Objective To investigate the feasibility of a long-term left ventricular assist device placed in the aortic valve annulus for terminal cardiopathy. Methods An implantable aortic valve pump （23ram outer diameter, weighing 31g） was developed. There were a central rotor and a stator in the device. The rotor was consisted of driven magnets and an impeller, the stator was consisted of a motor coil with an iron core and outflow guide vanes. The device was implanted identical to an aortic valve replacement, occupying no additional anatomic space. The blood was delivered directly from left ventricle to the aortic root by aortic valve pump like natural ventricle, neither connecting conduits nor ＂bypass＂ circuits were necessary, therefore physiologic disturbances of natural circulation was less. Results Aortic valve pump was designed to cycle between a peak flow and zero net flow to approximate systole and diastole. Bench testing indicated that a blood flow of 7L/min with 50 mmHg（1kPa = 7.5mmHg） pressure could be produced by aortic valve pump at 15 000r/min. A diastole aortic pressure of 80mmHg could be maintained by aortic valve pump at 0L/min and the same rotating speed. Conclusions This paper exhibits the possibility that an aortic valve pump with sufficient hemodynamic capacity could be made in 23mm outer diameter, 31g and it could be implantable. This achievement is a great progress to extend the applications of aortic valve pump in clinic and finally in replacing the natural donor heart for heart transplantation. Meanwhile, this is only a little step, because many important problems, such as blood compatibility and durability, require further investigation.
We propose a control model of the cardiovascular system coupled with a rotary blood pump in the present paper. A new mathematical model of the rotary heart pump is presented considering the hydraulic characteristics and the similarity principle of pumps. A seven-order nonlinear spatial state equation adopting lumped parameter is used to describe the combined cardiovascular-pump model. Pump speed is used as the control variable. To achieve sufficient perfusion and to avoid suction, a feedback strategy based on minimum (diastolic) pump flow is used in the control model. The results showed that left ventricular assist device (LVAD) could improve hemodynamics of the cardiovascular system of the patient with heart failure in open loop. When rotation speed was 9,000 r/min, cardiac output reached 82 mL/s while the initial cardiac output was only 34 mL/s without the LVAD support. When the rotation speed was above 12 800 r/min, suction was found because the high rotating speed resulted in insufficient venous return volume. Suction was avoided by adopting the feedback control. The model reveals the interaction of LVAD and the cardiovascular system, which provides theoretical basis for the therapy of heart failure in the left ventricular and for the design of a physiological control strategy.
Regurgitation is an abnormal condition happens when left ventricular assist devices (LVADs) operated at a low speed, which causes LVAD to fail to assist natural blood-pumping by heart and thus affects patients’ health. According to the degree of regurgitation, three LVAD’s regurgitation states were identified in this paper: no regurgitation, slight regurgitation and severe regurgitation. Regurgitation index (RI), which is presented based on the theory of dynamic closed cavity, is used to grade the regurgitation of LVAD. Numerical results showed that when patients are in exercising, resting and sleeping state, the critical speed between slight regurgitation and no regurgitation are 6 650 r/min, 7 000 r/min and 7 250 r/min, respectively, with corresponding RI of 0.401, 0.300 and 0.238, respectively. And the critical speed between slight regurgitation and severe regurgitation are 5 500 r/min, 6 000 r/min and 6 450 r/min, with corresponding RI of 0.488, 0.359 and 0.284 respectively. In addition, there is a negative relation correction between RI and rotational speed, so that grading the LVAD’s regurgitation can be achieved by determining the corresponding critical speed. Therefore, the detective parameter RI based on the signal of flow is proved to be able to grade LVAD’s regurgitation states effectively and contribute to the detection of LVAD’s regurgitation, which provides theoretical basis and technology support for developing a LVADs controlling system with high reliability.
The rotary left ventricular assist device (LVAD) has been an effective option for end-stage heart failure. However, while clinically using the LVAD, patients are often at significant risk for ventricular collapse, called suction, mainly due to higher LVAD speeds required for adequate cardiac output. Some proposed suction detection algorithms required the external implantation of sensors, which were not reliable in long-term use due to baseline drift and short lifespan. Therefore, this study presents a new suction detection system only using the LVAD intrinsic blood pump parameter (pump speed) without using any external sensor. Three feature indices are derived from the pump speed and considered as the inputs to four different classifiers to classify the pumping states as no suction or suction. The in-silico results using a combined human circulatory system and LVAD model show that the proposed method can detect ventricular suction effectively, demonstrating that it has high classification accuracy, stability, and robustness. The proposed suction detection system could be an important part in the LVAD for detecting and avoiding suction, while at the same time making the LVAD meet the cardiac output demand for the patients. It could also provide theoretical basis and technology support for designing and optimizing the control system of the LVAD.
