Luke MacLean (MHSc): Cardiac Suspension for Mitigating Tight Syndrome in Postoperative Newborns Design of a Mechanical Tensioner Device

November 15, 2017 @ 9:00 am – 9:30 am
Rosebrugh Building
Rosebrugh Bldg, Toronto, ON M5S 3G9

Room: RS 211


Newborns with heart defects often need to undergo immediate open-heart surgery. Upon attempted chest closure, edema can cause a set of complications termed tight syndrome. The condition is characterized by hemodynamic instabilities, respiratory instabilities, and heart failure. Therefore, the chest is left open for days to weeks postoperatively in a Delayed Sternal Closure (DSC). However, similar complications arise due to spikes in pressure caused by the unsupported chest-wall. To mitigate, SickKids has pioneered Cardiac Suspension (CS) where the chest is raised by tension sutures.

The presentation will discuss the clinical mechanisms and a preliminary review of the surgical approach. This review is based on critical-care patient observations and interviews with the cardiac surgeons and nurse practitioners. Stakeholder feedback then established the design requirements for improving the methodology. A chart-review was then performed comparing the outcomes of immediate closure, DSC and CS patients. This will offer basic statistics comparing the patient populations.

The remainder will focus on the design of a mechanical tensioner unit to compliment CS. In improvised suspension, costal cartilage is fixed to the heat lamp via wires. This has several limitations including unquantified tension, problematic X-ray imaging, and parental anxieties. The Cardiac Suspension Unit was designed in response, and manufactured through 3D printing and machining. The design process, alternatives, and prototyping will be discussed. This includes analytical and numerical modelling of safety considerations. The implications of thoracic biomechanics will be briefly addressed. The material, manufacturing and mechanism choices will be discussed in relation to their clinical usability. Finally, the design of benchtop experiments, mimicking clinical requirements, will be presented. The tool must be verified for its mechanical, thermal, radiolucency, and usability performance.