Atrial MI

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]

Overview

In approximately 10% of patients with acute myocardial infarction involving the ventricular territory, an atrial infarct also occurs. An atrial infarct can manifest itself in atrial rhytm disturbances such as atrial fibrillation. Because the atria may be of minor consequences hemodynamically, an atrial infarct may be missed.

On the ECG, an atrial infarct manifests by rhythm changes and/or change of the P-Ta segment (sometimes called PTA (P - atriale T) segment or PR or PQ or PTp (P - T wave of P wave) segment). This is the part between the end of the P wave and the Q. The ST segment indicates an infarct in the ventricle, the P-Ta segment indicates an infarct in the atria.

Diagnostic criteria for an atrial infarct include:

• P-Ta elevation >0.5mm in V5 and V6 with reciprocal depression in V1 and V2
• P-Ta elevation >0.5mm in I and depression in II and III
• >1.5mm P-Ta depression in precordial leads
• >1.2mm P-Ta depression in I,II or III in combination with atrial arrhytmias

Several diagnostic criteria are in use, and this is just an example of one. An important differential diagnosis of PTa segment elevation or depression is pericarditis.