Gupta Sunil, Muthiah Kavitha, Woldendorp Kei, Robson Desiree, Jansz Paul, Hayward Christopher S
Heart Failure and Transplant Unit, St. Vincent's Hospital, Sydney, New South Wales, Australia; Faculty of Medicine, The University of New South Wales, Sydney, New South Wales, Australia.
Artif Organs. 2014 Dec;38(12):1029-34. doi: 10.1111/aor.12292. Epub 2014 Mar 24.
It is important to accurately monitor residual cardiac function in patients under long-term continuous-flow left ventricular assist device (cfLVAD) support. Two new measures of left ventricular (LV) chamber contractility in the cfLVAD-unloaded ventricle include IQ, a regression coefficient between maximum flow acceleration and flow pulsatility at different pump speeds; and K, a logarithmic relationship between volumes moved in systole and diastole. We sought to optimize these indices. We also propose RIQ, a ratio between maximum flow acceleration and flow pulsatility at baseline pump speed, as an alternative to IQ. Eleven patients (mean age 49 ± 11 years) were studied. The K index was derived at baseline pump speed by defining systolic and diastolic onset as time points at which maximum and minimum volumes move through the pump. IQ across the full range of pump speeds was markedly different between patients. It was unreliable in three patients with underlying atrial fibrillation (coefficient of determination R(2) range: 0.38-0.74) and also when calculated without pump speed manipulation (R(2) range: 0.01-0.74). The K index was within physiological ranges, but poorly correlated to both IQ (P = 0.42) and RIQ (P = 0.92). In four patients there was excellent correspondence between RIQ and IQ, while four other patients showed a poor relationship between these indices. As RIQ does not require pump speed changes, it may be a more clinically appropriate measure. Further studies are required to determine the validity of these indices.
准确监测长期接受连续流左心室辅助装置（cfLVAD）支持的患者的残余心功能非常重要。cfLVAD卸载心室中左心室（LV）腔收缩性的两种新测量方法包括IQ，即不同泵速下最大血流加速度与血流搏动性之间的回归系数；以及K，即收缩期和舒张期移动容积之间的对数关系。我们试图优化这些指标。我们还提出了RIQ，即基线泵速下最大血流加速度与血流搏动性的比值，作为IQ的替代指标。对11名患者（平均年龄49±11岁）进行了研究。通过将收缩期和舒张期开始定义为最大和最小容积通过泵的时间点，在基线泵速下得出K指数。不同患者在整个泵速范围内的IQ明显不同。在3名患有潜在心房颤动的患者中，IQ不可靠（决定系数R(2)范围：0.38 - 0.74），在不进行泵速操作计算时也是如此（R(2)范围：0.01 - 0.74）。K指数在生理范围内，但与IQ（P = 0.42）和RIQ（P = 0.92）的相关性都很差。在4名患者中，RIQ与IQ之间有很好的对应关系，而在其他4名患者中，这些指标之间的关系很差。由于RIQ不需要改变泵速，它可能是一种临床上更合适的测量方法。需要进一步研究来确定这些指标的有效性。
