Dr Rajendra K Pachauri, who quit as head of the UN's climate panel on Tuesday following accusation of sexual harassment, was hospitalised at New Delhi's Fortis Escorts Heart Institute on Monday evening after he arrived with complaints of high blood pressure and palpitation.
Pachauri had undergone an angioplasty - a procedure where metal scaffolding is used to prop open blocked arteries - at Escorts in 2011 and since then has been under the care of senior invasive cardiologist Dr Ashok Seth. He gets his annual check-ups and follow-ups done at the hospital.
"He is suffering from a cardiac problem and underwent a stent procedure some years ago. He has been frequently visiting doctors for checkups," said his lawyer Shankh Sengupta on Wednesday.
Pachauri, 74, resigned on Tuesday as chairman of the Nobel Prize-winning Intergovernmental Panel on Climate Change (IPCC) and went on to quit as the head of TERI after a 29-year-old researcher at TERI filed an FIR against him.
She accused him of repeated inappropriate behavior and harassment through emails, texts and WhatsApp messages. Pachauri has denied the allegations, claiming his emails and mobile phone were hacked.
His resignation comes just as the IPCC is setting the ground for the Paris climate change summit where world leaders are expected to strike a deal on address global warming.