The ornamental design for a ring-shaped electrocardiographic device, as shown and described.
1. Ring-shaped electrocardiographic device
1.1 : Perspective
1.2 : Front
1.3 : Back
1.4 : Left
1.5 : Right
1.6 : Top
1.7 : Bottom
1.8 : Perspective
Fig. 1.1 is a top front perspective view of a ring-shaped electrocardiographic device showing our new design; fig. 1.2 is a front view thereof; fig. 1.3 is a rear view thereof; fig. 1.4 is a left side view thereof; fig. 1.5 is a right side view thereof; fig. 1.6 is a top view thereof; fig. 1.7 is a bottom view thereof; and, fig. 1.8 is a bottom front perspective view thereof; the dashed broken lines in the figures show portions of the ring-shaped electrocardiographic device that form no part of the claimed design; the shade lines in the figures show contour but do not represent surface ornamentation; the dot-dash broken lines in the figures show boundaries that form no part of the claimed design.