PQ-segment elevation and depression
In this patient, cardiac ultrasound revealed moderate pericardial effusion. The combination of chest pain (worsened by inspiration and relieved by bending forward), the ECG (diffuse PQ segment depression), pericardial effusion and an inflammatory syndrome enabled the diagnosis of acute pericarditis. In pericarditis, atrial repolarization abnormalities are common and are related to a subepicardial atrial injury current; they result in the presence of inconsistent PQ-segment depression, of the discordant type (in the opposite direction of the P-wave), often discreet (< 1 mm), more common in limb leads than in precordial leads and generally absent in aVR or V1 (where an elevation is conversely observed). This sign is often precocious, relatively specific (even if a PQ segment depression can also be observed for example during sinus tachycardia), and may represent the sole abnormality found during acute pericarditis.
A PR segment depression with opposite polarity to the P-wave may reflect the presence of an atrial lesion observed primarily during acute pericarditis or myocardial infarction, most often with an elevation in V1 and aVR (leads where the P-wave is negative). When a PR segment elevation > 1 mm, concordant with a positive P-wave, is detected, this represents a specific sign of atrial infarction which is rarely isolated and typically associated with a posteroinferior ventricular infarction.