Three-dimensional cardiac accelerometry for cardiac monitoring

描述(申请人提供)：心脏病是佐治亚州的主要死亡原因，糖尿病患者、老年人和非裔美国妇女面临的风险最大。心脏负荷试验是评估心脏功能的标准筛查工具，而心电图、超声(超声心动图、超声心动图)和核心肌灌注成像(MPI)是常用的检测缺血和室壁运动异常的方法。心电图受代谢状态的影响，回声不能可靠地预测结果，因为可靠性依赖于操作员，而且它只检测到高度缺血。MPI只显示心肌灌注的区域差异，而不是整体灌注效率，而且它是常用核诊断方法中最高的单次辐射暴露。需要一种检测心脏功能障碍的方法，1)足够便宜以提供广泛的患者通道，2)安全和非侵入性，3)至少与ECHO一样灵敏，而不固有地依赖操作员的熟练程度，以及4)独立于电离辐射。我们假设，在确定的频率范围内测量心脏加速度，再加上最近开发的时间域和频域分析技术，可以提供目前心功能诊断所缺乏的安全性、敏感性、可靠性和低成本。该提案的目的是在临床上评估基于加速度计的、低成本、非侵入性、缺血检测和功能评估系统在物理或化学负荷测试过程中用于心脏监测的诊断价值。该系统利用一种新的商用非侵入性低频三轴加速度计，结合新颖的数据采集和时间和频域分析来量化心脏的机械活动。单轴心脏加速度计(地震心动图，SCG)作为MRI期间监测心肌缺血和评估失重环境下心肌收缩能力的可靠方法已经得到了很好的应用。在初步研究中，对新型低频三轴SCG(3D-SCG)数据的时间和频域数据分析显示，心脏在三维上的加速一致地指示特定的实验条件，但与心脏负荷、体型或附带的身体运动无关。新的频域分析表明，低频3D-SCG可以识别室壁运动的变化和瓣膜功能的缺陷。这一资助机会将使我们能够评估新型3D-SCG系统作为一种压力测试诊断与心电图、ECHO和MPI模式的比较。对于第二供应商来说，3D-SCG可以1)提高可靠性，作为当前负荷测试诊断的低成本补充或替代；2)提供不依赖于操作员专业知识的改进的缺血检测；3)允许对手术后或慢性病患者进行实时持续的心脏监测。由于3D-SCG潜在的低成本和广泛的可及性，3D-SCG最终可能被用于初级保健，以1)提供对高危患者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定点评估。 公共卫生相关性：心脏负荷试验是检测冠心病引起的缺血的最经济有效的方法，但其缺乏敏感性限制了其对未来心脏事件的预测能力。这项研究利用无创三轴加速度计(三维地震心动图，3D-SCG)和针对地震数据开发的新分析方法来改进缺血检测和心功能评估。这项技术显示出作为心脏负荷测试的低成本附加技术的前景，作为手术后心脏病患者的持续监测工具，以及作为初级保健中的低成本心脏病筛查工具。

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.