Prison authorities claimed James “Whitey’’ Bulger’s health had improved dramatically before they sent him to the West Virginia prison where he was murdered last month, brutally beaten by inmates just hours after he arrived.

But the gangster’s own words, like a voice from beyond the grave, tell a different story.

In a series of letters written over the past several years to a former convict who, like Bulger, served time at the Alcatraz penitentiary, the ex-South Boston crime boss described a litany of worsening health problems that included several heart attacks and blackouts.