A Suction Detection System for Rotary Blood Pumps Based on the Lagrangian Support Vector Machine Algorithm

Abstract

The Left Ventricular Assist Device (LVAD) is a rotary mechanical pump that is implanted in patients with congestive heart failure to help the left ventricle in pumping blood in the circulatory system. However, using such a device may result in a very dangerous event, called ventricular suction that can cause ventricular collapse due to overpumping of blood from the left ventricle when the rotational speed of the pump is high. Therefore, a reliable technique for detecting ventricular suction is crucial. This paper presents a new suction detection system that can precisely classify pump flow patterns, based on a Lagrangian Support Vector Machine (LSVM) model that combines six suction indices extracted from the pump flow signal to make a decision about whether the pump is in suction, approaching suction, or not in suction. The proposed method has been tested using in vivo experimental data based on two different pumps. The simulation results show that the system can produce superior performance in terms of classification accuracy, stability, learning speed, and good robustness compared to three other existing suction detection methods and the original SVM-based algorithm. The ability of the proposed algorithm to detect suction provides a reliable platform for the development of a feedback control system to control the speed of the pump while at the same time ensuring that suction is avoided.

Do Axial-Flow LVADs Unload Better than Centrifugal-Flow LVADs?

“…Integration of suction prevention and physiologic control algorithm(s) for continuous-flow LVAD is in development. 12,13 Centrifugal-flow LVADs produce a higher aortic pressure pulsatility compared with axial-flow LVADs at the same mean LVAD flow rate (Figure 2). However, pressure and flow waveform pulsatility are diminished for all continuous-flow devices.…”

Detection of aortic valve dynamics in bridge-to-recovery feedback control of the Left Ventricular Assist Device

“…The LSVM is a modified standard Support Vector Machine (SVM) [19], which is a reliable and powerful classification technology and has been successfully applied to various pattern recognition problems [20]- [22], especially to the problems in the LVAD field [23], [24]. Like SVM, the main idea of LSVM is to find the optimal separating hyperplane (with the maximum margin) between two different classes of the data points.…”

“…The classifier is trained on a randomly selected set of 50% of the data and then tested on the remaining 50% of the data. The training and testing procedures are similar to those described in [23], [24]. Due to the random selection of data samples, the classification is repeated 100 times.…”

“…1.43%) are incorrectly classified as aortic valve normal operation. In addition, Table IV shows the mean and standard deviation of the sensitivity, specificity, and accuracy which are important indicators of the performance of this classification algorithm with respect to the proposed detection indicator I V in discriminating between the normal operation of the aortic valve state and its permanent closure state [24].…”

“…In its use as bridge-to-transplantation for patients with severe heart failure the controller must increase the power to the device so that the pump (almost always by itself) can provide the necessary blood support to the circulation system because of the inability of the left ventricle to contribute any pumping through the aortic valve. However, as is pointed out in [23] and [24] the controller must also be aware that increased power which leads to increased rotational speed of the pump may lead to ventricular suction which is a dangerous phenomenon that may be a fatal. In the use of the LVAD as a bridge-to-recovery for patients with mild heart failure the controller must also increase the power to the device so that it can provide the necessary blood support to the circulation system; however, it must recognize that it cannot take over this function totally by itself by shutting the direct path of blood flow from the left ventricle to the aorta through the aortic valve.…”