Mutahidda Qaumi Movement leader Rauf Siddiqui suffered a heart attack in Karachi on Monday, reported 24News HD TV channel.
The MQM leader was shifted to the National Institute of Cardiovascular Diseases after the attack.
He was sitting in the cafeteria of the Sindh High Court when he felt pain in his chest.
He came to the court to attend a case hearing.
He was immediately shifted to the NICVD in Karachi where his angiography was completed.
Rauf Siddiqui is being provided further treatment at the cardio hospital.
Reporter Shoaib Mukhtar