Historically, the pulmonary artery catheter (PAC) has been utilized for measuring cardiac filling pressures, with pulmonary capillary wedge pressure (PCWP) serving as a proxy for left atrial pressure (LAP) and left ventricular end-diastolic pressure. Numerous extensive studies have demonstrated a correlation between PCWP and LAP in patients afflicted with cardiovascular diseases.

Assessing left atrial pressure (LAP) is integral to the evaluation of left ventricular diastolic function.  Increased left ventricular filling pressures are predictive of unfavourable long-term outcomes, even in individuals with normal ejection fractions. Furthermore, a restrictive diastolic filling pattern has been associated with heightened major morbidity and mortality rates in patients undergoing cardiac surgery.

The utility of the pulmonary artery catheter (PAC) in the perioperative setting has come under scrutiny, as numerous extensive studies have failed to conclusively establish its benefits across patient cohorts. Consequently, its utilization during the perioperative period has dwindled. There is now a growing need for alternative non-invasive approaches to estimate left-sided filling pressures.

In the absence of mitral valve disease, left atrial pressure (LAP) is often considered equivalent to left ventricular end-diastolic pressure (LVEDP). Various echocardiographic parameters have been confirmed for assessing left ventricular filling pressures (LVFP).  Among these, the ratio of mitral early diastolic velocity to early diastolic mitral annular velocity (E/e′) is commonly utilized and has been found to be superior among available Doppler indices.

The e′ velocity, representing mitral annular velocities, adjusts the E wave velocity for relaxation impact. A lateral E/e′ ratio of ≥12 or septal E/e′ ratio of ≥15 correlates with an elevated left atrial pressure (LAP). However, E/e′ may lack reliability in conditions where the mitral annulus is tethered by calcium or a prosthetic ring, as well as in left ventricular disorders like hypertrophic cardiomyopathy and regional wall motion abnormalities. Therefore, this study aimed to identify a parameter capable of indirectly estimating left atrial pressure (LAP) irrespective of left ventricular and mitral valve disorders.

The deceleration time of the pulmonary vein diastolic wave (DT(D)) has shown strong correlations with invasive pulmonary capillary pressure in numerous studies, independent of left ventricular systolic function and mitral annular disorders.  However, the practical application is hindered by challenges in recording pulmonary venous flow (PVF) from apical windows in critically ill patients using transthoracic echocardiography.      Transesophageal echocardiography offers a superior imaging window for visualizing pulmonary veins, given their posterior location. Additionally NT pro-BNP levels have been found to have strong linear correlation with LAP.

 Therefore, this study aims to correlate transesophageal echocardiography (TEE)-derived deceleration time of the pulmonary vein diastolic wave (DT(D),  calculated left atrial pressure (LAP) obtained by the E/e’ ratio, and LAP measured directly via needle insertion in patients with coronary artery disease undergoing off-pump coronary artery bypass grafting (OPCAB). Additionally, NT-proBNP samples will be collected at the beginning of surgery

PCWP, an invasive technique, is considered the gold standard for estimating left atrial pressure. The use of non-invasive methods in place of pulmonary artery catheterization is still controversial. There are various studies comparing PCWP and E/e’ via TTE but very few studies comparing (TEE)-derived deceleration time of the pulmonary vein diastolic wave DT(D) and LA pressure measured directly via needle insertion. Even those studies that have been done have varying and contradictory findings. Therefore this study is designed to compare DT(D) measured via TEE and left atrial pressure obtained directly via needle insertion in patients undergoing elective Off pump CABG.