PRs
The PR segment is the flat line between the end of the P wave and the start of the QRS complex. During this time the impulse is delayed in the atrioventricular (AV) node and then passes through the His bundle and bundle branches. This delay lets the atria finish emptying blood into the ventricles before the ventricles contract. The PR segment, together with the TP segment, also serves as the baseline (isoelectric line) from which ST elevation or depression is measured.
Changes of the PR segment
- PR depression (below the TP baseline) in many leads, with PR elevation in aVR: typical of acute pericarditis, usually together with widespread concave ST elevation. PR depression or widespread ST elevation is one of the four diagnostic criteria for acute pericarditis.
- Atrial repolarisation (the "Ta wave") can slightly depress the PR segment, especially at fast heart rates and during exercise; this is normal
- Atrial infarction or ischaemia can rarely cause PR segment elevation or depression
- A long PR segment lengthens the PR interval (AV block); a very short or absent segment with a delta wave suggests pre-excitation
for chest pain, especially if it is severe, crushing or accompanied by breathlessness or sweating. Pericarditis pain is typically sharp, worse when lying down and better when leaning forward, but only a doctor can distinguish it from a heart attack.
References
- Adler Y, Charron P, Imazio M, et al. 2015 ESC Guidelines for the diagnosis and management of pericardial diseases. Eur Heart J. 2015;36(42):2921–2964. doi:10.1093/eurheartj/ehv318
- Kusumoto FM, Schoenfeld MH, Barrett C, et al. 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay. Circulation. 2019;140(8):e382–e482. doi:10.1161/CIR.0000000000000628
This article is for general information and does not replace a consultation with a doctor. ECG findings must be interpreted by a physician together with symptoms and other tests.
Published on 2 July 2019