<h2>Lorem ipsum dolor sit</h2>

h2 {
    text-align: center;
    position: relative;
    text-transform: uppercase;
    overflow: hidden;
}

h2::before {
    content: "";
    width: 170px;
    height: 2px;
    background: #fff;
    position: absolute;
    top: 50%;
    margin-left: -200px;
}

h2::after {
    content: "";
    width: 170px;
    height: 2px;
    background: #fff;
    position: absolute;
    top: 50%;
    margin-left: 30px;
}

@media screen and (max-width: 700px) {

    h2 {
        overflow: visible;
    }

    h2::before {
        width: 350px;
        top: -8px;
        left: 50%;
        margin-left: -175px;
    }

    h2::after {
        width: 350px;
        bottom: -8px;
        left: 50%;
        margin-left: -175px;
    }
}