hi thank you for asking your concern on hcm. answering to your first question it is very much unlikely to develop these symptoms due to diclofenac. most common side effect of diclofenac or diclofenac like drugs which we call NSAIDs is stomach ulcer and then so much acidity. gastritis can present with rapid heart beat, shorntness of breath in few instances. antacids should be taken along with diclofenac to decrease gastric damage. but i would like to suggest to consult your physician for these symptoms to check for hypertension, diabetes. i would suggest to do an electrocardiogram (ECG), urine for microprotein or protein. i will be important to check kidney status because you are having a long history of taking diclofenac. answering to your second question is yes long term diclofenac is dangerous not only for you but to anybody. gastric ulcer and kidney failure are the most devastating complication it gives. feel free to ask any doubts thank you regards dr. abhijit