People having silent heart attacks just don't realize what's happening, so they're not seeking medical attention, which means they're less likely to receive the treatment that they need at the critical moment.
Orang yang mengalami serangan jantung mendadak tidak menyadari hal itu, sehingga merasa tidak memerlukan pertolongan medis, akibatnya mereka tidak mendapat perawatan yang dibutuhkan di saat kritis.