Cannula Tip With Integrated Volume Sensor for Rotary Blood Pump Control: Early-Stage Development

Abstract

The lack of direct measurement of left ventricular unloading is a significant impediment to the development of an automatic speed control system for continuous-flow left ventricular assist devices (cf-LVADs). We have developed an inlet cannula tip for cf-LVADs with integrated electrodes for volume sensing based on conductance. Four platinum-iridium ring electrodes were installed into grooves on a cannula body constructed from polyetheretherketone (PEEK). A sinusoidal current excitation waveform (250 μA pk-pk, 50 kHz) was applied across one pair of electrodes, and the conductance-dependent voltage was sensed across the second pair of electrodes. The conductance catheter was tested in an acute ovine model (n = 3) in conjunction with the HeartMate II rotary blood pump to provide circulatory support and unload the ventricle. Echocardiography was used to measure ventricular size during pump support for verification for the conductance measurements. The conductance measurements correlated linearly with the echocardiography dimension measurements more than the full range of pump support from minimum support to suction. This cannula tip will enable the development of automatic control systems to optimize pump support based on a real-time measurement of ventricular size.

Physiology of the Assisted Circulation in Cardiogenic Shock: A State-of-the-Art Perspective

“…Preclinical studies have investigated in vivo performance of pressure or volume sensors to improve the real-time management of patients supported with durable LVADs (Figure 5). 70 Real-time measurement of blood viscosity in LVAD patients has also been recently reported to improve the management of centrifugal pumps. 71 Similarly, real-time monitoring of aortic valve opening associated with automatic feed-back adjustment of LV unloading has been investigated in sheep by Jansen-Park et al 72 Additional research is being applied to make pressure-regulated rotary blood flow closer to the physiology of the normal heart.…”

Continuous Heart Volume Monitoring by Fully Implantable Soft Strain Sensor

“…Cysyk et al. [ 35 ] have successfully integrated electric impedance technology in the cannula of an LVAD, but accuracy was limited in an animal study with two pigs. In humans, electric impedance was measured between left‐ and right‐ventricular pacemaker leads with limits of agreement of 25 mL (9.7%) in 22 patients and with a two‐point calibration.…”

Real-Time Ventricular Volume Measured Using the Intracardiac Electromyogram

“…Impedance has also been integrated into the cannula of an LVAD and successfully tested in vivo . 25 The measurement was, however, limited to measuring apical blood volumes, as the electric field for measurement is only spanned in the apex. On the contrary, the unipolar amplifier measures the far-field and thus enables the measurement to also be sensitive to changes in volume in the mid-ventricle.…”