Which ECG finding is indicative of non-ST-segment elevation ACS (NSTE-ACS)?

The presence of ST-segment depression on an ECG is indicative of non-ST-segment elevation acute coronary syndrome (NSTE-ACS). This finding suggests that there may be an ischemic condition in the myocardium due to reduced blood flow, often associated with unstable angina or non-ST elevation myocardial infarction.

When analyzing the ECG pattern, ST-segment depression can appear as a horizontal or downsloping segment that dips below the baseline after the P wave. This is a key marker that reflects subendocardial ischemia, which is commonly seen in NSTE-ACS situations where there is a less severe disruption in blood flow compared to ST-segment elevation.

In contrast, other findings such as ST-segment elevation are associated with ST-elevation myocardial infarction (STEMI) and signify more severe, often full-thickness ischemia of the heart muscle. Q-wave formation typically indicates old myocardial infarction and suggests that there has been significant heart tissue damage, while PR interval prolongation is not directly indicative of acute coronary syndromes but rather more related to atrioventricular conduction issues.

Thus, the identification of ST-segment depression is crucial in quickly diagnosing and managing patients with NSTE-ACS, guiding further evaluation and treatment