The accessible SVG line graphs post explains how to use ARIA table semantics to make that form of data visualisation accessible to screen readers. This article uses the same ARIA based approach to make a screen reader accessible SVG flowchart.
SVG is often used for data visualisation, but because SVG lacks the semantics to express structures like bar charts, line graphs, and scatter plots, the content is difficult for screen reader users to interpret. The solution is to use the technique for creating accessible SVG tables as your starting point.
SVG has no native semantics for representing structures like tables, but ARIA1.1 introduces a number of roles that can be used to polyfill the necessary semantic information.