ST Segment elevation

Myocardial infarction with ST segment elevation occurs when an occlusive thrombus forms on a ruptured atherosclerotic plaque.

The prevalence of ST-segment elevation of at least 1 mm in one or more of EKG leads V1 through V4 is 93% in men 17-24 years of age, with decreasing likelihood with increasing age reaching 30% in men 76 years or older.

20% of women with normal electrocardiograms have ST-segment elevations of 1 mm or more regardless of age.

Majority of men have ST elevation of 1 mm or more in precordial leads, designated a normal male pattern.

Of less than 1mm is designated as a female pattern.

When ST elevation is present initial analysis is to determine whether acute epicardial coronary artery occlusion is present.

Isolated ST-segment elevation in the anteroseptal leads has a differential diagnosis including: right ventricular infarction, Ebstein’s anomaly, anteroseptal infarction, and arrhythmogenic right ventricular cardiomyopathy.

Differential diagnosis in patients with chest pain include myocardial infarction with occlusive thrombus, acute pericarditis, myocarditis, Prinzmetal�s angina, pulmonary embolus, Type A aortic dissection, apical ballooning syndrome and ventricular contusion.

Alternative diagnoses for ST elevation include pericarditis, ventricular aneurysm with akinesis, or severe hypokininesis, early repolarization pattern and metabolic abnormalities

ST elevation in anteriot precordial leads can be seen with hyperkalemia, and Brugada pattern.

RV infarction is associated with a combination of ST elevations in the inferior leads, with greater elevation in lead V1 carries a sensitivity of 79% and a specificity of 100%.

Patients presenting with chest pain, persistent elevation of the ST-segment with progression to Q waves, elevated cardiac enzymes have an 87% total thrombotic occlusion rate (DeWood).

Widespread ST elevation across the precordial leads and limb leads with upward concave ST segments and PR segment depression is characteristic of pericarditis.

The ratio of ST segment elevation in millimeters to T-wave amplitude in millimeters in excess of 0.24 in lead V6 supports diagnosis of pericarditis, and helps distinguish pericarditis from other repolarization abnormalities.

With ST elevation myocardial infarction oral administration of beta blockers is associated with decreased risk of cardiogenic shock, ventricular arrhythmias, and acute heart failure (Grace).

In the above study the Global Registry of Acute Coronary Events investigators found early receipt of any form of beta blockers was associated with an increase in hospital mortality.