WWII injury to both maxillary sinuses, chronic cough linked to Heart attacked

Veteran injured during WW II.  Shrapnel wounds passed through both maxillary sinuses and disrupted some of the posterior oropharynx.  He suffered all these 64 years with chronic sinusitis with chronic cough and a certain degree of aspiration on a recurring basis.  He was also on oxygen.  On the day of his death, he was exposed to heavy pollen via flowers in his garden, washing "hosing"  the pollen off of the patio and also off of the car.  After doing so, he had a severe attack of coughing with apiration and heavy mucus for the rest of day and into the night.  In the afternoon the Home Health Nurse came and gave him a breathing treatment (with nebulizer).  He was not well enough to eat supper and went to bed with his mucous cup by his bed and his oxygen on.  He died during the night of a heart attack.
We need a medical opinion -  Is it possible that the uncontrolled, severe coughing spells during the day and night including spitting up heavy mucus could have caused a strain on his heart thus causing the heart attack during his sleep.