ST-segment elevation myocardial infa rctions

(STEM I).

• Patients with STEMI req uire immediate reperfusion

therapy with either thrombolytics or percutaneous

coronary intervention to salvage the maximum amount

of viable myocardium.

arteries of adolescent patients and progresses by early

adulthood to the formation of organized fibro-fatty

plaques. As plaques enlarge throughout adulthood, they

progressively limit coronary blood flow and may eventually induce the development of anginal symptoms with

exertion. In time, plaques can rupture, causing secondary

intraluminal thrombus formation and a sudden reduction

in coronary perfusion (ie, AMI).

UA is a clinical diagnosis that has no pathognomonic

ECG findings or confirmatory elevations in cardiac bio ­

markers. Patients with classic anginal symptoms that are

either new, accelerating in frequency or severity, or that

occur without exertion are considered to have UA. UA and

NSTEMI are very similar from a pathophysiologic standpoint with the latter being distinguished by the presence of

elevated cardiac biomarkers. Both conditions arise from

the non-complete occlusion of coronary blood flow with

the secondary development of ischemia and infarction,

respectively. Complete occlusions of the coronary arteries

typically result in transmural infarctions of the myocardium with associated ST segment elevation (STEM!) on

the ECG and increased biomarker levels. Of note, the mor ­

tality rates of patients with NSTEMI and STEM! are iden ­

tical at the 6-month follow-up point.

ACUTE CORONARY SYN DROMES

It is very important to understand the basic anatomy of

the coronary arteries to identify concerning ECG patterns

and predict clinical complications. The left coronary artery

(ie, left mainstem artery) arises from the aortic root and

branches almost immediately into the left anterior

descending artery (LAD) and left circumflex artery (LCX).

The LAD runs down the anterior aspect of the heart and

provides the main blood supply to the anterior left ventride and ventricular septum, whereas the LCX runs in the

atrioventricular (AV) sulcus between the left atrium and

left ventricle and provides blood to the lateral and posterior regions of the heart. The right coronary artery (RCA)

also arises directly from the aortic root. It runs in the AV

sulcus between the right atrium and right ventricle and

provides blood to the right side of the heart and inferior

portion of the left ventricle. The sinoatrial node is perfused

by the RCA, whereas the AV node is perfused by a combination of the RCA and LAD in most patients.

Risk factors predictive of underlying coronary artery disease (CAD) have been identified and include age >40 years,