Why its dangerous to have anesthesia for heart patient?

Anesthesia : Anesthesia can lower blood pressure and cause the heart to have to compensate by increasing its rate. This can stress the heart and if there is an underlying issue is can worsen it.

Not Necessarily: Although it's true that certain heart conditions pose added anesthesia risks (coronary disease, high bp, valve problems, enlarged or dilated chambers, irregular rhythms) if these conditions are optimized and controlled, in experienced hands, the risks are minimized. The heart, as the pump that delivers blood and oxygen and anesthesia, must work optimally for your safety in surgery..

Weak heart: Patients who have heart problems usually have an underlying perfusion problem with their heart muscle. This means that it is somewhat dependent on a "normal" blood pressure. Anesthetic drugs can cause a decrease in blood pressure that can adversely affect the heart. The patient should discuss their condition with the anesthesiologist prior to surgery so that preventative steps can be taken.