Complex sentence: Although they declared no proof, pathologists suggested a link between her heart attack and a viral infection causing a myocarditis--an inflammation of the heart muscle that could have been triggered anywhere between the last few years of her life and the last weeks.
Split into simpler sentences: Although they declared no proof, pathologists suggested a link between her heart attack and a viral infection causing a myocarditis Myocarditis. Myocarditis is an inflammation of the heart muscle that could have been triggered anywhere between the last few years of her life and the last weeks.