HI Thank for choosing HCM, You mean to say that because of your fatigue condition you are being switch over from Atenolo to Lisipril, if this statement is true to my knowledge then you are in wrong impression or wrongly interpreted, first these two drug is simply antihypertensive drugs Atenolo is betablocker and lisipril is Angiotensin converting enzyme inhibitors, has nothing to take with your fatigue, or if your are thinking that your high blood pressure causing you fatigue, and antihypertensive drug controlled the pressure and this relieved the fatigue then also it is not true, it must be placebo effect of the drugs, you must be having functional fatigue,,, please take care of your self have nice day.