My Dad Had A Heart Attack Last Month. A Total

My dad had a heart attack last month. A total right artery block. His symptoms were burping and numbness in the arms. He is now burping all the time with no other symptoms. Complains of weakness upon any activity. In addition, he has IPF and has had it for 8 years. Should I be concerned about the belching? Also when he was in the hospital my dad was coughing up black tar, they told us it was old blood. They said that happens with IPF, is that correct?