Correlation of Euroscore-II, STS Risk Scoring Systems and Frailty Tests with Cardiac Histopathological Findings in Coronary Bypass Surgery

Various risk classification systems are used to predict postoperative mortality and morbidity development in cardiac surgery. Risk calculation with these systems is a guide in determining preoperative strategies, performing cost analyses, creating different treatment options and classifying diseases according to their severity. In recent years, tests defined as Frailty, which show how independently a person can perform daily living activities and are also associated with postoperative complications, have also been used. These tests allow for a personalized approach such as determining the most appropriate treatment options and pre- and postoperative rehabilitation.

This study aims to evaluate the risk scores used to predict mortality during the preoperative preparation process in cases planned for elective Coronary Artery Bypass Graft (CABG) using the European System for Cardiac Operative Risk Evaluation (Euroscore)-II and Society of Thoracic Surgeons (STS) as well as Frailty with the Katz Index and modified Rockwood Clinical Frailty Scale, and to correlate the findings obtained from the histopathological study of the tissue sample taken from the right atrium during the operation with the test results.

Secondary objectives are to investigate the compatibility of the age-related changes detected histopathologically with chronological age, to reveal which of the Frailty tests used gives better results in predicting mortality, and on the other hand, to reveal the relationship between Frailty tests and STS and Euroscore-II.

The STS scoring system was developed in 1994 and is a widely used system in the world that allows for the evaluation of morbidity as well as expected mortality for open heart surgery. The Euroscore -II system is also one of the most widely used systems in this field. Both methods are simple, accurate, provable and inexpensive.

In the assessment of frailty, the Clinical Frailty Scale (CFS) was first introduced by Rockwood and colleagues in 2005. This scale was modified by Pulok and colleagues in 2020. CFS is shown to be the most practical method (can be completed in less than a minute) that can also be applied in the field of Emergency Medicine. In 1963, Katz developed the Katz Activities of Daily Living (ADL) Scale, which shows how independently older individuals can perform daily activities. Although frailty is defined as related to aging, it has been accepted as a concept independent of age in recent years.

When evaluated histopathologically, changes such as hypertrophy, fibrosis, protein misfolding, and accumulation of dysfunctional mitochondria have been shown in the aging heart. Age-related changes in the heart are thought to be due to oxidative stress, non-enzymatic glycation, inflammation, and changes in cardiovascular gene expression. Age is a risk factor for the development of many diseases, and it has been shown that frail individuals have a higher susceptibility to disease than healthy individuals of the same age.

The investigators aimed to demonstrate the histopathological prediction degree and corresponding value of risk scores and fragility index values on cardiac tissue and to demonstrate the reality and importance of these scoring systems at the tissue level and to evaluate their reliability in predicting postoperative mortality and morbidity development. In addition, the investigators aimed to reveal the relationship of fragility tests with both age and STS and Euroscore-II by examining the compatibility of age-related changes detected histopathologically with chronological age.

The tests to be used for this study are routine tests and there is no risk. The cardiac tissue to be used for histopathological examination is tissue pieces that are dissected from the right atrial appendage while removing the venous cannula and routinely removed from the body and sent for histopathological examination. Since no non-routine tissue or blood sample will be taken from the patient, there is no risk.