A patient may develop cardiac ischemic if hypotension causes a decrease in coronary artery perfusion. Owens and O'Brien reported criteria for making this diagnosis based on changes in the electrocardiogram (ECG). The authors are from Beaumont Hospital in Dublin, Ireland.
A patient with coronary artery disease will be more susceptible to this event.
Requirements for the diagnosis:
(1) ST depression in the ECG
(2) documented hypotensive episode
(3) correlation between the two
(3a) The onset of ST depression should start >= 1 minute after the start of the hypotensive event.
(3b) The ST segment changes normalize when the blood pressure is normalized (coincidental or shortly thereafter).
If the patient suffers a myocardial infarct as a result of the hypotension then the ST segment changes may persist after normalization of the blood pressure.
Definition of a hypotensive event - one or more of the following detected on at least 2 consecutive blood pressure measurements:
(1) systolic blood pressure < 100 mm Hg during the day
(2) diastolic blood pressure < 65 mm Hg during the day
(3) systolic blood pressure < 90 mm Hg at night
(4) diastolic blood pressure > 50 mm Hg at night
Differential diagosis:
(1) hypotension secondary to myocardial ischemia (in which case the ST segment changes precede the hypotensive event)
