TP interval

  starts from the end of T wave to the beginning of P wave.

  is the
isoelectric baseline.

  is taken as the reference line when PR segment elevation or depression is looked for (as in pericarditis
, atrial infarction , etc.).

  During tachycardia, P wave may merge with the preceding T wave. Then PR segment
is chosen as the isoelectric line (baseline).

ECG 1. When looking for PR segment deviation,
TP interval is taken as the isoelectric baseline. The ECG above belongs to a
65 years-old woman complaining of chest pain. Her coronary angiography showed only minimal atherosclerosis (40% stenosis)
in the Cx artery. She also had leukocytosis. The ECG shows
PR segment elevation in lead aVR and ST segment elevation in
lead aVR
. Most of the leads show PR segment depression and ST segment depression. Her ECG suggests pericarditis.

Click here for a more detailed ECG