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Pulse
Winter 2012-2013

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Complex Matters of the Heart

Ultrasound image of blood flow
An ultrasound image of blood flow in the left ventricle of a patient implanted with a biventricular pacemaker.

Juan Carlos del Álamo, a professor of mechanical and aerospace engineering and one of the medical device researchers whose lab moved into the new SME building, has combined Doppler ultrasound with the principles of fluid mechanics to develop a new method of studying the complex, multidimensional blood flow patterns within the heart. The ultimate goal is to synchronize blood flow with ventricle wall motion in heart patients with pacemakers. Del Álamo's focus is to optimize the programming of biventricular pacemakers, which are designed to not only control heart rate, but also the timing of specific events in the heartbeat such as the length of time between the contraction of the atrium and the contraction of the ventricle, or the length of time between the contraction of the right ventricle and the left ventricle. Blood flow imaging in patients with implanted pacemakers has been complicated thus far because these patients cannot undergo cardiac magnetic resonance safely. Doppler ultrasound, which relies on a handheld transducer positioned over the skin, is already used to measure blood flow in heart patients but provides limited one-directional blood flow velocity. In a study recently presented to the American Heart Association, Del Álamo's team applied their new multi-dimensional imaging modality to study the spatio-temporal evolution of the blood flow patterns within the heart, and how these dynamic patterns are modified in each specific patient by the programming of the pacemaker.

A Better Cardiac Pump for Children with Heart Defects

Alison Marsden with her students
Alison Marsden, a professor of mechanical and aerospace engineering, and her students examine some of the simulations her research group developed in the StarCAVE imaging space on the UC San Diego campus.

Structural and mechanical engineers at the Jacobs School are working together to create blood flow simulations that could lead to improvements in the design of a cardiac pump for children born with heart defects. They hope that the design changes will improve young patients' outcomes.

The Berlin Heart is currently the only FDA-approved cardiac pump for young children who can't be outfitted with an adult-sized pump. The device is used to extend a patient's life until a transplant becomes available. Accurate simulations of the way blood flows inside the pump are important because the device is associated with as much as a 40 percent risk of developing blood clots, which can lead to strokes or embolisms. This in turn can have devastating consequences on the children using the pump, who can be anywhere from just a few months old to about 9 years of age.

Two researchers have combined their strengths to solve this problem. Alison Marsden, a mechanical and aerospace engineering professor, focuses on the development of blood flow simulation tools that can be used to test and optimize new heart surgery designs on the computer before trying them on patients. Yuri Bazilevs, a structural engineering professor, focuses on computational science and engineering to develop methods for large-scale, high-performance computing applications.

Marsden, Bazilevs and their teams have successfully simulated blood flow within the device. They are now trying to understand how blood clots form inside the pump. The next step is to figure out, through simulations, what design changes are needed to reduce that risk.

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