A device for examining the heart is provided with a catheter adapted to be placed within the heart and including at one end thereof, circumferentially arranged, equidistantly distributed elements, serving for the transmission and reception of ultrasonic waves. The catheter has an axis and the elements have no directivity in a plane perpendicular to this axis. The elements are so dimensioned in axial direction that in a plane through the axis they do show directivity. An excitation device is provided which successively excites groups of adjacently arranged elements and time delays are provided for delaying the transmitted and received pulses for the elements of a group that the differences in travel times are compensated. An adder is provided for the summation of echo pulses and a device is provided for visually displaying the part of the examined heart surrounding the catheter.