Figure 4

Tree data analysis-based novel spatiotemporal data exploration and visualization assess myocardial tissue contraction in interdependency, synchronicity, and propagation. (A) A tree data structure is defined to determine contraction origins and the interdependency between contracting regions. The contraction origin is considered as the leaf (at time T₁) belonging to one big contracting area (at time T₅) which is the root of the data tree. (B) The ASC map plotting the depth of the tree data distinguishes contracting regions based on their functional beating activity. More yellowish color regions having more depth in data tree can represent the primary beating areas (or contraction origins), while green then blue areas are neighboring regions contracting due to the contraction waves originating from the primary regions. The highest (O′) and second highest (O″) peaks are marked in the 3D ASC map (the third highest O″′ is not seen due to the location). (C) Three major contracting origins (O′, O″, O″′) are shown as well as centroids of other contracting regions for those larger than 10 DIC vector units or 4840 µm². Centroids are color-coded to show the contracting area (µm²). Centroids around O″′ are not seen due to contracting area size or overlapping with O″′. (D) Displacements at O′, O″, and O″′ are plotted over time. (E) The data tree analysis also identified small independently beating regions (black dots), indicating there are also contractions less dependent of the primary contractions at O′, O″, and O″′. (F) The ASTC map representing the contracting data tree through space and time axes visualizes the interaction of the contraction origins. This map thus illustrates the synchronicity and propagation of the beating among the contraction origins. The primary contracting origin (O′) is the most active, and the contraction timing between O′ and the secondary (O″) and tertiary (O″′) origins are evident along the vertical time axis. Frame units in all relevant figures are in µm.