Pune, April 18: M. Tahir Merchant alias Tahir Takla, one of the convicts in the March 1993 Mumbai serial blasts who was sentenced to death, died of a heart attack here on Wednesday, a police officer said. Merchant, who was lodged in the Yerawada Central Jail, suffered a heart attack in the prison around 3 a.m. and was rushed to the Sassoon Hospital. However, he failed to respond to the treatment and breathed his last around 3.45 a.m., said Additional Director General of Police (Prisons) B.K. Upadhyay.