Tissue Doppler Em and Instantaneous End-diastolic Stiffness: Validation Against Pressure–Volume Loops in Patients Undergoing Coronary Artery Bypass Surgery

Abstract

The assessment of diastolic function using trans-mitral Doppler and tissue Doppler imaging during coronary artery bypass surgery (CABG) is complex, with anaesthesia, blood loss and ischaemia all contributing to altered loading conditions. Ten patients undergoing coronary artery bypass grafting underwent simultaneous transoesophageal and pressure volume loop analysis of diastolic function at different loading conditions (baseline, preload reduction, afterload increase, increased heart rate and post cardiopulmonary bypass). The mean age was 59±9 years and 3 (range 2-5) grafts. Altered loading conditions resulted in no significant changes in Tau or the end diastolic pressure volume relationship. dP/dtmin varied significantly across loading conditions (p<0.001). Tissue Doppler peak Em measured at the lateral mitral annulus was affected significantly with increased heart rate (p<0.01), but was insensitive to changes in preload and afterload. Instantaneous end diastolic stiffness (IEDS=log(10)PCWP/EDA) did not alter during loading conditions (p=0.99). Peak Em (lateral annulus) and IEDS appear promising as measures of diastolic function over a range of haemodynamic alterations, although changes in Peak Em may not reflect diastolic function accurately if the heart rate substantially changes.