The ECG shows characteristic ______ changes in the precordial leads, suggesting acute pericarditis.

Diffuse ST-segment changes across multiple precordial leads are characteristic of acute pericarditis. This widespread pattern helps distinguish it from localized changes seen in myocardial infarction or ischemia.

ECG Changes in Acute Pericarditis:
- Diffuse ST elevation in multiple leads (typically concave up)
- PR segment depression
- Absence of reciprocal ST depression
- Four stages of ECG evolution:
1. Diffuse ST elevation, PR depression
2. ST segments return to baseline
3. T wave inversion
4. ECG returns to normal

Key Differentiating Features:
- Widespread involvement vs localized changes
- ST elevation in both limb and precordial leads
- Spares aVR and V1
- PR depression (especially in lead II)
- Preserved R wave progression
- No Q waves

Clinical Associations:
- Viral infections
- Post-myocardial injury
- Autoimmune conditions
- Uremia
- Neoplastic disease
- Post-cardiac surgery