My father is a heart patient, he had 4 bypasses done last year on september. since last week he has had dry cough which bis irritable which is a worry?

Check his meds : After ruling out viral and bacterial causes of cough.... Consider Ace inhibitor associated cough. Most cardiac patients are on Lisinopril or OTHER ACE inhibitor meds. Commonly dry cough is a side effect. If he has been on an ace inhibitor discuss this with your doctor he will replace it with a ARB, alternative treatment.

See doctor...: There are many possible causes for a cough. If it is of recent onset, it could be due to acute bronchitis, post-nasal drip, etc. A more chronic cough could be due to bronchospasm, GERD, post-nasal drip, etc. In this case, heart failure would be a concern as well especially if he is also complaining of shortness of breath, leg swelling, coughing pink sputum, etc. Take him to his doc for diagnosis.