I have exactly the same issue. I have had a persistent cough for a few years now, yet they seem to think it’s not caused by my diastolic heart failure with preserved ejection. I have had a chest x-ray that was clear. I went to an ENT who thinks it might be silent reflux and I’ve been taking Pepcid for many months with no change at all in the cough. I really wonder if it isn’t a side effect of the blood pressure medication, my first one was lisinopril which made me cough like crazy. I switched then to losartan , and then eventually to valsartan. Although the cough was never as bad as on lisinopril, it has remained ever since.