Sentence:  Before kick-off, a section of Chelsea's support sadly let themselves and their club down by noisily interrupting the silence held in memory of the Hillsborough disaster and for Livorno midfielder Piermario Morosini, who collapsed and died after suffering a <WSD>heart attack</WSD> during a Serie B game on Saturday. 
Meaning of the word marked with <WSD> tags:  An acute myocardial infarction, sometimes fatal, caused by the sudden occurrence of coronary thrombosis, which obstructs the blood supply to the heart and leads to necrosis of heart muscle tissue.