Date Published: January 28, 2019
Publisher: Public Library of Science
Author(s): Victor Chien-Chia Wu, Tetuji Kitano, Yosuke Nabeshima, Kyoko Otani, Pao-Hsien Chu, Masaaki Takeuchi, Otavio Rizzi Coelho-Filho.
Novel fully automated left chamber quantification software for three-dimensional echocardiography (3DE) has a potential for reliable measurement of left ventricular (LV) volumes and ejection fraction (LVEF). However, the optimal setting of global LV endocardial border threshold has not been settled.
We performed LV volumes and LVEF analysis using fully automated left chamber quantification software (Dynamic HeartModelA.I., Philips Medical Systems) in 65 patients who had undergone both 3DE and cardiac magnetic resonance (CMR) examinations on the same day. We recorded LV end-diastolic volume (LVEDV) and LV end-systolic volume (LVESV) according to the change in LV global border threshold settings from 0-point to 100-point with each increment of 10-point. These values were compared to the corresponding values of CMR with disk-area summation method and feature tracking (FT) method. Coverage probability (CP) was calculated as an index of accuracy and reliability. Fully automated software provided LV volumes and LVEF in 57 patients (Feasibility: 88%). LVEDV and LVESV increased steadily according to the increase in border threshold and reached minimal bias when border threshold setting was 80 against CMR disk-summation method and 90 against CMR FT method. Corresponding CP of LVEF was 0.74 and 0.84 against disk-area summation method and FT method.
With CMR values as a reference, LV endocardial border threshold value can be set around 80 to 90 with the same number of LV end-diastole and end-systole threshold to approximate LVEDV, LVESV and LVEF with clinically acceptable CP values of LVEF.
Left ventricular (LV) ejection fraction (LVEF) using transthoracic two-dimensional echocardiography (2DE) is still one of the most important cardiac metrics to quantify LV function. Several cut-off values of LVEF has been used to select candidates for implantable cardiac defibrillator  and to determine discontinuation of cancer therapy [2, 3]. However, manual tracing on the endocardial border produces inter-observer measurement variabilities that may not be negligible. To overcome this problem, several ultrasound vendors have produced semiautomated LV border detection software that have still limitations due to several reasons.
Table 1 describes clinical characteristics in study population. 3DE datasets had good image quality in 18%, fair image quality in 45% and poor image quality in 37%, respectively. Among 65 patients, 8 patients were excluded because of no 3DE datasets acquisition due to extremely poor echocardiographic image quality (n = 6) or erroneous LV cast construction (n = 2) by 3DE fully automated software (Feasibility: 88%). Thus, final analysis was conducted in 57 patients. Standard CMR measurements (disk-area summation method) provided LV volumes and LVEF in all patients. CMR FT method provided LV volumes and LVEF in 55 patients (Fig 1). The mean values of LVEF measured on standard CMR method and CMR FT method were 35 ±17% and 35 ±14%.
This is the first systematic study to investigate optimal endocardial border threshold values for determination of LV volumes and LVEF using 3DE fully automated left chamber quantification software (Dynamic HeartModel) and its earlier version (HeartModel) against CMR as a reference. Our results showed that the bias between both Dynamic HeartModel and HeartModel determined LVEDV and LVEDV were smallest when the border threshold value was set to 80-point against CMR disk-area summation method, or 90-point when compared to CMR FT method. Dynamic HeartModel could improve measurement accuracy over previous version of the software because the former was yielded with higher values of CP with equivalent border setting.
We concluded that LV endocardial border threshold value can be set around 80 to 90 with the same number of LV ED and ES threshold to approximate LVEDV, LVESV and LVEF with clinically acceptable CP values of LVEF as CMR values as a reference.