A closed-chest model of selective atrial myocardial infarction for the study of induced electrophysiological and structural derangements

Abstract

Abstract Background The diagnosis of atrial infarction is often masked by the frequent association with ventricular infarction. For this reason, the electrophysiological and structural consequences of selective atrial ischemia are poorly understood. Purpose The objective of this study was to analyze the alterations in the ECG, local electrograms, and multifrequential atrial myocardial impedance in a new experimental model of acute and chronic atrial infarction. Methods Seven anesthetized pigs were subjected to 4h of atrial ischemia induced by selective catheter occlusion of the atrial coronary branches originating in the left circumflex coronary artery. The surface ECG was recorded and the changes in P-wave morphology analyzed. Four weeks later the animals were subjected to endocardial voltage mapping (Carto) and multifrequential impedance. The hearts were processed for anatomopathological study. Results Selective occlusion of the coronary atrial branches induced atrial infarction with fibrosis in the left atrium in 6 of the 7 cases (Figure). The surface ECG showed prolongation of the P-wave duration (Figure) (P-wave in lead II: from 72±8ms at baseline vs. 97±18ms at 4 weeks, ANOVA p<0.01; P-wave in lead aVR: from 71±3ms at baseline vs 87±9ms at 4 weeks, ANOVA p<0.01) with no appreciable displacement of the PR segment. Endocardial mapping of the left atrium showed low-voltage bipolar zones with decreased multi-frequency impedance phase angle values, as compared with preserved zones of the same atrium (bipolar electrograms: from 0.6±1mV to 2.0±1.9mV, T-Test p<0.01; Phase angle at 300KHz: from −5.5±2° to −9.0±4.4° T-Test p<0.05). Conclusion We developed a closed-chest swine model of selective atrial infarction suitable for the study of ECG patterns and electrophysiological mechanisms linked to atrial myocardial ischemia and infarction. The structural derangements are detectable by endocardial mapping of local voltage electrograms and local tissue impedance. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Supported by grants from ISCI-MINECO (FIS PI17/00069), FEDER, CIBERCV (CB16/11/00276)