<h1 class="cp_h1title">見出しテキスト</h1>

.cp_h1title {
  position: relative;
  background: #F8BBD0;
  box-shadow:0 1px 3px rgba(0,0,0,0.4);
}
.cp_h1title:before,
.cp_h1title:after {
  content: "";
  position: absolute;
  top: 100%;
  height: 0;
  width: 0;
  border: 8px solid transparent;
  border-top: 8px solid #EC407A;
}
.cp_h1title:before {/*右の折り返し*/
  right: 0;
  border-left: 8px solid #EC407A;
}
.cp_h1title:after {/*左の折り返し*/
  left: 0;
  border-right: 8px solid #EC407A;
}