Calcific aortic stenosis (AS) is the most prevalent heart valve disorder in developed countries. It is characterized by progressive fibro-calcific remodelling and thickening of the aortic valve leaflets that, over years, evolve to cause severe obstruction to cardiac outflow. In developed countries, AS is the third-most frequent cardiovascular disease after coronary artery disease and systemic arterial hypertension, with a prevalence of 0.4% in the general population and 1.7% in the population >65 years old. Congenital abnormality (bicuspid valve) and older age are powerful risk factors for calcific AS. Metabolic syndrome and an elevated plasma level of lipoprotein(a) have also been associated with increased risk of calcific AS. The pathobiology of calcific AS is complex and involves genetic factors, lipoprotein deposition and oxidation, chronic inflammation, osteoblastic transition of cardiac valve interstitial cells and active leaflet calcification. Although no pharmacotherapy has proved to be effective in reducing the progression of AS, promising therapeutic targets include lipoprotein(a), the renin-angiotensin system, receptor activator of NF-κB ligand (RANKL; also known as TNFSF11) and ectonucleotidases. Currently, aortic valve replacement (AVR) remains the only effective treatment for severe AS. The diagnosis and staging of AS are based on the assessment of stenosis severity and left ventricular systolic function by Doppler echocardiography, and the presence of symptoms. The introduction of transcatheter AVR in the past decade has been a transformative therapeutic innovation for patients at high or prohibitive risk for surgical valve replacement, and this new technology might extend to lower-risk patients in the near future.

Calcific aortic stenosis.

Control Systems Engineering

Various “contactless” bearing mechanisms including hydrodynamic and magnetic bearings are provided for a rotary pump as alternatives to mechanical contact bearings. In one embodiment, a pump apparatus includes a pump housing defining a pumping chamber. The housing has a spindle extending into the pumping chamber. A spindle magnet assembly includes first and second magnets disposed within the spindle. The first and second magnets are arranged proximate each other with their respective magnetic vectors opposing each other. The lack of mechanical contact bearings enables longer life pump operation and less damage to working fluids such as blood.

Rotary blood pump

An extracardiac pumping for supplementing the circulation of blood, including the cardiac output, in a patient without any component thereof being connected to the patient's heart, and methods of using same. One embodiment provides a vascular graft that has a first end that is sized and configured to couple to a non-primary blood vessel and a second end that is fluidly coupled to a pump to conduct blood between the pump and the non-primary blood vessel. An outflow conduit is also provided that has a first end sized and configured to be positioned within the same or different blood vessel, whether primary or non-primary, through the vascular graft. The outflow conduit is fluidly coupled to the pump to conduct blood between the pump and the patient. The vascular graft may be connected to the blood vessel subcutaneously to permit application of the extracardiac pumping system in a minimally-invasive procedure.

Implantable heart assist system and method of applying same

https://artiforgans.files.wordpress.com/2010/02/heartmate_ii_left_ventricular_assist_system1.pdf

HeartMate II left ventricular assist system: from concept to first clinical use.

An axial-flow ventricular assist device (VAD) under development at the authors' facility is intended for use as a long-term implantable device. At high speeds axial-flow VADs can collapse the native ventricle and damage the heart muscle, lung tissue, and blood. A prototype algorithm was developed to maintain physiologic perfusion to the vital organs while preventing ventricular collapse, through analysis of the electrical current waveform of the motor. The premise of the control algorithm is that the hemodynamics of the patient are reflected in the shape of this waveform. This approach is intended to eliminate the need for invasive sensors, thus effectively using the pump itself as a transducer. The control algorithm regulates the speed of the pump by comparing the motor-current waveform with reference waveforms using a matched filter. The matched filter was evaluated by its classification and differentiation performance. Thus far, the authors have been able to classify the waveforms into one of the four physiologic regions (below, within, or above the optimal range, and ventricular suction) with over 90% reliability. Ongoing work is directed toward improving the detection of ventricular suction, as this condition must be strictly avoided.

Controller for an axial-flow blood pump.

A system for assisting flow of blood by a patient's heart. The system includes a transseptal cannula (12) adapted to be inserted percutaneously in the femoral view and extend through the atrial septum from the right atrium to the left atrium. The system includes a blood pump mechanism (30) having a blood pump (316) for pumping blood received from the transseptal cannula (12) that has been oxygenated at a specified flow rates over a range of physiological pressures. The blood pump (316) is connected to the transseptal cannula (12). The system includes a perfusion cannula (100) adapted to be inserted percutaneously in the femoral artery for returning oxygenated blood to the atrial system of the patient. The perfusion cannula (100) is connected to the blood pump (316). A method for assisting blood flow by a patient's heart.

Method and system for closed chest blood flow support

This invention is an apparatus for non-invasive flow indication through a rotary pump. The apparatus includes a blood pump (12) adapted for implantation into a patient. The blood pump (12) has a moving mechanism (14) which contacts blood, and imparts energy to the blood to move the blood in the patient at a desired flow rate. The apparatus includes a mechanism (16) for causing the moving mechanism to move the blood. The causing mechanism (16) is engaged with the moving mechanism. The causing mechanism receives energy to power the causing mechanism. The apparatus comprises a non-sensor flow indicator (18) connected to the blood pump to identify the flow of blood through the pump based only on an energy balance between the energy imparted to the blood by the moving mechanism, and the energy received by the causing mechanism. A method for determining blood flow in a patient is also included.

Non-invasive flow indicator for a rotary blood pump

An extended Kalman filter estimator for the identification of systemic circulation model parameters during cardiac ejection and cardiac filling is described. The estimator has been developed for use in the control of a cardiac ventricular assist device. A lumped element circuit with a time-varying capacitor was used to represent the systemic circulation and the left ventricle. Since the haemodynamic variables that are measurable in patients with impaired cardiac function vary dramatically as the patients move through different levels of care, the estimator was designed so that it can be used with different sets of blood pressure and flow measurements. Preliminary evaluation of the performance of the estimator using data from a computer simulation and from a patient during open-heart surgery is presented. The robustness of the estimator to variations in parameter initialization is also described.

Estimation of systemic vascular bed parameters for artificial heart control

Heart assist devices are blood pumps used to augment the cardiac output of patients with left ventricular failure. A new generation of devices being evaluated for human use is based on turbo-hydrodynamic methods of pumping, which offer several advantages over the reciprocating, pulsatile methods used in current devices. However, the new devices pose a more difficult control problem because of their sensitivity to circulatory load and other patient cardiovascular parameters. The paper describes the design of a control structure to regulate the operation of these devices. The controller has three different types of algorithm available: a model-based patient-adaptive algorithm; two heuristic algorithms that rely only on the device characteristics; and a default algorithm. The patient-adaptive algorithm uses a model of the patient's systemic circulation to determine the required cardiac output for a given level of activity. The heuristic algorithms use the known operating characteristics of the device to adjust the cardiac output to changes in demand without knowledge of patient-specific conditions. The default algorithm provides a fixed speed operation to be used in case of system or sensor failure. An intelligent supervisor determines the cardiac output required from the assist device and selects the control algorithm to use, based on a multidimensional measure of the patient's level of activity, available estimates of hemodynamic variables, reliability of the patient model, and the past history of the patient.

Yih-Choung Yu

Papers

Controller for an axial-flow blood pump.

Method and system for closed chest blood flow support

Non-invasive flow indicator for a rotary blood pump

Estimation of systemic vascular bed parameters for artificial heart control

Intelligent control design for heart assist devices