The Collaborative International Dictionary of English v.0.48:

Heartache \Heart"ache`\ (-[=a]k`), n. [Cf. AS. heortece.]
   Sorrow; anguish of mind; mental pang. --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

heartache
    n 1: intense sorrow caused by loss of a loved one (especially by
         death) [syn: grief, heartache, heartbreak,
         brokenheartedness]

Moby Thesaurus II by Grady Ward, 1.0:

35 Moby Thesaurus words for "heartache":
   aching heart, affliction, agony, agony of mind, anguish, bale,
   bitterness, bleeding heart, broken heart, brokenheartedness, care,
   crushing, depression, depth of misery, desolation, despair, dole,
   extremity, grief, heartbreak, heartbrokenness, heartsickness,
   heartsoreness, heavy heart, infelicity, melancholia, melancholy,
   misery, prostration, regret, rue, sadness, suicidal despair, woe,
   wretchedness