Intraoperative Transesophageal Echocardiography in On-pump Mitral Surgery: A Single Center Prospective Observational Study of Global Longitudinal Strain and Global Longitudinal Strain Rate as Predictors of Unfavorable Outcome

Low cardiac output syndrome (LCOS) is a common complication in cardiac surgery after weaning from cardiopulmonary bypass (CPB) associated with high morbidity and mortality. Its prompt recognition and management may mitigate the effect of LCOS on the outcome. To date, advanced age, prolonged CPB, urgent surgery and impaired left ventricular function assessed by left ventricular ejection fraction (LVEF) are commonly considered strong predictors of postoperative LCOS. Nevertheless, LVEF has several limitations including image quality, operator experience, limited reproducibility, inter- and intra-observer discrepancy and load/volume dependency. Global Longitudinal Strain (GLS), with automated speckle-tracking echocardiography (STE) may overcome several of the LVEF limitations. In fact, while the LVEF detects changes in left ventricular chamber volume, GLS reflects myocardial longitudinal deformation due to contraction. The rate of myocardial deformation over time (expressed as 1/s) is called GLS Rate. Global Longitudinal Strain, mostly evaluated from transthoracic echocardiography (TTE), has shown lower inter- and intra-observer variability, a better reproducibility and prognostic value compared to LVEF in a generic cardiac population. In addition the results of the GLS with TTE (GLS-TTE) may not be shifted in cardiac surgery due to the effect of the general anesthesia (GA) and positive pressure ventilation. Thus, these factors should be considered when the global longitudinal strain, evaluated from transesophageal echocardiography (GLS-TEE) is used as predictor of early outcome. Amabili et al. have shown that GLS-TEE is better than LVEF in predicting LCOS in a general cardiac surgery population. Similarly Sonny et al. in patients undergoing aortic valve surgery for stenosis have reported that a GLS-TEE and GLS-TEE Rate are superior to standard echocardiographic parameters in predicting a complicated course. To the best of our knowledge, there are no studies investigating the role of intraoperative evaluation of GLS-TEE and GLS-TEE Rate as predictors of LCOS in mitral valve surgery. In this setting LVEF is not a reliable marker of cardiac function due to a systematic overestimation of the ejection fraction. Moreover these patients are at high risk of postoperative cardiac dysfunction and LCOS owing to the afterload mismatch after mitral surgery. For the reasons mentioned above, more effective predictors are advocated. In the present study we try to fill the gap. Thus, aim of present study is to assess the role of GLS-TEE, GLS-TEE Rate and standard echocardiographic parameters in predicting LCOS in on-pump mitral surgery. In doing so, the best cut-off for each echocardiographic parameter will be provided. Finally to detect the effect of the GA, the echocardiographic parameters calculated after the induction of GA will be compared with those collected preoperatively.

A telephonic follow-up will be performed at 30 days and 12-months investigating mortality and rehospitalization due to heart failure.