) ◽  
Author(s):  
Jason C. Nanna ◽  
Michael A. Navitsky ◽  
Stephen R. Topper ◽  
Steven Deutsch ◽  
Keefe B. Manning
Keyword(s):  
Heart Rate ◽  
Shear Rate ◽  
Data Collection ◽  
Fluid Mechanics ◽  
Wall Shear Rate ◽  
Ventricular Assist ◽  
Shear Rates ◽  
Penn State ◽  
Wall Shear

Although left ventricular assist devices (LVADs) have had success in supporting severe heart failure patients, thrombus formation within these devices still limits their long term use. Research has shown that thrombosis in the Penn State pulsatile LVAD, on a polyurethane blood sac, is largely a function of the underlying fluid mechanics and may be correlated to wall shear rates below 500 s−1. Given the large range of heart rate and systolic durations employed, in vivo it is useful to study the fluid mechanics of pulsatile LVADs under these conditions. Particle image velocimetry (PIV) was used to capture planar flow in the pump body of a Penn State 50 cubic centimeters (cc) LVAD for heart rates of 75–150 bpm and respective systolic durations of 38–50%. Shear rates were calculated along the lower device wall with attention given to the uncertainty of the shear rate measurement as a function of pixel magnification. Spatial and temporal shear rate changes associated with data collection frequency were also investigated. The accuracy of the shear rate calculation improved by approximately 40% as the resolution increased from 35 to 12 μm/pixel. In addition, data collection in 10 ms, rather than 50 ms, intervals was found to be preferable. Increasing heart rate and systolic duration showed little change in wall shear rate patterns, with wall shear rate magnitude scaling by approximately the kinematic viscosity divided by the square of the average inlet velocity, which is essentially half the friction coefficient. Changes in in vivo operating conditions strongly influence wall shear rates within our device, and likely play a significant role in thrombus deposition. Refinement of PIV techniques at higher magnifications can be useful in moving towards better prediction of thrombosis in LVADs.

High-frequency operation of pulsatile ventricular assist devices: A computational study on circular and elliptically shaped pumps

2019 ◽  
Vol 42 (12) ◽  
pp. 725-734 ◽  
Author(s):  
Christian Loosli ◽  
Stephan Rupp ◽  
Bente Thamsen ◽  
Mathias Rebholz ◽  
Gerald Kress ◽  
...  
Keyword(s):  
High Frequency ◽  
Flow Patterns ◽  
Ventricular Assist Devices ◽  
Shear Stresses ◽  
Residence Times ◽  
Pump Frequency ◽  
Ventricular Assist ◽  
Assist Devices ◽  
High Frequency Operation ◽  
Wall Shear

Pulsatile positive displacement pumps as ventricular assist devices were gradually replaced by rotary devices due to their large volume and high adverse event rates. Nevertheless, pulsatile ventricular assist devices might be beneficial with regard to gastrointestinal bleeding and cardiac recovery. Therefore, aim of this study was to investigate the flow field in new pulsatile ventricular assist devices concepts with an increased pump frequency, which would allow lower stroke volumes to reduce the pump size. We developed a novel elliptically shaped pulsatile ventricular assist devices, which we compared to a design based on a circular shape. The pump size was adjusted to deliver similar flow rates at pump frequencies of 80, 160, and 240 bpm. Through a computational fluid dynamics study, we investigated flow patterns, residence times, and wall shear stresses for different frequencies and pump sizes. A pump size reduction by almost 50% is possible when using a threefold pump frequency. We show that flow patterns inside the circular pump are frequency dependent, while they remain similar for the elliptic pump. With slightly increased wall shear stresses for higher frequencies, maximum wall shear stresses on the pump housing are higher for the circular design (42.2 Pa vs 18.4 Pa). The calculated blood residence times within the pump decrease significantly with increasing pump rates. A smaller pump size leads to a slight increase of wall shear stresses and a significant improvement of residence times. Hence, high-frequency operation of pulsatile ventricular assist devices, especially in combination with an elliptical shape, might be a feasible mean to reduce the size, without any expectable disadvantages in terms of hemocompatibility.

Design Optimization of a Mechanical Heart Valve for Reducing Valve Thrombogenicity: A Case Study With ATS Valve

2010 ◽  
Author(s):  
Gaurav Girdhar ◽  
Yared Alemu ◽  
Michalis Xenos ◽  
Jawaad Sheriff ◽  
Jolyon Jesty ◽  
...  
Keyword(s):  
Heart Valves ◽  
Thrombus Formation ◽  
Anticoagulation Therapy ◽  
Mechanical Heart Valve ◽  
Ventricular Assist Devices ◽  
Circulatory Support ◽  
Ventricular Assist ◽  
Mechanical Circulatory Support Devices ◽  
Artificial Hearts

Flow past mechanical heart valves (MHV) in mechanical circulatory support devices including total artificial hearts and ventricular assist devices, is primarily implicated in thromboembolism due to non-physiological flow conditions where the elevated stresses and exposure times are sufficiently high to cause platelet activation and thrombus formation. Mitigation of this risk requires lifelong anticoagulation therapy and less thrombogenic MHV designs should therefore be developed by device manufacturers [1].

Thrombus Formation Patterns in HeartMate II Continuous-Flow Left Ventricular Assist Devices

ASAIO Journal ◽  
2014 ◽  
Vol 60 (4) ◽  
pp. 369-371 ◽  
Author(s):  
Nicholas G. Kounis ◽  
George D. Soufras ◽  
Periklis Davlouros ◽  
Grigorios Tsigkas ◽  
George Hahalis
Keyword(s):  
Continuous Flow ◽  
Thrombus Formation ◽  
Left Ventricular ◽  
Ventricular Assist Devices ◽  
Left Ventricular Assist Devices ◽  
Heartmate Ii ◽  
Ventricular Assist ◽  
Assist Devices ◽  
Left Ventricular Assist
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