hourglass pattern

hour·glass pat·tern

a vigorous ringlike contraction observed angiographically in the left ventricular angiogram in the right anterior oblique projection, resembling an hourglass; it is seen in the prolapsed mitral valve leaflet syndrome.
References in periodicals archive ?
Common dolphins, slim and streamlined with precise markings and an hourglass pattern on their sides streaked around and under the boat, twisting and turning as they rode on the bow wave.
This, by the way, was the only one of two dozen spectacular Badula corundum crystals which showed the hourglass pattern distinctly.
COPPERHEAD FAMILY (AKA HIGHLAND MOCCASIN): a brown, copper or tan pit viper with darker brown, hourglass patterns on its back.