Right ventricular (RV) failure has become a deadly complication of left ventricular assist device (LVAD) implantation, for which desynchrony in bi-ventricular pulse resulting from a LVAD is among the important factor. This paper investigated how different control modes affect the synchronization of pulse between LV (left ventricular) and RV by numerical method. The numerical results showed that the systolic duration between LV and RV did not significantly differ at baseline (LVAD off and cannula clamped) (48.52% vs. 51.77%, respectively). The systolic period was significantly shorter than the RV systolic period in the continuous-flow mode (LV vs. RV: 24.38% vs. 49.16%) and the LV systolic period at baseline. The LV systolic duration was significantly shorter than the RV systolic duration in the pulse mode (LV vs. RV: 28.38% vs. 50.41%), but longer than the LV systolic duration in the continuous-flow mode. There was no significant difference between the LV and RV systolic periods in the counter-pulse mode (LV vs. RV: 43.13% vs. 49.23%). However, the LV systolic periods was shorter than the no-pump mode and much longer than the continuous-flow mode. Compared with continuous-flow and pulse mode, the reduction in rotational speed (RS) brought out by counter-pulse mode significantly corrected the duration of LV systolic phase. The shortened duration of systolic phase in the continuous-flow mode was corrected as re-synchronization in the counter-pulse mode between LV and RV. Hence, we postulated that the beneficial effects on RV function were due to re-synchronizing of RV and LV contraction. In conclusion, decreased RS delivered during the systolic phase using the counter-pulse mode holds promise for the clinical correction of desynchrony in bi-ventricular pulse resulting from a LVAD and confers a benefit on RV function.
ObjectiveTo explore the value of transthoracic echocardiography (TTE) to monitor and evaluate aortic insufficiency (AI) within one year after the implantation of the left ventricular assist device (LVAD).MethodsWe retrospectively collected and analyzed the TTE data of 12 patients who received LVAD implantation from 2018 to 2020 in our hospital. All patients were males, with an average age of 43.3±8.6 years. We analyzed temporal changes in the aortic annulus (AA), aortic sinus (AoS), ascending aorta (AAo), the severity of AI and the opening of aortic valve before operation and 1 month, 3 months, 6 months and 12 months after LVAD implantation.ResultsAll 12 patients survived within 1 year after LVAD implantation. One patient was bridged to heart transplantation 6 months after implantation, and two patients did not receive TTE after 3 and 6 months. Compared to pre-implantation, AoS increased at 1 month after implantation (31.58±5.09 mm vs. 33.83±4.69 mm). The inner diameters of AA, AoS and AAo increased at 3, 6 and 12 months after LVAD implantation compared to pre-implantation (P<0.05), but all were within the normal range except for one patient whose AoS slightly increased before operation. After LVAD pump speed was adjusted, the opening of aortic valve improved. The severity of AI increased at 6 and 12 months after LVAD implantation compared to pre-implantation, and increased at 12 months compared to 6 months after LVAD implantation (P<0.05).ConclusionTTE can evaluate aortic regurgitation before and after LVAD implantation and monitor the optimization and adjustment of LVAD pump function, which has a positive impact on the prognosis after LVAD implantation.
Implantable left ventricular assist device (LVAD) has become an essential treatment for end-stage heart failure, and its effect has been continuously improved. In the world, magnetic levitation LVAD has become mainstream and is increasingly used as a destination treatment. China has also entered the era of ventricular assist device. The continuous improvement of the ventricular assist device will further improve the treatment effect. This article reviews the current situation and development trend of LVAD treatment in China and abroad.
Objective To compare the early outcomes of domestic third-generation magnetically levitated left ventricular assist device (LVAD) with or without concomitant mitral valvuloplasty (MVP). Methods The clinical data of 17 end-stage heart failure patients who underwent LVAD implantation combined with preoperative moderate to severe mitral regurgitation in Fuwai Central China Cardiovascular Hospital from May 2018 to March 2023 were retrospectively analyzed. The patients were divided into a LVAD group and a LVAD+MVP group based on whether MVP was performed simultaneously, and early outcomes were compared between the two groups. Results There were 4 patients in the LVAD group, all males, aged (43.5±5.9) years, and 13 patients in the LVAD+MVP group, including 10 males and 3 females, aged (46.8±16.7) years. All the patients were successful in concomitant MVP without mitral reguragitation occurrence. Compared with the LVAD group, the LVAD+MVP group had a lower pulmonary artery systolic pressure and pulmonary artery mean pressure 72 h after operation, but the difference was not statistically different (P>0.05). Pulmonary artery systolic pressure was significantly lower 1 week after operation, as well as pulmonary artery systolic blood pressure and pulmonary artery mean pressure at 1 month after operation (P<0.01). There was no statistically significant difference in blood loss, operation time, cardiopulmonary bypass time, aortic cross-clamping time, mechanical ventilation time, or ICU stay time between the two groups (P>0.05). The differences in 1-month postoperative mortality, acute kidney injury, reoperation, gastrointestinal bleeding, and thrombosis and other complications between the two groups were not statistically significant (P>0.05). Conclusion Concomitant MVP with implantation of domestic third-generation magnetically levitated LVAD is safe and feasible, and concomitant MVP may improve postoperative hemodynamics without significantly increasing perioperative mortality and complication rates.