TORVAD

Toroidal Ventricular Assist Device

Synchronous Pulsatility

The TORVAD senses cardiac rhythm to provide synchronous pulsatile support

Low Shear

Low rotational speeds and controlled gaps result in phsyiological levels of shear, one to two orders of magnitude less than continuous flow devices

Adaptive Pumping

The TORVAD measures pressure and detects arrhythmias and will automatically adjust pump flow rate if more or less flow is needed

Synchronous Pulsatility

Two independently controlled pistons rotate in a toroidal pumping chamber. One piston acts as a valve while the other rotates to produce pulsatile 30ml ejections. After each pump ejection, the pistons exchange roles. Beat-to-beat synchronization is achieved by timing pumping with the cardiac rhythm obtained from an integrated ECG sensor.

Counterpulsation is the normal operation mode, which 1) preserves aortic valve flow, minimizing the risk of aortic valve complications associated with continuous flow devices, and 2) maintains natural preload sensitivity, preventing overpumping and right heart failure.

 

Low Shear

Estimated shear for CF and the TORVAD. (1) hemolysis and platelet activation range. (2) vWF unfolding (threshold not well defined but likely occurs between 15-50 Pa). WBC function may also be inhibited in this range. *CF shear estimate based on literature review, rotational speed, and gaps.

Blood shear is minimized by the combination of low pump speed (mean rpm equal to heart rate, typically 60-120 beats per minute) and a predetermined fixed gap between the piston and torus walls. A fixed gap (approximately 0.003” or 75 µm in the current configuration) is achieved using small ceramic hydrodynamic bearings.

Benchtop and chronic animal studies have shown the TORVAD preserves high-molecular-weight von Willebrand factor, an easily damaged blood protein essential to hemostasis. A ventricular assist device (VAD) with this low level of shear stress has the potential to greatly reduce adverse events including strokes, bleeding, and thrombus. All clinically available VADs use an impeller operating at thousands of rotations per minute. These designs have proven durability but unfortunately impart significant trauma to blood constituents due to the high speed of the impeller.

Adaptive Pumping

The TORVAD accurately measures the differential pressure across the pump, allowing for estimation of arterial pressure, systemic vascular resistance, and left ventricular contractility. Cardiac rhythm is continuously monitored by the TORVAD’s integrated ECG sensor, allowing for the detection of changes in heart rate and arrhythmias. The controller of the pump uses this information to make automatic pump adjustments to prevent LV overpuming and suction, minimize the risk of right heart failure, maintain healthy levels of blood pressure, and assess LV remodeling and myocardial recovery.