Anatomy of LA and RA circulation
- LA is supplied by branch from LCA, encircling the base of LV and reaching LA.
- RA is supplied by branch from RCA which then penetrates the septum and reaches the posterior wall, forming a plexus in which SA node artery arises.
- Atria walls are thin, so transmural infarction can happen easily if proximal occlusion of supplying vessels happen.
- Originally described by Clerc and Levy in 1925
- First ECG demonstration (retrospectively after postmortem examination) was made in 1937, but the first antemortem ECG diagnosis based on PTa changes was made in 1948.
Majority of atrial infarction involves the right side, and to a lesser degree biatrial and LA involvement.
- Potential complications include rhythm disturbances (especially Afib), thromboembolism, acute atrial rupture, atrial failure or loss of atrial kick which results in hemodynamic consequences.
- A study in Mexico showed that patients withright atrial infarction results in poorer RV functions compared to patients without RA infarction.
- Changes in ECG maybe absent due to low voltage and over-shadowing by the ventricular depolarization.
- Deviations in PTa segment (Ta is atrial repolarization wave; deviation of Ta wave relative to preceding P wave) has been proposed as the criteria to diagnose atrial infarction.
- PTa segment depression can also be seen in normal people as well as conditions eg pericarditis and atrial overload.
- Depression in PTa without reciprical elevation cannot be taken as a sign of atrial infarction.
- Similar to ST segment in STEMI, PTa deviations in atrial infarction is also localized to certain infarcted region.
eg Posterior basal wall (ie left atrium) should show PTa depression in Lead I and elevation in lead II,III
Anterior lesions (ie RA) should show PTa depression in lead III and elevation in lead I.
ECG criteria by Liu et al
- PTa-segment elevation >0.5 mm in leads V3 and V6 with reciprocal depression of PTa segments in V1 and V2 leads.
- PTa-segment elevation >0.5 mm in lead I with reciprocal depressions in leads II and III.
- PTa-segment depression >1.5mm in precordial leads and 1.2mm in leads I, II and III, associated with any atrial arrhythmia.
– Abormal P-waves, flattening of P-wave in M, flattening of P-wave in W, irregular or notched P wave.
PS: PTa segment is in opposite polarity of P wave. Therefore, a transmural RA infarction will cause PTa depression in inferior leads (this is the same as ST segment elevation in inferior MI) and reciprocal elevation in lateral leads.
Link to Dr. Smith’s ECG blog discussing Ta wave
- Consider looking for PTa segment deviation while looking at AMI ECG !
- Lazar EJ, Goldberger J, Peled H, Sherman M, Frishman WH. Atrial
infarction: Diagnosis and management. Am Heart J 1988;116:1058-63.
- DK Shakir, SOE Arafa. Right atrial infarction, atrial arrhythmia and inferior myocardial infarction form a missed triad: A case report and review of the literature. Can J Cardiol 2007;23(12):995-997.
- JESUS´ VARGAS-BARRON´ , M.D., MAURICIO LOPEZ ´ -MENESES, M.D.,† FRANCISCO-JAVIER ROLDAN´ , M.D., ÁNGELROMERO-CARDENAS ´ , M.D.,CANDACE KEIRNS, M.D., NILDA ESPINOLA-ZAVALETA, M.D., MARCO PEÑA-DUQUE, M.D., † CARLOSMART´INEZ-SANCHEZ ´ , M.D.,MARCO-ANTONIOMARTINEZR´IOS, M.D. The Impact of Right Atrial Ischemia on Inferior Myocardial Infarction with Extension to Right Ventricle: Transesophageal Echocardiographic Examination. Clin. Cardiol. April 2002;25:181–186.