Three-dimensional cardiac accelerometry for cardiac monitoring

描述（由申请人提供）：心脏病是佐治亚州死亡的主要原因，糖尿病患者、老年人和非裔美国妇女的风险最大。心脏负荷试验是评估心功能的标准筛选工具，心电图（ECG）、超声（ECHO）和核心肌灌注成像（MPI）是检测缺血和心壁运动异常的常用方法。心电图受代谢状态的影响，ECHO不能可靠地预测预后，因为可靠性依赖于操作者，它只能检测高度缺血。MPI仅显示心肌灌注的区域差异，而不是整体灌注效率，它是常用核诊断中单次辐射暴露最高的。我们需要一种检测心功能障碍的方法：1)价格低廉，能够提供广泛的患者访问；2)安全且无创；3)至少与ECHO一样敏感，而不依赖于操作人员的熟练程度；4)不依赖于电离辐射。我们假设在确定的频率范围内测量心脏加速，再加上最近开发的时域和频域分析技术，可以提供目前心功能诊断所缺乏的安全性、灵敏度、可靠性和低成本。本提案的目的是临床评估一种基于加速计、低成本、无创、缺血检测和功能评估系统在物理或化学应激测试过程中用于心脏监测的诊断价值。该系统采用了一种新型的商用、无创、低频三轴加速度计，结合了新颖的数据采集和时域和频域分析，可以量化心脏的机械活动。单轴心脏加速度计（seismocardiography， SCG）作为MRI期间监测心脏缺血和评估失重环境下心脏收缩力的可靠方法，已经得到了广泛的应用。在初步研究中，新型低频三轴SCG （3D-SCG）数据的时域和频域数据分析显示，三维心脏加速始终表明特定的实验条件，但与心脏负荷、体型或偶然的身体运动无关。新的频域分析表明，使用低频3D-SCG可以识别管壁运动的变化和阀功能的缺陷。这次拨款机会将使我们能够将新型3D-SCG系统作为压力测试诊断与ECG、ECHO和MPI模式进行比较。对于二级供应商来说，3D-SCG可以1)提高可靠性，作为当前压力测试诊断的低成本补充或替代方案，2)提供独立于操作人员专业知识的改进的缺血检测，3)允许对术后或慢性病患者进行实时持续心脏监测。由于潜在的低成本和广泛的可及性，3D-SCG最终可能适用于初级保健：1)为高危患者提供心脏机械能力的长期监测，或2)为学生运动员提供心脏机械功能的护理点评估。

DESCRIPTION (provided by applicant): Heart disease is the leading cause of death in Georgia, and diabetics, the elderly, and African American women are most at risk. The cardiac stress test is the standard screening tool for assessing cardiac function, and electrocardiography (ECG), ultrasound (echocardiography, ECHO) and nuclear myocardial perfusion imaging (MPI) are the modalities commonly used for detecting ischemia and cardiac wall motion abnormalities. ECG is affected by metabolic state, and ECHO is not reliably predictive of outcome, as reliability is operator-dependent and it detects only high-grade ischemia. MPI shows only regional differences in myocardial perfusion, rather than overall perfusion efficiency, and it contributes the highest single radiation exposure of commonly used nuclear diagnostics. A method for detecting cardiac dysfunction is needed that 1) is inexpensive enough to provide widespread patient access, 2) is safe and non-invasive, 3) is at least as sensitive as ECHO, without the inherent dependence on operator proficiency, and 4) is independent of ionizing radiation. We hypothesized that measurement of cardiac accelerations within a defined frequency range, coupled to recently developed time- and frequency-domain analytical techniques, could provide the safety, sensitivity, reliability, and low cost currently lacking in a cardiac function diagnostic. The goal of this proposal is to clinically assess the diagnostic value of an accelerometer-based, low-cost, non-invasive, ischemia detection and functional assessment system for cardiac monitoring during physical or chemical stress testing procedures. The proposed system utilizes a new class of commercially available, non-invasive, low-frequency triaxial accelerometer coupled with novel data acquisition and time- and frequency-domain analyses to quantify the mechanical activity of the heart. The utility of single-axis cardiac accelerometry (seismocardiography, SCG) as a reliable method for monitoring cardiac ischemia during MRI and for assessing cardiac contractility in weightless environments is well established. In preliminary studies time- and frequency-domain data analysis of the novel low-frequency, triaxial SCG (3D-SCG) data revealed cardiac accelerations in three dimensions that were consistently indicative of specific experimental conditions, yet were independent of cardiac loading, body type, or incidental body movement. Novel frequency domain analysis showed that changes in wall motion and defects in valve function could both be identified using low-frequency 3D-SCG. This grant opportunity will allow us to evaluate the novel 3D-SCG system as a stress test diagnostic in comparison with ECG, ECHO, and MPI modalities. For the secondary provider, 3D-SCG could 1) improve reliability as a low-cost addition or alternative to current stress test diagnostics, 2) provide improved ischemia detection independent of operator expertise, and 3) allow real-time constant cardiac monitoring of post-operative or chronically ill patients. Because of the potential low cost and widespread accessibility, 3D-SCG could ultimately be adapted for primary care to 1) provide long-term monitoring of cardiac mechanical ability in at-risk patients, or 2) provide point-of-care assessment of cardiac mechanical function in student athletes. PUBLIC HEALTH RELEVANCE: The cardiac stress test is the most cost-effective method for detecting ischemia due to coronary heart disease, but its lack of sensitivity limits its predictive ability for future cardiac events. This study utilizes non-invasive triaxial accelerometry (three-dimensional seismocardiography, 3D-SCG) and novel analytical methods developed for seismic data to improve ischemia detection and cardiac function assessment. This technique shows promise as a low-cost add-on technology for cardiac stress testing, as a constant monitoring tool for post-surgery cardiac patients, and as a low-cost screening tool for heart disease in primary care.