A Study of the Effect of an Elevated Beat Rate in the Left Side of the 12cc Penn State Pediatric Total Artificial Heart
Restricted (Penn State Only)
- Author:
- Raich, Emma
- Graduate Program:
- Biomedical Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 22, 2023
- Committee Members:
- Keefe B Manning, Thesis Advisor/Co-Advisor
Justin Lee Brown, Committee Member
Daniel Hayes, Program Head/Chair
William Joseph Weiss, Committee Member - Keywords:
- total artificial heart
pediatric
mechanical circulatory support devices
particle image velocimetry
elevated beat rate
cardiovascular fluid dynamics
thrombosis
wall shear rate - Abstract:
- The disparity between the number of patients in need of a heart transplantation and the number of hearts available has led to the development of mechanical circulatory support (MCS) devices as a bridge-to-transplant option. Children less than one year of age face the highest waitlist mortality rate due to this lack of organ availability. This rate has continually decreased over time due to the increased use of MCS devices. Penn State is currently developing a 12cc pediatric total artificial heart (pTAH) to provide MCS for patients with biventricular heart failure. One of the major complications with MCS devices is thrombosis. Previous studies have shown that certain flow conditions can decrease thrombosis risk in MCS devices, mainly through adequate surface washing that can be quantified by wall shear rates. Patient-specific parameters, such as beat rate, have also been shown to influence flow through MCS devices. Pediatric heart rates typically range from 100 to 180 bpm, making it important to understand the effect of beat rate on flow through pediatric MCS devices. The objective of this study was to analyze the fluid mechanics of the left side of the 12 cc Penn State pTAH (LpTAH) by investigating the effect of an elevated beat rate on the flow using particle image velocimetry (PIV). No prior flow visualization studies have been performed on this device. The study was conducted in a mock circulatory loop with a 40% hematocrit blood analog fluid to mimic physiologically relevant conditions with the same viscoelastic properties as blood. Data were collected at two beat rates: 75 bpm and 120 bpm. Flow and pressure waveforms were obtained for both beat rates, ensuring proper flow and pressure conditions were maintained throughout data collection. PIV was used to collect flow data at three planes within the LpTAH at 16 time points throughout the cardiac cycle. Wall shear rates were estimated to determine any potential problems areas for thrombosis, with shear rates less than 500 s-1 being more susceptible to platelet adhesion and thrombus formation. The same general flow patterns were observed at both beat rates. Diastole began with an inlet jet concentrated through the major orifice of the valve that transitioned to rotational flow in mid-to-late diastole. During systole, an outlet jet formed, with rotational flow dissipating. The higher beat rate maintained higher velocity magnitudes and wall shear rates. Additionally, rotational flow began earlier in diastole and was sustained later in systole than at the lower beat rate. These findings indicate better surface washing and a lower risk of platelet adhesion at the higher beat rate. A potential trouble spot for thrombosis was observed near the apex of the device at 75 bpm at the 7 mm plane, where low shear rates were sustained. The design of the LpTAH was based on the 12cc Penn State PVAD, with the only difference being the angle of the outlet port. Flow analysis showed the same general flow patterns through the two devices. Rotational flow was more sustained in the PVAD with higher velocity magnitudes achieved throughout the cardiac cycle. The geometry of the LpTAH may have induced additional flow three-dimensionality that was not fully evident at the parallel planes. However, LpTAH valve leakage was most likely the reason for the flow differences. Overall, through comparing the LpTAH directly to the Penn State PVAD and generally to other MCS devices, the LpTAH produced positive flow characteristics, indicating sufficient wall washing within the device.