"It could be a heart attack, and when the heart is damaged it causes respiratory damage, too."

"It isn't a heart attack, but your heart has gradually weakened over the years, causing respiratory disease."

It is probably a heart attack, since cor pulmonale means that the heart isn't getting enough blood and becomes too weak to pump effectively."

"You aren't having a heart attack, but your heart has been damaged by changes in your lungs caused by your respiratory disease."