Department of Cardiovascular and Thoracic Surgery, Soonchunhyang University Hospital, Bucheon-si, Republic of Korea.
Program of Mechanical and Biomedical Engineering, College of Engineering, Kangwon National University, Chuncheon-si, Republic of Korea.
Biomed Eng Online. 2018 Feb 2;17(1):18. doi: 10.1186/s12938-018-0440-5.
Counter-pulsation control (CPC) by ventricular assist devices (VADs) is believed to reduce cardiac load and increase coronary perfusion. However, patients with VADs have a higher risk of arrhythmia, which may cause the CPC to fail. Consequently, CPC has not been applied by VADs in clinical practice. The phase-locked loop (PLL) algorithm for CPC is readily implemented in VADs; however, it requires a normal, consistent heartbeat for adequate performance. When an arrhythmia occurs, the algorithm maintains a constant pumping rate despite the unstable heartbeat. Therefore, to apply the PLL algorithm to CPC, the hemodynamic effects of abnormal heartbeats must be analyzed.
This study sought to predict the hemodynamic effects in patients undergoing CPC using VADs, based on electrocardiogram (ECG) data, including a wide range of heart rate (HR) changes caused by premature ventricular contraction (PVC) or other reasons.
A four-element Windkessel hemodynamic model was used to reproduce the patient's aortic blood pressure in this study. ECG data from 15 patients with severe congestive heart failure were used to assess the effect of the CPC on the patients' hemodynamic state. The input and output flow characteristics of the pulsatile VAD (LibraHeart I, Cervika, Korea) were measured using an ultrasound blood flow meter (TS410, Transonic, USA), with the aortic pressure maintained at 80-120 mmHg. All other patient conditions were also reproduced.
In patients with PVCs or normal heartbeats, CPC controlled by a VAD reduced the cardiac load by 20 and 40%, respectively. When the HR was greater for other reasons, such as sinus tachycardia, simultaneous ejection from the heart and VAD was observed; however, the cardiac load was not increased by rapid cardiac contractions resulting from decreased left ventricle volume. These data suggest that the PLL algorithm reduces the cardiac load and maintains consistent hemodynamic changes.
心室辅助装置（VAD）的反搏控制（CPC）被认为可以降低心脏负荷并增加冠状动脉灌注。然而，VAD 患者发生心律失常的风险较高，这可能导致 CPC 失败。因此，CPC 在临床实践中并未应用于 VAD。CPC 的锁相环（PLL）算法很容易在 VAD 中实现；然而，它需要正常、一致的心跳才能达到足够的性能。当发生心律失常时，该算法会维持恒定的泵送率，而不顾不稳定的心跳。因此，要将 PLL 算法应用于 CPC，必须分析异常心跳的血液动力学影响。
本研究旨在根据心电图（ECG）数据预测接受 VAD 反搏控制的患者的血液动力学影响，包括由室性早搏（PVC）或其他原因引起的广泛心率（HR）变化。
本研究使用四元素风箱血液动力学模型来复制患者的主动脉血压。使用来自 15 名严重充血性心力衰竭患者的 ECG 数据来评估 CPC 对患者血液动力学状态的影响。使用超声血流仪（TS410，Transonic，美国）测量搏动性 VAD（LibraHeart I，Cervika，韩国）的输入和输出流量特性，主动脉压保持在 80-120mmHg。还复制了所有其他患者的情况。
在患有 PVC 或正常心跳的患者中，VAD 控制的 CPC 将心脏负荷分别降低了 20%和 40%。当 HR 因其他原因（如窦性心动过速）而增加时，会观察到心脏和 VAD 的同时射血；然而，由于左心室容积减少导致的快速心脏收缩不会增加心脏负荷。这些数据表明 PLL 算法降低了心脏负荷并维持了一致的血液动力学变化。
