Mashboor Hussain, 73, died at his home in Selkirk Road on 11 February 2014.
Pathologists said although Mr Hussain had coronary heart disease, his collapse was likely caused by the disturbance at home and his death is being treated as murder.
Officers will be on his road today.
Det Ch Insp Graeme Gwyn said: "I believe there are still people who have yet to speak to us and would urge them to contact us.
"Mr Hussain's family naturally remain devastated by his death and desperate to see those responsible for his murder brought to justice."
At around 11:45 GMT, Mr Hussain opened his front door and was confronted by two men, one armed with a gun. They forced their way into his house and got into a scuffle with him in the hall.
The two men ran off with a red Nike show box containing cash and other belongings, such as a mobile phone.
Both suspects were wearing hooded tops and one is described as slim and wearing black gloves.
Mr Hussain's daughter was in his house at the time of the incident.
A £20,000 reward has been offered for anyone who can help find the killers of a pensioner who died after a scuffle with burglars in Tooting last year.