Electrocardiographic evolution during acute pericarditis
The typical electrical pattern of acute pericarditis is that of a viral, dry pericarditis or with effusion of low abundance. The electrocardiogram classically evolves into 4 stages:
- stage 1: subepicardial lesion pattern observed in the first 24 hours with ST-segment elevation concave upwards followed by a positive T-wave, sometimes of great amplitude (camel saddle pattern); the elevation is diffuse, observed in a majority of leads except for aVR and V1 and can last from a few hours to several days; a PQ segment depression can also be observed in this initial phase;
- stage 2: during this transition phase, a return to the isoelectric line is observed with a flattening of the T-waves with possible biphasic pattern of small amplitude;
- stage 3: this is the most constant phase observed during the first week with evidence of subepicardial ischemia with often symmetrical and peaked T-waves with amplitude generally limited in the leads in which the elevation was previously present;
- stage 4: this is the remission and return to normal phase of the T-waves which resume their initial positivity; electrical healing is usually delayed compared to clinical healing and is seen within 6 weeks to several months;
This 4-phase sequence is not always respected with an incomplete electrocardiographic semiology and sometimes very discrete signs (useful to repeat the tracings for comparison purposes). The classic changes in ST-segment and T-wave are more frequently observed in purulent pericarditis forms than in viral, rheumatic or malignant pericarditis.
The modifications are generally widespread, but can be localized after pericardiotomy for example in which the elevation is more regional.