Of or relating to the heart; another variant form emphasizing heart-related medical conditions.
From Greek 'kardia' + obsolete English suffix '-cle' (variant of '-cal'). This appears to be a Middle English or Early Modern English variant that didn't survive in modern medical terminology.
Medical English created dozens of near-identical synonyms through different suffixes—'cardiac,' 'cardiacal,' and 'cardiacle' all mean basically the same thing, showing how languages generate alternatives even when one form already works perfectly.
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