Description

The overall objective is to improve the prediction of the risk of developing arrhythmias in the postoperative period with non-invasive techniques that are sensitive to detect inter- and intra-atrial dysrhythmias.

Specific objectives

1. To describe the alterations in left and right atrial deformation by strain method to identify intra- and inter-atrial activation dyssynchrony.
2. To determine that dyssynchrony predicts a higher incidence of atrial fibrillation in the postoperative period after cardiovascular surgery.
3. To evaluate whether novel atrial function analysis techniques, such as left atrial ejection fraction assessed via 3D echocardiography, are associated with a higher incidence of postoperative atrial fibrillation.

All patients will undergo a full Doppler echocardiogram with two-dimensional atrial Strain determination with speckle tracking, using an Philips EPIC CVx series echocardiogram machine with S5-1 and X5-1 probes. The images will be obtained in left lateral decubitus. In forced expiration, 3 consecutive beats will be recorded and digitally saved for later analysis in the 4 and 2 chamber views. Both atria must be visualized so that neither atrial wall are lost in the evaluation. Echocardiographic measurements will focus primarily on the indexed left atrial volume obtained by averaging the values obtained in 2 and 4 chambers by the multiple disc method. In these views, the left ventricular ejection fraction will be obtained by the Simpson biplane method. The left atrium will be further subdivided into basal, medial and atrial roof segments, resulting in a total of 12 segments, 6 of which can be observed in the four-chamber view and 6 in the two-chamber view. The right atrium will be divided similarly but will contribute a mere three additional segments to the total (for a total of 15 segments), as the right septal segments were previously regarded as part of the left atrium. The time to maximum deflection, defined as the interval between the onset of the P wave on the electrocardiogram and the maximum deflection of the atrial contraction determined by strain rate, will be measured for each of the 15 atrial segments previously described. To determine interatrial synchrony, an adaptation of the atrial strain will be made so that both atria can be evaluated simultaneously. This new evaluation, which we have designated "OMEGA" (ω) due to its resemblance to the shape of the strain image, will yield the time to maximum deformation of the lateral segments of the right atrium and the lateral segments of the left atrium. Consequently, the difference in activation timing between the lateral segments of the right and left atria will determine the presence of an activation delta between the walls.

A comprehensive analysis of atrial deformation using left and right atrial strain will also be performed. Subsequently, the time-to-peak deformation will be measured from the onset of the P-wave to the peak negative atrial strain deflection, which correlates with atrial contractile strain. Activation time differences derived from this methodology will also be measured to provide an additional assessment of the interatrial activation delay (delta).

Patients will be followed during hospitalization with continuous electrocardiographic monitoring for the first 5 days after surgery to detect the incidence of atrial fibrillation. Patients will undergo telephonic follow-up at 28 and 365 days post-intervention, utilizing a targeted interview to evaluate for the onset of supraventricular arrhythmias.

Study data will be collected and managed using REDCap electronic data capture tools hosted at Faculty of Medicine, National University of Cuyo to a protocol designed specifically for this study.

The sample size calculation is performed according to Schoenfeld's method for Cox models. To detect a hazard ratio of 2.5 for atrial fibrillation events based on the presence or absence of interatrial dyssynchrony-estimating a cumulative event rate of 0.38 in the dyssynchronous group and 0.18 in the synchronous group, with a 0.44 proportion of dyssynchronous patients-and assuming a two-sided alpha level of 0.05 and 80% power, a total sample of 138 patients is determined.

Statistical analysis results are reported as mean (SD), median (p25-p75) or frequency (%). Comparisons between groups were performed with the Student t test or chi-squared analysis. The association between clinical variables and the study end-points was evaluated using survival analysis methodology (Cox regression models). The Kaplan-Meier method was used to estimate the cumulative probability of PAF detection and stroke recurrence in both groups, and comparisons were made by the log-rank test. Significance was set at P \< 0.05.