According to Apollo Hospitals, Chennai, the Chief Minister was in a "critical" condition following the cardiac arrest.
The AIADMK supremo is undergoing treatment in the hospital since September 22.
In these hours of crisis, Jayalalithaa's supporters prayed hard for her recovery.
From Mumbai to Madurai, several prayer meetings were hosted across the country.
Here we bring you a glimpse of how anxious fans of Amma are waiting for some good news from the hospital: