The former general is being treated for a heart condition at an army hospital.
The trial has been adjourned until tomorrow.
Musharraf, who seized power after toppling the elected government of Prime Minister Nawaz Sharif in a military coup on October 12, 1999, was forced to resign in August 2008 when the then ruling party Pakistan Peoples Party, and opposition Pakistan Muslim League (PML) threatened to impeach him.
The federal government last month appointed a special court of three judges to try Musharraf for high treason under Article 6 for imposing a state of emergency in the country, and suspending the constitution on November 3, 2007. He is also facing trial in murder cases of former Prime Minister Benazir Bhutto, and former Chief Minister of Southwestern Baluchistan and a veteran politician, Nawab Akbar Bugti.
