The cause of Jan Kaplický's death was heart failure

Prague - The cause of the sudden death of architect Jan Kaplický was likely heart failure. The architect died just a few hours after the birth of his second child. "His heart betrayed him at the moment he wanted to celebrate this joyful event," Kaplický's family informed ČTK today.
The doctor who unsuccessfully attempted to revive Kaplický on Wednesday evening estimated that his death was caused by heart failure; however, the exact cause will be clarified only by an autopsy, said Zdeněk Schwarz, director of the Prague emergency service, to ČTK.
Those closest to the architect requested in a statement to the media not to contact them at this time with requests for interviews or statements.
Seventy-one-year-old Kaplický collapsed on the street near Vítězné náměstí in Prague on Wednesday evening. The rescuers were unable to revive him.
The architect was born on April 18, 1937, into an artistic family—his father was a painter, sculptor, and architect, and his mother was a draftsman. He also studied at the Academy of Art, Architecture and Design in Prague and then worked briefly as a freelancer. Since his emigration in 1968, he lived in Britain.
His most significant realization is also located there. The design for the National Library building was to be Kaplický's first major construction in his homeland. Even though the project won an international competition, it will almost certainly not be built in Prague's Letná due to politicians' reluctance. However, the disputes surrounding the building called the Octopus brought Kaplický into the wider public consciousness in the country.
Kaplický was married for the second time; he has a son, Josef, from his first marriage. He married Eliška, who is 41 years younger, in the autumn of the year before last.