INTRODUCTION
Lung dysfunction after cardiac surgery remains an important cause of postoperative morbidity despite continuing improvement in cardiopulmonary bypass techniques and postoperative intensive care management. There is a significant co-existence of cardiac and pulmonary disease. Moreover, most of the patients who are candidates for cardiac surgery have pre-existing pulmonary pathology. The important correlation of lung function and cardiac surgical outcomes is emphasized by the prognostic value of chronic lung disease assessment in the Society of Thoracic Surgeons (STS) and EuroSCORE II operative mortality estimation tools 1. This led some centers to perform pulmonary function testing (PFT) routinely before any elective cardiac surgery procedure based on the evidence that spirometry evidence of obstructive ventilatory pattern may predict the duration of mechanical ventilation and intensive care unit (ICU) stay following elective cardiac surgery2. Additionally, different levels of chronic obstructive pulmonary disease (COPD) severity may impact the prediction of postoperative morbidity and prolonged lengths of ICU and hospital stay in patients undergoing coronary artery bypass grafting (CABG)3.
However, pulmonary congestion secondary to heart failure or left-sided heart valve disease is known to cause both obstructive and restrictive abnormalities in PFT, which obviously could influence the preoperative spirometry results of cardiac surgical patients. It is debatable whether abnormal PFT results in those patients represent a real risk of postoperative pulmonary complications or they are just a reflection of the left-sided heart congestion. This led some centers to adopt the selective performance of preoperative spirometry at the discretion of the individual physician or departmental standards based on patient history of respiratory symptoms or smoking habits. Some authors did not even include PFT in their proposed model for predicting patients who require prolonged ventilation post cardiac surgery 4, that included parsonnet score, ejection fraction (EF), age, and emergency re-operation for bleeding or cardiac arrest.
Very few studies have looked at the interaction between left-sided heart valve dysfunction or ventricular dysfunction and the results of lung spirometry and suggested that lung function parameters may provide prognostic information in patients with heart failure and may help to guide treatment decisions 5.
Hence, our study aimed to focus on this subgroup of cardiac surgery patients with congestive heart failure caused by left ventricular dysfunction or left-sided heart valve disease and study the prognostic value of performing preoperative PFT on their postoperative outcomes.