This one will go into the Vince Foster Memorial Coincidence File....
There's little doubt that Foster was indeed murdered; all the credible circumstantial, physical, and forensic evidence is consistent with that conclusion.
In the Foster case, the cover-up was his purported "depression" leading to "suicide." No way anyone could use that same farce with Breitbart, who had much more of a public profile than Foster had, and who was obviously not clinically depressed in the weeks before his death.
Savage is merely thinking out loud and thinking appropriately here about Breitbart. He could have died of natural causes (43 year old men do die suddenly and unexpectedly), but there is also a chance he was murdered (perhaps by poisoning, to which he might be particularly vulnerable because of his frequent traveling and chances for contact with possible enemies).
There isn't enough information available at present, particularly with respect to his medical history and his family medical history, to evaluate Breitbart's risk for a fatal heart attack. Furthermore, there are other rarer causes for a sudden natural death.
In Foster's case, there was a fraudulent autopsy report by the Virginia state medical examiner attempting to support the predetermined "suicide" conclusion. In Beitbart's case, the politics could militate against an objective autopsy by the LA County medical examiner. Only time will tell.