Thinking about a water only fast for 10 days.. but...?

Ok well I actually already went 2 days two weeks ago but stopped because someone told me since I already have high blood pressure my body could go into shock and I'd have a heart attack. Does anyone know if that's true? I was going to fast for 10 days.. but.. a heart attack because I already have hypertension?? Fasting would get rid of the hypertension I was thinking, not cause a heart attack.