AUTHOR=Amorós-Figueras Gerard , Roselló-Diez Elena , Sanchez-Quintana Damian , Casabella-Ramon Sergi , Jorge Esther , Nevado-Medina Jorge , Arzamendi Dabit , Millán Xavier , Alonso-Martin Concepción , Guerra Jose M. , Cinca Juan 

TITLE=Changes in Local Atrial Electrograms and Surface ECG Induced by Acute Atrial Myocardial Infarction

JOURNAL=Frontiers in Physiology

VOLUME=Volume 11 - 2020

YEAR=2020

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2020.00264

DOI=10.3389/fphys.2020.00264

ISSN=1664-042X

ABSTRACT=Background: Atrial coronary branch occlusion is a hardly recognizable clinical entity that can promote atrial fibrillation. The low diagnostic accuracy of the ECG could deal with the characteristics of the ischemia-induced changes in local atrial electrograms, but these have not been described. 
Objectives: We analyzed the effects of selective acute atrial branch occlusion on local myocardial structure, atrial electrograms, and surface ECG in an experimental model close to human cardiac anatomy and electrophysiology.
Methods: Six anesthetized open-chest anaesthetized pigs underwent surgical occlusion of an atrial coronary branch arising from the right coronary artery during 4 hours. Atrial electrograms and ECG were simultaneously recorded. One additional pig acted as sham control. In all cases, the hearts were processed for anatomopathological analysis.
Results: Atrial branch occlusion induced patchy atrial necrosis with sharp border zone. During the first 30min of occlusion, atrial electrograms showed progressive R-wave enlargement (1.8±0.6mV vs. 2.5±1.1mV, p<0.01), delayed local activation times (28.5±8.9ms vs. 36.1±16.4ms, p<0.01), ST-segment elevation (-0.3±0.3mV vs. 1.0±1.0mV, p<0.01), and presence of monophasic potentials. Atrial ST-segment elevation decreased after 2h of occlusion. The electrical border zone was about 1mm and expanded over time. After 2h of occlusion the ECG showed a decrease in P-wave amplitude (from 0.09±0.04mV to 0.05±0.04mV after 165 min occlusion, p<0.05) and duration (64.4±8.0ms vs. 80.9±12.6ms, p<0.01). 
Conclusions: Selective atrial branch occlusion induces patchy atrial infarction and characteristic changes in atrial activation, R/S-wave, and ST-segment that are not discernible at the ECG. Only indirect changes in P-wave amplitude and duration were appreciated in advanced stages of acute coronary occlusion.