Global ST-T Wave Changes: Ischemic vs Nonischemic.

Abstract

Scenario: This prehospital 12-lead electrocardiogram (ECG) was obtained on a 70-year-old white man who called 9-1-1 for chest pain that started suddenly while at rest. The patient remained alert and oriented but had a low blood pressure of 80/50 mm Hg. The only significant feature in his medical history was hypertension, for which he had been taking a β-blocker. The initial cardiac troponin level was negative.Normal sinus rhythm with global ST-T wave changes. No evidence of secondary (nonischemic) repolarization abnormalities that can alter the ST-T wave (ie, bundle branch block, ventricular pacing, ventricular rhythm, or left ventricular hypertrophy) is apparent. The observed ST-T wave changes in this patient appear to be ischemic in nature. Differential diagnoses include non-ST elevation acute coronary syndrome (NSTE-ACS); other uncommon diagnoses could include myocarditis, aortic dissection, cardiomyopathy, pulmonary embolism, and acute pancreatitis.Within the context of acute chest pain at rest, new horizontal or down-sloping ST-segment depression of 0.5 mm or more in 2 contiguous leads with or without T-wave inversion greater than 1 mm is indicative of ACS. Patients with NSTE-ACS who have severe myocardial ischemia and have multiple risk factors would benefit from early cardiac catheterization. ST-segment depression of 2 mm or greater and/or ST-segment depression in 5 or more leads carries about a 6-fold increased risk of mortality, which justifies the decision to send the patient for immediate cardiac catheterization. Interestingly, cardiac catheterization revealed that this patient had normal coronary arteries but had an acute ascending aortic dissection. The patient was referred for emergent surgery to repair the aortic dissection.When primary (ischemic) ST-T changes are identified, clinicians should assess the entire clinical picture to rule in or out other potential differential diagnoses. Acute aortic dissection can mimic ischemic ECG changes in more than 30% of patients, which makes distinguishing dissection from acute myocardial infarction very difficult. A key observation in this case alerting to a potential aortic dissection was profound low blood pressure in a patient with a prior history of hypertension. Severe hypotension at presentation has a poor prognosis and can suggest severe aortic insufficiency. Aortic dissection frequently requires surgical treatment, depending on the area of the aorta involved. One important challenge as demonstrated in this case is that antiplatelet/anticoagulants, although recommended to patients with suspected NSTE-ACS, would be harmful to patients with aortic dissection.