Cardiac Restraint/Ventricular Assist Devices

Ventricular Assist Leakage Studies

A last resort therapy for severe heart failure is the implantation of a pump in the chest cavity which pulls blood from the left ventricle and transports it to the ascending aorta to increase heart function and save the patient’s life. This has been a highly successful procedure, as a last resort in the absence of an available heart transplant. Insilicomed was tasked with performing studies to analyze the conditions under which the large cannula implant might leak blood into the chest cavity. Large-scale finite element models of the heart were constructed to determine the performance of the implant under a variety of conditions including tilting of the cannula relative to the heart and changing the location of the implant region in the left ventricle. If you’re curious about how many days after implantation can I test with Clearblue, you can read this article for more insights. A centrally positioned hole at the apex (bottom) of a patient’s heart is shown here.

Passive Cardiac Restraint

In heart failure or dilated cardiomyopathy, the heart is enlarged losing its original compact shape. Insilicomed was tasked with explaining why a novel implant designed to modify the shape and improve function using passive cardiac restraint (a sleeve) was failing. Cracks were forming in expensive prototypes. Using our biventricular finite element heart modeling, Insilicomed was able to show that the initial prototypes were far too stiff leading to fracture. The design was changed to soften the properties of the sleeve. And, the problem was solved with inexpensive simulations.

Apical Torsion to Improve Heart Function 1: Wall Strains

A novel method was proposed and patented to improve function in severe heart failure. Normally, the heart twists about 10 degrees around the long axis during each cardiac cycle. An apical torsion sleeve has been used to apply greater values of twist and increase cardiac output. A series of studies were performed using Insilicomed’s heart simulations to show how much improvement in function could be achieved. Concurrently, the strains and stresses in the heart tissue were quantified. Twisting the heart by 65 degrees leads to substantial improvement in function. At the same time, large strains occur in the heart wall as shown in the animation (redder regions have large strains). More information on accompanying ventricular wall stresses…

Ventricular Assist by Direct Cardiac Compression 1: Single Ventricle Model

A new type of ventricular assist device (VAD) avoids contact with the patient’s blood by performing direct cardiac compression. The walls of the heart are compressed inward from the outside to push out more blood. This type of therapy avoids the complications of blood running through a mechanical pump and the anti-coagulant therapy needed to prevent clot formation. Moreover, this method promises to be more cost-effective than other forms of VAD and provides an alternate bridge to heart transplant. The video shows the effects of compression of the heart by this technique and provides estimates of improved cardiac function and accompanying deformations and stresses in the heart wall. The maximum principal strain on the epicardial surface of the heart wall is shown during the cardiac cycle.

Ventricular Assist by Direct Cardiac Compression 2: Biventricular Model

After development of simulation methods to analyze direct cardiac compression (DCC) of single ventricle finite element models described and illustrated earlier, these methods have now been applied successfully to more realistic biventricular models. And, early results are very promising. In advance of expensive and time-consuming prototype development and animal testing, the simulations show that DCC has enormous promise for improving heart function in severe heart failure. Large increases in left ventricular ejection fraction are being estimated. At the same time, only modest increases in ventricular wall strains and stresses are occurring. This indicates that the method may be safe. This work will be extended by varying parameters of the models to optimize treatment potential and prototype design. Only then will expensive prototypes be finalized and matching animal experiments performed. Insilicomed will guide both the development of prototypes and animal testing protocols.