Hi, My father is suffering from dilated cardiomyopathy from around 10-12 years and now it has reached the stage of congestive heart failure . His heart is functioning only 14%.Now a days, he is facing a problem of severe headache . When he sits, his blood pressure is low but as he lies down, blood pressure shoots up suddenly by 20-25% and he gets severe headache which is unbearable.please tell what could be the cause behind it and please suggest some medication for this headache. Thanks