How low would your blood pressure need to get to cause a heart attack or stroke?

Stroke: Depends on many variables including duration of low blood pressure, age, oxygen delivery capacity and pre-existent arterial disease. A very low diastolic blood pressure may result in insufficient perfusion of the coronary arteries which can result in a heart attack(especially in the presence of coronary artery disease). Brain circulation has an autoregulatory mechanism that sustains blood flow to brain during very low blood pressure with a limit at near 30 to 40 of mean arterial pressure.

It can happen: Blood pressure is an element and the very high can tear the aorta or the coronaries, but blockage by plaque and clot occurs with or without BP elevation. The very low- shock can cause low coronary or brain blood flow. Generally less than 70-80 mm hg is a concern. Brain maintains good auto regulation from about 60 -160 if there is not other blockage or micro vessel disease.